/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* * The contents of this file are subject to the Mozilla Public * License Version 1.1 (the "License"); you may not use this file * except in compliance with the License. You may obtain a copy of * the License at http://www.mozilla.org/MPL/ * * Software distributed under the License is distributed on an "AS * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or * implied. See the License for the specific language governing * rights and limitations under the License. * * The Original Code is Mozilla. * * The Initial Developer of the Original Code is Netscape * Communications. Portions created by Netscape Communications are * Copyright (C) 2001 by Netscape Communications. All * Rights Reserved. * * Contributor(s): * Scott Collins (original author) */ #ifndef nsXPIDLString_h___ #define nsXPIDLString_h___ #ifndef nsSharableString_h___ #include "nsSharableString.h" #endif #if DEBUG_STRING_STATS #include #endif /** * |nsXPIDLC?String| extends |nsSharableC?String| with the ability * to defer calculation of its length. This is crucial to allowing * the |getter_Copies| assignment behavior. * * The mechanism relies on the fact that |GetSharedBufferHandle| * must be called before any other object can share the buffer, * and as the default implementation for |GetBufferHandle|, which is * the operation on which all other flat string operations are based. * A valid handle will either have all |NULL| or all non-|NULL| * pointers. After use as an `out' string pointer parameter, an * |nsXPIDLC?String|'s handle will have a non-|NULL| storage start, but * all other members will be |NULL|. This is the signal that the * length needs to be recalculated. |GetSharedBufferHandle| detects * this situation and repairs it. * * The one situation this _doesn't_ catch, is if no one ever tries to use * the string before it's destruction. In this case, because the start of * storage is known, storage can still be freed in the usual way. * * An |nsXPIDLC?String| is now a sharable object, just like |nsSharableC?String|. * This simple implementation always allocates an intermediary handle * object. This cost might turn out to be a burden, it's something we'll * want to measure. A couple of optimizations spring to mind if allocation * of the handle objects shows up on the performance radar: * (1) introduce a custom allocator for the handles, e.g., keep free lists * or arena allocate them, or (2) fatten up the |nsXPIDLC?String| with a * local handle, and only allocate a shared handle in the event that * someone actually wants to share. Both of these alternatives add * complexity or space costs, and so we start with the simplest thing * that could possibly work :-) */ class NS_COM nsXPIDLString : public nsSharableString { public: typedef nsXPIDLString self_type; public: nsXPIDLString() { #if DEBUG_STRING_STATS ++sCreatedCount; if ( ++sAliveCount > sHighWaterCount ) sHighWaterCount = sAliveCount; #endif } nsXPIDLString( const self_type& aString ) : nsSharableString(aString.GetSharedBufferHandle()) // copy-constructor required (or else C++ generates one for us) { #if DEBUG_STRING_STATS ++sCreatedCount; if ( ++sAliveCount > sHighWaterCount ) sHighWaterCount = sAliveCount; #endif } #if DEBUG_STRING_STATS ~nsXPIDLString() { --sAliveCount; } #endif self_type& operator=( const self_type& rhs ) // copy-assignment operator required (or else C++ generates one for us) { // self-assignment is handled by the underlying |nsAutoBufferHandle| mBuffer = rhs.GetSharedBufferHandle(); return *this; } void Adopt( char_type* aNewValue ) { *PrepareForUseAsOutParam() = aNewValue; } // overridden to make getter_Copies mechanism work const char_type* get() const { const buffer_handle_type* handle = GetBufferHandle(); // NS_ASSERTION(handle, "handle is null!"); return handle ? handle->DataStart() : 0; } // deprecated, to be eliminated operator const char_type*() const { return get(); } char_type operator[]( int i ) const { return get()[ i ]; } class getter_Copies_t { public: getter_Copies_t( nsXPIDLString& aString ) : mString(&aString) { } // getter_Copies_t( const getter_Copies_t& ); // auto-generated copy-constructor OK // getter_Copies_t& operator=( const getter_Copies_t& ); // auto-generated assignment operator OK operator char_type**() const { return mString->PrepareForUseAsOutParam(); } private: nsXPIDLString* mString; }; friend class getter_Copies_t; protected: #if DEBUG_STRING_STATS virtual const buffer_handle_type* GetFlatBufferHandle() const; virtual const buffer_handle_type* GetBufferHandle() const; #endif virtual const shared_buffer_handle_type* GetSharedBufferHandle() const; // overridden to fix the length after `out' parameter assignment, if necessary char_type** PrepareForUseAsOutParam(); #if DEBUG_STRING_STATS static size_t sCreatedCount; // total number of |nsXPIDLString|s ever created static size_t sAliveCount; // total number of |nsXPIDLStrings|s alive right now static size_t sHighWaterCount; // greatest number of |nsXPIDLString|s alive at once static size_t sAssignCount; // total number of times |nsXPIDLString|s were // assigned into with |getter_Copies| static size_t sShareCount; // total number times |nsXPIDLString|s were asked to share public: static void DebugPrintStats( FILE* ); #endif }; inline nsXPIDLString::getter_Copies_t getter_Copies( nsXPIDLString& aString ) { return nsXPIDLString::getter_Copies_t(aString); } class NS_COM nsXPIDLCString : public nsSharableCString { public: typedef nsXPIDLCString self_type; public: nsXPIDLCString() { #if DEBUG_STRING_STATS ++sCreatedCount; if ( ++sAliveCount > sHighWaterCount ) sHighWaterCount = sAliveCount; #endif } nsXPIDLCString( const self_type& aString ) : nsSharableCString(aString.GetSharedBufferHandle()) // copy-constructor required (or else C++ generates one for us) { #if DEBUG_STRING_STATS ++sCreatedCount; if ( ++sAliveCount > sHighWaterCount ) sHighWaterCount = sAliveCount; #endif } #if DEBUG_STRING_STATS ~nsXPIDLCString() { --sAliveCount; } #endif self_type& operator=( const self_type& rhs ) // copy-assignment operator required (or else C++ generates one for us) { // self-assignment is handled by the underlying |nsAutoBufferHandle| mBuffer = rhs.GetSharedBufferHandle(); return *this; } void Adopt( char_type* aNewValue ) { *PrepareForUseAsOutParam() = aNewValue; } // overridden to make getter_Copies mechanism work const char_type* get() const { const buffer_handle_type* handle = GetBufferHandle(); // NS_ASSERTION(handle, "handle is null!"); return handle ? handle->DataStart() : 0; } // deprecated, to be eliminated operator const char_type*() const { return get(); } char_type operator[]( int i ) const { return get()[ i ]; } class getter_Copies_t { public: getter_Copies_t( nsXPIDLCString& aString ) : mString(&aString) { } // getter_Copies_t( const getter_Copies_t& ); // auto-generated copy-constructor OK // getter_Copies_t& operator=( const getter_Copies_t& ); // auto-generated assignment operator OK operator char_type**() const { return mString->PrepareForUseAsOutParam(); } private: nsXPIDLCString* mString; }; friend class getter_Copies_t; protected: #if DEBUG_STRING_STATS virtual const buffer_handle_type* GetFlatBufferHandle() const; virtual const buffer_handle_type* GetBufferHandle() const; #endif virtual const shared_buffer_handle_type* GetSharedBufferHandle() const; // overridden to fix the length after `out' parameter assignment, if necessary char_type** PrepareForUseAsOutParam(); #if DEBUG_STRING_STATS static size_t sCreatedCount; // total number of |nsXPIDLCString|s ever created static size_t sAliveCount; // total number of |nsXPIDLCStrings|s alive right now static size_t sHighWaterCount; // greatest number of |nsXPIDLCString|s alive at once static size_t sAssignCount; // total number of times |nsXPIDLCString|s were // assigned into with |getter_Copies| static size_t sShareCount; // total number times |nsXPIDLCString|s were asked to share public: static void DebugPrintStats( FILE* ); #endif }; inline nsXPIDLCString::getter_Copies_t getter_Copies( nsXPIDLCString& aString ) { return nsXPIDLCString::getter_Copies_t(aString); } #endif /* !defined(nsXPIDLString_h___) */