/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* * The contents of this file are subject to the Netscape 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/NPL/ * * 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 mozilla.org code. * * The Initial Developer of the Original Code is Netscape * Communications Corporation. Portions created by Netscape are * Copyright (C) 2000 Netscape Communications Corporation. All * Rights Reserved. * * Contributor(s): * Scott Collins (original author) */ #ifndef nsAReadableString_h___ #define nsAReadableString_h___ #ifndef nscore_h___ #include "nscore.h" // for |PRUnichar| #endif #ifndef nsCharTraits_h___ #include "nsCharTraits.h" #endif #ifndef nsAlgorithm_h___ #include "nsAlgorithm.h" // for |NS_MIN|, |NS_MAX|, and |NS_COUNT|... #endif #include "nsMemory.h" /* This file defines the abstract interfaces |nsAReadableString| and |nsAReadableCString| (the 'A' is for 'abstract', as opposed to the 'I' in [XP]COM interface names). These types are intended to be as source compatible as possible with the original definitions of |const nsString&| and |const nsCString&|, respectively. In otherwords, these interfaces provide only non-mutating access to the underlying strings. We split the these interfaces out from the mutating parts (see "nsAWritableString.h") because tests showed that we could exploit specialized implementations in some areas; we need an abstract interface to bring the whole family of strings together. |nsAReadableString| is a string of |PRUnichar|s. |nsAReadableCString| (note the 'C') is a string of |char|s. */ enum nsFragmentRequest { kPrevFragment, kFirstFragment, kLastFragment, kNextFragment, kFragmentAt }; template struct nsReadableFragment { const CharT* mStart; const CharT* mEnd; void* mFragmentIdentifier; nsReadableFragment() : mStart(0), mEnd(0), mFragmentIdentifier(0) { // nothing else to do here } }; template class basic_nsAReadableString; template class basic_nsAWritableString; // ...because we sometimes use them as `out' params #ifdef _MSC_VER // Under VC++, at the highest warning level, we are overwhelmed with warnings // about a possible error when |operator->()| is used against something that // doesn't have members, e.g., a |PRUnichar|. This is to be expected with // templates, so we disable the warning. #pragma warning( disable: 4284 ) #endif template class nsReadingIterator // : public bidirectional_iterator_tag { public: typedef ptrdiff_t difference_type; typedef CharT value_type; typedef const CharT* pointer; typedef const CharT& reference; // typedef bidirectional_iterator_tag iterator_category; private: friend class basic_nsAReadableString; nsReadableFragment mFragment; const CharT* mPosition; const basic_nsAReadableString* mOwningString; nsReadingIterator( const nsReadableFragment& aFragment, const CharT* aStartingPosition, const basic_nsAReadableString& aOwningString ) : mFragment(aFragment), mPosition(aStartingPosition), mOwningString(&aOwningString) { // nothing else to do here } public: nsReadingIterator() { } // nsReadingIterator( const nsReadingIterator& ); // auto-generated copy-constructor OK // nsReadingIterator& operator=( const nsReadingIterator& ); // auto-generated copy-assignment operator OK inline void normalize_forward(); inline void normalize_backward(); pointer get() const { return mPosition; } CharT operator*() const { return *get(); } #if 0 // An iterator really deserves this, but some compilers (notably IBM VisualAge for OS/2) // don't like this when |CharT| is a type without members. pointer operator->() const { return get(); } #endif nsReadingIterator& operator++() { ++mPosition; normalize_forward(); return *this; } nsReadingIterator operator++( int ) { nsReadingIterator result(*this); ++mPosition; normalize_forward(); return result; } nsReadingIterator& operator--() { normalize_backward(); --mPosition; return *this; } nsReadingIterator operator--( int ) { nsReadingIterator result(*this); normalize_backward(); --mPosition; return result; } const nsReadableFragment& fragment() const { return mFragment; } difference_type size_forward() const { return mFragment.mEnd - mPosition; } difference_type size_backward() const { return mPosition - mFragment.mStart; } nsReadingIterator& advance( difference_type n ) { while ( n > 0 ) { difference_type one_hop = NS_MIN(n, size_forward()); NS_ASSERTION(one_hop>0, "Infinite loop: can't advance a reading iterator beyond the end of a string"); // perhaps I should |break| if |!one_hop|? mPosition += one_hop; normalize_forward(); n -= one_hop; } while ( n < 0 ) { normalize_backward(); difference_type one_hop = NS_MAX(n, -size_backward()); NS_ASSERTION(one_hop<0, "Infinite loop: can't advance (backward) a reading iterator beyond the end of a string"); // perhaps I should |break| if |!one_hop|? mPosition += one_hop; n -= one_hop; } return *this; } /** * Really don't want to call these two operations |+=| and |-=|. * Would prefer a single function, e.g., |advance|, which doesn't imply a constant time operation. * * We'll get rid of these as soon as we can. */ nsReadingIterator& operator+=( difference_type n ) // deprecated { return advance(n); } nsReadingIterator& operator-=( difference_type n ) // deprecated { return advance(-n); } }; #if 0 template nsReadingIterator& nsReadingIterator::advance( difference_type n ) { while ( n > 0 ) { difference_type one_hop = NS_MIN(n, size_forward()); NS_ASSERTION(one_hop>0, "Infinite loop: can't advance a reading iterator beyond the end of a string"); // perhaps I should |break| if |!one_hop|? mPosition += one_hop; normalize_forward(); n -= one_hop; } while ( n < 0 ) { normalize_backward(); difference_type one_hop = NS_MAX(n, -size_backward()); NS_ASSERTION(one_hop<0, "Infinite loop: can't advance (backward) a reading iterator beyond the end of a string"); // perhaps I should |break| if |!one_hop|? mPosition += one_hop; n -= one_hop; } return *this; } #endif template inline PRBool SameFragment( const Iterator& lhs, const Iterator& rhs ) { return lhs.fragment().mStart == rhs.fragment().mStart; } // // nsAReadable[C]String // template class basic_nsAReadableString /* ... */ { public: typedef CharT char_type; typedef PRUint32 size_type; typedef PRUint32 index_type; typedef nsReadingIterator const_iterator; // basic_nsAReadableString(); // auto-generated default constructor OK (we're abstract anyway) // basic_nsAReadableString( const basic_nsAReadableString& ); // auto-generated copy-constructor OK (again, only because we're abstract) private: // NOT TO BE IMPLEMENTED void operator=( const basic_nsAReadableString& ); // but assignment is _not_ OK (we're immutable) so make it impossible public: virtual ~basic_nsAReadableString() { } // ...yes, I expect to be sub-classed. nsReadingIterator& BeginReading( nsReadingIterator& ) const; nsReadingIterator BeginReading() const; // deprecated nsReadingIterator& EndReading( nsReadingIterator& ) const; nsReadingIterator EndReading() const; // deprecated virtual PRUint32 Length() const = 0; PRBool IsEmpty() const; /** * |CharAt|, |operator[]|, |First()|, and |Last()| are not guaranteed to be constant-time operations. * These signatures should be pushed down into interfaces that guarantee flat allocation. * Clients at _this_ level should always use iterators. */ CharT CharAt( PRUint32 ) const; CharT operator[]( PRUint32 ) const; CharT First() const; CharT Last() const; PRUint32 CountChar( CharT ) const; /* |Left|, |Mid|, and |Right| are annoying signatures that seem better almost any _other_ way than they are now. Consider these alternatives aWritable = aReadable.Left(17); // ...a member function that returns a |Substring| aWritable = Left(aReadable, 17); // ...a global function that returns a |Substring| Left(aReadable, 17, aWritable); // ...a global function that does the assignment as opposed to the current signature aReadable.Left(aWritable, 17); // ...a member function that does the assignment or maybe just stamping them out in favor of |Substring|, they are just duplicate functionality aWritable = Substring(aReadable, 0, 17); */ PRUint32 Left( basic_nsAWritableString&, PRUint32 ) const; PRUint32 Mid( basic_nsAWritableString&, PRUint32, PRUint32 ) const; PRUint32 Right( basic_nsAWritableString&, PRUint32 ) const; // Find( ... ) const; PRInt32 FindChar( CharT, PRUint32 aOffset = 0 ) const; // FindCharInSet( ... ) const; // RFind( ... ) const; // RFindChar( ... ) const; // RFindCharInSet( ... ) const; int Compare( const basic_nsAReadableString& rhs ) const; int Compare( const CharT* ) const; // int Compare( const CharT*, PRUint32 ) const; // int Compare( CharT ) const; // |Equals()| is a synonym for |Compare()| PRBool Equals( const basic_nsAReadableString& rhs ) const; PRBool Equals( const CharT* ) const; // PRBool Equals( const CharT*, PRUint32 ) const; // PRBool Equals( CharT ) const; // Comparison operators are all synonyms for |Compare()| PRBool operator!=( const basic_nsAReadableString& rhs ) const { return Compare(rhs)!