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gecko-dev/xpcom/ds/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.
*
* Original Author:
* Scott Collins <scc@mozilla.org>
*
* Contributor(s):
*/
#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
/*
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 <class CharT>
struct nsReadableFragment
{
const CharT* mStart;
const CharT* mEnd;
PRUint32 mFragmentIdentifier;
nsReadableFragment()
: mStart(0), mEnd(0), mFragmentIdentifier(0)
{
// nothing else to do here
}
};
template <class CharT> class basic_nsAReadableString;
template <class CharT> 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 CharT>
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<CharT>;
nsReadableFragment<CharT> mFragment;
const CharT* mPosition;
const basic_nsAReadableString<CharT>* mOwningString;
inline void normalize_forward();
inline void normalize_backward();
nsReadingIterator( const nsReadableFragment<CharT>& aFragment,
const CharT* aStartingPosition,
const basic_nsAReadableString<CharT>& aOwningString )
: mFragment(aFragment),
mPosition(aStartingPosition),
mOwningString(&aOwningString)
{
// nothing else to do here
}
public:
// nsReadingIterator( const nsReadingIterator<CharT>& ); ...use default copy-constructor
// nsReadingIterator<CharT>& operator=( const nsReadingIterator<CharT>& ); ...use default copy-assignment operator
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<CharT>&
operator++()
{
++mPosition;
normalize_forward();
return *this;
}
nsReadingIterator<CharT>
operator++( int )
{
nsReadingIterator<CharT> result(*this);
++mPosition;
normalize_forward();
return result;
}
nsReadingIterator<CharT>&
operator--()
{
normalize_backward();
--mPosition;
return *this;
}
nsReadingIterator<CharT>
operator--( int )
{
nsReadingIterator<CharT> result(*this);
normalize_backward();
--mPosition;
return result;
}
const nsReadableFragment<CharT>&
fragment() const
{
return mFragment;
}
difference_type
size_forward() const
{
return mFragment.mEnd - mPosition;
}
difference_type
size_backward() const
{
return mPosition - mFragment.mStart;
}
nsReadingIterator<CharT>&
operator+=( difference_type n )
{
if ( n < 0 )
return operator-=(-n);
while ( n )
{
difference_type one_hop = NS_MIN(n, size_forward());
NS_ASSERTION(one_hop>0, "Infinite loop: can't advance a readable iterator beyond the end of a string");
mPosition += one_hop;
normalize_forward();
n -= one_hop;
}
return *this;
}
nsReadingIterator<CharT>&
operator-=( difference_type n )
{
if ( n < 0 )
return operator+=(-n);
while ( n )
{
difference_type one_hop = NS_MIN(n, size_backward());
NS_ASSERTION(one_hop>0, "Infinite loop: can't advance (backward) a readable iterator beyond the end of a string");
mPosition -= one_hop;
normalize_backward();
n -= one_hop;
}
return *this;
}
};
template <class Iterator>
inline
PRBool
SameFragment( const Iterator& lhs, const Iterator& rhs )
{
return lhs.fragment().mStart == rhs.fragment().mStart;
}
//
// nsAReadable[C]String
//
template <class CharT>
class basic_nsAReadableString
/*
...
*/
{
public:
typedef PRUint32 size_type;
typedef PRUint32 index_type;
typedef nsReadingIterator<CharT> const_iterator;
virtual ~basic_nsAReadableString() { }
// ...yes, I expect to be sub-classed.
