diff --git a/base/src/nsStr.cpp b/base/src/nsStr.cpp
index e4b976254248..79e7afc99107 100644
--- a/base/src/nsStr.cpp
+++ b/base/src/nsStr.cpp
@@ -31,101 +31,9 @@
 #include "nsStr.h"
 #include "bufferRoutines.h"
 #include "stdio.h"  //only used for printf
-#include "nsDeque.h"
-#include "nsCRT.h"
 
 static const char* kFoolMsg = "Error: Some fool overwrote the shared buffer.";
 
-//----------------------------------------------------------------------------------------
-//  The following is a memory agent who knows how to recycled (pool) freed memory...
-//----------------------------------------------------------------------------------------
-
-/**************************************************************
-  Define the char* (pooled) deallocator class...
- **************************************************************/
-class nsBufferDeallocator: public nsDequeFunctor{
-public:
-  virtual void* operator()(void* anObject) {
-    char* aCString= (char*)anObject;
-    delete [] aCString;
-    return 0;
-  }
-};
-
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-class nsPoolingMemoryAgent : public nsMemoryAgent{
-public:
-  nsPoolingMemoryAgent()  {
-    memset(mPools,0,sizeof(mPools));
-  }
-
-  ~nsPoolingMemoryAgent() {
-    nsBufferDeallocator theDeallocator;
-    int i=0;
-    for(i=0;i<10;i++){
-      if(mPools[i]){
-        mPools[i]->ForEach(theDeallocator); //now delete the buffers
-      }
-      delete mPools[i];
-      mPools[i]=0;
-    }
-  }
-
-  virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
-    
-    //we're given the acount value in charunits; we have to scale up by the charsize.
-    int     theShift=4;
-    PRInt32 theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-      theNewCapacity<<=1;
-      theShift++;
-    } 
-    
-    aDest.mCapacity=theNewCapacity++;
-    theShift=(theShift<<aDest.mMultibyte)-4;
-    if((theShift<12) && (mPools[theShift])){
-      aDest.mStr=(char*)mPools[theShift]->Pop();
-    }
-    if(!aDest.mStr) {
-      //we're given the acount value in charunits; we have to scale up by the charsize.
-      size_t theSize=(theNewCapacity<<aDest.mMultibyte);
-      aDest.mStr=new char[theSize];    
-    }
-    aDest.mOwnsBuffer=1;
-    return PR_TRUE;
-    
-  }
-
-  virtual PRBool Free(nsStr& aDest){
-    if(aDest.mStr){
-      if(aDest.mOwnsBuffer){
-        int theShift=1;
-        unsigned int theValue=1;
-        while((theValue<<=1)<aDest.mCapacity){ 
-          theShift++;
-        }
-        theShift-=4;
-        if(theShift<12){
-          if(!mPools[theShift]){
-            mPools[theShift]=new nsDeque(0);
-          }
-          mPools[theShift]->Push(aDest.mStr);
-        }
-        else delete [] aDest.mStr; //it's too big. Just delete it.
-      }
-      aDest.mStr=0;
-      aDest.mOwnsBuffer=0;
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-  nsDeque* mPools[16]; 
-};
 
 //----------------------------------------------------------------------------------------
 
@@ -166,21 +74,6 @@ void nsStr::Initialize(nsStr& aDest,eCharSize aCharSize) {
   NS_ASSERTION(aDest.mStr[0]==0,kFoolMsg);
 }
 
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer){
-  aDest.mStr=(aCString) ? aCString : GetSharedEmptyBuffer();
-  aDest.mLength=aLength;
-  aDest.mCapacity=aCapacity;
-  aDest.mMultibyte=aCharSize;
-  aDest.mOwnsBuffer=aOwnsBuffer;
-  aDest.mUnused=0;
-}
-
 /**
  * 
  * @update	gess10/30/98
@@ -188,9 +81,13 @@ void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 a
  * @return
  */
 nsIMemoryAgent* GetDefaultAgent(void){
-//  static nsPoolingMemoryAgent gDefaultAgent;
-  static nsMemoryAgent gDefaultAgent;
-  return (nsIMemoryAgent*)&gDefaultAgent;
+  static nsIMemoryAgent* gDefaultAgent=0;
+  if(!gDefaultAgent)
+    gDefaultAgent=new nsMemoryAgent();
+  
+  NS_ASSERTION(gDefaultAgent,"You MUST always have an allocator!");
+
+  return gDefaultAgent;
 }
 
 /**
@@ -213,6 +110,20 @@ void nsStr::Destroy(nsStr& aDest,nsIMemoryAgent* anAgent) {
   }
 }
 
+/**
+ * 
+ * @update	gess11/12/98
+ * @param 
+ * @return
+ */
+PRUnichar nsStr::GetCharAt(const nsStr& aDest,PRUint32 anIndex) {
+  PRUnichar result=0;
+  if((anIndex>=0) && (anIndex<aDest.mLength))  {
+    result=(eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
+  }//if
+  return result;
+}
+
 
 /**
  * This method gets called when the internal buffer needs
@@ -244,8 +155,8 @@ void nsStr::GrowCapacity(nsStr& aDest,PRUint32 aNewLength,nsIMemoryAgent* anAgen
     nsIMemoryAgent* theAgent=(anAgent) ? anAgent : GetDefaultAgent();
     EnsureCapacity(theTempStr,aNewLength,theAgent);
 
-    if(aDest.mLength) {
-      Append(theTempStr,aDest,0,aDest.mLength,theAgent);        
+    if(0<aDest.mLength) {
+      Append(theTempStr,aDest,0,aDest.mLength,anAgent);        
     } 
     theAgent->Free(aDest);
     aDest.mStr = theTempStr.mStr;
@@ -271,13 +182,14 @@ void nsStr::Assign(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 a
 /**
  * This method appends the given nsStr to this one. Note that we have to 
  * pay attention to the underlying char-size of both structs.
- * @update	gess10/30/98
+ * @update	gess 04/04/99
  * @param   aDest is the nsStr to be manipulated
  * @param   aSource is where char are copied from
  * @aCount  is the number of bytes to be copied 
  */
 void nsStr::Append(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
-  if(anOffset<aSource.mLength) {
+
+  if(anOffset<aSource.mLength){
     PRUint32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
     PRUint32 theLength=(anOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-anOffset);
     if(0<theLength){
@@ -309,31 +221,30 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
   //  1. You're inserting chars into an empty string (assign)
   //  2. You're inserting onto the end of a string (append)
   //  3. You're inserting onto the 1..n-1 pos of a string (the hard case).
-  if(0<aSource.mLength){
-    ToRange(aDestOffset,0,aDest.mLength);
+  if((0<aSource.mLength) && (aDestOffset<aDest.mLength-1)){
     if(aDest.mLength){
       if(aDestOffset<aDest.mLength){
+        if(aSrcOffset<aSource.mLength-1) {
+          PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
+          PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
 
-        ToRange(aSrcOffset,0,aSource.mLength-1);
-        PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
-        PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
+          if(aSrcOffset<aSource.mLength) {
+              //here's the only new case we have to handle. 
+              //chars are really being inserted into our buffer...
+            GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
 
-        if(aSrcOffset<aSource.mLength) {
-            //here's the only new case we have to handle. 
-            //chars are really being inserted into our buffer...
-          GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
-
-            //shift the chars right by theDelta...
-          (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+              //shift the chars right by theDelta...
+            (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
       
-          //now insert new chars, starting at offset
-          (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
+            //now insert new chars, starting at offset
+            (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
 
-          //finally, make sure to update the string length...
-          aDest.mLength+=theLength;
+            //finally, make sure to update the string length...
+            aDest.mLength+=theLength;
 
-        }//if
-        //else nothing to do!
+          }//if
+          //else nothing to do!
+        }
       }
       else Append(aDest,aSource,0,aCount,anAgent);
     }
@@ -349,21 +260,22 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
  * @param   aDestOffset is where in aDest deletion is to occur
  * @param   aCount is the number of chars to be deleted in aDest
  */
-void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent){
+void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
+  if(0<aCount){
+    if(aDestOffset<aDest.mLength){
 
-  if(aDestOffset<aDest.mLength){
+      PRInt32 theDelta=aDest.mLength-aDestOffset;
+      PRInt32 theLength=(theDelta<aCount) ? theDelta : aCount;
 
-    PRUint32 theDelta=aDest.mLength-aDestOffset;
-    PRUint32 theLength=(theDelta<aCount) ? theDelta : aCount;
+      if(aDestOffset+theLength<aDest.mLength) {
 
-    if(aDestOffset+theLength<aDest.mLength) {
-
-      //if you're here, it means we're cutting chars out of the middle of the string...
-      //so shift the chars left by theLength...
-      (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
-      aDest.mLength-=theLength;
-    }
-    else Truncate(aDest,aDestOffset,anAgent);
+        //if you're here, it means we're cutting chars out of the middle of the string...
+        //so shift the chars left by theLength...
+        (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+        aDest.mLength-=theLength;
+      }
+      else Truncate(aDest,aDestOffset,anAgent);
+    }//if
   }//if
 }
 
@@ -431,28 +343,28 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
    **************************************************************/
 
 
-PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=anOffset-1;
   PRInt32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
     while(++index<=theMax) {
       PRInt32 theSubIndex=-1;
       PRBool  matches=PR_TRUE;
       while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+        PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
         if(theSubIndex>0) {
           if(theFirstTargetChar==theChar){
-            PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+            PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
             if(theDestJumpChar==theLastTargetChar) {
               theNewStartPos=index; //this lets us jump ahead during our search where possible.
             }//if
           }//if
         }//if
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+        PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
         matches=PRBool(theChar==theTargetChar);
       }
       if(matches)
@@ -472,8 +384,8 @@ PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnor
  * @param 
  * @return
  */
-PRInt32 nsStr::FindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::FindChar(const nsStr& aDest, PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -503,12 +415,12 @@ PRInt32 nsStr::FindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnore
    **************************************************************/
 