=0; } PRBool operator< ( const basic_nsAReadableString& rhs ) const { return Compare(rhs)< 0; } PRBool operator<=( const basic_nsAReadableString& rhs ) const { return Compare(rhs)<=0; } PRBool operator==( const basic_nsAReadableString& rhs ) const { return Compare(rhs)==0; } PRBool operator>=( const basic_nsAReadableString& rhs ) const { return Compare(rhs)>=0; } PRBool operator> ( const basic_nsAReadableString& rhs ) const { return Compare(rhs)> 0; } /* Shouldn't be implemented because they're i18n sensitive. Let's leave them in |nsString| for now. */ // ToLowerCase // ToUpperCase // EqualsIgnoreCase // IsASCII // IsSpace // IsAlpha // IsDigit // ToFloat // ToInteger // char* ToNewCString() const; // char* ToNewUTF8String() const; // PRUnichar* ToNewUnicode() const; // char* ToCString( char*, PRUint32, PRUint32 ) const; /* Shouldn't be implemented because it's wrong duplication. Let's leave it in |nsString| for now. */ // nsString* ToNewString() const; // NO! The right way to say this is |new nsString( fromAReadableString )| /* Shouldn't be implemented because they're not generally applicable. Let's leave them in |nsString| for now. */ // IsOrdered // BinarySearch // protected: virtual const void* Implementation() const; virtual const CharT* GetReadableFragment( nsReadableFragment&, nsFragmentRequest, PRUint32 = 0 ) const = 0; virtual PRBool Promises( const basic_nsAReadableString& aString ) const { return &aString == this; } // virtual PRBool PromisesExactly( const basic_nsAReadableString& aString ) const { return false; } private: // NOT TO BE IMPLEMENTED typedef typename nsCharTraits::incompatible_char_type incompatible_char_type; PRUint32 CountChar( incompatible_char_type ) const; // in Compare( incompatible_char_type ) const; // PRBool Equals( incompatible_char_type ) const; }; /* The following macro defines a cast that helps us solve type-unification error problems on compilers with poor template support. String clients probably _never_ need to use it. String implementors sometimes will. */ #ifdef NEED_CPP_TEMPLATE_CAST_TO_BASE #define NS_READABLE_CAST(CharT, expr) (NS_STATIC_CAST(const basic_nsAReadableString&, (expr))) #else #define NS_READABLE_CAST(CharT, expr) (expr) #endif template inline void nsReadingIterator::normalize_forward() { while ( mPosition == mFragment.mEnd && mOwningString->GetReadableFragment(mFragment, kNextFragment) ) mPosition = mFragment.mStart; } template inline void nsReadingIterator::normalize_backward() { while ( mPosition == mFragment.mStart && mOwningString->GetReadableFragment(mFragment, kPrevFragment) ) mPosition = mFragment.mEnd; } /** * Note: measure -- should the |BeginReading| and |EndReading| be |inline|? */ template inline nsReadingIterator& basic_nsAReadableString::BeginReading( nsReadingIterator& aResult ) const { aResult.mOwningString = this; GetReadableFragment(aResult.mFragment, kFirstFragment); aResult.mPosition = aResult.mFragment.mStart; aResult.normalize_forward(); return aResult; } // deprecated template inline nsReadingIterator basic_nsAReadableString::BeginReading() const { nsReadingIterator result; return BeginReading(result); // copies (since I return a value, not a reference) } template inline nsReadingIterator& basic_nsAReadableString::EndReading( nsReadingIterator& aResult ) const { aResult.mOwningString = this; GetReadableFragment(aResult.mFragment, kLastFragment); aResult.mPosition = aResult.mFragment.mEnd; // must not |normalize_backward| as that would likely invalidate tests like |while ( first != last )| return aResult; } // deprecated template inline nsReadingIterator basic_nsAReadableString::EndReading() const { nsReadingIterator result; return EndReading(result); // copies (since I return a value, not a reference) } template inline PRBool basic_nsAReadableString::IsEmpty() const { return Length() == 0; } template inline PRBool basic_nsAReadableString::Equals( const basic_nsAReadableString& rhs ) const { return Compare(rhs) == 0; } template inline PRBool operator==( const nsReadingIterator& lhs, const nsReadingIterator& rhs ) { return lhs.get() == rhs.get(); } template inline PRBool operator!=( const nsReadingIterator& lhs, const nsReadingIterator& rhs ) { return lhs.get() != rhs.get(); } #define NS_DEF_1_STRING_PTR_COMPARISON_OPERATOR(comp, _StringT, _CharT) \ inline \ PRBool \ operator comp( const _StringT& lhs, const _CharT* rhs ) \ { \ return PRBool(Compare(NS_READABLE_CAST(_CharT, lhs), rhs) comp 0); \ } #define NS_DEF_1_PTR_STRING_COMPARISON_OPERATOR(comp, _StringT, _CharT) \ inline \ PRBool \ operator comp( const _CharT* lhs, const _StringT& rhs ) \ { \ return PRBool(Compare(lhs, NS_READABLE_CAST(_CharT, rhs)) comp 0); \ } #define NS_DEF_1_STRING_STRING_COMPARISON_OPERATOR(comp, _StringT, _CharT) \ inline \ PRBool \ operator comp( const _StringT& lhs, const _StringT& rhs ) \ { \ return PRBool(Compare(NS_READABLE_CAST(_CharT, lhs), NS_READABLE_CAST(_CharT, rhs)) comp 0); \ } #define NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(comp, _StringT, _CharT) \ template NS_DEF_1_STRING_PTR_COMPARISON_OPERATOR(comp, _StringT, _CharT) \ template NS_DEF_1_PTR_STRING_COMPARISON_OPERATOR(comp, _StringT, _CharT) #define NS_DEF_3_STRING_COMPARISON_OPERATORS(comp, _StringT, _CharT) \ NS_DEF_1_STRING_STRING_COMPARISON_OPERATOR(comp, _StringT, _CharT) \ NS_DEF_1_STRING_PTR_COMPARISON_OPERATOR(comp, _StringT, _CharT) \ NS_DEF_1_PTR_STRING_COMPARISON_OPERATOR(comp, _StringT, _CharT) #define NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(_StringT, _CharT) \ NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(!