Bug 161982 - need an autobuffer impl available to all code. This is a template version of nsSpillableStackBuffer, which is defined in more than 1 place. r=brade/sr=bryner

xpcom/ds/Makefile.in

@@ -113,6 +113,7 @@ EXPORTS		= \
 		nsArrayEnumerator.h \
 		nsCOMArray.h \
 		nsStringEnumerator.h \
+		nsAutoBuffer.h \
 		$(NULL)			
 
 XPIDLSRCS	= \

xpcom/ds/nsAutoBuffer.h

@@ -0,0 +1,105 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is auto buffer template.
+ *
+ * The Initial Developer of the Original Code is
+ * Conrad Carlen <ccarlen@mac.com>.
+ * Portions created by the Initial Developer are Copyright (C) 2004
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef nsAutoBuffer_h__
+#define nsAutoBuffer_h__
+
+#ifndef nsMemory_h__
+#include "nsMemory.h"
+#endif
+
+/**
+ * A buffer which will use stack space if the requested size will
+ * fit in the stack buffer and allocate from the heap if not.
+ */
+
+template <class T>
+class nsAutoBuffer
+{
+public:
+  nsAutoBuffer() :
+    mBufferPtr(mStackBuffer),
+    mCurElemCapacity(kStackBufferNumElems)
+  {
+  }
+
+  ~nsAutoBuffer()
+  {
+    DeleteBuffer();
+  }
+
+  PRBool EnsureElemCapacity(PRInt32 inElemCapacity)
+  {
+    if (inElemCapacity <= mCurElemCapacity)
+      return PR_TRUE;
+    
+    if (inElemCapacity > kStackBufferNumElems)
+    {
+      DeleteBuffer();
+      mBufferPtr = (T*)nsMemory::Alloc(inElemCapacity * sizeof(T));
+      mCurElemCapacity = inElemCapacity;
+      return (mBufferPtr != NULL);
+    }
+    
+    mCurElemCapacity = kStackBufferNumElems;
+    return PR_TRUE;
+  }
+
+  PRInt32     GetElemCapacity()   { return mCurElemCapacity;  } const
+
+  T*          get()     { return mBufferPtr;    } const
+
+protected:
+
+  void DeleteBuffer()
+  {
+    if (mBufferPtr != mStackBuffer)
+    {
+      nsMemory::Free(mBufferPtr);
+      mBufferPtr = mStackBuffer;
+    }
+  }
+
+protected:
+  enum { kStackBufferNumElems = 256 };
+
+  T             *mBufferPtr;
+  T             mStackBuffer[kStackBufferNumElems];
+  PRInt32       mCurElemCapacity;
+};
+
+#endif // nsAutoBuffer_h__