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gecko-dev/string/public/nsAReadableString.h

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/* -*- 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) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
* Scott Collins <scc@netscape.com>
*/
#ifndef _nsAReadableString_h__
#define _nsAReadableString_h__
// WORK IN PROGRESS
#ifndef nscore_h___
#include "nscore.h"
// for |PRUnichar|
#endif
#ifndef _nsCharTraits_h__
#include "nsCharTraits.h"
#endif
#include <iterator>
// for |bidirectional_iterator_tag|
#include <algorithm>
// for |min|, |copy|
#ifdef HAVE_CPP_USING
using namespace std;
#endif
/*
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.
*/
template <class CharT> class basic_nsAWritableString;
// ...because we sometimes use them as `out' params
template <class CharT> class basic_nsLiteralString;
// ...because we sometimes use them as in params to force the conversion of |CharT*|s
//
// nsAReadable[C]String
//
template <class CharT>
class basic_nsAReadableString
/*
...
*/
{
public:
struct ReadableFragment
{
const CharT* mStart;
const CharT* mEnd;
PRUint32 mFragmentIdentifier;
ReadableFragment()
: mStart(0), mEnd(0), mFragmentIdentifier(0)
{
// nothing else to do here
}
};
public:
virtual const void* Implementation() const;
enum FragmentRequest { kPrevFragment, kFirstFragment, kLastFragment, kNextFragment, kFragmentAt };
// Damn! Had to make |GetReadableFragment| public because the compilers suck. Should be protected.
virtual const CharT* GetReadableFragment( ReadableFragment&, FragmentRequest, PRUint32 = 0 ) const = 0;
friend class ReadingIterator;
class ReadingIterator
: 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<CharT>;
ReadableFragment mFragment;
const CharT* mPosition;
const basic_nsAReadableString<CharT>* mOwningString;
void
normalize_forward()
{
if ( mPosition == mFragment.mEnd )
if ( mOwningString->GetReadableFragment(mFragment, kNextFragment) )
mPosition = mFragment.mStart;
}
void
normalize_backward()
{
if ( mPosition == mFragment.mStart )
if ( mOwningString->GetReadableFragment(mFragment, kPrevFragment) )
mPosition = mFragment.mEnd;
}
ReadingIterator( const ReadableFragment& aFragment,
const CharT* aStartingPosition,
const basic_nsAReadableString<CharT>& aOwningString )
: mFragment(aFragment),
mPosition(aStartingPosition),
mOwningString(&aOwningString)
{
// nothing else to do here
}
public:
// ReadingIterator( const ReadingIterator& ); ...use default copy-constructor
// ReadingIterator& operator=( const ReadingIterator& ); ...use default copy-assignment operator
CharT
operator*() const
{
return *mPosition;
}
pointer
operator->() const
{
return mPosition;
}
ReadingIterator&
operator++()
{
++mPosition;
normalize_forward();
return *this;
}
ReadingIterator
operator++( int )
{
ReadingIterator result(*this);
++mPosition;
normalize_forward();
return result;
}
ReadingIterator&
operator--()
{
normalize_backward();
--mPosition;
return *this;
}
ReadingIterator
operator--( int )
{
ReadingIterator result(*this);
normalize_backward();
--mPosition;
return result;
}
const ReadableFragment&
fragment() const
{
return mFragment;
}
difference_type
size_forward() const
{
return mFragment.mEnd - mPosition;
}
difference_type
size_backward() const
{
return mPosition - mFragment.mStart;
}
ReadingIterator&
operator+=( difference_type n )
{
if ( n < 0 )
return operator-=(-n);
while ( n )
{
difference_type one_hop = NS_MIN(n, size_forward());
mPosition += one_hop;
normalize_forward();
n -= one_hop;
}
return *this;
}
ReadingIterator&
operator-=( difference_type n )
{
if ( n < 0 )
return operator+=(-n);
while ( n )
{
difference_type one_hop = NS_MIN(n, size_backward());
mPosition -= one_hop;
normalize_backward();
n -= one_hop;
}
return *this;
}
// Damn again! Problems with templates made me implement comparisons as members.