=, _StringT, _CharT) \ NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(< , _StringT, _CharT) \ NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(<=, _StringT, _CharT) \ NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(==, _StringT, _CharT) \ NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(>=, _StringT, _CharT) \ NS_DEF_2_TEMPLATE_STRING_COMPARISON_OPERATORS(> , _StringT, _CharT) #define NS_DEF_STRING_COMPARISON_OPERATORS(_StringT, _CharT) \ NS_DEF_3_STRING_COMPARISON_OPERATORS(!=, _StringT, _CharT) \ NS_DEF_3_STRING_COMPARISON_OPERATORS(< , _StringT, _CharT) \ NS_DEF_3_STRING_COMPARISON_OPERATORS(<=, _StringT, _CharT) \ NS_DEF_3_STRING_COMPARISON_OPERATORS(==, _StringT, _CharT) \ NS_DEF_3_STRING_COMPARISON_OPERATORS(>=, _StringT, _CharT) \ NS_DEF_3_STRING_COMPARISON_OPERATORS(> , _StringT, _CharT) NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(basic_nsAReadableString, CharT) template const void* basic_nsAReadableString::Implementation() const { return 0; } template CharT basic_nsAReadableString::CharAt( PRUint32 aIndex ) const { NS_ASSERTION(aIndex iter; return *(BeginReading(iter).advance(PRInt32(aIndex))); } template inline CharT basic_nsAReadableString::operator[]( PRUint32 aIndex ) const { return CharAt(aIndex); } template CharT basic_nsAReadableString::First() const { NS_ASSERTION(Length()>0, "|First()| on an empty string"); nsReadingIterator iter; return *BeginReading(iter); } template CharT basic_nsAReadableString::Last() const { NS_ASSERTION(Length()>0, "|Last()| on an empty string"); nsReadingIterator iter; EndReading(iter); if ( !IsEmpty() ) iter.advance(-1); return *iter; // Note: this has undefined results if |IsEmpty()| } template PRUint32 basic_nsAReadableString::CountChar( CharT c ) const { #if 0 nsReadingIterator countBegin, countEnd; return PRUint32(NS_COUNT(BeginReading(countBegin), EndReading(countEnd), c)); #else PRUint32 result = 0; PRUint32 lengthToExamine = Length(); nsReadingIterator iter; for ( BeginReading(iter); ; ) { PRInt32 lengthToExamineInThisFragment = iter.size_forward(); const CharT* fromBegin = iter.get(); result += PRUint32(NS_COUNT(fromBegin, fromBegin+lengthToExamineInThisFragment, c)); if ( !(lengthToExamine -= lengthToExamineInThisFragment) ) return result; iter.advance(lengthToExamineInThisFragment); } // never reached; quiets warnings return 0; #endif } template PRUint32 basic_nsAReadableString::Mid( basic_nsAWritableString& aResult, PRUint32 aStartPos, PRUint32 aLengthToCopy ) const { // If we're just assigning our entire self, give |aResult| the opportunity to share if ( aStartPos == 0 && aLengthToCopy >= Length() ) aResult = *this; else aResult = Substring(*this, aStartPos, aLengthToCopy); return aResult.Length(); } template inline PRUint32 basic_nsAReadableString::Left( basic_nsAWritableString& aResult, PRUint32 aLengthToCopy ) const { return Mid(aResult, 0, aLengthToCopy); } template PRUint32 basic_nsAReadableString::Right( basic_nsAWritableString& aResult, PRUint32 aLengthToCopy ) const { PRUint32 myLength = Length(); aLengthToCopy = NS_MIN(myLength, aLengthToCopy); return Mid(aResult, myLength-aLengthToCopy, aLengthToCopy); } template PRInt32 basic_nsAReadableString::FindChar( CharT aChar, PRUint32 aOffset ) const { nsReadingIterator iter, done_searching; BeginReading(iter).advance( PRInt32(aOffset) ); EndReading(done_searching); PRUint32 lengthSearched = 0; while ( iter != done_searching ) { PRInt32 fragmentLength = iter.size_forward(); const CharT* charFoundAt = nsCharTraits::find(iter.get(), fragmentLength, aChar); if ( charFoundAt ) return lengthSearched + (charFoundAt-iter.get()); lengthSearched += fragmentLength; iter.advance(fragmentLength); } return -1; } template inline int basic_nsAReadableString::Compare( const basic_nsAReadableString& rhs ) const { return ::Compare(*this, rhs); } // // nsLiteral[C]String // template class basic_nsLiteralString : public basic_nsAReadableString /* ...this class wraps a constant literal string and lets it act like an |nsAReadable...