src/core/SkData.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkData.h"
#include "SkOSFile.h"
#include "SkOnce.h"
#include "SkReadBuffer.h"
#include "SkStream.h"
#include "SkWriteBuffer.h"

SkData::SkData(const void* ptr, size_t size, ReleaseProc proc, void* context) {
    fPtr = const_cast<void*>(ptr);
    fSize = size;
    fReleaseProc = proc;
    fReleaseProcContext = context;
}

/** This constructor means we are inline with our fPtr's contents.
 *  Thus we set fPtr to point right after this.
 */
SkData::SkData(size_t size) {
    fPtr = (char*)(this + 1);   // contents are immediately after this
    fSize = size;
    fReleaseProc = nullptr;
    fReleaseProcContext = nullptr;
}

SkData::~SkData() {
    if (fReleaseProc) {
        fReleaseProc(fPtr, fReleaseProcContext);
    }
}

bool SkData::equals(const SkData* other) const {
    if (nullptr == other) {
        return false;
    }

    return fSize == other->fSize && !memcmp(fPtr, other->fPtr, fSize);
}

size_t SkData::copyRange(size_t offset, size_t length, void* buffer) const {
    size_t available = fSize;
    if (offset >= available || 0 == length) {
        return 0;
    }
    available -= offset;
    if (length > available) {
        length = available;
    }
    SkASSERT(length > 0);

    memcpy(buffer, this->bytes() + offset, length);
    return length;
}

sk_sp<SkData> SkData::PrivateNewWithCopy(const void* srcOrNull, size_t length) {
    if (0 == length) {
        return SkData::MakeEmpty();
    }

    const size_t actualLength = length + sizeof(SkData);
    SkASSERT_RELEASE(length < actualLength);  // Check for overflow.

    void* storage = ::operator new (actualLength);
    sk_sp<SkData> data(new (storage) SkData(length));
    if (srcOrNull) {
        memcpy(data->writable_data(), srcOrNull, length);
    }
    return data;
}

void SkData::DummyReleaseProc(const void*, void*) {}

///////////////////////////////////////////////////////////////////////////////

sk_sp<SkData> SkData::MakeEmpty() {
    static SkOnce once;
    static SkData* empty;

    once([]{ empty = new SkData(nullptr, 0, nullptr, nullptr); });
    return sk_ref_sp(empty);
}

// assumes fPtr was allocated via sk_malloc
static void sk_free_releaseproc(const void* ptr, void*) {
    sk_free((void*)ptr);
}

sk_sp<SkData> SkData::MakeFromMalloc(const void* data, size_t length) {
    return sk_sp<SkData>(new SkData(data, length, sk_free_releaseproc, nullptr));
}

sk_sp<SkData> SkData::MakeWithCopy(const void* src, size_t length) {
    SkASSERT(src);
    return PrivateNewWithCopy(src, length);
}

sk_sp<SkData> SkData::MakeUninitialized(size_t length) {
    return PrivateNewWithCopy(nullptr, length);
}

sk_sp<SkData> SkData::MakeWithProc(const void* ptr, size_t length, ReleaseProc proc, void* ctx) {
    return sk_sp<SkData>(new SkData(ptr, length, proc, ctx));
}

// assumes fPtr was allocated with sk_fmmap
static void sk_mmap_releaseproc(const void* addr, void* ctx) {
    size_t length = reinterpret_cast<size_t>(ctx);
    sk_fmunmap(addr, length);
}

sk_sp<SkData> SkData::MakeFromFILE(FILE* f) {
    size_t size;
    void* addr = sk_fmmap(f, &size);
    if (nullptr == addr) {
        return nullptr;
    }

    return SkData::MakeWithProc(addr, size, sk_mmap_releaseproc, reinterpret_cast<void*>(size));
}

sk_sp<SkData> SkData::MakeFromFileName(const char path[]) {
    FILE* f = path ? sk_fopen(path, kRead_SkFILE_Flag) : nullptr;
    if (nullptr == f) {
        return nullptr;
    }
    auto data = MakeFromFILE(f);
    sk_fclose(f);
    return data;
}

sk_sp<SkData> SkData::MakeFromFD(int fd) {
    size_t size;
    void* addr = sk_fdmmap(fd, &size);
    if (nullptr == addr) {
        return nullptr;
    }
    return SkData::MakeWithProc(addr, size, sk_mmap_releaseproc, reinterpret_cast<void*>(size));
}

// assumes context is a SkData
static void sk_dataref_releaseproc(const void*, void* context) {
    SkData* src = reinterpret_cast<SkData*>(context);
    src->unref();
}

sk_sp<SkData> SkData::MakeSubset(const SkData* src, size_t offset, size_t length) {
    /*
        We could, if we wanted/need to, just make a deep copy of src's data,
        rather than referencing it. This would duplicate the storage (of the
        subset amount) but would possibly allow src to go out of scope sooner.
     */

    size_t available = src->size();
    if (offset >= available || 0 == length) {
        return SkData::MakeEmpty();
    }
    available -= offset;
    if (length > available) {
        length = available;
    }
    SkASSERT(length > 0);

    src->ref(); // this will be balanced in sk_dataref_releaseproc
    return sk_sp<SkData>(new SkData(src->bytes() + offset, length, sk_dataref_releaseproc,
                                    const_cast<SkData*>(src)));
}

sk_sp<SkData> SkData::MakeWithCString(const char cstr[]) {
    size_t size;
    if (nullptr == cstr) {
        cstr = "";
        size = 1;
    } else {
        size = strlen(cstr) + 1;
    }
    return MakeWithCopy(cstr, size);
}

///////////////////////////////////////////////////////////////////////////////

sk_sp<SkData> SkData::MakeFromStream(SkStream* stream, size_t size) {
    sk_sp<SkData> data(SkData::MakeUninitialized(size));
    if (stream->read(data->writable_data(), size) != size) {
        return nullptr;
    }
    return data;
}