mirror of
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257 lines
8.8 KiB
C++
257 lines
8.8 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/*
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* The contents of this file are subject to the Mozilla Public
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* License Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing
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* rights and limitations under the License.
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*
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* The Original Code is Mozilla.
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*
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* The Initial Developer of the Original Code is Netscape
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* Communications. Portions created by Netscape Communications are
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* Copyright (C) 2001 by Netscape Communications. All
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* Rights Reserved.
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*
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* Contributor(s):
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* Scott Collins <scc@mozilla.org> (original author)
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*/
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#ifndef nsXPIDLString_h___
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#define nsXPIDLString_h___
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#ifndef nsSharableString_h___
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#include "nsSharableString.h"
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#endif
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#if DEBUG_STRING_STATS
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#include <stdio.h>
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#endif
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/**
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* |nsXPIDLC?String| extends |nsSharableC?String| with the ability
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* to defer calculation of its length. This is crucial to allowing
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* the |getter_Copies| assignment behavior.
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*
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* The mechanism relies on the fact that |GetSharedBufferHandle|
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* must be called before any other object can share the buffer,
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* and as the default implementation for |GetBufferHandle|, which is
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* the operation on which all other flat string operations are based.
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* A valid handle will either have all |NULL| or all non-|NULL|
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* pointers. After use as an `out' string pointer parameter, an
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* |nsXPIDLC?String|'s handle will have a non-|NULL| storage start, but
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* all other members will be |NULL|. This is the signal that the
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* length needs to be recalculated. |GetSharedBufferHandle| detects
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* this situation and repairs it.
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*
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* The one situation this _doesn't_ catch, is if no one ever tries to use
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* the string before it's destruction. In this case, because the start of
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* storage is known, storage can still be freed in the usual way.
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*
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* An |nsXPIDLC?String| is now a sharable object, just like |nsSharableC?String|.
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* This simple implementation always allocates an intermediary handle
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* object. This cost might turn out to be a burden, it's something we'll
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* want to measure. A couple of optimizations spring to mind if allocation
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* of the handle objects shows up on the performance radar:
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* (1) introduce a custom allocator for the handles, e.g., keep free lists
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* or arena allocate them, or (2) fatten up the |nsXPIDLC?String| with a
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* local handle, and only allocate a shared handle in the event that
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* someone actually wants to share. Both of these alternatives add
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* complexity or space costs, and so we start with the simplest thing
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* that could possibly work :-)
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*/
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class NS_COM nsXPIDLString
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: public nsSharableString
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{
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public:
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nsXPIDLString()
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{
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#if DEBUG_STRING_STATS
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++sCreatedCount;
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if ( ++sAliveCount > sHighWaterCount )
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sHighWaterCount = sAliveCount;
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#endif
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}
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nsXPIDLString( const nsXPIDLString& aString )
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: nsSharableString(aString.GetSharedBufferHandle())
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// copy-constructor required (or else C++ generates one for us)
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{
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#if DEBUG_STRING_STATS
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++sCreatedCount;
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if ( ++sAliveCount > sHighWaterCount )
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sHighWaterCount = sAliveCount;
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#endif
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}
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#if DEBUG_STRING_STATS
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~nsXPIDLString()
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{
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--sAliveCount;
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}
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#endif
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nsXPIDLString&
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operator=( const nsXPIDLString& rhs )
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// copy-assignment operator required (or else C++ generates one for us)
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{
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// self-assignment is handled by the underlying |nsAutoBufferHandle|
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mBuffer = rhs.GetSharedBufferHandle();
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return *this;
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}
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void Adopt( PRUnichar* aNewValue ) { *PrepareForUseAsOutParam() = aNewValue; }
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// deprecated, to be eliminated
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operator const PRUnichar*() const { return get(); }
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PRUnichar operator[]( int i ) const { return get()[ i ]; }
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class getter_Copies_t
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{
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public:
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getter_Copies_t( nsXPIDLString& aString ) : mString(&aString) { }
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// getter_Copies_t( const getter_Copies_t& ); // auto-generated copy-constructor OK
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// getter_Copies_t& operator=( const getter_Copies_t& ); // auto-generated assignment operator OK
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operator PRUnichar**() const { return mString->PrepareForUseAsOutParam(); }