|. Use it like this: SomeFunctionTakingACString( nsLiteralCString("Hello, World!") ); With some tweaking, I think I can make this work as well... SomeStringFunc( nsLiteralString( L"Hello, World!" ) ); This class just holds a pointer. If you don't supply the length, it must calculate it. No copying or allocations are performed. |const basic_nsLiteralString&| appears frequently in interfaces because it allows the automatic conversion of a |CharT*|. */ { protected: virtual const CharT* GetReadableFragment( nsReadableFragment&, nsFragmentRequest, PRUint32 ) const; public: explicit basic_nsLiteralString( const CharT* aLiteral ) : mStart(aLiteral), mEnd(mStart ? (mStart + nsCharTraits::length(mStart)) : mStart) { // nothing else to do here } basic_nsLiteralString( const CharT* aLiteral, PRUint32 aLength ) : mStart(aLiteral), mEnd(mStart + aLength) { // This is an annoying hack. Callers should be fixed to use the other // constructor if they don't really know the length. if ( aLength == PRUint32(-1) ) { // NS_WARNING("Tell scc: Caller constructing a string doesn't know the real length. Please use the other constructor."); mEnd = mStart ? (mStart + nsCharTraits::length(mStart)) : mStart; } } // basic_nsLiteralString( const basic_nsLiteralString& ); // auto-generated copy-constructor OK // ~basic_nsLiteralString(); // auto-generated destructor OK private: // NOT TO BE IMPLEMENTED void operator=( const basic_nsLiteralString& ); // we're immutable public: virtual PRUint32 Length() const; operator const CharT*() const { return mStart; } private: const CharT* mStart; const CharT* mEnd; }; // NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(basic_nsLiteralString, CharT) template const CharT* basic_nsLiteralString::GetReadableFragment( nsReadableFragment& aFragment, nsFragmentRequest aRequest, PRUint32 aOffset ) const { switch ( aRequest ) { case kFirstFragment: case kLastFragment: case kFragmentAt: aFragment.mStart = mStart; aFragment.mEnd = mEnd; return mStart + aOffset; case kPrevFragment: case kNextFragment: default: return 0; } } template PRUint32 basic_nsLiteralString::Length() const { return PRUint32(mEnd - mStart); } // XXX Note that these are located here because some compilers are // sensitive to the ordering of declarations with regard to templates. template inline PRBool basic_nsAReadableString::Equals( const CharT* rhs ) const { return Compare(basic_nsLiteralString(rhs)) == 0; } #if 0 template inline PRBool basic_nsAReadableString::Equals( const CharT* rhs, PRUint32 rhs_length ) const { return Compare(basic_nsLiteralString(rhs, rhs_length)) == 0; } #endif template inline int basic_nsAReadableString::Compare( const CharT* rhs ) const { return ::Compare(*this, NS_READABLE_CAST(CharT, basic_nsLiteralString(rhs))); } #if 0 template inline int basic_nsAReadableString::Compare( const CharT* rhs, PRUint32 rhs_length ) const { return ::Compare(*this, NS_READABLE_CAST(CharT, basic_nsLiteralString(rhs, rhs_length))); } #endif // // nsLiteralChar, nsLiteralPRUnichar // template class basic_nsLiteralChar : public basic_nsAReadableString { protected: virtual const CharT* GetReadableFragment( nsReadableFragment&, nsFragmentRequest, PRUint32 ) const; public: explicit basic_nsLiteralChar( CharT aChar ) : mChar(aChar) { // nothing else to do here } // basic_nsLiteralChar( const basic_nsLiteralString& ); // auto-generated copy-constructor OK // ~basic_nsLiteralChar(); // auto-generated destructor OK private: // NOT TO BE IMPLEMENTED void operator=( const basic_nsLiteralChar& ); // we're immutable public: virtual PRUint32 Length() const { return 1; } private: CharT mChar; }; template const CharT* basic_nsLiteralChar::GetReadableFragment( nsReadableFragment& aFragment, nsFragmentRequest aRequest, PRUint32 aOffset ) const { switch ( aRequest ) { case kFirstFragment: case kLastFragment: case kFragmentAt: aFragment.mEnd = (aFragment.mStart = &mChar) + 1; return aFragment.mStart + aOffset; case kPrevFragment: case kNextFragment: default: return 0; } } // // nsPromiseConcatenation // template class nsPromiseReadable : public basic_nsAReadableString { }; template class nsPromiseConcatenation : public nsPromiseReadable /* NOT FOR USE BY HUMANS Instances of this class only exist as anonymous temporary results from |operator+()|. This is the machinery that makes string concatenation efficient. No allocations or character copies are required unless and until a final assignment is made. It works its magic by overriding and forwarding calls to |GetReadableFragment()|. Note: |nsPromiseConcatenation| imposes some limits on string concatenation with |operator+()|. - no more than 33 strings, e.g., |s1 + s2 + s3 + ... s32 + s33| - left to right evaluation is required ... do not use parentheses to override this In practice, neither of these is onerous. Parentheses do not change the semantics of the concatenation, only the order in which the result is assembled ... so there's no reason for a user to need to control it. Too many strings summed together can easily be worked around with an intermediate assignment. I wouldn't have the parentheses limitation if I assigned the identifier mask starting at the top, the first time anybody called |GetReadableFragment()|. */ { protected: virtual const CharT* GetReadableFragment( nsReadableFragment&, nsFragmentRequest, PRUint32 ) const; enum { kLeftString, kRightString }; int