 
-PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=(anOffset ? anOffset : aDest.mLength-aTarget.mLength+1);
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
 
     while(index--) {
@@ -517,16 +429,16 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
     
       if(anOffset+aTarget.mLength<=aDest.mLength) {
         while((++theSubIndex<theTargetMax) && (matches)){
-          PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+          PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
           if(theSubIndex>0) {
             if(theFirstTargetChar==theChar){
-              PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+              PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
               if(theDestJumpChar==theLastTargetChar) {
                 theNewStartPos=index; //this lets us jump ahead during our search where possible.
               }//if
             }//if
           }//if
-          PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+          PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
           matches=PRBool(theChar==theTargetChar);
         } //while
       } //if
@@ -547,8 +459,8 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
  * @param 
  * @return
  */
-PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -560,11 +472,11 @@ PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnor
  *  @return  
  */
 PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 offset=aDest.mLength-anOffset;
+  PRInt32  offset=aDest.mLength-anOffset;
   PRInt32  thePos;
 
   while(--offset>=0) {
-    PRUnichar theChar=GetCharAt(aDest,offset);
+    PRUnichar theChar=GetCharAt(aDest,PRUint32(offset));
     thePos=gRFindChars[aSet.mMultibyte](aSet.mStr,aSet.mLength,0,theChar,aIgnoreCase);
     if(kNotFound!=thePos)
       return offset;
@@ -579,7 +491,7 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
  * @param 
  * @return  aDest<aSource=-1;aDest==aSource==0;aDest>aSource=1
  */
-PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PRBool aIgnoreCase) {
+PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 /*aCount*/,PRBool aIgnoreCase) {
   int minlen=(aSource.mLength<aDest.mLength) ? aSource.mLength : aDest.mLength;
 
   if(0==minlen) {
diff --git a/base/src/nsStr.h b/base/src/nsStr.h
index 209f7efd93eb..856ed34f3ce9 100644
--- a/base/src/nsStr.h
+++ b/base/src/nsStr.h
@@ -27,6 +27,8 @@
        We chose the option B for performance reasons. 
 
     2  Our internal buffer always holds capacity+1 bytes.
+    3. Note that our internal format for this class makes our memory 
+       layout compatible with BStrings.
 
     The nsStr struct is a simple structure (no methods) that contains
     the necessary info to be described as a string. This simple struct
@@ -42,7 +44,8 @@
 #ifndef _nsStr
 #define _nsStr
 
-#include "nsCore.h"
+#include "prtypes.h"
+#include "nscore.h"
 
 //----------------------------------------------------------------------------------------
 
@@ -50,6 +53,34 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kDefaultCharSize eTwoByte
 
 
+union UStrPtr { 
+  char*       mCharBuf;
+  PRUnichar*  mUnicharBuf;
+}; 
+
+/**************************************************************************
+  Here comes the nsBufDescriptor class which describes buffer properties.
+ **************************************************************************/
+
+struct nsBufDescriptor {
+  nsBufDescriptor(char* aBuffer,PRUint32 aBufferSize,eCharSize aCharSize,PRBool aOwnsBuffer) {
+    mStr=aBuffer;
+    mMultibyte=aCharSize;
+    mCapacity=(aBufferSize>>mMultibyte)-1;
+    mOwnsBuffer=aOwnsBuffer;
+  }
+
+  PRUint32        mCapacity;
+  PRBool          mOwnsBuffer;
+  eCharSize       mMultibyte;
+//  UStrPtr         mStr;
+  union { 
+    char*         mStr;
+    PRUnichar*    mUStr;
+  };
+};
+
+
 class nsIMemoryAgent;
 
 //----------------------------------------------------------------------------------------
@@ -66,15 +97,6 @@ struct nsStr {
   */
   static void Initialize(nsStr& aDest,eCharSize aCharSize);
 
- /**
-  * This method initializes an nsStr for use
-  *
-  * @update	gess 01/04/99
-  * @param  aString is the nsStr to be initialized
-  * @param  aCharSize tells us the requested char size (1 or 2 bytes)
-  */
-  static void Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer);
-
  /**
   * This method destroys the given nsStr, and *MAY* 
   * deallocate it's memory depending on the setting
@@ -144,7 +166,7 @@ struct nsStr {
   * @param  aCount tells us the (max) # of chars to delete
   * @param  anAgent is the allocator to be used for alloc/free operations
   */
-  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent=0);
+  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent=0);
 
  /**
   * This method is used to truncate the given string.
@@ -232,20 +254,21 @@ struct nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset);
 
+ /**
+  * This method is used to access a given char in the given string
+  *
+  * @update	gess 01/04/99
+  * @param  aDest is the nsStr to be appended to
+  * @param  anIndex tells us where in dest to get the char from
+  * @return the given char, or 0 if anIndex is out of range
+  */
+  static PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex);
 
-#ifdef  NS_DEBUG
-  PRUint32        mLength;
-  eCharSize       mMultibyte;
-  PRUint32        mCapacity;
-  PRUint32        mOwnsBuffer;
-  PRUint32        mUnused;
-#else
-  PRUint32        mLength:      30;
-  eCharSize       mMultibyte:    2;
+  PRUint32        mLength   :   30;
+  eCharSize       mMultibyte :   2;
   PRUint32        mCapacity:    30;
-  PRUint32        mOwnsBuffer:   1;
-  PRUint32        mUnused:       1;
-#endif
+  PRUint32        mOwnsBuffer:  1;
+  PRUint32        mUnused:      1;
   union { 
     char*         mStr;
     PRUnichar*    mUStr;
@@ -284,21 +307,6 @@ inline void AddNullTerminator(nsStr& aDest) {
   else aDest.mStr[aDest.mLength]=0;
 }
 
-/**
-* This method is used to access a given char in the given string
-*
-* @update	gess 01/04/99
-* @param  aDest is the nsStr to be appended to
-* @param  anIndex tells us where in dest to get the char from
-* @return the given char, or 0 if anIndex is out of range
-*/
-inline PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex){
-  if(anIndex<aDest.mLength)  {
-    return (eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
-  }//if
-  return 0;
-}
-
 //----------------------------------------------------------------------------------------
 
 class nsIMemoryAgent {
@@ -309,18 +317,25 @@ public:
 };
 
 class nsMemoryAgent : public nsIMemoryAgent {
-protected:
-  enum eDelta{eDefaultSize=16};
+  enum eDelta{eGrowthDelta=8};
 public:
-
   virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
     
-    //we're given the acount value in charunits; now scale up to next multiple.
-  	PRInt32	theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-		  theNewCapacity<<=1;
+    //we're given the acount value in charunits; we have to scale up by the charsize.
+
+    PRInt32 theNewCapacity;
+    if (aDest.mCapacity > 64) {
+      // When the string starts getting large, double the capacity as we grow.
+      theNewCapacity = aDest.mCapacity * 2;
+      if (theNewCapacity < aCount) {
+        theNewCapacity = aDest.mCapacity + aCount;
+      }
+    } else {
+      // When the string is small, keep it's capacity a multiple of kGrowthDelta
+      PRInt32 unitDelta=(aCount/eGrowthDelta)+1;
+      theNewCapacity=unitDelta*eGrowthDelta;
     }
-	  
+
     aDest.mCapacity=theNewCapacity++;
     size_t theSize=(theNewCapacity<<aDest.mMultibyte);
     aDest.mStr=new char[theSize];
@@ -347,5 +362,6 @@ public:
 
 };
 
+
 #endif
 
diff --git a/base/src/nsString2.cpp b/base/src/nsString2.cpp
index 580bfebb9b17..aa3ff505446e 100644
--- a/base/src/nsString2.cpp
+++ b/base/src/nsString2.cpp
@@ -252,10 +252,10 @@ PRBool nsString2::IsOrdered(void) const {
   if(mLength>1) {
     PRUint32 theIndex;
     PRUnichar c1=0;
-    PRUnichar c2=nsStr::GetCharAt(*this,0);
+    PRUnichar c2=GetCharAt(*this,0);
     for(theIndex=1;theIndex<mLength;theIndex++) {
       c1=c2;
-      c2=nsStr::GetCharAt(*this,theIndex);
+      c2=GetCharAt(*this,theIndex);
       if(c1>c2) {
         result=PR_FALSE;
         break;
@@ -315,19 +315,19 @@ PRUnichar* nsString2::GetUnicode(void) const {
  * Get nth character.
  */
 PRUnichar nsString2::operator[](int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::CharAt(int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::First(void) const{
-  return nsStr::GetCharAt(*this,0);
+  return GetCharAt(*this,0);
 }
 
 PRUnichar nsString2::Last(void) const{
-  return nsStr::GetCharAt(*this,mLength-1);
+  return GetCharAt(*this,mLength-1);
 }
 
 PRBool nsString2::SetCharAt(PRUnichar aChar,PRUint32 anIndex){
@@ -1130,7 +1130,7 @@ PRInt32 nsString2::BinarySearch(PRUnichar aChar) const{
 
   while (low <= high) {
     int middle = (low + high) >> 1;
-    PRUnichar theChar=nsStr::GetCharAt(*this,middle);
+    PRUnichar theChar=GetCharAt(*this,middle);
     if (theChar==aChar)
       return middle;
     if (theChar>aChar)
diff --git a/string/obsolete/nsStr.cpp b/string/obsolete/nsStr.cpp
index e4b976254248..79e7afc99107 100644
--- a/string/obsolete/nsStr.cpp
+++ b/string/obsolete/nsStr.cpp
@@ -31,101 +31,9 @@
 #include "nsStr.h"
 #include "bufferRoutines.h"
 #include "stdio.h"  //only used for printf
-#include "nsDeque.h"
-#include "nsCRT.h"
 
 static const char* kFoolMsg = "Error: Some fool overwrote the shared buffer.";
 
