C++ SkStream::rewind方法代码示例

    static unsigned long sk_stream_read(FT_Stream       stream,
                                        unsigned long   offset,
                                        unsigned char*  buffer,
                                        unsigned long   count ) {
        SkStream* str = (SkStream*)stream->descriptor.pointer;

        if (count) {
            if (!str->rewind()) {
                return 0;
            } else {
                unsigned long ret;
                if (offset) {
                    ret = str->read(NULL, offset);
                    if (ret != offset) {
                        return 0;
                    }
                }
                ret = str->read(buffer, count);
                if (ret != count) {
                    return 0;
                }
                count = ret;
            }
        }
        return count;
    }

bool SkXMLParser::parse(SkStream& input)
{
    size_t          len = input.read(NULL, 0);
    SkAutoMalloc    am(len);
    char*           doc = (char*)am.get();

    input.rewind();
    size_t  len2 = input.read(doc, len);
    SkASSERT(len2 == len);

    return this->parse(doc, len2);
}

SkStream* FontConfigTypeface::onOpenStream(int* ttcIndex) const {
    SkStream* stream = this->getLocalStream();
    if (stream) {
        // should have been provided by CreateFromStream()
        *ttcIndex = 0;

        SkAutoTUnref<SkStream> dupStream(stream->duplicate());
        if (dupStream) {
            return dupStream.detach();
        }

        // TODO: update interface use, remove the following code in this block.
        size_t length = stream->getLength();

        const void* memory = stream->getMemoryBase();
        if (NULL != memory) {
            return new SkMemoryStream(memory, length, true);
        }

        SkAutoTMalloc<uint8_t> allocMemory(length);
        stream->rewind();
        if (length == stream->read(allocMemory.get(), length)) {
            SkAutoTUnref<SkMemoryStream> copyStream(new SkMemoryStream());
            copyStream->setMemoryOwned(allocMemory.detach(), length);
            return copyStream.detach();
        }

        stream->rewind();
        stream->ref();
    } else {
        SkAutoTUnref<SkFontConfigInterface> fci(RefFCI());
        if (NULL == fci.get()) {
            return NULL;
        }
        stream = fci->openStream(this->getIdentity());
        *ttcIndex = this->getIdentity().fTTCIndex;
    }
    return stream;
}

    static FPDFEMB_RESULT file_readblock(FPDFEMB_FILE_ACCESS* file, void* dst,
                                    unsigned int offset, unsigned int size) {
        SkStream* stream = (SkStream*)file->user;
//        SkDebugf("---- readblock %p %p %d %d\n", stream, dst, offset, size);
        if (!stream->rewind()) {
            SkDebugf("---- rewind failed\n");
            return FPDFERR_ERROR;
        }
        if (stream->skip(offset) != offset) {
            SkDebugf("---- skip failed\n");
            return FPDFERR_ERROR;
        }
        if (stream->read(dst, size) != size) {
            SkDebugf("---- read failed\n");
            return FPDFERR_ERROR;
        }
        return FPDFERR_SUCCESS;
    }

size_t SkFontHost::GetTableData(SkFontID fontID, SkFontTableTag tag,
                                size_t offset, size_t length, void* data) {
    SkStream* stream = SkFontHost::OpenStream(fontID);
    if (NULL == stream) {
        return 0;
    }

    SkAutoUnref au(stream);
    SfntHeader  header;
    if (!header.init(stream)) {
        return 0;
    }

    for (int i = 0; i < header.fCount; i++) {
        if (SkEndian_SwapBE32(header.fDir[i].fTag) == tag) {
            size_t realOffset = SkEndian_SwapBE32(header.fDir[i].fOffset);
            size_t realLength = SkEndian_SwapBE32(header.fDir[i].fLength);
            // now sanity check the caller's offset/length
            if (offset >= realLength) {
                return 0;
            }
            // if the caller is trusting the length from the file, then a
            // hostile file might choose a value which would overflow offset +
            // length.
            if (offset + length < offset) {
                return 0;
            }
            if (offset + length > realLength) {
                length = realLength - offset;
            }
            // skip the stream to the part of the table we want to copy from
            stream->rewind();
            size_t bytesToSkip = realOffset + offset;
            if (stream->skip(bytesToSkip) != bytesToSkip) {
                return 0;
            }
            if (stream->read(data, length) != length) {
                return 0;
            }
            return length;
        }
    }
    return 0;
}

SkStream* FontConfigTypeface::onOpenStream(int* ttcIndex) const {
    SkStream* stream = this->getLocalStream();
    if (stream) {
        // TODO: fix issue 1176.
        // As of now open_stream will return a stream and unwind it, but the
        // SkStream is not thread safe, and if two threads use the stream they
        // may collide and print preview for example could still fail,
        // or there could be some failures in rendering if this stream is used
        // there.
        stream->rewind();
        stream->ref();
        // should have been provided by CreateFromStream()
        *ttcIndex = 0;
    } else {
        SkAutoTUnref<SkFontConfigInterface> fci(RefFCI());
        if (NULL == fci.get()) {
            return NULL;
        }
        stream = fci->openStream(this->getIdentity());
        *ttcIndex = this->getIdentity().fTTCIndex;
    }
    return stream;
}