nsReadingIterator<CharT> BeginReading( PRUint32 aOffset = 0 ) const;
nsReadingIterator<CharT> EndReading( PRUint32 aOffset = 0 ) const;
virtual PRUint32 Length() const = 0;
PRBool IsEmpty() const;
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<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 CharT* ) const;
// int Compare( const CharT*, PRUint32 ) const;
// int Compare( CharT ) const;
// |Equals()| is a synonym for |Compare()|
PRBool Equals( const basic_nsAReadableString<CharT>& 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<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; }
/*
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<CharT>&, nsFragmentRequest, PRUint32 = 0 ) const = 0;
virtual PRBool Promises( const basic_nsAReadableString<CharT>& aString ) const { return &aString == this; }
// virtual PRBool PromisesExactly( const basic_nsAReadableString<CharT>& aString ) const { return false; }
private:
// NOT TO BE IMPLEMENTED
typedef typename nsCharTraits<CharT>::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<CharT>&, (expr)))
#else
#define NS_READABLE_CAST(CharT, expr) (expr)
#endif
template <class CharT>
inline
void
nsReadingIterator<CharT>::normalize_forward()
{
if ( mPosition == mFragment.mEnd )
if ( mOwningString->GetReadableFragment(mFragment, kNextFragment) )
mPosition = mFragment.mStart;
}
template <class CharT>
inline
void
nsReadingIterator<CharT>::normalize_backward()
{
if ( mPosition == mFragment.mStart )
if ( mOwningString->GetReadableFragment(mFragment, kPrevFragment) )
mPosition = mFragment.mEnd;
}
template <class CharT>
inline
nsReadingIterator<CharT>
basic_nsAReadableString<CharT>::BeginReading( PRUint32 aOffset ) const
{
nsReadableFragment<CharT> fragment;
const CharT* startPos = GetReadableFragment(fragment, kFragmentAt, aOffset);
return nsReadingIterator<CharT>(fragment, startPos, *this);
}
template <class CharT>
inline
nsReadingIterator<CharT>
basic_nsAReadableString<CharT>::EndReading( PRUint32 aOffset ) const
{
nsReadableFragment<CharT> fragment;
const CharT* startPos = GetReadableFragment(fragment, kFragmentAt, NS_MAX(0U, Length()-aOffset));
return nsReadingIterator<CharT>(fragment, startPos, *this);
}
template <class CharT>
inline
PRBool
basic_nsAReadableString<CharT>::IsEmpty() const
{
return Length() == 0;
}
template <class CharT>
inline
PRBool
basic_nsAReadableString<CharT>::Equals( const basic_nsAReadableString<CharT>& rhs ) const
{
return Compare(rhs) == 0;
}
template <class CharT>
inline
PRBool
operator==( const nsReadingIterator<CharT>& lhs, const nsReadingIterator<CharT>& rhs )
{
return lhs.get() == rhs.get();
}
template <class CharT>
inline
PRBool
operator!=( const nsReadingIterator<CharT>& lhs, const nsReadingIterator<CharT>& 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 <class _CharT> NS_DEF_1_STRING_PTR_COMPARISON_OPERATOR(comp, _StringT, _CharT) \
template <class _CharT> 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>, CharT)
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>
CharT
basic_nsAReadableString<CharT>::CharAt( PRUint32 aIndex ) const
{
NS_ASSERTION(aIndex<Length(), "|CharAt| out-of-range");
nsReadableFragment<CharT> 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 0
return PRUint32(NS_COUNT(BeginReading(), EndReading(), c));
#else
PRUint32 result = 0;
PRUint32 lengthToExamine = Length();
nsReadingIterator<CharT> iter( BeginReading() );
for (;;)
{
PRInt32 lengthToExamineInThisFragment = iter.size_forward();
result += PRUint32(NS_COUNT(iter.get(), iter.get()+lengthToExamineInThisFragment, c));
if ( !(lengthToExamine -= lengthToExamineInThisFragment) )
return result;
iter += lengthToExamineInThisFragment;
}
#endif
}
template <class CharT>
PRUint32
basic_nsAReadableString<CharT>::Mid( basic_nsAWritableString<CharT>& 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 <class CharT>
inline
PRUint32
basic_nsAReadableString<CharT>::Left( basic_nsAWritableString<CharT>& aResult, PRUint32 aLengthToCopy ) const
{
return Mid(aResult, 0, aLengthToCopy);
}
template <class CharT>
PRUint32
basic_nsAReadableString<CharT>::Right( basic_nsAWritableString<CharT>& aResult, PRUint32 aLengthToCopy ) const
{
PRUint32 myLength = Length();
aLengthToCopy = NS_MIN(myLength, aLengthToCopy);
return Mid(aResult, myLength-aLengthToCopy, aLengthToCopy);
}
template <class CharT>
inline
int
basic_nsAReadableString<CharT>::Compare( const basic_nsAReadableString<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*|.