-//----------------------------------------------------------------------------------------
-//  The following is a memory agent who knows how to recycled (pool) freed memory...
-//----------------------------------------------------------------------------------------
-
-/**************************************************************
-  Define the char* (pooled) deallocator class...
- **************************************************************/
-class nsBufferDeallocator: public nsDequeFunctor{
-public:
-  virtual void* operator()(void* anObject) {
-    char* aCString= (char*)anObject;
-    delete [] aCString;
-    return 0;
-  }
-};
-
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-class nsPoolingMemoryAgent : public nsMemoryAgent{
-public:
-  nsPoolingMemoryAgent()  {
-    memset(mPools,0,sizeof(mPools));
-  }
-
-  ~nsPoolingMemoryAgent() {
-    nsBufferDeallocator theDeallocator;
-    int i=0;
-    for(i=0;i<10;i++){
-      if(mPools[i]){
-        mPools[i]->ForEach(theDeallocator); //now delete the buffers
-      }
-      delete mPools[i];
-      mPools[i]=0;
-    }
-  }
-
-  virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
-    
-    //we're given the acount value in charunits; we have to scale up by the charsize.
-    int     theShift=4;
-    PRInt32 theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-      theNewCapacity<<=1;
-      theShift++;
-    } 
-    
-    aDest.mCapacity=theNewCapacity++;
-    theShift=(theShift<<aDest.mMultibyte)-4;
-    if((theShift<12) && (mPools[theShift])){
-      aDest.mStr=(char*)mPools[theShift]->Pop();
-    }
-    if(!aDest.mStr) {
-      //we're given the acount value in charunits; we have to scale up by the charsize.
-      size_t theSize=(theNewCapacity<<aDest.mMultibyte);
-      aDest.mStr=new char[theSize];    
-    }
-    aDest.mOwnsBuffer=1;
-    return PR_TRUE;
-    
-  }
-
-  virtual PRBool Free(nsStr& aDest){
-    if(aDest.mStr){
-      if(aDest.mOwnsBuffer){
-        int theShift=1;
-        unsigned int theValue=1;
-        while((theValue<<=1)<aDest.mCapacity){ 
-          theShift++;
-        }
-        theShift-=4;
-        if(theShift<12){
-          if(!mPools[theShift]){
-            mPools[theShift]=new nsDeque(0);
-          }
-          mPools[theShift]->Push(aDest.mStr);
-        }
-        else delete [] aDest.mStr; //it's too big. Just delete it.
-      }
-      aDest.mStr=0;
-      aDest.mOwnsBuffer=0;
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-  nsDeque* mPools[16]; 
-};
 
 //----------------------------------------------------------------------------------------
 
@@ -166,21 +74,6 @@ void nsStr::Initialize(nsStr& aDest,eCharSize aCharSize) {
   NS_ASSERTION(aDest.mStr[0]==0,kFoolMsg);
 }
 
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer){
-  aDest.mStr=(aCString) ? aCString : GetSharedEmptyBuffer();
-  aDest.mLength=aLength;
-  aDest.mCapacity=aCapacity;
-  aDest.mMultibyte=aCharSize;
-  aDest.mOwnsBuffer=aOwnsBuffer;
-  aDest.mUnused=0;
-}
-
 /**
  * 
  * @update	gess10/30/98
@@ -188,9 +81,13 @@ void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 a
  * @return
  */
 nsIMemoryAgent* GetDefaultAgent(void){
-//  static nsPoolingMemoryAgent gDefaultAgent;
-  static nsMemoryAgent gDefaultAgent;
-  return (nsIMemoryAgent*)&gDefaultAgent;
+  static nsIMemoryAgent* gDefaultAgent=0;
+  if(!gDefaultAgent)
+    gDefaultAgent=new nsMemoryAgent();
+  
+  NS_ASSERTION(gDefaultAgent,"You MUST always have an allocator!");
+
+  return gDefaultAgent;
 }
 
 /**
@@ -213,6 +110,20 @@ void nsStr::Destroy(nsStr& aDest,nsIMemoryAgent* anAgent) {
   }
 }
 
+/**
+ * 
+ * @update	gess11/12/98
+ * @param 
+ * @return
+ */
+PRUnichar nsStr::GetCharAt(const nsStr& aDest,PRUint32 anIndex) {
+  PRUnichar result=0;
+  if((anIndex>=0) && (anIndex<aDest.mLength))  {
+    result=(eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
+  }//if
+  return result;
+}
+
 
 /**
  * This method gets called when the internal buffer needs
@@ -244,8 +155,8 @@ void nsStr::GrowCapacity(nsStr& aDest,PRUint32 aNewLength,nsIMemoryAgent* anAgen
     nsIMemoryAgent* theAgent=(anAgent) ? anAgent : GetDefaultAgent();
     EnsureCapacity(theTempStr,aNewLength,theAgent);
 
-    if(aDest.mLength) {
-      Append(theTempStr,aDest,0,aDest.mLength,theAgent);        
+    if(0<aDest.mLength) {
+      Append(theTempStr,aDest,0,aDest.mLength,anAgent);        
     } 
     theAgent->Free(aDest);
     aDest.mStr = theTempStr.mStr;
@@ -271,13 +182,14 @@ void nsStr::Assign(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 a
 /**
  * This method appends the given nsStr to this one. Note that we have to 
  * pay attention to the underlying char-size of both structs.
- * @update	gess10/30/98
+ * @update	gess 04/04/99
  * @param   aDest is the nsStr to be manipulated
  * @param   aSource is where char are copied from
  * @aCount  is the number of bytes to be copied 
  */
 void nsStr::Append(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
-  if(anOffset<aSource.mLength) {
+
+  if(anOffset<aSource.mLength){
     PRUint32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
     PRUint32 theLength=(anOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-anOffset);
     if(0<theLength){
@@ -309,31 +221,30 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
   //  1. You're inserting chars into an empty string (assign)
   //  2. You're inserting onto the end of a string (append)
   //  3. You're inserting onto the 1..n-1 pos of a string (the hard case).
-  if(0<aSource.mLength){
-    ToRange(aDestOffset,0,aDest.mLength);
+  if((0<aSource.mLength) && (aDestOffset<aDest.mLength-1)){
     if(aDest.mLength){
       if(aDestOffset<aDest.mLength){
+        if(aSrcOffset<aSource.mLength-1) {
+          PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
+          PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
 
-        ToRange(aSrcOffset,0,aSource.mLength-1);
-        PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
-        PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
+          if(aSrcOffset<aSource.mLength) {
+              //here's the only new case we have to handle. 
+              //chars are really being inserted into our buffer...
+            GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
 
-        if(aSrcOffset<aSource.mLength) {
-            //here's the only new case we have to handle. 
-            //chars are really being inserted into our buffer...
-          GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
-
-            //shift the chars right by theDelta...
-          (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+              //shift the chars right by theDelta...
+            (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
       
-          //now insert new chars, starting at offset
-          (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
+            //now insert new chars, starting at offset
+            (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
 
-          //finally, make sure to update the string length...
-          aDest.mLength+=theLength;
+            //finally, make sure to update the string length...
+            aDest.mLength+=theLength;
 
-        }//if
-        //else nothing to do!
+          }//if
+          //else nothing to do!
+        }
       }
       else Append(aDest,aSource,0,aCount,anAgent);
     }
@@ -349,21 +260,22 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
  * @param   aDestOffset is where in aDest deletion is to occur
  * @param   aCount is the number of chars to be deleted in aDest
  */
-void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent){
+void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
+  if(0<aCount){
+    if(aDestOffset<aDest.mLength){
 
-  if(aDestOffset<aDest.mLength){
+      PRInt32 theDelta=aDest.mLength-aDestOffset;
+      PRInt32 theLength=(theDelta<aCount) ? theDelta : aCount;
 
-    PRUint32 theDelta=aDest.mLength-aDestOffset;
-    PRUint32 theLength=(theDelta<aCount) ? theDelta : aCount;
+      if(aDestOffset+theLength<aDest.mLength) {
 
-    if(aDestOffset+theLength<aDest.mLength) {
-
-      //if you're here, it means we're cutting chars out of the middle of the string...
-      //so shift the chars left by theLength...
-      (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
-      aDest.mLength-=theLength;
-    }
-    else Truncate(aDest,aDestOffset,anAgent);
+        //if you're here, it means we're cutting chars out of the middle of the string...
+        //so shift the chars left by theLength...
+        (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+        aDest.mLength-=theLength;
+      }
+      else Truncate(aDest,aDestOffset,anAgent);
+    }//if
   }//if
 }
 
@@ -431,28 +343,28 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
    **************************************************************/
 
 
-PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=anOffset-1;
   PRInt32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
     while(++index<=theMax) {
       PRInt32 theSubIndex=-1;
       PRBool  matches=PR_TRUE;
       while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+        PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
         if(theSubIndex>0) {
           if(theFirstTargetChar==theChar){
-            PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+            PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
             if(theDestJumpChar==theLastTargetChar) {
               theNewStartPos=index; //this lets us jump ahead during our search where possible.
             }//if
           }//if
         }//if
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+        PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
         matches=PRBool(theChar==theTargetChar);
       }
       if(matches)
@@ -472,8 +384,8 @@ PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnor
  * @param 
  * @return
  */
-PRInt32 nsStr::FindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::FindChar(const nsStr& aDest, PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -503,12 +415,12 @@ PRInt32 nsStr::FindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnore
    **************************************************************/
 
 
-PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=(anOffset ? anOffset : aDest.mLength-aTarget.mLength+1);
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
 
     while(index--) {
@@ -517,16 +429,16 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
     
       if(anOffset+aTarget.mLength<=aDest.mLength) {
         while((++theSubIndex<theTargetMax) && (matches)){
-          PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+          PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
           if(theSubIndex>0) {
             if(theFirstTargetChar==theChar){
-              PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+              PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
               if(theDestJumpChar==theLastTargetChar) {
                 theNewStartPos=index; //this lets us jump ahead during our search where possible.
               }//if
             }//if
           }//if
-          PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+          PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
           matches=PRBool(theChar==theTargetChar);
         } //while
       } //if
@@ -547,8 +459,8 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
  * @param 
  * @return
  */
-PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -560,11 +472,11 @@ PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnor
  *  @return  
  */
 PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 offset=aDest.mLength-anOffset;
+  PRInt32  offset=aDest.mLength-anOffset;
   PRInt32  thePos;
 
   while(--offset>=0) {
-    PRUnichar theChar=GetCharAt(aDest,offset);
+    PRUnichar theChar=GetCharAt(aDest,PRUint32(offset));
     thePos=gRFindChars[aSet.mMultibyte](aSet.mStr,aSet.mLength,0,theChar,aIgnoreCase);
     if(kNotFound!=thePos)
       return offset;
@@ -579,7 +491,7 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
  * @param 
  * @return  aDest<aSource=-1;aDest==aSource==0;aDest>aSource=1
  */
-PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PRBool aIgnoreCase) {
+PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 /*aCount*/,PRBool aIgnoreCase) {
   int minlen=(aSource.mLength<aDest.mLength) ? aSource.mLength : aDest.mLength;
 
   if(0==minlen) {
diff --git a/string/obsolete/nsStr.h b/string/obsolete/nsStr.h
index 209f7efd93eb..856ed34f3ce9 100644
--- a/string/obsolete/nsStr.h
+++ b/string/obsolete/nsStr.h
@@ -27,6 +27,8 @@
        We chose the option B for performance reasons. 
 