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private:
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nsXPIDLString* mString;
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};
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friend class getter_Copies_t;
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protected:
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#if DEBUG_STRING_STATS
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virtual const nsBufferHandle<PRUnichar>* GetFlatBufferHandle() const;
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virtual const nsBufferHandle<PRUnichar>* GetBufferHandle() const;
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#endif
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virtual const nsSharedBufferHandle<PRUnichar>* GetSharedBufferHandle() const;
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// overridden to fix the length after `out' parameter assignment, if necessary
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PRUnichar** PrepareForUseAsOutParam();
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#if DEBUG_STRING_STATS
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static size_t sCreatedCount; // total number of |nsXPIDLString|s ever created
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static size_t sAliveCount; // total number of |nsXPIDLStrings|s alive right now
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static size_t sHighWaterCount; // greatest number of |nsXPIDLString|s alive at once
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static size_t sAssignCount; // total number of times |nsXPIDLString|s were
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// assigned into with |getter_Copies|
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static size_t sShareCount; // total number times |nsXPIDLString|s were asked to share
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public:
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static void DebugPrintStats( FILE* );
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#endif
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};
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inline
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nsXPIDLString::getter_Copies_t
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getter_Copies( nsXPIDLString& aString )
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{
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return nsXPIDLString::getter_Copies_t(aString);
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}
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class NS_COM nsXPIDLCString
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: public nsSharableCString
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{
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public:
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nsXPIDLCString()
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{
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#if DEBUG_STRING_STATS
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++sCreatedCount;
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if ( ++sAliveCount > sHighWaterCount )
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sHighWaterCount = sAliveCount;
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#endif
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}
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nsXPIDLCString( const nsXPIDLCString& aString )
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: nsSharableCString(aString.GetSharedBufferHandle())
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// copy-constructor required (or else C++ generates one for us)
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{
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#if DEBUG_STRING_STATS
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++sCreatedCount;
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if ( ++sAliveCount > sHighWaterCount )
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sHighWaterCount = sAliveCount;
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#endif
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}
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#if DEBUG_STRING_STATS
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~nsXPIDLCString()
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{
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--sAliveCount;
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}
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#endif
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nsXPIDLCString&
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operator=( const nsXPIDLCString& rhs )
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// copy-assignment operator required (or else C++ generates one for us)
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{
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// self-assignment is handled by the underlying |nsAutoBufferHandle|
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mBuffer = rhs.GetSharedBufferHandle();
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return *this;
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}
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void Adopt( char* aNewValue ) { *PrepareForUseAsOutParam() = aNewValue; }
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// deprecated, to be eliminated
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operator const char*() const { return get(); }
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char operator[]( int i ) const { return get()[ i ]; }
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class getter_Copies_t
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{
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public:
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getter_Copies_t( nsXPIDLCString& aString ) : mString(&aString) { }
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// getter_Copies_t( const getter_Copies_t& ); // auto-generated copy-constructor OK
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// getter_Copies_t& operator=( const getter_Copies_t& ); // auto-generated assignment operator OK
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operator char**() const { return mString->PrepareForUseAsOutParam(); }
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private:
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nsXPIDLCString* mString;
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};
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friend class getter_Copies_t;
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protected:
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#if DEBUG_STRING_STATS
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virtual const nsBufferHandle<char>* GetFlatBufferHandle() const;
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virtual const nsBufferHandle<char>* GetBufferHandle() const;
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#endif
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virtual const nsSharedBufferHandle<char>* GetSharedBufferHandle() const;
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// overridden to fix the length after `out' parameter assignment, if necessary
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char** PrepareForUseAsOutParam();
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#if DEBUG_STRING_STATS
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static size_t sCreatedCount; // total number of |nsXPIDLCString|s ever created
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static size_t sAliveCount; // total number of |nsXPIDLCStrings|s alive right now
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static size_t sHighWaterCount; // greatest number of |nsXPIDLCString|s alive at once
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static size_t sAssignCount; // total number of times |nsXPIDLCString|s were
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// assigned into with |getter_Copies|
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static size_t sShareCount; // total number times |nsXPIDLCString|s were asked to share
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public:
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static void DebugPrintStats( FILE* );
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#endif
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};
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inline
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nsXPIDLCString::getter_Copies_t
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getter_Copies( nsXPIDLCString& aString )
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{
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return nsXPIDLCString::getter_Copies_t(aString);
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}
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#endif /* !defined(nsXPIDLString_h___) */
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