PRBool
operator==( const ReadingIterator& rhs ) const
{
return mPosition == rhs.mPosition;
}
PRBool
operator!=( const ReadingIterator& rhs ) const
{
return mPosition != rhs.mPosition;
}
};
typedef ReadingIterator ConstIterator;
public:
basic_nsAReadableString<CharT>::ReadingIterator
BeginReading( PRUint32 aOffset = 0 ) const
{
ReadableFragment fragment;
const CharT* startPos = GetReadableFragment(fragment, kFragmentAt, aOffset);
return basic_nsAReadableString<CharT>::ReadingIterator(fragment, startPos, *this);
}
basic_nsAReadableString<CharT>::ReadingIterator
EndReading( PRUint32 aOffset = 0 ) const
{
ReadableFragment fragment;
const CharT* startPos = GetReadableFragment(fragment, kFragmentAt, NS_MAX(0U, Length()-aOffset));
return basic_nsAReadableString<CharT>::ReadingIterator(fragment, startPos, *this);
}
public:
virtual ~basic_nsAReadableString() { }
// ...yes, I expect to be sub-classed.
virtual PRUint32 Length() const = 0;
PRBool
IsEmpty() const
{
return Length() == 0;
}
/*
RickG says the following three routines, |IsUnicode()|, |GetBuffer()|, and |GetUnicode()|
shouldn't be implemented because they're wrong access. I agree. Callers who really need
this access should use the iterators instead. We'll use these to ease the transition to
|nsAReadable...|, and then remove them as soon as possible.
*/
PRBool IsUnicode() const { return PR_FALSE; }
// ...but note specialization for |PRUnichar|, below
const char* GetBuffer() const { return 0; }
const PRUnichar* GetUnicode() const { return 0; }
// ...but note specializations for |char| and |PRUnichar|, below
CharT CharAt( PRUint32 ) const;
CharT operator[]( PRUint32 ) const;
CharT First() const;
CharT Last() const;
PRUint32 CountChar( CharT ) const;
PRUint32 Left( basic_nsAWritableString<CharT>&, PRUint32 ) const;
PRUint32 Mid( basic_nsAWritableString<CharT>&, PRUint32, PRUint32 ) const;
PRUint32 Right( basic_nsAWritableString<CharT>&, PRUint32 ) const;
// Find( ... ) const;
// FindChar( ... ) const;
// FindCharInSet( ... ) const;
// RFind( ... ) const;
// RFindChar( ... ) const;
// RFindCharInSet( ... ) const;
int Compare( const basic_nsAReadableString<CharT>& rhs ) const;
int Compare( const basic_nsLiteralString<CharT>& rhs ) const;
// |Equals()| is a synonym for |Compare()|
PRBool
Equals( const basic_nsAReadableString<CharT>& rhs ) const
{
return Compare(rhs) == 0;
}
PRBool
Equals( const basic_nsLiteralString<CharT>& 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
// Comparison operators are all synonyms for |Compare()|
PRBool operator!=( const basic_nsAReadableString<CharT>& rhs ) const { return Compare(rhs)!=0; }
PRBool operator< ( const basic_nsAReadableString<CharT>& rhs ) const { return Compare(rhs)< 0; }
PRBool operator<=( const basic_nsAReadableString<CharT>& rhs ) const { return Compare(rhs)<=0; }
PRBool operator==( const basic_nsAReadableString<CharT>& rhs ) const { return Compare(rhs)==0; }