     2  Our internal buffer always holds capacity+1 bytes.
+    3. Note that our internal format for this class makes our memory 
+       layout compatible with BStrings.
 
     The nsStr struct is a simple structure (no methods) that contains
     the necessary info to be described as a string. This simple struct
@@ -42,7 +44,8 @@
 #ifndef _nsStr
 #define _nsStr
 
-#include "nsCore.h"
+#include "prtypes.h"
+#include "nscore.h"
 
 //----------------------------------------------------------------------------------------
 
@@ -50,6 +53,34 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kDefaultCharSize eTwoByte
 
 
+union UStrPtr { 
+  char*       mCharBuf;
+  PRUnichar*  mUnicharBuf;
+}; 
+
+/**************************************************************************
+  Here comes the nsBufDescriptor class which describes buffer properties.
+ **************************************************************************/
+
+struct nsBufDescriptor {
+  nsBufDescriptor(char* aBuffer,PRUint32 aBufferSize,eCharSize aCharSize,PRBool aOwnsBuffer) {
+    mStr=aBuffer;
+    mMultibyte=aCharSize;
+    mCapacity=(aBufferSize>>mMultibyte)-1;
+    mOwnsBuffer=aOwnsBuffer;
+  }
+
+  PRUint32        mCapacity;
+  PRBool          mOwnsBuffer;
+  eCharSize       mMultibyte;
+//  UStrPtr         mStr;
+  union { 
+    char*         mStr;
+    PRUnichar*    mUStr;
+  };
+};
+
+
 class nsIMemoryAgent;
 
 //----------------------------------------------------------------------------------------
@@ -66,15 +97,6 @@ struct nsStr {
   */
   static void Initialize(nsStr& aDest,eCharSize aCharSize);
 
- /**
-  * This method initializes an nsStr for use
-  *
-  * @update	gess 01/04/99
-  * @param  aString is the nsStr to be initialized
-  * @param  aCharSize tells us the requested char size (1 or 2 bytes)
-  */
-  static void Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer);
-
  /**
   * This method destroys the given nsStr, and *MAY* 
   * deallocate it's memory depending on the setting
@@ -144,7 +166,7 @@ struct nsStr {
   * @param  aCount tells us the (max) # of chars to delete
   * @param  anAgent is the allocator to be used for alloc/free operations
   */
-  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent=0);
+  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent=0);
 
  /**
   * This method is used to truncate the given string.
@@ -232,20 +254,21 @@ struct nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset);
 
+ /**
+  * This method is used to access a given char in the given string
+  *
+  * @update	gess 01/04/99
+  * @param  aDest is the nsStr to be appended to
+  * @param  anIndex tells us where in dest to get the char from
+  * @return the given char, or 0 if anIndex is out of range
+  */
+  static PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex);
 
-#ifdef  NS_DEBUG
-  PRUint32        mLength;
-  eCharSize       mMultibyte;
-  PRUint32        mCapacity;
-  PRUint32        mOwnsBuffer;
-  PRUint32        mUnused;
-#else
-  PRUint32        mLength:      30;
-  eCharSize       mMultibyte:    2;
+  PRUint32        mLength   :   30;
+  eCharSize       mMultibyte :   2;
   PRUint32        mCapacity:    30;
-  PRUint32        mOwnsBuffer:   1;
-  PRUint32        mUnused:       1;
-#endif
+  PRUint32        mOwnsBuffer:  1;
+  PRUint32        mUnused:      1;
   union { 
     char*         mStr;
     PRUnichar*    mUStr;
@@ -284,21 +307,6 @@ inline void AddNullTerminator(nsStr& aDest) {
   else aDest.mStr[aDest.mLength]=0;
 }
 
-/**
-* This method is used to access a given char in the given string
-*
-* @update	gess 01/04/99
-* @param  aDest is the nsStr to be appended to
-* @param  anIndex tells us where in dest to get the char from
-* @return the given char, or 0 if anIndex is out of range
-*/
-inline PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex){
-  if(anIndex<aDest.mLength)  {
-    return (eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
-  }//if
-  return 0;
-}
-
 //----------------------------------------------------------------------------------------
 
 class nsIMemoryAgent {
@@ -309,18 +317,25 @@ public:
 };
 
 class nsMemoryAgent : public nsIMemoryAgent {
-protected:
-  enum eDelta{eDefaultSize=16};
+  enum eDelta{eGrowthDelta=8};
 public:
-
   virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
     
-    //we're given the acount value in charunits; now scale up to next multiple.
-  	PRInt32	theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-		  theNewCapacity<<=1;
+    //we're given the acount value in charunits; we have to scale up by the charsize.
+
+    PRInt32 theNewCapacity;
+    if (aDest.mCapacity > 64) {
+      // When the string starts getting large, double the capacity as we grow.
+      theNewCapacity = aDest.mCapacity * 2;
+      if (theNewCapacity < aCount) {
+        theNewCapacity = aDest.mCapacity + aCount;
+      }
+    } else {
+      // When the string is small, keep it's capacity a multiple of kGrowthDelta
+      PRInt32 unitDelta=(aCount/eGrowthDelta)+1;
+      theNewCapacity=unitDelta*eGrowthDelta;
     }
-	  
+
     aDest.mCapacity=theNewCapacity++;
     size_t theSize=(theNewCapacity<<aDest.mMultibyte);
     aDest.mStr=new char[theSize];
@@ -347,5 +362,6 @@ public:
 
 };
 
+
 #endif
 
diff --git a/string/obsolete/nsString2.cpp b/string/obsolete/nsString2.cpp
index 580bfebb9b17..aa3ff505446e 100644
--- a/string/obsolete/nsString2.cpp
+++ b/string/obsolete/nsString2.cpp
@@ -252,10 +252,10 @@ PRBool nsString2::IsOrdered(void) const {
   if(mLength>1) {
     PRUint32 theIndex;
     PRUnichar c1=0;
-    PRUnichar c2=nsStr::GetCharAt(*this,0);
+    PRUnichar c2=GetCharAt(*this,0);
     for(theIndex=1;theIndex<mLength;theIndex++) {
       c1=c2;
-      c2=nsStr::GetCharAt(*this,theIndex);
+      c2=GetCharAt(*this,theIndex);
       if(c1>c2) {
         result=PR_FALSE;
         break;
@@ -315,19 +315,19 @@ PRUnichar* nsString2::GetUnicode(void) const {
  * Get nth character.
  */
 PRUnichar nsString2::operator[](int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::CharAt(int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::First(void) const{
-  return nsStr::GetCharAt(*this,0);
+  return GetCharAt(*this,0);
 }
 
 PRUnichar nsString2::Last(void) const{
-  return nsStr::GetCharAt(*this,mLength-1);
+  return GetCharAt(*this,mLength-1);
 }
 
 PRBool nsString2::SetCharAt(PRUnichar aChar,PRUint32 anIndex){
@@ -1130,7 +1130,7 @@ PRInt32 nsString2::BinarySearch(PRUnichar aChar) const{
 
   while (low <= high) {
     int middle = (low + high) >> 1;
-    PRUnichar theChar=nsStr::GetCharAt(*this,middle);
+    PRUnichar theChar=GetCharAt(*this,middle);
     if (theChar==aChar)
       return middle;
     if (theChar>aChar)
diff --git a/xpcom/ds/nsStr.cpp b/xpcom/ds/nsStr.cpp
index e4b976254248..79e7afc99107 100644
--- a/xpcom/ds/nsStr.cpp
+++ b/xpcom/ds/nsStr.cpp
@@ -31,101 +31,9 @@
 #include "nsStr.h"
 #include "bufferRoutines.h"
 #include "stdio.h"  //only used for printf
-#include "nsDeque.h"
-#include "nsCRT.h"
 
 static const char* kFoolMsg = "Error: Some fool overwrote the shared buffer.";
 
-//----------------------------------------------------------------------------------------
-//  The following is a memory agent who knows how to recycled (pool) freed memory...
-//----------------------------------------------------------------------------------------
-
-/**************************************************************
-  Define the char* (pooled) deallocator class...
- **************************************************************/
-class nsBufferDeallocator: public nsDequeFunctor{
-public:
-  virtual void* operator()(void* anObject) {
-    char* aCString= (char*)anObject;
-    delete [] aCString;
-    return 0;
-  }
-};
-
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-class nsPoolingMemoryAgent : public nsMemoryAgent{
-public:
-  nsPoolingMemoryAgent()  {
-    memset(mPools,0,sizeof(mPools));
-  }
-
-  ~nsPoolingMemoryAgent() {
-    nsBufferDeallocator theDeallocator;
-    int i=0;
-    for(i=0;i<10;i++){
-      if(mPools[i]){
-        mPools[i]->ForEach(theDeallocator); //now delete the buffers
-      }
-      delete mPools[i];
-      mPools[i]=0;
-    }
-  }
-
-  virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
-    
-    //we're given the acount value in charunits; we have to scale up by the charsize.
-    int     theShift=4;
-    PRInt32 theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-      theNewCapacity<<=1;
-      theShift++;
-    } 
-    
-    aDest.mCapacity=theNewCapacity++;
-    theShift=(theShift<<aDest.mMultibyte)-4;
-    if((theShift<12) && (mPools[theShift])){
-      aDest.mStr=(char*)mPools[theShift]->Pop();
-    }
-    if(!aDest.mStr) {
-      //we're given the acount value in charunits; we have to scale up by the charsize.
-      size_t theSize=(theNewCapacity<<aDest.mMultibyte);
-      aDest.mStr=new char[theSize];    
-    }
-    aDest.mOwnsBuffer=1;
-    return PR_TRUE;
-    
-  }
-
-  virtual PRBool Free(nsStr& aDest){
-    if(aDest.mStr){
-      if(aDest.mOwnsBuffer){
-        int theShift=1;
-        unsigned int theValue=1;
-        while((theValue<<=1)<aDest.mCapacity){ 
-          theShift++;
-        }
-        theShift-=4;
-        if(theShift<12){
-          if(!mPools[theShift]){
-            mPools[theShift]=new nsDeque(0);
-          }
-          mPools[theShift]->Push(aDest.mStr);
-        }
-        else delete [] aDest.mStr; //it's too big. Just delete it.
-      }
-      aDest.mStr=0;
-      aDest.mOwnsBuffer=0;
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-  nsDeque* mPools[16]; 
-};
 
