SkData.cpp

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/*
 * 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 "include/core/SkData.h"
 
#include "include/core/SkStream.h"
#include "include/private/base/SkAssert.h"
#include "include/private/base/SkMalloc.h"
#include "include/private/base/SkOnce.h"
#include "src/core/SkOSFile.h"
#include "src/core/SkStreamPriv.h"
 
#include <cstring>
#include <new>
 
SkData::SkData(const void* ptr, size_t size, ReleaseProc proc, void* context)
    : fReleaseProc(proc)
    , fReleaseProcContext(context)
    , fPtr(ptr)
    , fSize(size)
{}
 
/** 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)
    : fReleaseProc(nullptr)
    , fReleaseProcContext(nullptr)
    , fPtr((const char*)(this + 1))
    , fSize(size)
{}
 
SkData::~SkData() {
    if (fReleaseProc) {
        fReleaseProc(fPtr, fReleaseProcContext);
    }
}
 
bool SkData::equals(const SkData* other) const {
    if (this == other) {
        return true;
    }
    if (nullptr == other) {
        return false;
    }
    return fSize == other->fSize && !sk_careful_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);
 
    if (buffer) {
        memcpy(buffer, this->bytes() + offset, length);
    }
    return length;
}
 
void SkData::operator delete(void* p) {
    ::operator delete(p);
}
 
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::NoopReleaseProc(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(const_cast<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::MakeZeroInitialized(size_t length) {
    auto data = MakeUninitialized(length);
    if (length != 0) {
        memset(data->writable_data(), 0, data->size());
    }
    return data;
}
 
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) {
    // reduce the chance of OOM by checking that the stream has enough bytes to read from before
    // allocating that potentially large buffer.
    if (StreamRemainingLengthIsBelow(stream, size)) {
        return nullptr;
    }
    sk_sp<SkData> data(SkData::MakeUninitialized(size));
    if (stream->read(data->writable_data(), size) != size) {
        return nullptr;
    }
    return data;
}