PRBool operator>=( const basic_nsAReadableString<CharT>& rhs ) const { return Compare(rhs)>=0; }
PRBool operator> ( const basic_nsAReadableString<CharT>& rhs ) const { return Compare(rhs)> 0; }
};
#define NS_DEF_1_STRING_COMPARISON_OPERATOR(comp, T1, T2) \
inline \
PRBool \
operator comp( T1 lhs, T2 rhs ) \
{ \
return PRBool(Compare(lhs, rhs) comp 0); \
}
#define NS_DEF_STRING_COMPARISON_OPERATORS(T1, T2) \
template <class CharT> NS_DEF_1_STRING_COMPARISON_OPERATOR(!=, T1, T2) \
template <class CharT> NS_DEF_1_STRING_COMPARISON_OPERATOR(< , T1, T2) \
template <class CharT> NS_DEF_1_STRING_COMPARISON_OPERATOR(<=, T1, T2) \
template <class CharT> NS_DEF_1_STRING_COMPARISON_OPERATOR(==, T1, T2) \
template <class CharT> NS_DEF_1_STRING_COMPARISON_OPERATOR(>=, T1, T2) \
template <class CharT> NS_DEF_1_STRING_COMPARISON_OPERATOR(> , T1, T2)
#define NS_DEF_NON_TEMPLATE_STRING_COMPARISON_OPERATORS(T1, T2) \
NS_DEF_1_STRING_COMPARISON_OPERATOR(!=, T1, T2) \
NS_DEF_1_STRING_COMPARISON_OPERATOR(< , T1, T2) \
NS_DEF_1_STRING_COMPARISON_OPERATOR(<=, T1, T2) \
NS_DEF_1_STRING_COMPARISON_OPERATOR(==, T1, T2) \
NS_DEF_1_STRING_COMPARISON_OPERATOR(>=, T1, T2) \
NS_DEF_1_STRING_COMPARISON_OPERATOR(> , T1, T2)
#define NS_DEF_STRING_COMPARISONS(T) \
NS_DEF_STRING_COMPARISON_OPERATORS(const T&, const CharT*) \
NS_DEF_STRING_COMPARISON_OPERATORS(const CharT*, const T&)
NS_DEF_STRING_COMPARISONS(basic_nsAReadableString<CharT>)
NS_SPECIALIZE_TEMPLATE
inline
PRBool
basic_nsAReadableString<PRUnichar>::IsUnicode() const
{
return PR_TRUE;
}
NS_SPECIALIZE_TEMPLATE
inline
const char*
basic_nsAReadableString<char>::GetBuffer() const
// DEPRECATED: use the iterators instead
{
ReadableFragment fragment;
GetReadableFragment(fragment, kFirstFragment);
return fragment.mStart;
}
NS_SPECIALIZE_TEMPLATE
inline
const PRUnichar*
basic_nsAReadableString<PRUnichar>::GetUnicode() const
// DEPRECATED: use the iterators instead
{
ReadableFragment fragment;
GetReadableFragment(fragment, kFirstFragment);
return fragment.mStart;
}
template <class CharT>
const void*
basic_nsAReadableString<CharT>::Implementation() const
{
return 0;
}
/*
Note: the following four functions, |CharAt|, |operator[]|, |First|, and |Last|, are implemented
in the simplest reasonable scheme; by calling |GetReadableFragment| and resolving the pointer it
returns. The alternative is to force at least one of these methods to be |virtual|. The ideal
candidate for that change would be |CharAt|.
This is something to measure in the context of how string classes are actually used. In practice,
do people extract a character at a time in performance critical places? If so, can they use
iterators instead? If they must extract single characters, _and_ they can't use iterators, _and_
it happens enough to notice, then we'll take the hit and make |CharAt| virtual.
*/
template <class CharT>
inline
CharT
basic_nsAReadableString<CharT>::CharAt( PRUint32 aIndex ) const
{
// ??? Is |CharAt()| supposed to be the 'safe' version?