 //----------------------------------------------------------------------------------------
 
@@ -166,21 +74,6 @@ void nsStr::Initialize(nsStr& aDest,eCharSize aCharSize) {
   NS_ASSERTION(aDest.mStr[0]==0,kFoolMsg);
 }
 
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer){
-  aDest.mStr=(aCString) ? aCString : GetSharedEmptyBuffer();
-  aDest.mLength=aLength;
-  aDest.mCapacity=aCapacity;
-  aDest.mMultibyte=aCharSize;
-  aDest.mOwnsBuffer=aOwnsBuffer;
-  aDest.mUnused=0;
-}
-
 /**
  * 
  * @update	gess10/30/98
@@ -188,9 +81,13 @@ void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 a
  * @return
  */
 nsIMemoryAgent* GetDefaultAgent(void){
-//  static nsPoolingMemoryAgent gDefaultAgent;
-  static nsMemoryAgent gDefaultAgent;
-  return (nsIMemoryAgent*)&gDefaultAgent;
+  static nsIMemoryAgent* gDefaultAgent=0;
+  if(!gDefaultAgent)
+    gDefaultAgent=new nsMemoryAgent();
+  
+  NS_ASSERTION(gDefaultAgent,"You MUST always have an allocator!");
+
+  return gDefaultAgent;
 }
 
 /**
@@ -213,6 +110,20 @@ void nsStr::Destroy(nsStr& aDest,nsIMemoryAgent* anAgent) {
   }
 }
 
+/**
+ * 
+ * @update	gess11/12/98
+ * @param 
+ * @return
+ */
+PRUnichar nsStr::GetCharAt(const nsStr& aDest,PRUint32 anIndex) {
+  PRUnichar result=0;
+  if((anIndex>=0) && (anIndex<aDest.mLength))  {
+    result=(eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
+  }//if
+  return result;
+}
+
 
 /**
  * This method gets called when the internal buffer needs
@@ -244,8 +155,8 @@ void nsStr::GrowCapacity(nsStr& aDest,PRUint32 aNewLength,nsIMemoryAgent* anAgen
     nsIMemoryAgent* theAgent=(anAgent) ? anAgent : GetDefaultAgent();
     EnsureCapacity(theTempStr,aNewLength,theAgent);
 
-    if(aDest.mLength) {
-      Append(theTempStr,aDest,0,aDest.mLength,theAgent);        
+    if(0<aDest.mLength) {
+      Append(theTempStr,aDest,0,aDest.mLength,anAgent);        
     } 
     theAgent->Free(aDest);
     aDest.mStr = theTempStr.mStr;
@@ -271,13 +182,14 @@ void nsStr::Assign(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 a
 /**
  * This method appends the given nsStr to this one. Note that we have to 
  * pay attention to the underlying char-size of both structs.
- * @update	gess10/30/98
+ * @update	gess 04/04/99
  * @param   aDest is the nsStr to be manipulated
  * @param   aSource is where char are copied from
  * @aCount  is the number of bytes to be copied 
  */
 void nsStr::Append(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
-  if(anOffset<aSource.mLength) {
+
+  if(anOffset<aSource.mLength){
     PRUint32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
     PRUint32 theLength=(anOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-anOffset);
     if(0<theLength){
@@ -309,31 +221,30 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
   //  1. You're inserting chars into an empty string (assign)
   //  2. You're inserting onto the end of a string (append)
   //  3. You're inserting onto the 1..n-1 pos of a string (the hard case).
-  if(0<aSource.mLength){
-    ToRange(aDestOffset,0,aDest.mLength);
+  if((0<aSource.mLength) && (aDestOffset<aDest.mLength-1)){
     if(aDest.mLength){
       if(aDestOffset<aDest.mLength){
+        if(aSrcOffset<aSource.mLength-1) {
+          PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
+          PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
 
-        ToRange(aSrcOffset,0,aSource.mLength-1);
-        PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
-        PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
+          if(aSrcOffset<aSource.mLength) {
+              //here's the only new case we have to handle. 
+              //chars are really being inserted into our buffer...
+            GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
 
-        if(aSrcOffset<aSource.mLength) {
-            //here's the only new case we have to handle. 
-            //chars are really being inserted into our buffer...
-          GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
-
-            //shift the chars right by theDelta...
-          (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+              //shift the chars right by theDelta...
+            (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
       
-          //now insert new chars, starting at offset
-          (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
+            //now insert new chars, starting at offset
+            (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
 
-          //finally, make sure to update the string length...
-          aDest.mLength+=theLength;
+            //finally, make sure to update the string length...
+            aDest.mLength+=theLength;
 
-        }//if
-        //else nothing to do!
+          }//if
+          //else nothing to do!
+        }
       }
       else Append(aDest,aSource,0,aCount,anAgent);
     }
@@ -349,21 +260,22 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
  * @param   aDestOffset is where in aDest deletion is to occur
  * @param   aCount is the number of chars to be deleted in aDest
  */
-void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent){
+void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
+  if(0<aCount){
+    if(aDestOffset<aDest.mLength){
 
-  if(aDestOffset<aDest.mLength){
+      PRInt32 theDelta=aDest.mLength-aDestOffset;
+      PRInt32 theLength=(theDelta<aCount) ? theDelta : aCount;
 
-    PRUint32 theDelta=aDest.mLength-aDestOffset;
-    PRUint32 theLength=(theDelta<aCount) ? theDelta : aCount;
+      if(aDestOffset+theLength<aDest.mLength) {
 
-    if(aDestOffset+theLength<aDest.mLength) {
-
-      //if you're here, it means we're cutting chars out of the middle of the string...
-      //so shift the chars left by theLength...
-      (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
-      aDest.mLength-=theLength;
-    }
-    else Truncate(aDest,aDestOffset,anAgent);
+        //if you're here, it means we're cutting chars out of the middle of the string...
+        //so shift the chars left by theLength...
+        (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+        aDest.mLength-=theLength;
+      }
+      else Truncate(aDest,aDestOffset,anAgent);
+    }//if
   }//if
 }
 
@@ -431,28 +343,28 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
    **************************************************************/
 
 
-PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=anOffset-1;
   PRInt32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
     while(++index<=theMax) {
       PRInt32 theSubIndex=-1;
       PRBool  matches=PR_TRUE;
       while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+        PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
         if(theSubIndex>0) {
           if(theFirstTargetChar==theChar){
-            PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+            PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
             if(theDestJumpChar==theLastTargetChar) {
               theNewStartPos=index; //this lets us jump ahead during our search where possible.
             }//if
           }//if
         }//if
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+        PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
         matches=PRBool(theChar==theTargetChar);
       }
       if(matches)
@@ -472,8 +384,8 @@ PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnor
  * @param 
  * @return
  */
-PRInt32 nsStr::FindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::FindChar(const nsStr& aDest, PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -503,12 +415,12 @@ PRInt32 nsStr::FindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnore
    **************************************************************/
 
 
-PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=(anOffset ? anOffset : aDest.mLength-aTarget.mLength+1);
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
 
     while(index--) {
@@ -517,16 +429,16 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
     
       if(anOffset+aTarget.mLength<=aDest.mLength) {
         while((++theSubIndex<theTargetMax) && (matches)){
-          PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+          PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
           if(theSubIndex>0) {
             if(theFirstTargetChar==theChar){
-              PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+              PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
               if(theDestJumpChar==theLastTargetChar) {
                 theNewStartPos=index; //this lets us jump ahead during our search where possible.
               }//if
             }//if
           }//if
-          PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+          PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
           matches=PRBool(theChar==theTargetChar);
         } //while
       } //if
@@ -547,8 +459,8 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
  * @param 
  * @return
  */
-PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -560,11 +472,11 @@ PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnor
  *  @return  
  */
 PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 offset=aDest.mLength-anOffset;
+  PRInt32  offset=aDest.mLength-anOffset;
   PRInt32  thePos;
 
   while(--offset>=0) {
-    PRUnichar theChar=GetCharAt(aDest,offset);
+    PRUnichar theChar=GetCharAt(aDest,PRUint32(offset));
     thePos=gRFindChars[aSet.mMultibyte](aSet.mStr,aSet.mLength,0,theChar,aIgnoreCase);
     if(kNotFound!=thePos)
       return offset;
@@ -579,7 +491,7 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
  * @param 
  * @return  aDest<aSource=-1;aDest==aSource==0;aDest>aSource=1
  */
-PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PRBool aIgnoreCase) {
+PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 /*aCount*/,PRBool aIgnoreCase) {
   int minlen=(aSource.mLength<aDest.mLength) ? aSource.mLength : aDest.mLength;
 
   if(0==minlen) {
diff --git a/xpcom/ds/nsStr.h b/xpcom/ds/nsStr.h
index 209f7efd93eb..856ed34f3ce9 100644
--- a/xpcom/ds/nsStr.h
+++ b/xpcom/ds/nsStr.h
@@ -27,6 +27,8 @@
        We chose the option B for performance reasons. 
 
     2  Our internal buffer always holds capacity+1 bytes.
+    3. Note that our internal format for this class makes our memory 
+       layout compatible with BStrings.
 