*/
{
protected:
virtual const CharT* GetReadableFragment( nsReadableFragment<CharT>&, nsFragmentRequest, PRUint32 ) const;
public:
// Note: _not_ explicit
basic_nsLiteralString( const CharT* aLiteral )
: mStart(aLiteral),
mEnd(mStart ? (mStart + nsCharTraits<CharT>::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<CharT>::length(mStart)) : mStart;
}
}
virtual PRUint32 Length() const;
private:
const CharT* mStart;
const CharT* mEnd;
};
NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(basic_nsLiteralString<CharT>, CharT)
template <class CharT>
const CharT*
basic_nsLiteralString<CharT>::GetReadableFragment( nsReadableFragment<CharT>& 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 <class CharT>
PRUint32
basic_nsLiteralString<CharT>::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 <class CharT>
inline
PRBool
basic_nsAReadableString<CharT>::Equals( const CharT* rhs ) const
{
return Compare(basic_nsLiteralString<CharT>(rhs)) == 0;
}
#if 0
template <class CharT>
inline
PRBool
basic_nsAReadableString<CharT>::Equals( const CharT* rhs, PRUint32 rhs_length ) const
{
return Compare(basic_nsLiteralString<CharT>(rhs, rhs_length)) == 0;
}
#endif
template <class CharT>
inline
int
basic_nsAReadableString<CharT>::Compare( const CharT* rhs ) const
{
return ::Compare(*this, NS_READABLE_CAST(CharT, basic_nsLiteralString<CharT>(rhs)));
}
#if 0
template <class CharT>
inline
int
basic_nsAReadableString<CharT>::Compare( const CharT* rhs, PRUint32 rhs_length ) const
{
return ::Compare(*this, NS_READABLE_CAST(CharT, basic_nsLiteralString<CharT>(rhs, rhs_length)));
}
#endif
//
// nsLiteralChar, nsLiteralPRUnichar
//
template <class CharT>
class basic_nsLiteralChar
: public basic_nsAReadableString<CharT>
{
protected:
virtual const CharT* GetReadableFragment( nsReadableFragment<CharT>&, nsFragmentRequest, PRUint32 ) const;
public:
basic_nsLiteralChar( CharT aChar )
: mChar(aChar)
{
// nothing else to do here
}
virtual
PRUint32
Length() const
{
return 1;
}
private:
CharT mChar;
};
template <class CharT>
const CharT*
basic_nsLiteralChar<CharT>::GetReadableFragment( nsReadableFragment<CharT>& 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 CharT> class nsPromiseReadable : public basic_nsAReadableString<CharT> { };
template <class CharT>
class nsPromiseConcatenation
: public nsPromiseReadable<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()|.
*/
{
protected:
virtual const CharT* GetReadableFragment( nsReadableFragment<CharT>&, nsFragmentRequest, PRUint32 ) const;
enum { kLeftString, kRightString };
int
GetCurrentStringFromFragment( const nsReadableFragment<CharT>& aFragment ) const
{
return (aFragment.mFragmentIdentifier & mFragmentIdentifierMask) ? kRightString : kLeftString;
}
int
SetLeftStringInFragment( nsReadableFragment<CharT>& aFragment ) const
{
aFragment.mFragmentIdentifier &= ~mFragmentIdentifierMask;
return kLeftString;
}
int
SetRightStringInFragment( nsReadableFragment<CharT>& 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;
}
nsPromiseConcatenation( const nsPromiseConcatenation<CharT>& aLeftString, const basic_nsAReadableString<CharT>& aRightString )
: mFragmentIdentifierMask(aLeftString.mFragmentIdentifierMask<<1)
{
mStrings[kLeftString] = &aLeftString;
mStrings[kRightString] = &aRightString;
}
virtual PRUint32 Length() const;
virtual PRBool Promises( const basic_nsAReadableString<CharT>& ) const;
// virtual PRBool PromisesExactly( const basic_nsAReadableString<CharT>& ) 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_TEMPLATE_STRING_COMPARISON_OPERATORS(nsPromiseConcatenation<CharT>, CharT)
template <class CharT>
PRUint32
nsPromiseConcatenation<CharT>::Length() const
{
return mStrings[kLeftString]->Length() + mStrings[kRightString]->Length();
}
template <class CharT>
PRBool
nsPromiseConcatenation<CharT>::Promises( const basic_nsAReadableString<CharT>& aString ) const
{
return mStrings[0]->Promises(aString) || mStrings[1]->Promises(aString);
}
#if 0
PRBool
nsPromiseConcatenation<CharT>::PromisesExactly( const basic_nsAReadableString<CharT>& 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 <class CharT>
const CharT*
nsPromiseConcatenation<CharT>::GetReadableFragment( nsReadableFragment<CharT>& 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;
}
template <class CharT>
inline
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 nsPromiseReadable<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()|.
