sharedbuffer.cpp

Android 一些工具

/*
 *  SharedBuffer.cpp
 *  Android  
 *
 *  Copyright 2005 The Android Open Source Project
 *
 */

#include <stdlib.h>
#include <string.h>

#include <cutils/atomic.h>

#include "tinyutils/SharedBuffer.h"

// ---------------------------------------------------------------------------

namespace android {

SharedBuffer* SharedBuffer::alloc(size_t size)
{
    SharedBuffer* sb = static_cast<SharedBuffer *>(malloc(sizeof(SharedBuffer) + size));
    if (sb) {
        sb->mRefs = 1;
        sb->mSize = size;
    }
    return sb;
}


ssize_t SharedBuffer::dealloc(const SharedBuffer* released)
{
    if (released->mRefs != 0) return -1; // XXX: invalid operation
    free(const_cast<SharedBuffer*>(released));
    return 0;
}

SharedBuffer* SharedBuffer::edit() const
{
    if (onlyOwner()) {
        return const_cast<SharedBuffer*>(this);
    }
    SharedBuffer* sb = alloc(mSize);
    if (sb) {
        memcpy(sb->data(), data(), size());
        release();
    }
    return sb;    
}

SharedBuffer* SharedBuffer::editResize(size_t newSize) const
{
    if (onlyOwner()) {
        SharedBuffer* buf = const_cast<SharedBuffer*>(this);
        if (buf->mSize == newSize) return buf;
        buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize);
        if (buf != NULL) {
            buf->mSize = newSize;
            return buf;
        }
    }
    SharedBuffer* sb = alloc(newSize);
    if (sb) {
        const size_t mySize = mSize;
        memcpy(sb->data(), data(), newSize < mySize ? newSize : mySize);
        release();
    }
    return sb;    
}

SharedBuffer* SharedBuffer::attemptEdit() const
{
    if (onlyOwner()) {
        return const_cast<SharedBuffer*>(this);
    }
    return 0;
}

SharedBuffer* SharedBuffer::reset(size_t new_size) const
{
    // cheap-o-reset.
    SharedBuffer* sb = alloc(new_size);
    if (sb) {
        release();
    }
    return sb;
}

void SharedBuffer::acquire() const {
    android_atomic_inc(&mRefs);
}

int32_t SharedBuffer::release(uint32_t flags) const
{
    int32_t prev = 1;
    if (onlyOwner() || ((prev = android_atomic_dec(&mRefs)) == 1)) {
        mRefs = 0;
        if ((flags & eKeepStorage) == 0) {
            free(const_cast<SharedBuffer*>(this));
        }
    }
    return prev;
}


}; // namespace android