ReadableFragment fragment;
return *GetReadableFragment(fragment, kFragmentAt, aIndex);
}
template <class CharT>
inline
CharT
basic_nsAReadableString<CharT>::operator[]( PRUint32 aIndex ) const
{
return CharAt(aIndex);
}
template <class CharT>
inline
CharT
basic_nsAReadableString<CharT>::First() const
{
return CharAt(0);
}
template <class CharT>
inline
CharT
basic_nsAReadableString<CharT>::Last() const
{
return CharAt(Length()-1);
}
template <class CharT>
PRUint32
basic_nsAReadableString<CharT>::CountChar( CharT c ) const
{
#if 1
return PRUint32(count(BeginReading(), EndReading(), c));
#else
PRUint32 result = 0;
PRUint32 lengthToExamine = Length();
ReadingIterator iter( BeginReading() );
for (;;)
{
PRUint32 lengthToExamineInThisFragment = iter.size_forward();
result += PRUint32(count(iter.operator->(), iter.operator->()+lengthToExamineInThisFragment, c));
if ( !(lengthToExamine -= lengthToExamineInThisFragment) )
return result;
iter += lengthToExamineInThisFragment;
}
#endif
}
/*
Note: |Left()|, |Mid()|, and |Right()| could be modified to notice when they degenerate into copying the
entire string, and call |Assign()| instead. This would be a win when the underlying implementation of
both strings could do buffer sharing. This is _definitely_ something that should be measured before
being implemented.
*/
template <class CharT>
PRUint32
basic_nsAReadableString<CharT>::Left( basic_nsAWritableString<CharT>& aResult, PRUint32 aLengthToCopy ) const
{
aResult = Substring(*this, 0, aLengthToCopy);
return aResult.Length();
}
template <class CharT>
PRUint32
basic_nsAReadableString<CharT>::Mid( basic_nsAWritableString<CharT>& aResult, PRUint32 aStartPos, PRUint32 aLengthToCopy ) const
{
aResult = Substring(*this, aStartPos, aLengthToCopy);
return aResult.Length();
}
template <class CharT>
PRUint32
basic_nsAReadableString<CharT>::Right( basic_nsAWritableString<CharT>& aResult, PRUint32 aLengthToCopy ) const
{
PRUint32 myLength = Length();
aLengthToCopy = NS_MIN(myLength, aLengthToCopy);
aResult = Substring(*this, myLength-aLengthToCopy, aLengthToCopy);
return aResult.Length();
}
template <class CharT>
inline
int
basic_nsAReadableString<CharT>::Compare( const basic_nsAReadableString<CharT>& rhs ) const
{
return ::Compare(*this, rhs);
}
template <class CharT>
inline
int
basic_nsAReadableString<CharT>::Compare( const basic_nsLiteralString<CharT>& rhs ) const
{
return ::Compare(*this, rhs);
}
//
// nsLiteral[C]String
//
template <class CharT>
class basic_nsLiteralString
: public basic_nsAReadableString<CharT>
/*
...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<CharT>&| appears frequently in interfaces because it
allows the automatic conversion of a |CharT*|.
*/
{
typedef typename basic_nsAReadableString<CharT>::FragmentRequest FragmentRequest;
typedef typename basic_nsAWritableString<CharT>::ReadableFragment ReadableFragment;
protected:
virtual const CharT* GetReadableFragment( ReadableFragment&, FragmentRequest, PRUint32 ) const;
public:
// Note: _not_ explicit
basic_nsLiteralString( const CharT* aLiteral )
: mStart(aLiteral),
mEnd(mStart + nsCharTraits<CharT>::length(mStart))
{
// nothing else to do here
}
basic_nsLiteralString( const CharT* aLiteral, PRUint32 aLength )
: mStart(aLiteral),
mEnd(mStart + aLength)
{
// nothing else to do here
}
virtual PRUint32 Length() const;
private:
const CharT* mStart;
const CharT* mEnd;
};
NS_DEF_STRING_COMPARISONS(basic_nsLiteralString<CharT>)
template <class CharT>
const CharT*
basic_nsLiteralString<CharT>::GetReadableFragment( ReadableFragment& aFragment, FragmentRequest 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 <class CharT>
PRUint32
basic_nsLiteralString<CharT>::Length() const
{
return PRUint32(mEnd - mStart);
}
//
// nsPromiseConcatenation
//
template <class CharT>
class nsPromiseConcatenation
: public basic_nsAReadableString<CharT>
/*
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()|.