GetCurrentStringFromFragment( const nsReadableFragment& aFragment ) const { return (NS_REINTERPRET_CAST(PRUint32, aFragment.mFragmentIdentifier) & mFragmentIdentifierMask) ? kRightString : kLeftString; } int SetLeftStringInFragment( nsReadableFragment& aFragment ) const { aFragment.mFragmentIdentifier = NS_REINTERPRET_CAST(void*, NS_REINTERPRET_CAST(PRUint32, aFragment.mFragmentIdentifier) & ~mFragmentIdentifierMask); return kLeftString; } int SetRightStringInFragment( nsReadableFragment& aFragment ) const { aFragment.mFragmentIdentifier = NS_REINTERPRET_CAST(void*, NS_REINTERPRET_CAST(PRUint32, aFragment.mFragmentIdentifier) | mFragmentIdentifierMask); return kRightString; } public: nsPromiseConcatenation( const basic_nsAReadableString& aLeftString, const basic_nsAReadableString& aRightString, PRUint32 aMask = 1 ) : mFragmentIdentifierMask(aMask) { mStrings[kLeftString] = &aLeftString; mStrings[kRightString] = &aRightString; } nsPromiseConcatenation( const nsPromiseConcatenation& aLeftString, const basic_nsAReadableString& aRightString ) : mFragmentIdentifierMask(aLeftString.mFragmentIdentifierMask<<1) { mStrings[kLeftString] = &aLeftString; mStrings[kRightString] = &aRightString; } // nsPromiseConcatenation( const nsPromiseConcatenation& ); // auto-generated copy-constructor should be OK // ~nsPromiseConcatenation(); // auto-generated destructor OK private: // NOT TO BE IMPLEMENTED void operator=( const nsPromiseConcatenation& ); // we're immutable, you can't assign into a concatenation public: virtual PRUint32 Length() const; virtual PRBool Promises( const basic_nsAReadableString& ) const; // virtual PRBool PromisesExactly( const basic_nsAReadableString& ) const; // nsPromiseConcatenation operator+( const basic_nsAReadableString& rhs ) const; PRUint32 GetFragmentIdentifierMask() const { return mFragmentIdentifierMask; } private: void operator+( const nsPromiseConcatenation& ); // NOT TO BE IMPLEMENTED // making this |private| stops you from over parenthesizing concatenation expressions, e.g., |(A+B) + (C+D)| // which would break the algorithm for distributing bits in the fragment identifier private: const basic_nsAReadableString* mStrings[2]; PRUint32 mFragmentIdentifierMask; }; // NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(nsPromiseConcatenation, CharT) template PRUint32 nsPromiseConcatenation::Length() const { return mStrings[kLeftString]->Length() + mStrings[kRightString]->Length(); } template PRBool nsPromiseConcatenation::Promises( const basic_nsAReadableString& aString ) const { return mStrings[0]->Promises(aString) || mStrings[1]->Promises(aString); } #if 0 PRBool nsPromiseConcatenation::PromisesExactly( const basic_nsAReadableString& aString ) const { // Not really like this, test for the empty string, etc return mStrings[0] == &aString && !mStrings[1] || !mStrings[0] && mStrings[1] == &aString; } #endif template const CharT* nsPromiseConcatenation::GetReadableFragment( nsReadableFragment& aFragment, nsFragmentRequest aRequest, PRUint32 aPosition ) const { int whichString; // based on the request, pick which string we will forward the |GetReadableFragment()| call into switch ( aRequest ) { case kPrevFragment: case kNextFragment: whichString = GetCurrentStringFromFragment(aFragment); break; case kFirstFragment: whichString = SetLeftStringInFragment(aFragment); break; case kLastFragment: whichString = SetRightStringInFragment(aFragment); break; case kFragmentAt: PRUint32 leftLength = mStrings[kLeftString]->Length(); if ( aPosition < leftLength ) whichString = SetLeftStringInFragment(aFragment); else { whichString = SetRightStringInFragment(aFragment); aPosition -= leftLength; } break; } const CharT* result; PRBool done; do { done = PR_TRUE; result = mStrings[whichString]->GetReadableFragment(aFragment, aRequest, aPosition); if ( !result ) { done = PR_FALSE; if ( aRequest == kNextFragment && whichString == kLeftString ) { aRequest = kFirstFragment; whichString = SetRightStringInFragment(aFragment); } else if ( aRequest == kPrevFragment && whichString == kRightString ) { aRequest = kLastFragment; whichString = SetLeftStringInFragment(aFragment); } else done = PR_TRUE; } } while ( !done ); return result; } #if 0 template inline nsPromiseConcatenation nsPromiseConcatenation::operator+( const basic_nsAReadableString& rhs ) const { return nsPromiseConcatenation(*this, rhs, mFragmentIdentifierMask<<1); } #endif // // nsPromiseSubstring // template class nsPromiseSubstring : public nsPromiseReadable /* NOT FOR USE BY HUMANS (mostly) ...not unlike |nsPromiseConcatenation|. Instances of this class exist only as anonymous temporary results from |Substring()|. Like |nsPromiseConcatenation|, this class only holds a pointer, no string data of its own. It does its magic by overriding and forwarding calls to |GetReadableFragment()|. */ { protected: virtual const CharT* GetReadableFragment( nsReadableFragment&, nsFragmentRequest, PRUint32 ) const; public: nsPromiseSubstring( const basic_nsAReadableString& aString, PRUint32 aStartPos, PRUint32 aLength ) : mString(aString), mStartPos( NS_MIN(aStartPos, aString.Length()) ), mLength( NS_MIN(aLength, aString.Length()-mStartPos) ) { // nothing else to do here } // nsPromiseSubstring( const nsPromiseSubstring& ); // auto-generated copy-constructor should be OK // ~nsPromiseSubstring(); // auto-generated destructor OK private: // NOT TO BE IMPLEMENTED void operator=( const nsPromiseSubstring& ); // we're immutable, you can't assign into a substring public: virtual PRUint32 Length() const; virtual PRBool Promises( const basic_nsAReadableString& aString ) const { return mString.Promises(aString); } private: const basic_nsAReadableString& mString; PRUint32 mStartPos; PRUint32 mLength; }; // NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(nsPromiseSubstring, CharT) template PRUint32 nsPromiseSubstring::Length() const { return mLength; } template const CharT* nsPromiseSubstring::GetReadableFragment( nsReadableFragment& aFragment, nsFragmentRequest aRequest, PRUint32 aPosition ) const { // Offset any request for a specific position (First, Last, At) by our // substrings startpos within the owning string if ( aRequest == kFirstFragment ) { aPosition = mStartPos; aRequest = kFragmentAt; } else if ( aRequest == kLastFragment ) { aPosition = mStartPos + mLength; aRequest = kFragmentAt; } else if ( aRequest == kFragmentAt ) aPosition += mStartPos; // requests for |kNextFragment| or |kPrevFragment| are just relayed down into the string we're slicing const CharT* position_ptr = mString.GetReadableFragment(aFragment, aRequest, aPosition); // If |GetReadableFragment| returns |0|, then we are off the string, the contents of the // fragment are garbage. // Therefore, only need to fix up the fragment boundaries when |position_ptr| is not null if ( position_ptr ) { // if there's more physical data in the returned fragment than I logically have left... size_t logical_size_backward = aPosition - mStartPos; if ( size_t(position_ptr - aFragment.mStart) > logical_size_backward ) aFragment.mStart = position_ptr - logical_size_backward; size_t logical_size_forward = mLength - logical_size_backward; if ( size_t(aFragment.mEnd - position_ptr) > logical_size_forward ) aFragment.mEnd = position_ptr + logical_size_forward; } return position_ptr; } // // Global functions // template inline PRBool SameImplementation( const basic_nsAReadableString& lhs, const basic_nsAReadableString& rhs ) { const void* imp_tag = lhs.Implementation(); return imp_tag && (imp_tag==rhs.Implementation()); } template nsPromiseSubstring Substring( const basic_nsAReadableString& aString, PRUint32 aStartPos, PRUint32 aSubstringLength ) { return nsPromiseSubstring(aString, aStartPos, aSubstringLength); } template int Compare( const basic_nsAReadableString& lhs, const basic_nsAReadableString& rhs ) { if ( &lhs == &rhs ) return 0; PRUint32 lLength = lhs.Length(); PRUint32 rLength = rhs.Length(); PRUint32 lengthToCompare = NS_MIN(lLength, rLength); nsReadingIterator leftIter, rightIter; lhs.BeginReading(leftIter); rhs.BeginReading(rightIter); int result; for (;;) { PRUint32 lengthAvailable = PRUint32( NS_MIN(leftIter.size_forward(), rightIter.size_forward()) ); if ( lengthAvailable > lengthToCompare ) lengthAvailable = lengthToCompare; // Note: |result| should be declared in this |if| expression, but some compilers don't like that if ( (result = nsCharTraits::compare(leftIter.get(), rightIter.get(), lengthAvailable)) != 0 ) return result; if ( !(lengthToCompare -= lengthAvailable) ) break; leftIter.advance( PRInt32(lengthAvailable) ); rightIter.advance( PRInt32(lengthAvailable) ); } if ( lLength < rLength ) return -1; else if ( rLength < lLength ) return 1; else return 0; } template inline int Compare( const basic_nsAReadableString& lhs, const CharT* rhs ) { return Compare(lhs, NS_READABLE_CAST(CharT, basic_nsLiteralString(rhs))); } template inline int Compare( const CharT* lhs, const basic_nsAReadableString& rhs ) { return Compare(NS_READABLE_CAST(CharT, basic_nsLiteralString(lhs)), rhs); } /* How shall we provide |operator+()|? What would it return? It has to return a stack based object, because the client will not be given an opportunity to handle memory management in an expression like myWritableString = stringA + stringB + stringC; ...so the `obvious' answer of returning a new |nsSharedString| is no good. We could return an |nsString|, if that name were in scope here, though there's no telling what the client will really want to do with the result. What might be better, though, is to return a `promise' to concatenate some