     The nsStr struct is a simple structure (no methods) that contains
     the necessary info to be described as a string. This simple struct
@@ -42,7 +44,8 @@
 #ifndef _nsStr
 #define _nsStr
 
-#include "nsCore.h"
+#include "prtypes.h"
+#include "nscore.h"
 
 //----------------------------------------------------------------------------------------
 
@@ -50,6 +53,34 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kDefaultCharSize eTwoByte
 
 
+union UStrPtr { 
+  char*       mCharBuf;
+  PRUnichar*  mUnicharBuf;
+}; 
+
+/**************************************************************************
+  Here comes the nsBufDescriptor class which describes buffer properties.
+ **************************************************************************/
+
+struct nsBufDescriptor {
+  nsBufDescriptor(char* aBuffer,PRUint32 aBufferSize,eCharSize aCharSize,PRBool aOwnsBuffer) {
+    mStr=aBuffer;
+    mMultibyte=aCharSize;
+    mCapacity=(aBufferSize>>mMultibyte)-1;
+    mOwnsBuffer=aOwnsBuffer;
+  }
+
+  PRUint32        mCapacity;
+  PRBool          mOwnsBuffer;
+  eCharSize       mMultibyte;
+//  UStrPtr         mStr;
+  union { 
+    char*         mStr;
+    PRUnichar*    mUStr;
+  };
+};
+
+
 class nsIMemoryAgent;
 
 //----------------------------------------------------------------------------------------
@@ -66,15 +97,6 @@ struct nsStr {
   */
   static void Initialize(nsStr& aDest,eCharSize aCharSize);
 
- /**
-  * This method initializes an nsStr for use
-  *
-  * @update	gess 01/04/99
-  * @param  aString is the nsStr to be initialized
-  * @param  aCharSize tells us the requested char size (1 or 2 bytes)
-  */
-  static void Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer);
-
  /**
   * This method destroys the given nsStr, and *MAY* 
   * deallocate it's memory depending on the setting
@@ -144,7 +166,7 @@ struct nsStr {
   * @param  aCount tells us the (max) # of chars to delete
   * @param  anAgent is the allocator to be used for alloc/free operations
   */
-  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent=0);
+  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent=0);
 
  /**
   * This method is used to truncate the given string.
@@ -232,20 +254,21 @@ struct nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset);
 
+ /**
+  * This method is used to access a given char in the given string
+  *
+  * @update	gess 01/04/99
+  * @param  aDest is the nsStr to be appended to
+  * @param  anIndex tells us where in dest to get the char from
+  * @return the given char, or 0 if anIndex is out of range
+  */
+  static PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex);
 
-#ifdef  NS_DEBUG
-  PRUint32        mLength;
-  eCharSize       mMultibyte;
-  PRUint32        mCapacity;
-  PRUint32        mOwnsBuffer;
-  PRUint32        mUnused;
-#else
-  PRUint32        mLength:      30;
-  eCharSize       mMultibyte:    2;
+  PRUint32        mLength   :   30;
+  eCharSize       mMultibyte :   2;
   PRUint32        mCapacity:    30;
-  PRUint32        mOwnsBuffer:   1;
-  PRUint32        mUnused:       1;
-#endif
+  PRUint32        mOwnsBuffer:  1;
+  PRUint32        mUnused:      1;
   union { 
     char*         mStr;
     PRUnichar*    mUStr;
@@ -284,21 +307,6 @@ inline void AddNullTerminator(nsStr& aDest) {
   else aDest.mStr[aDest.mLength]=0;
 }
 
-/**
-* This method is used to access a given char in the given string
-*
-* @update	gess 01/04/99
-* @param  aDest is the nsStr to be appended to
-* @param  anIndex tells us where in dest to get the char from
-* @return the given char, or 0 if anIndex is out of range
-*/
-inline PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex){
-  if(anIndex<aDest.mLength)  {
-    return (eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
-  }//if
-  return 0;
-}
-
 //----------------------------------------------------------------------------------------
 
 class nsIMemoryAgent {
@@ -309,18 +317,25 @@ public:
 };
 
 class nsMemoryAgent : public nsIMemoryAgent {
-protected:
-  enum eDelta{eDefaultSize=16};
+  enum eDelta{eGrowthDelta=8};
 public:
-
   virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
     
-    //we're given the acount value in charunits; now scale up to next multiple.
-  	PRInt32	theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-		  theNewCapacity<<=1;
+    //we're given the acount value in charunits; we have to scale up by the charsize.
+
+    PRInt32 theNewCapacity;
+    if (aDest.mCapacity > 64) {
+      // When the string starts getting large, double the capacity as we grow.
+      theNewCapacity = aDest.mCapacity * 2;
+      if (theNewCapacity < aCount) {
+        theNewCapacity = aDest.mCapacity + aCount;
+      }
+    } else {
+      // When the string is small, keep it's capacity a multiple of kGrowthDelta
+      PRInt32 unitDelta=(aCount/eGrowthDelta)+1;
+      theNewCapacity=unitDelta*eGrowthDelta;
     }
-	  
+
     aDest.mCapacity=theNewCapacity++;
     size_t theSize=(theNewCapacity<<aDest.mMultibyte);
     aDest.mStr=new char[theSize];
@@ -347,5 +362,6 @@ public:
 
 };
 
+
 #endif
 
diff --git a/xpcom/ds/nsString2.cpp b/xpcom/ds/nsString2.cpp
index 580bfebb9b17..aa3ff505446e 100644
--- a/xpcom/ds/nsString2.cpp
+++ b/xpcom/ds/nsString2.cpp
@@ -252,10 +252,10 @@ PRBool nsString2::IsOrdered(void) const {
   if(mLength>1) {
     PRUint32 theIndex;
     PRUnichar c1=0;
-    PRUnichar c2=nsStr::GetCharAt(*this,0);
+    PRUnichar c2=GetCharAt(*this,0);
     for(theIndex=1;theIndex<mLength;theIndex++) {
       c1=c2;
-      c2=nsStr::GetCharAt(*this,theIndex);
+      c2=GetCharAt(*this,theIndex);
       if(c1>c2) {
         result=PR_FALSE;
         break;
@@ -315,19 +315,19 @@ PRUnichar* nsString2::GetUnicode(void) const {
  * Get nth character.
  */
 PRUnichar nsString2::operator[](int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::CharAt(int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::First(void) const{
-  return nsStr::GetCharAt(*this,0);
+  return GetCharAt(*this,0);
 }
 
 PRUnichar nsString2::Last(void) const{
-  return nsStr::GetCharAt(*this,mLength-1);
+  return GetCharAt(*this,mLength-1);
 }
 
 PRBool nsString2::SetCharAt(PRUnichar aChar,PRUint32 anIndex){
@@ -1130,7 +1130,7 @@ PRInt32 nsString2::BinarySearch(PRUnichar aChar) const{
 
   while (low <= high) {
     int middle = (low + high) >> 1;
-    PRUnichar theChar=nsStr::GetCharAt(*this,middle);
+    PRUnichar theChar=GetCharAt(*this,middle);
     if (theChar==aChar)
       return middle;
     if (theChar>aChar)
diff --git a/xpcom/string/obsolete/nsStr.cpp b/xpcom/string/obsolete/nsStr.cpp
index e4b976254248..79e7afc99107 100644
--- a/xpcom/string/obsolete/nsStr.cpp
+++ b/xpcom/string/obsolete/nsStr.cpp
@@ -31,101 +31,9 @@
 #include "nsStr.h"
 #include "bufferRoutines.h"
 #include "stdio.h"  //only used for printf
-#include "nsDeque.h"
-#include "nsCRT.h"
 
 static const char* kFoolMsg = "Error: Some fool overwrote the shared buffer.";
 
-//----------------------------------------------------------------------------------------
-//  The following is a memory agent who knows how to recycled (pool) freed memory...
-//----------------------------------------------------------------------------------------
-
-/**************************************************************
-  Define the char* (pooled) deallocator class...
- **************************************************************/
-class nsBufferDeallocator: public nsDequeFunctor{
-public:
-  virtual void* operator()(void* anObject) {
-    char* aCString= (char*)anObject;
-    delete [] aCString;
-    return 0;
-  }
-};
-
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-class nsPoolingMemoryAgent : public nsMemoryAgent{
-public:
-  nsPoolingMemoryAgent()  {
-    memset(mPools,0,sizeof(mPools));
-  }
-
-  ~nsPoolingMemoryAgent() {
-    nsBufferDeallocator theDeallocator;
-    int i=0;
-    for(i=0;i<10;i++){
-      if(mPools[i]){
-        mPools[i]->ForEach(theDeallocator); //now delete the buffers
-      }
-      delete mPools[i];
-      mPools[i]=0;
-    }
-  }
-
-  virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
-    
-    //we're given the acount value in charunits; we have to scale up by the charsize.
-    int     theShift=4;
-    PRInt32 theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-      theNewCapacity<<=1;
-      theShift++;
-    } 
-    
-    aDest.mCapacity=theNewCapacity++;
-    theShift=(theShift<<aDest.mMultibyte)-4;
-    if((theShift<12) && (mPools[theShift])){
-      aDest.mStr=(char*)mPools[theShift]->Pop();
-    }
-    if(!aDest.mStr) {
-      //we're given the acount value in charunits; we have to scale up by the charsize.
-      size_t theSize=(theNewCapacity<<aDest.mMultibyte);
-      aDest.mStr=new char[theSize];    
-    }
-    aDest.mOwnsBuffer=1;
-    return PR_TRUE;
-    
-  }
-
-  virtual PRBool Free(nsStr& aDest){
-    if(aDest.mStr){
-      if(aDest.mOwnsBuffer){
-        int theShift=1;
-        unsigned int theValue=1;
-        while((theValue<<=1)<aDest.mCapacity){ 
-          theShift++;
-        }
-        theShift-=4;
-        if(theShift<12){
-          if(!mPools[theShift]){
-            mPools[theShift]=new nsDeque(0);
-          }
-          mPools[theShift]->Push(aDest.mStr);
-        }
-        else delete [] aDest.mStr; //it's too big. Just delete it.
-      }
-      aDest.mStr=0;
-      aDest.mOwnsBuffer=0;
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-  nsDeque* mPools[16]; 
-};
 
 //----------------------------------------------------------------------------------------
 
@@ -166,21 +74,6 @@ void nsStr::Initialize(nsStr& aDest,eCharSize aCharSize) {
   NS_ASSERTION(aDest.mStr[0]==0,kFoolMsg);
 }
 