*/
{
typedef typename basic_nsAReadableString<CharT>::FragmentRequest FragmentRequest;
typedef typename basic_nsAWritableString<CharT>::ReadableFragment ReadableFragment;
protected:
virtual const CharT* GetReadableFragment( ReadableFragment&, FragmentRequest, PRUint32 ) const;
enum { kLeftString, kRightString };
int
GetCurrentStringFromFragment( const ReadableFragment& aFragment ) const
{
return (aFragment.mFragmentIdentifier & mFragmentIdentifierMask) ? kRightString : kLeftString;
}
int
SetLeftStringInFragment( ReadableFragment& aFragment ) const
{
aFragment.mFragmentIdentifier &= ~mFragmentIdentifierMask;
return kLeftString;
}
int
SetRightStringInFragment( ReadableFragment& aFragment ) const
{
aFragment.mFragmentIdentifier |= mFragmentIdentifierMask;
return kRightString;
}
public:
nsPromiseConcatenation( const basic_nsAReadableString<CharT>& aLeftString, const basic_nsAReadableString<CharT>& aRightString, PRUint32 aMask = 1 )
: mFragmentIdentifierMask(aMask)
{
mStrings[kLeftString] = &aLeftString;
mStrings[kRightString] = &aRightString;
}
virtual PRUint32 Length() const;
nsPromiseConcatenation<CharT> operator+( const basic_nsAReadableString<CharT>& rhs ) const;
private:
void operator+( const nsPromiseConcatenation<CharT>& ); // 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<CharT>* mStrings[2];
PRUint32 mFragmentIdentifierMask;
};
NS_DEF_STRING_COMPARISONS(nsPromiseConcatenation<CharT>)
template <class CharT>
PRUint32
nsPromiseConcatenation<CharT>::Length() const
{
return mStrings[kLeftString]->Length() + mStrings[kRightString]->Length();
}
template <class CharT>
const CharT*
nsPromiseConcatenation<CharT>::GetReadableFragment( ReadableFragment& aFragment, FragmentRequest 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;
bool done;
do
{
done = true;
result = mStrings[whichString]->GetReadableFragment(aFragment, aRequest, aPosition);
if ( !result )
{
done = false;
if ( aRequest == kNextFragment && whichString == kLeftString )
{
aRequest = kFirstFragment;
whichString = SetRightStringInFragment(aFragment);
}
else if ( aRequest == kPrevFragment && whichString == kRightString )
{
aRequest = kLastFragment;
whichString = SetLeftStringInFragment(aFragment);
}
else
done = true;
}
}
while ( !done );
return result;
}
template <class CharT>
nsPromiseConcatenation<CharT>
nsPromiseConcatenation<CharT>::operator+( const basic_nsAReadableString<CharT>& rhs ) const
{
return nsPromiseConcatenation<CharT>(*this, rhs, mFragmentIdentifierMask<<1);
}
//
// nsPromiseSubstring
//
template <class CharT>
class nsPromiseSubstring
: public basic_nsAReadableString<CharT>
/*
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()|.