strings... By making |nsPromiseConcatenation| inherit from readable strings, we automatically handle assignment and other interesting uses within writable strings, plus we drastically reduce the number of cases we have to write |operator+()| for. The cost is extra temporary concat strings in the evaluation of strings of '+'s, e.g., |A + B + C + D|, and that we have to do some work to implement the virtual functions of readables. */ template inline nsPromiseConcatenation operator+( const nsPromiseConcatenation& lhs, const basic_nsAReadableString& rhs ) { return nsPromiseConcatenation(lhs, rhs, lhs.GetFragmentIdentifierMask()<<1); } template inline nsPromiseConcatenation operator+( const basic_nsAReadableString& lhs, const basic_nsAReadableString& rhs ) { return nsPromiseConcatenation(lhs, rhs); } #ifdef NEED_CPP_DERIVED_TEMPLATE_OPERATORS #define NS_DEF_DERIVED_STRING_STRING_OPERATOR_PLUS(_String1T, _String2T, _CharT) \ inline \ nsPromiseConcatenation<_CharT> \ operator+( const _String1T& lhs, const _String2T& rhs ) \ { \ return nsPromiseConcatenation<_CharT>(lhs, rhs); \ } #define NS_DEF_DERIVED_STRING_OPERATOR_PLUS(_StringT, _CharT) \ NS_DEF_DERIVED_STRING_STRING_OPERATOR_PLUS(_StringT, _StringT, _CharT) \ NS_DEF_DERIVED_STRING_STRING_OPERATOR_PLUS(nsPromiseConcatenation<_CharT>, _StringT, _CharT) #define NS_DEF_2_STRING_STRING_OPERATOR_PLUS(_String1T, _String2T, _CharT) \ NS_DEF_DERIVED_STRING_STRING_OPERATOR_PLUS(_String1T, _String2T, _CharT) \ NS_DEF_DERIVED_STRING_STRING_OPERATOR_PLUS(_String2T, _String1T, _CharT) #else #define NS_DEF_DERIVED_STRING_OPERATOR_PLUS(_StringT, _CharT) #define NS_DEF_2_STRING_STRING_OPERATOR_PLUS(_String1T, _String2T, _CharT) #endif #define kDefaultFlatStringSize 64 template class basic_nsPromiseFlatString : public basic_nsAReadableString { public: explicit basic_nsPromiseFlatString( const basic_nsAReadableString& ); virtual ~basic_nsPromiseFlatString( ) { if (mOwnsBuffer) { nsMemory::Free((void*)mBuffer); } } virtual PRUint32 Length() const { return mLength; } virtual const CharT* GetReadableFragment( nsReadableFragment&, nsFragmentRequest, PRUint32 = 0 ) const; operator const CharT*() const { return mBuffer; } protected: PRUint32 mLength; const CharT *mBuffer; PRBool mOwnsBuffer; CharT mInlineBuffer[kDefaultFlatStringSize]; }; template basic_nsPromiseFlatString::basic_nsPromiseFlatString( const basic_nsAReadableString& aString ) : mLength(aString.Length()), mOwnsBuffer(PR_FALSE) { typedef nsReadingIterator iterator; iterator start( aString.BeginReading() ); iterator end( aString.EndReading() ); // First count the number of buffers PRInt32 buffer_count = 0; while ( start != end ) { buffer_count++; start += start.size_forward(); } // Now figure out what we want to do with the string start = aString.BeginReading(); // XXX Not guaranteed null-termination in the first case // If it's a single buffer, we just use the implementation's buffer if ( buffer_count == 1 ) mBuffer = start.get(); // If it's too big for our inline buffer, we allocate a new one else if ( mLength > kDefaultFlatStringSize-1 ) { CharT* result = NS_STATIC_CAST(CharT*, nsMemory::Alloc((mLength+1) * sizeof(CharT))); CharT* toBegin = result; *copy_string(start, end, toBegin) = CharT(0); mBuffer = result; mOwnsBuffer = PR_TRUE; } // Otherwise copy into our internal buffer else { mBuffer = mInlineBuffer; CharT* toBegin = &mInlineBuffer[0]; copy_string( start, end, toBegin); mInlineBuffer[mLength] = 0; } } template const CharT* basic_nsPromiseFlatString::GetReadableFragment( nsReadableFragment& aFragment, nsFragmentRequest aRequest, PRUint32 aOffset ) const { switch ( aRequest ) { case kFirstFragment: case kLastFragment: case kFragmentAt: aFragment.mEnd = (aFragment.mStart = mBuffer) + mLength; return aFragment.mStart + aOffset; case kPrevFragment: case kNextFragment: default: return 0; } } typedef basic_nsAReadableString nsAReadableString; typedef basic_nsAReadableString nsAReadableCString; typedef basic_nsLiteralString nsLiteralString; typedef basic_nsLiteralString nsLiteralCString; typedef basic_nsPromiseFlatString nsPromiseFlatString; typedef basic_nsPromiseFlatString nsPromiseFlatCString; #ifdef HAVE_CPP_2BYTE_WCHAR_T #define NS_LITERAL_STRING(s) nsLiteralString(L##s, (sizeof(L##s)/sizeof(wchar_t))-1) #define NS_NAMED_LITERAL_STRING(n,s) nsLiteralString n(L##s, (sizeof(L##s)/sizeof(wchar_t))-1) #else #define NS_LITERAL_STRING(s) NS_ConvertASCIItoUCS2(s, sizeof(s)-1) #define NS_NAMED_LITERAL_STRING(n,s) NS_ConvertASCIItoUCS2 n(s, sizeof(s)-1) #endif #define NS_LITERAL_CSTRING(s) nsLiteralCString(s, sizeof(s)-1) #define NS_NAMED_LITERAL_CSTRING(n,s) nsLiteralCString n(s, sizeof(s)-1) typedef basic_nsLiteralChar nsLiteralChar; typedef basic_nsLiteralChar nsLiteralPRUnichar; #endif // !defined(nsAReadableString_h___)