Source/wtf/text/StringImplCF.cpp

/*
 * Copyright (C) 2006, 2009, 2012 Apple Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"
#include "wtf/text/StringImpl.h"

#if USE(CF)

#include "wtf/MainThread.h"
#include "wtf/PassRefPtr.h"
#include "wtf/RetainPtr.h"
#include "wtf/Threading.h"
#include <CoreFoundation/CoreFoundation.h>

namespace WTF {

namespace StringWrapperCFAllocator {

static StringImpl* currentString;

static const void* retain(const void* info)
{
    return info;
}

NO_RETURN_DUE_TO_ASSERT
static void release(const void*)
{
    ASSERT_NOT_REACHED();
}

static CFStringRef copyDescription(const void*)
{
    return CFSTR("WTF::String-based allocator");
}

static void* allocate(CFIndex size, CFOptionFlags, void*)
{
    StringImpl* underlyingString = 0;
    if (isMainThread()) {
        underlyingString = currentString;
        if (underlyingString) {
            currentString = 0;
            underlyingString->ref(); // Balanced by call to deref in deallocate below.
        }
    }
    StringImpl** header = static_cast<StringImpl**>(fastMalloc(sizeof(StringImpl*) + size));
    *header = underlyingString;
    return header + 1;
}

static void* reallocate(void* pointer, CFIndex newSize, CFOptionFlags, void*)
{
    size_t newAllocationSize = sizeof(StringImpl*) + newSize;
    StringImpl** header = static_cast<StringImpl**>(pointer) - 1;
    ASSERT(!*header);
    header = static_cast<StringImpl**>(fastRealloc(header, newAllocationSize));
    return header + 1;
}

static void deallocateOnMainThread(void* headerPointer)
{
    StringImpl** header = static_cast<StringImpl**>(headerPointer);
    StringImpl* underlyingString = *header;
    ASSERT(underlyingString);
    underlyingString->deref(); // Balanced by call to ref in allocate above.
    fastFree(header);
}

static void deallocate(void* pointer, void*)
{
    StringImpl** header = static_cast<StringImpl**>(pointer) - 1;
    StringImpl* underlyingString = *header;
    if (!underlyingString) {
        fastFree(header);
    } else {
        if (!isMainThread()) {
            callOnMainThread(deallocateOnMainThread, header);
        } else {
            underlyingString->deref(); // Balanced by call to ref in allocate above.
            fastFree(header);
        }
    }
}

static CFIndex preferredSize(CFIndex size, CFOptionFlags, void*)
{
    // FIXME: If FastMalloc provided a "good size" callback, we'd want to use it here.
    // Note that this optimization would help performance for strings created with the
    // allocator that are mutable, and those typically are only created by callers who
    // make a new string using the old string's allocator, such as some of the call
    // sites in CFURL.
    return size;
}

static CFAllocatorRef create()
{
    CFAllocatorContext context = { 0, 0, retain, release, copyDescription, allocate, reallocate, deallocate, preferredSize };
    return CFAllocatorCreate(0, &context);
}

static CFAllocatorRef allocator()
{
    static CFAllocatorRef allocator = create();
    return allocator;
}

}

RetainPtr<CFStringRef> StringImpl::createCFString()
{
    // Since garbage collection isn't compatible with custom allocators, we
    // can't use the NoCopy variants of CFStringCreate*() when GC is enabled.
    if (!m_length || !isMainThread()) {
        if (is8Bit())
            return adoptCF(CFStringCreateWithBytes(0, reinterpret_cast<const UInt8*>(characters8()), m_length, kCFStringEncodingISOLatin1, false));
        return adoptCF(CFStringCreateWithCharacters(0, reinterpret_cast<const UniChar*>(characters16()), m_length));
    }
    CFAllocatorRef allocator = StringWrapperCFAllocator::allocator();

    // Put pointer to the StringImpl in a global so the allocator can store it with the CFString.
    ASSERT(!StringWrapperCFAllocator::currentString);
    StringWrapperCFAllocator::currentString = this;

    CFStringRef string;
    if (is8Bit())
        string = CFStringCreateWithBytesNoCopy(allocator, reinterpret_cast<const UInt8*>(characters8()), m_length, kCFStringEncodingISOLatin1, false, kCFAllocatorNull);
    else
        string = CFStringCreateWithCharactersNoCopy(allocator, reinterpret_cast<const UniChar*>(characters16()), m_length, kCFAllocatorNull);
    // CoreFoundation might not have to allocate anything, we clear currentString in case we did not execute allocate().
    StringWrapperCFAllocator::currentString = 0;

    return adoptCF(string);
}

// On StringImpl creation we could check if the allocator is the StringWrapperCFAllocator.
// If it is, then we could find the original StringImpl and just return that. But to
// do that we'd have to compute the offset from CFStringRef to the allocated block;
// the CFStringRef is *not* at the start of an allocated block. Testing shows 1000x
// more calls to createCFString than calls to the create functions with the appropriate
// allocator, so it's probably not urgent optimize that case.

}

#endif // USE(CF)