-/**
- * 
- * @update	gess10/30/98
- * @param 
- * @return
- */
-void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer){
-  aDest.mStr=(aCString) ? aCString : GetSharedEmptyBuffer();
-  aDest.mLength=aLength;
-  aDest.mCapacity=aCapacity;
-  aDest.mMultibyte=aCharSize;
-  aDest.mOwnsBuffer=aOwnsBuffer;
-  aDest.mUnused=0;
-}
-
 /**
  * 
  * @update	gess10/30/98
@@ -188,9 +81,13 @@ void nsStr::Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 a
  * @return
  */
 nsIMemoryAgent* GetDefaultAgent(void){
-//  static nsPoolingMemoryAgent gDefaultAgent;
-  static nsMemoryAgent gDefaultAgent;
-  return (nsIMemoryAgent*)&gDefaultAgent;
+  static nsIMemoryAgent* gDefaultAgent=0;
+  if(!gDefaultAgent)
+    gDefaultAgent=new nsMemoryAgent();
+  
+  NS_ASSERTION(gDefaultAgent,"You MUST always have an allocator!");
+
+  return gDefaultAgent;
 }
 
 /**
@@ -213,6 +110,20 @@ void nsStr::Destroy(nsStr& aDest,nsIMemoryAgent* anAgent) {
   }
 }
 
+/**
+ * 
+ * @update	gess11/12/98
+ * @param 
+ * @return
+ */
+PRUnichar nsStr::GetCharAt(const nsStr& aDest,PRUint32 anIndex) {
+  PRUnichar result=0;
+  if((anIndex>=0) && (anIndex<aDest.mLength))  {
+    result=(eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
+  }//if
+  return result;
+}
+
 
 /**
  * This method gets called when the internal buffer needs
@@ -244,8 +155,8 @@ void nsStr::GrowCapacity(nsStr& aDest,PRUint32 aNewLength,nsIMemoryAgent* anAgen
     nsIMemoryAgent* theAgent=(anAgent) ? anAgent : GetDefaultAgent();
     EnsureCapacity(theTempStr,aNewLength,theAgent);
 
-    if(aDest.mLength) {
-      Append(theTempStr,aDest,0,aDest.mLength,theAgent);        
+    if(0<aDest.mLength) {
+      Append(theTempStr,aDest,0,aDest.mLength,anAgent);        
     } 
     theAgent->Free(aDest);
     aDest.mStr = theTempStr.mStr;
@@ -271,13 +182,14 @@ void nsStr::Assign(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 a
 /**
  * This method appends the given nsStr to this one. Note that we have to 
  * pay attention to the underlying char-size of both structs.
- * @update	gess10/30/98
+ * @update	gess 04/04/99
  * @param   aDest is the nsStr to be manipulated
  * @param   aSource is where char are copied from
  * @aCount  is the number of bytes to be copied 
  */
 void nsStr::Append(nsStr& aDest,const nsStr& aSource,PRUint32 anOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
-  if(anOffset<aSource.mLength) {
+
+  if(anOffset<aSource.mLength){
     PRUint32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
     PRUint32 theLength=(anOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-anOffset);
     if(0<theLength){
@@ -309,31 +221,30 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
   //  1. You're inserting chars into an empty string (assign)
   //  2. You're inserting onto the end of a string (append)
   //  3. You're inserting onto the 1..n-1 pos of a string (the hard case).
-  if(0<aSource.mLength){
-    ToRange(aDestOffset,0,aDest.mLength);
+  if((0<aSource.mLength) && (aDestOffset<aDest.mLength-1)){
     if(aDest.mLength){
       if(aDestOffset<aDest.mLength){
+        if(aSrcOffset<aSource.mLength-1) {
+          PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
+          PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
 
-        ToRange(aSrcOffset,0,aSource.mLength-1);
-        PRInt32 theRealLen=(aCount<0) ? aSource.mLength : MinInt(aCount,aSource.mLength);
-        PRInt32 theLength=(aSrcOffset+theRealLen<aSource.mLength) ? theRealLen : (aSource.mLength-aSrcOffset);
+          if(aSrcOffset<aSource.mLength) {
+              //here's the only new case we have to handle. 
+              //chars are really being inserted into our buffer...
+            GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
 
-        if(aSrcOffset<aSource.mLength) {
-            //here's the only new case we have to handle. 
-            //chars are really being inserted into our buffer...
-          GrowCapacity(aDest,aDest.mLength+theLength,anAgent);
-
-            //shift the chars right by theDelta...
-          (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+              //shift the chars right by theDelta...
+            (*gShiftChars[aDest.mMultibyte][PR_TRUE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
       
-          //now insert new chars, starting at offset
-          (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
+            //now insert new chars, starting at offset
+            (*gCopyChars[aSource.mMultibyte][aDest.mMultibyte])(aDest.mStr,aDestOffset,aSource.mStr,aSrcOffset,theLength);
 
-          //finally, make sure to update the string length...
-          aDest.mLength+=theLength;
+            //finally, make sure to update the string length...
+            aDest.mLength+=theLength;
 
-        }//if
-        //else nothing to do!
+          }//if
+          //else nothing to do!
+        }
       }
       else Append(aDest,aSource,0,aCount,anAgent);
     }
@@ -349,21 +260,22 @@ void nsStr::Insert( nsStr& aDest,PRUint32 aDestOffset,const nsStr& aSource,PRUin
  * @param   aDestOffset is where in aDest deletion is to occur
  * @param   aCount is the number of chars to be deleted in aDest
  */
-void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent){
+void nsStr::Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent){
+  if(0<aCount){
+    if(aDestOffset<aDest.mLength){
 
-  if(aDestOffset<aDest.mLength){
+      PRInt32 theDelta=aDest.mLength-aDestOffset;
+      PRInt32 theLength=(theDelta<aCount) ? theDelta : aCount;
 
-    PRUint32 theDelta=aDest.mLength-aDestOffset;
-    PRUint32 theLength=(theDelta<aCount) ? theDelta : aCount;
+      if(aDestOffset+theLength<aDest.mLength) {
 
-    if(aDestOffset+theLength<aDest.mLength) {
-
-      //if you're here, it means we're cutting chars out of the middle of the string...
-      //so shift the chars left by theLength...
-      (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
-      aDest.mLength-=theLength;
-    }
-    else Truncate(aDest,aDestOffset,anAgent);
+        //if you're here, it means we're cutting chars out of the middle of the string...
+        //so shift the chars left by theLength...
+        (*gShiftChars[aDest.mMultibyte][PR_FALSE])(aDest.mStr,aDest.mLength,aDestOffset,theLength);
+        aDest.mLength-=theLength;
+      }
+      else Truncate(aDest,aDestOffset,anAgent);
+    }//if
   }//if
 }
 
@@ -431,28 +343,28 @@ void nsStr::CompressSet(nsStr& aDest,const char* aSet,PRUint32 aChar,PRBool aEli
    **************************************************************/
 
 
-PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=anOffset-1;
   PRInt32 theMax=aDest.mLength-aTarget.mLength;
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
     while(++index<=theMax) {
       PRInt32 theSubIndex=-1;
       PRBool  matches=PR_TRUE;
       while((++theSubIndex<theTargetMax) && (matches)){
-        PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+        PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
         if(theSubIndex>0) {
           if(theFirstTargetChar==theChar){
-            PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+            PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
             if(theDestJumpChar==theLastTargetChar) {
               theNewStartPos=index; //this lets us jump ahead during our search where possible.
             }//if
           }//if
         }//if
-        PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+        PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
         matches=PRBool(theChar==theTargetChar);
       }
       if(matches)
@@ -472,8 +384,8 @@ PRInt32 nsStr::FindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnor
  * @param 
  * @return
  */
-PRInt32 nsStr::FindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::FindChar(const nsStr& aDest, PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -503,12 +415,12 @@ PRInt32 nsStr::FindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnore
    **************************************************************/
 
 
-PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgnoreCase,PRUint32 anOffset) {
+PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool /*aIgnoreCase*/,PRUint32 anOffset) {
   PRInt32 index=(anOffset ? anOffset : aDest.mLength-aTarget.mLength+1);
   if((aDest.mLength>0) && (aTarget.mLength>0)){
     PRInt32 theNewStartPos=-1;
-    PRUnichar theFirstTargetChar=GetCharAt(aTarget,0);
-    PRUnichar theLastTargetChar=GetCharAt(aTarget,aTarget.mLength-1);
+    PRUnichar theFirstTargetChar=nsStr::GetCharAt(aTarget,0);
+    PRUnichar theLastTargetChar=nsStr::GetCharAt(aTarget,aTarget.mLength-1);
     PRInt32   theTargetMax=aTarget.mLength;
 
     while(index--) {
@@ -517,16 +429,16 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
     
       if(anOffset+aTarget.mLength<=aDest.mLength) {
         while((++theSubIndex<theTargetMax) && (matches)){
-          PRUnichar theChar=GetCharAt(aDest,index+theSubIndex);
+          PRUnichar theChar=nsStr::GetCharAt(aDest,index+theSubIndex);
           if(theSubIndex>0) {
             if(theFirstTargetChar==theChar){
-              PRUnichar theDestJumpChar=GetCharAt(aDest,index+theTargetMax);
+              PRUnichar theDestJumpChar=nsStr::GetCharAt(aDest,index+theTargetMax);
               if(theDestJumpChar==theLastTargetChar) {
                 theNewStartPos=index; //this lets us jump ahead during our search where possible.
               }//if
             }//if
           }//if
-          PRUnichar theTargetChar=GetCharAt(aTarget,theSubIndex);
+          PRUnichar theTargetChar=nsStr::GetCharAt(aTarget,theSubIndex);
           matches=PRBool(theChar==theTargetChar);
         } //while
       } //if
@@ -547,8 +459,8 @@ PRInt32 nsStr::RFindSubstr(const nsStr& aDest,const nsStr& aTarget, PRBool aIgno
  * @param 
  * @return
  */
-PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,0,aChar,aIgnoreCase);
+PRInt32 nsStr::RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset) {
+  PRInt32 result=gRFindChars[aDest.mMultibyte](aDest.mStr,aDest.mLength,anOffset,aChar,aIgnoreCase);
   return result;
 }
 