*/
{
typedef typename basic_nsAReadableString<CharT>::FragmentRequest FragmentRequest;
typedef typename basic_nsAWritableString<CharT>::ReadableFragment ReadableFragment;
protected:
virtual const CharT* GetReadableFragment( ReadableFragment&, FragmentRequest, PRUint32 ) const;
public:
nsPromiseSubstring( const basic_nsAReadableString<CharT>& 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
}
virtual PRUint32 Length() const;
private:
const basic_nsAReadableString<CharT>& mString;
PRUint32 mStartPos;
PRUint32 mLength;
};
NS_DEF_STRING_COMPARISONS(nsPromiseSubstring<CharT>)
template <class CharT>
PRUint32
nsPromiseSubstring<CharT>::Length() const
{
return mLength;
}
template <class CharT>
const CharT*
nsPromiseSubstring<CharT>::GetReadableFragment( ReadableFragment& aFragment, FragmentRequest 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;
return mString.GetReadableFragment(aFragment, aRequest, aPosition);
}
//
// Global functions
//
template <class CharT>
nsPromiseSubstring<CharT>
Substring( const basic_nsAReadableString<CharT>& aString, PRUint32 aStartPos, PRUint32 aSubstringLength )
{
return nsPromiseSubstring<CharT>(aString, aStartPos, aSubstringLength);
}
template <class CharT>
int
Compare( const basic_nsAReadableString<CharT>& lhs, const basic_nsAReadableString<CharT>& rhs )
{
if ( &lhs == &rhs )
return 0;
PRUint32 lLength = lhs.Length();
PRUint32 rLength = rhs.Length();
PRUint32 lengthToCompare = NS_MIN(lLength, rLength);
basic_nsAReadableString<CharT>::ReadingIterator leftIter( lhs.BeginReading() );
basic_nsAReadableString<CharT>::ReadingIterator rightIter( rhs.BeginReading() );
for (;;)
{
PRUint32 lengthAvailable = PRUint32( NS_MIN(leftIter.size_forward(), rightIter.size_forward()) );
// assert( lengthAvailable >= 0 );
if ( lengthAvailable > lengthToCompare )
lengthAvailable = lengthToCompare;
if ( int result = nsCharTraits<CharT>::compare(leftIter.operator->(), rightIter.operator->(), lengthAvailable) )
return result;
if ( !(lengthToCompare -= lengthAvailable) )
break;
leftIter += PRInt32(lengthAvailable);
rightIter += PRInt32(lengthAvailable);
}
if ( lLength < rLength )
return -1;
else if ( rLength < lLength )
return 1;
else
return 0;
}
template <class CharT>
inline
int
Compare( const basic_nsAReadableString<CharT>& lhs, const CharT* rhs )
{
return Compare(lhs, basic_nsLiteralString<CharT>(rhs));
}
template <class CharT>
inline
int
Compare( const CharT* lhs, const basic_nsAReadableString<CharT>& rhs )
{
return Compare(basic_nsLiteralString<CharT>(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 <class CharT>
nsPromiseConcatenation<CharT>
operator+( const basic_nsAReadableString<CharT>& lhs, const basic_nsAReadableString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
template <class CharT>
nsPromiseConcatenation<CharT>
operator+( const basic_nsAReadableString<CharT>& lhs, const basic_nsLiteralString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
template <class CharT>
nsPromiseConcatenation<CharT>
operator+( const basic_nsLiteralString<CharT>& lhs, const basic_nsAReadableString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
template <class CharT>
nsPromiseConcatenation<CharT>
operator+( const basic_nsLiteralString<CharT>& lhs, const basic_nsLiteralString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
#ifdef SCC_TESTS
template <class CharT, class TraitsT>
basic_ostream<CharT, TraitsT>&
operator<<( basic_ostream<CharT, TraitsT>& os, const basic_nsAReadableString<CharT>& s )
{
copy(s.BeginReading(), s.EndReading(), ostream_iterator<CharT, CharT, TraitsT>(os));
return os;
}
#endif
typedef basic_nsAReadableString<PRUnichar> nsAReadableString;
typedef basic_nsAReadableString<char> nsAReadableCString;
typedef basic_nsLiteralString<PRUnichar> nsLiteralString;
typedef basic_nsLiteralString<char> nsLiteralCString;
#endif // !defined(_nsAReadableString_h__)
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