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      1 /*
      2  * Copyright (C) 2006, 2009 Apple Inc. All rights reserved.
      3  *
      4  * This library is free software; you can redistribute it and/or
      5  * modify it under the terms of the GNU Library General Public
      6  * License as published by the Free Software Foundation; either
      7  * version 2 of the License, or (at your option) any later version.
      8  *
      9  * This library is distributed in the hope that it will be useful,
     10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     12  * Library General Public License for more details.
     13  *
     14  * You should have received a copy of the GNU Library General Public License
     15  * along with this library; see the file COPYING.LIB.  If not, write to
     16  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     17  * Boston, MA 02110-1301, USA.
     18  *
     19  */
     20 
     21 #include "config.h"
     22 #include "StringImpl.h"
     23 
     24 #if PLATFORM(CF)
     25 
     26 #include <CoreFoundation/CoreFoundation.h>
     27 #include <wtf/MainThread.h>
     28 #include <wtf/PassRefPtr.h>
     29 #include <wtf/Threading.h>
     30 
     31 #if PLATFORM(MAC) && !defined(BUILDING_ON_TIGER)
     32 #include <objc/objc-auto.h>
     33 #endif
     34 
     35 namespace WebCore {
     36 
     37 namespace StringWrapperCFAllocator {
     38 
     39     static StringImpl* currentString;
     40 
     41     static const void* retain(const void* info)
     42     {
     43         return info;
     44     }
     45 
     46     static void release(const void*)
     47     {
     48         ASSERT_NOT_REACHED();
     49     }
     50 
     51     static CFStringRef copyDescription(const void*)
     52     {
     53         return CFSTR("WebCore::String-based allocator");
     54     }
     55 
     56     static void* allocate(CFIndex size, CFOptionFlags, void*)
     57     {
     58         StringImpl* underlyingString = 0;
     59         if (isMainThread()) {
     60             underlyingString = currentString;
     61             if (underlyingString) {
     62                 currentString = 0;
     63                 underlyingString->ref(); // Balanced by call to deref in deallocate below.
     64             }
     65         }
     66         StringImpl** header = static_cast<StringImpl**>(fastMalloc(sizeof(StringImpl*) + size));
     67         *header = underlyingString;
     68         return header + 1;
     69     }
     70 
     71     static void* reallocate(void* pointer, CFIndex newSize, CFOptionFlags, void*)
     72     {
     73         size_t newAllocationSize = sizeof(StringImpl*) + newSize;
     74         StringImpl** header = static_cast<StringImpl**>(pointer) - 1;
     75         ASSERT(!*header);
     76         header = static_cast<StringImpl**>(fastRealloc(header, newAllocationSize));
     77         return header + 1;
     78     }
     79 
     80     static void deallocateOnMainThread(void* headerPointer)
     81     {
     82         StringImpl** header = static_cast<StringImpl**>(headerPointer);
     83         StringImpl* underlyingString = *header;
     84         ASSERT(underlyingString);
     85         underlyingString->deref(); // Balanced by call to ref in allocate above.
     86         fastFree(header);
     87     }
     88 
     89     static void deallocate(void* pointer, void*)
     90     {
     91         StringImpl** header = static_cast<StringImpl**>(pointer) - 1;
     92         StringImpl* underlyingString = *header;
     93         if (!underlyingString)
     94             fastFree(header);
     95         else {
     96             if (!isMainThread())
     97                 callOnMainThread(deallocateOnMainThread, header);
     98             else {
     99                 underlyingString->deref(); // Balanced by call to ref in allocate above.
    100                 fastFree(header);
    101             }
    102         }
    103     }
    104 
    105     static CFIndex preferredSize(CFIndex size, CFOptionFlags, void*)
    106     {
    107         // FIXME: If FastMalloc provided a "good size" callback, we'd want to use it here.
    108         // Note that this optimization would help performance for strings created with the
    109         // allocator that are mutable, and those typically are only created by callers who
    110         // make a new string using the old string's allocator, such as some of the call
    111         // sites in CFURL.
    112         return size;
    113     }
    114 
    115     static CFAllocatorRef create()
    116     {
    117 #if PLATFORM(MAC) && !defined(BUILDING_ON_TIGER)
    118         // Since garbage collection isn't compatible with custom allocators, don't use this at all when garbage collection is active.
    119         if (objc_collectingEnabled())
    120             return 0;
    121 #endif
    122         CFAllocatorContext context = { 0, 0, retain, release, copyDescription, allocate, reallocate, deallocate, preferredSize };
    123         return CFAllocatorCreate(0, &context);
    124     }
    125 
    126     static CFAllocatorRef allocator()
    127     {
    128         static CFAllocatorRef allocator = create();
    129         return allocator;
    130     }
    131 
    132 }
    133 
    134 CFStringRef StringImpl::createCFString()
    135 {
    136     CFAllocatorRef allocator = (m_length && isMainThread()) ? StringWrapperCFAllocator::allocator() : 0;
    137     if (!allocator)
    138         return CFStringCreateWithCharacters(0, reinterpret_cast<const UniChar*>(m_data), m_length);
    139 
    140     // Put pointer to the StringImpl in a global so the allocator can store it with the CFString.
    141     ASSERT(!StringWrapperCFAllocator::currentString);
    142     StringWrapperCFAllocator::currentString = this;
    143 
    144     CFStringRef string = CFStringCreateWithCharactersNoCopy(allocator, reinterpret_cast<const UniChar*>(m_data), m_length, kCFAllocatorNull);
    145 
    146     // The allocator cleared the global when it read it, but also clear it here just in case.
    147     ASSERT(!StringWrapperCFAllocator::currentString);
    148     StringWrapperCFAllocator::currentString = 0;
    149 
    150     return string;
    151 }
    152 
    153 // On StringImpl creation we could check if the allocator is the StringWrapperCFAllocator.
    154 // If it is, then we could find the original StringImpl and just return that. But to
    155 // do that we'd have to compute the offset from CFStringRef to the allocated block;
    156 // the CFStringRef is *not* at the start of an allocated block. Testing shows 1000x
    157 // more calls to createCFString than calls to the create functions with the appropriate
    158 // allocator, so it's probably not urgent optimize that case.
    159 
    160 }
    161 
    162 #endif // PLATFORM(CF)
    163