@@ -560,11 +472,11 @@ PRInt32 nsStr::RFindChar(const nsStr& aDest,const PRUnichar aChar, PRBool aIgnor
  *  @return  
  */
 PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset) {
-  PRUint32 offset=aDest.mLength-anOffset;
+  PRInt32  offset=aDest.mLength-anOffset;
   PRInt32  thePos;
 
   while(--offset>=0) {
-    PRUnichar theChar=GetCharAt(aDest,offset);
+    PRUnichar theChar=GetCharAt(aDest,PRUint32(offset));
     thePos=gRFindChars[aSet.mMultibyte](aSet.mStr,aSet.mLength,0,theChar,aIgnoreCase);
     if(kNotFound!=thePos)
       return offset;
@@ -579,7 +491,7 @@ PRInt32 nsStr::RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnor
  * @param 
  * @return  aDest<aSource=-1;aDest==aSource==0;aDest>aSource=1
  */
-PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 aCount,PRBool aIgnoreCase) {
+PRInt32 nsStr::Compare(const nsStr& aDest,const nsStr& aSource,PRInt32 /*aCount*/,PRBool aIgnoreCase) {
   int minlen=(aSource.mLength<aDest.mLength) ? aSource.mLength : aDest.mLength;
 
   if(0==minlen) {
diff --git a/xpcom/string/obsolete/nsStr.h b/xpcom/string/obsolete/nsStr.h
index 209f7efd93eb..856ed34f3ce9 100644
--- a/xpcom/string/obsolete/nsStr.h
+++ b/xpcom/string/obsolete/nsStr.h
@@ -27,6 +27,8 @@
        We chose the option B for performance reasons. 
 
     2  Our internal buffer always holds capacity+1 bytes.
+    3. Note that our internal format for this class makes our memory 
+       layout compatible with BStrings.
 
     The nsStr struct is a simple structure (no methods) that contains
     the necessary info to be described as a string. This simple struct
@@ -42,7 +44,8 @@
 #ifndef _nsStr
 #define _nsStr
 
-#include "nsCore.h"
+#include "prtypes.h"
+#include "nscore.h"
 
 //----------------------------------------------------------------------------------------
 
@@ -50,6 +53,34 @@ enum  eCharSize {eOneByte=0,eTwoByte=1};
 #define kDefaultCharSize eTwoByte
 
 
+union UStrPtr { 
+  char*       mCharBuf;
+  PRUnichar*  mUnicharBuf;
+}; 
+
+/**************************************************************************
+  Here comes the nsBufDescriptor class which describes buffer properties.
+ **************************************************************************/
+
+struct nsBufDescriptor {
+  nsBufDescriptor(char* aBuffer,PRUint32 aBufferSize,eCharSize aCharSize,PRBool aOwnsBuffer) {
+    mStr=aBuffer;
+    mMultibyte=aCharSize;
+    mCapacity=(aBufferSize>>mMultibyte)-1;
+    mOwnsBuffer=aOwnsBuffer;
+  }
+
+  PRUint32        mCapacity;
+  PRBool          mOwnsBuffer;
+  eCharSize       mMultibyte;
+//  UStrPtr         mStr;
+  union { 
+    char*         mStr;
+    PRUnichar*    mUStr;
+  };
+};
+
+
 class nsIMemoryAgent;
 
 //----------------------------------------------------------------------------------------
@@ -66,15 +97,6 @@ struct nsStr {
   */
   static void Initialize(nsStr& aDest,eCharSize aCharSize);
 
- /**
-  * This method initializes an nsStr for use
-  *
-  * @update	gess 01/04/99
-  * @param  aString is the nsStr to be initialized
-  * @param  aCharSize tells us the requested char size (1 or 2 bytes)
-  */
-  static void Initialize(nsStr& aDest,char* aCString,PRUint32 aCapacity,PRUint32 aLength,eCharSize aCharSize,PRBool aOwnsBuffer);
-
  /**
   * This method destroys the given nsStr, and *MAY* 
   * deallocate it's memory depending on the setting
@@ -144,7 +166,7 @@ struct nsStr {
   * @param  aCount tells us the (max) # of chars to delete
   * @param  anAgent is the allocator to be used for alloc/free operations
   */
-  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRUint32 aCount,nsIMemoryAgent* anAgent=0);
+  static void Delete(nsStr& aDest,PRUint32 aDestOffset,PRInt32 aCount,nsIMemoryAgent* anAgent=0);
 
  /**
   * This method is used to truncate the given string.
@@ -232,20 +254,21 @@ struct nsStr {
   static PRInt32 RFindChar(const nsStr& aDest,PRUnichar aChar, PRBool aIgnoreCase,PRUint32 anOffset);
   static PRInt32 RFindCharInSet(const nsStr& aDest,const nsStr& aSet,PRBool aIgnoreCase,PRUint32 anOffset);
 
+ /**
+  * This method is used to access a given char in the given string
+  *
+  * @update	gess 01/04/99
+  * @param  aDest is the nsStr to be appended to
+  * @param  anIndex tells us where in dest to get the char from
+  * @return the given char, or 0 if anIndex is out of range
+  */
+  static PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex);
 
-#ifdef  NS_DEBUG
-  PRUint32        mLength;
-  eCharSize       mMultibyte;
-  PRUint32        mCapacity;
-  PRUint32        mOwnsBuffer;
-  PRUint32        mUnused;
-#else
-  PRUint32        mLength:      30;
-  eCharSize       mMultibyte:    2;
+  PRUint32        mLength   :   30;
+  eCharSize       mMultibyte :   2;
   PRUint32        mCapacity:    30;
-  PRUint32        mOwnsBuffer:   1;
-  PRUint32        mUnused:       1;
-#endif
+  PRUint32        mOwnsBuffer:  1;
+  PRUint32        mUnused:      1;
   union { 
     char*         mStr;
     PRUnichar*    mUStr;
@@ -284,21 +307,6 @@ inline void AddNullTerminator(nsStr& aDest) {
   else aDest.mStr[aDest.mLength]=0;
 }
 
-/**
-* This method is used to access a given char in the given string
-*
-* @update	gess 01/04/99
-* @param  aDest is the nsStr to be appended to
-* @param  anIndex tells us where in dest to get the char from
-* @return the given char, or 0 if anIndex is out of range
-*/
-inline PRUnichar GetCharAt(const nsStr& aDest,PRUint32 anIndex){
-  if(anIndex<aDest.mLength)  {
-    return (eTwoByte==aDest.mMultibyte) ? aDest.mUStr[anIndex] : aDest.mStr[anIndex];
-  }//if
-  return 0;
-}
-
 //----------------------------------------------------------------------------------------
 
 class nsIMemoryAgent {
@@ -309,18 +317,25 @@ public:
 };
 
 class nsMemoryAgent : public nsIMemoryAgent {
-protected:
-  enum eDelta{eDefaultSize=16};
+  enum eDelta{eGrowthDelta=8};
 public:
-
   virtual PRBool Alloc(nsStr& aDest,PRInt32 aCount) {
     
-    //we're given the acount value in charunits; now scale up to next multiple.
-  	PRInt32	theNewCapacity=eDefaultSize;
-    while(theNewCapacity<aCount){ 
-		  theNewCapacity<<=1;
+    //we're given the acount value in charunits; we have to scale up by the charsize.
+
+    PRInt32 theNewCapacity;
+    if (aDest.mCapacity > 64) {
+      // When the string starts getting large, double the capacity as we grow.
+      theNewCapacity = aDest.mCapacity * 2;
+      if (theNewCapacity < aCount) {
+        theNewCapacity = aDest.mCapacity + aCount;
+      }
+    } else {
+      // When the string is small, keep it's capacity a multiple of kGrowthDelta
+      PRInt32 unitDelta=(aCount/eGrowthDelta)+1;
+      theNewCapacity=unitDelta*eGrowthDelta;
     }
-	  
+
     aDest.mCapacity=theNewCapacity++;
     size_t theSize=(theNewCapacity<<aDest.mMultibyte);
     aDest.mStr=new char[theSize];
@@ -347,5 +362,6 @@ public:
 
 };
 
+
 #endif
 
diff --git a/xpcom/string/obsolete/nsString2.cpp b/xpcom/string/obsolete/nsString2.cpp
index 580bfebb9b17..aa3ff505446e 100644
--- a/xpcom/string/obsolete/nsString2.cpp
+++ b/xpcom/string/obsolete/nsString2.cpp
@@ -252,10 +252,10 @@ PRBool nsString2::IsOrdered(void) const {
   if(mLength>1) {
     PRUint32 theIndex;
     PRUnichar c1=0;
-    PRUnichar c2=nsStr::GetCharAt(*this,0);
+    PRUnichar c2=GetCharAt(*this,0);
     for(theIndex=1;theIndex<mLength;theIndex++) {
       c1=c2;
-      c2=nsStr::GetCharAt(*this,theIndex);
+      c2=GetCharAt(*this,theIndex);
       if(c1>c2) {
         result=PR_FALSE;
         break;
@@ -315,19 +315,19 @@ PRUnichar* nsString2::GetUnicode(void) const {
  * Get nth character.
  */
 PRUnichar nsString2::operator[](int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::CharAt(int anIndex) const {
-  return nsStr::GetCharAt(*this,anIndex);
+  return GetCharAt(*this,anIndex);
 }
 
 PRUnichar nsString2::First(void) const{
-  return nsStr::GetCharAt(*this,0);
+  return GetCharAt(*this,0);
 }
 
 PRUnichar nsString2::Last(void) const{
-  return nsStr::GetCharAt(*this,mLength-1);
+  return GetCharAt(*this,mLength-1);
 }
 
 PRBool nsString2::SetCharAt(PRUnichar aChar,PRUint32 anIndex){
@@ -1130,7 +1130,7 @@ PRInt32 nsString2::BinarySearch(PRUnichar aChar) const{
 
   while (low <= high) {
     int middle = (low + high) >> 1;
-    PRUnichar theChar=nsStr::GetCharAt(*this,middle);
+    PRUnichar theChar=GetCharAt(*this,middle);
     if (theChar==aChar)
       return middle;
     if (theChar>aChar)