*/
{
protected:
virtual const CharT* GetReadableFragment( nsReadableFragment<CharT>&, nsFragmentRequest, 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;
virtual PRBool Promises( const basic_nsAReadableString<CharT>& aString ) const { return mString.Promises(aString); }
private:
const basic_nsAReadableString<CharT>& mString;
PRUint32 mStartPos;
PRUint32 mLength;
};
NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(nsPromiseSubstring<CharT>, CharT)
template <class CharT>
PRUint32
nsPromiseSubstring<CharT>::Length() const
{
return mLength;
}
template <class CharT>
const CharT*
nsPromiseSubstring<CharT>::GetReadableFragment( nsReadableFragment<CharT>& 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;
const CharT* position_ptr = mString.GetReadableFragment(aFragment, aRequest, aPosition);
// if there's more physical data in the returned fragment than I logically have left...
size_t logical_size_forward = mLength - aPosition;
if ( aFragment.mEnd - position_ptr > logical_size_forward )
aFragment.mEnd = position_ptr + logical_size_forward;
return position_ptr;
}
//
// Global functions
//
template <class CharT>
inline
PRBool
SameImplementation( const basic_nsAReadableString<CharT>& lhs, const basic_nsAReadableString<CharT>& rhs )
{
const void* imp_tag = lhs.Implementation();
return imp_tag && (imp_tag==rhs.Implementation());
}
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);
nsReadingIterator<CharT> leftIter( lhs.BeginReading() );
nsReadingIterator<CharT> rightIter( rhs.BeginReading() );
for (;;)
{
PRUint32 lengthAvailable = PRUint32( NS_MIN(leftIter.size_forward(), rightIter.size_forward()) );
if ( lengthAvailable > lengthToCompare )
lengthAvailable = lengthToCompare;
if ( int result = nsCharTraits<CharT>::compare(leftIter.get(), rightIter.get(), 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, NS_READABLE_CAST(CharT, basic_nsLiteralString<CharT>(rhs)));
}
template <class CharT>
inline
int
Compare( const CharT* lhs, const basic_nsAReadableString<CharT>& rhs )
{
return Compare(NS_READABLE_CAST(CharT, 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.
*/
/*
I probably need to add |operator+()| for appropriate |CharT| and |CharT*| comparisons, since
automatic conversion to a literal string will not happen.
*/
template <class CharT>
inline
nsPromiseConcatenation<CharT>
operator+( const basic_nsAReadableString<CharT>& lhs, const basic_nsAReadableString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(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)
#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
template <class CharT>
inline
nsPromiseConcatenation<CharT>
operator+( const basic_nsAReadableString<CharT>& lhs, const basic_nsLiteralString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
template <class CharT>
inline
nsPromiseConcatenation<CharT>
operator+( const basic_nsLiteralString<CharT>& lhs, const basic_nsAReadableString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
template <class CharT>
inline
nsPromiseConcatenation<CharT>
operator+( const basic_nsLiteralString<CharT>& lhs, const basic_nsLiteralString<CharT>& rhs )
{
return nsPromiseConcatenation<CharT>(lhs, rhs);
}
typedef basic_nsAReadableString<PRUnichar> nsAReadableString;
typedef basic_nsAReadableString<char> nsAReadableCString;
typedef basic_nsLiteralString<PRUnichar> nsLiteralString;
typedef basic_nsLiteralString<char> nsLiteralCString;
#ifdef HAVE_CPP_2BYTE_WCHAR_T
#define NS_LITERAL_STRING(s) nsLiteralString(L##s, (sizeof(L##s)/sizeof(wchar_t))-1)
#else
#define NS_LITERAL_STRING(s) NS_ConvertASCIItoUCS2(s, sizeof(s)-1)
#endif
#define NS_LITERAL_CSTRING(s) nsLiteralCString(s, sizeof(s)-1)
typedef basic_nsLiteralChar<char> nsLiteralChar;
typedef basic_nsLiteralChar<PRUnichar> nsLiteralPRUnichar;
#endif // !defined(nsAReadableString_h___)
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