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      1 /*
      2  * Copyright (C) 2006, 2009, 2012 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 "wtf/text/StringImpl.h"
     23 
     24 #if USE(CF)
     25 
     26 #include "wtf/MainThread.h"
     27 #include "wtf/PassRefPtr.h"
     28 #include "wtf/RetainPtr.h"
     29 #include "wtf/Threading.h"
     30 #include <CoreFoundation/CoreFoundation.h>
     31 
     32 namespace WTF {
     33 
     34 namespace StringWrapperCFAllocator {
     35 
     36 static StringImpl* currentString;
     37 
     38 static const void* retain(const void* info)
     39 {
     40     return info;
     41 }
     42 
     43 NO_RETURN_DUE_TO_ASSERT
     44 static void release(const void*)
     45 {
     46     ASSERT_NOT_REACHED();
     47 }
     48 
     49 static CFStringRef copyDescription(const void*)
     50 {
     51     return CFSTR("WTF::String-based allocator");
     52 }
     53 
     54 static void* allocate(CFIndex size, CFOptionFlags, void*)
     55 {
     56     StringImpl* underlyingString = 0;
     57     if (isMainThread()) {
     58         underlyingString = currentString;
     59         if (underlyingString) {
     60             currentString = 0;
     61             underlyingString->ref(); // Balanced by call to deref in deallocate below.
     62         }
     63     }
     64     StringImpl** header = static_cast<StringImpl**>(fastMalloc(sizeof(StringImpl*) + size));
     65     *header = underlyingString;
     66     return header + 1;
     67 }
     68 
     69 static void* reallocate(void* pointer, CFIndex newSize, CFOptionFlags, void*)
     70 {
     71     size_t newAllocationSize = sizeof(StringImpl*) + newSize;
     72     StringImpl** header = static_cast<StringImpl**>(pointer) - 1;
     73     ASSERT(!*header);
     74     header = static_cast<StringImpl**>(fastRealloc(header, newAllocationSize));
     75     return header + 1;
     76 }
     77 
     78 static void deallocateOnMainThread(void* headerPointer)
     79 {
     80     StringImpl** header = static_cast<StringImpl**>(headerPointer);
     81     StringImpl* underlyingString = *header;
     82     ASSERT(underlyingString);
     83     underlyingString->deref(); // Balanced by call to ref in allocate above.
     84     fastFree(header);
     85 }
     86 
     87 static void deallocate(void* pointer, void*)
     88 {
     89     StringImpl** header = static_cast<StringImpl**>(pointer) - 1;
     90     StringImpl* underlyingString = *header;
     91     if (!underlyingString) {
     92         fastFree(header);
     93     } else {
     94         if (!isMainThread()) {
     95             callOnMainThread(deallocateOnMainThread, header);
     96         } else {
     97             underlyingString->deref(); // Balanced by call to ref in allocate above.
     98             fastFree(header);
     99         }
    100     }
    101 }
    102 
    103 static CFIndex preferredSize(CFIndex size, CFOptionFlags, void*)
    104 {
    105     // FIXME: If FastMalloc provided a "good size" callback, we'd want to use it here.
    106     // Note that this optimization would help performance for strings created with the
    107     // allocator that are mutable, and those typically are only created by callers who
    108     // make a new string using the old string's allocator, such as some of the call
    109     // sites in CFURL.
    110     return size;
    111 }
    112 
    113 static CFAllocatorRef create()
    114 {
    115     CFAllocatorContext context = { 0, 0, retain, release, copyDescription, allocate, reallocate, deallocate, preferredSize };
    116     return CFAllocatorCreate(0, &context);
    117 }
    118 
    119 static CFAllocatorRef allocator()
    120 {
    121     static CFAllocatorRef allocator = create();
    122     return allocator;
    123 }
    124 
    125 }
    126 
    127 RetainPtr<CFStringRef> StringImpl::createCFString()
    128 {
    129     // Since garbage collection isn't compatible with custom allocators, we
    130     // can't use the NoCopy variants of CFStringCreate*() when GC is enabled.
    131     if (!m_length || !isMainThread()) {
    132         if (is8Bit())
    133             return adoptCF(CFStringCreateWithBytes(0, reinterpret_cast<const UInt8*>(characters8()), m_length, kCFStringEncodingISOLatin1, false));
    134         return adoptCF(CFStringCreateWithCharacters(0, reinterpret_cast<const UniChar*>(characters16()), m_length));
    135     }
    136     CFAllocatorRef allocator = StringWrapperCFAllocator::allocator();
    137 
    138     // Put pointer to the StringImpl in a global so the allocator can store it with the CFString.
    139     ASSERT(!StringWrapperCFAllocator::currentString);
    140     StringWrapperCFAllocator::currentString = this;
    141 
    142     CFStringRef string;
    143     if (is8Bit())
    144         string = CFStringCreateWithBytesNoCopy(allocator, reinterpret_cast<const UInt8*>(characters8()), m_length, kCFStringEncodingISOLatin1, false, kCFAllocatorNull);
    145     else
    146         string = CFStringCreateWithCharactersNoCopy(allocator, reinterpret_cast<const UniChar*>(characters16()), m_length, kCFAllocatorNull);
    147     // CoreFoundation might not have to allocate anything, we clear currentString in case we did not execute allocate().
    148     StringWrapperCFAllocator::currentString = 0;
    149 
    150     return adoptCF(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 // USE(CF)
    163