third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.h

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#ifndef ICOImageDecoder_h
#define ICOImageDecoder_h

#include "platform/image-decoders/FastSharedBufferReader.h"
#include "platform/image-decoders/bmp/BMPImageReader.h"
#include <memory>

namespace blink {

class PNGImageDecoder;

// This class decodes the ICO and CUR image formats.
class PLATFORM_EXPORT ICOImageDecoder final : public ImageDecoder {
    WTF_MAKE_NONCOPYABLE(ICOImageDecoder);
public:
    ICOImageDecoder(AlphaOption, GammaAndColorProfileOption, size_t maxDecodedBytes);
    ~ICOImageDecoder() override;

    // ImageDecoder:
    String filenameExtension() const override { return "ico"; }
    void onSetData(SegmentReader*) override;
    IntSize size() const override;
    IntSize frameSizeAtIndex(size_t) const override;
    bool setSize(unsigned width, unsigned height) override;
    bool frameIsCompleteAtIndex(size_t) const override;
    // CAUTION: setFailed() deletes all readers and decoders.  Be careful to
    // avoid accessing deleted memory, especially when calling this from
    // inside BMPImageReader!
    bool setFailed() override;
    bool hotSpot(IntPoint&) const override;

private:
    enum ImageType {
        Unknown,
        BMP,
        PNG,
    };

    enum FileType {
        ICON = 1,
        CURSOR = 2,
    };

    struct IconDirectoryEntry {
        DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
        IntSize m_size;
        uint16_t m_bitCount;
        IntPoint m_hotSpot;
        uint32_t m_imageOffset;
        uint32_t m_byteSize;
    };

    // Returns true if |a| is a preferable icon entry to |b|.
    // Larger sizes, or greater bitdepths at the same size, are preferable.
    static bool compareEntries(const IconDirectoryEntry& a, const IconDirectoryEntry& b);

    // ImageDecoder:
    void decodeSize() override { decode(0, true); }
    size_t decodeFrameCount() override;
    void decode(size_t index) override { decode(index, false); }

    // TODO (scroggo): These functions are identical to functions in BMPImageReader. Share code?
    inline uint8_t readUint8(size_t offset) const
    {
        return m_fastReader.getOneByte(m_decodedOffset + offset);
    }

    inline uint16_t readUint16(int offset) const
    {
        char buffer[2];
        const char* data = m_fastReader.getConsecutiveData(m_decodedOffset + offset, 2, buffer);
        return BMPImageReader::readUint16(data);
    }

    inline uint32_t readUint32(int offset) const
    {
        char buffer[4];
        const char* data = m_fastReader.getConsecutiveData(m_decodedOffset + offset, 4, buffer);
        return BMPImageReader::readUint32(data);
    }

    // If the desired PNGImageDecoder exists, gives it the appropriate data.
    void setDataForPNGDecoderAtIndex(size_t);

    // Decodes the entry at |index|.  If |onlySize| is true, stops decoding
    // after calculating the image size.  If decoding fails but there is no
    // more data coming, sets the "decode failure" flag.
    void decode(size_t index, bool onlySize);

    // Decodes the directory and directory entries at the beginning of the
    // data, and initializes members.  Returns true if all decoding
    // succeeded.  Once this returns true, all entries' sizes are known.
    bool decodeDirectory();

    // Decodes the specified entry.
    bool decodeAtIndex(size_t);

    // Processes the ICONDIR at the beginning of the data.  Returns true if
    // the directory could be decoded.
    bool processDirectory();

    // Processes the ICONDIRENTRY records after the directory.  Keeps the
    // "best" entry as the one we'll decode.  Returns true if the entries
    // could be decoded.
    bool processDirectoryEntries();

    // Stores the hot-spot for |index| in |hotSpot| and returns true,
    // or returns false if there is none.
    bool hotSpotAtIndex(size_t index, IntPoint& hotSpot) const;

    // Reads and returns a directory entry from the current offset into
    // |data|.
    IconDirectoryEntry readDirectoryEntry();

    // Determines whether the desired entry is a BMP or PNG.  Returns true
    // if the type could be determined.
    ImageType imageTypeAtIndex(size_t);

    FastSharedBufferReader m_fastReader;

    // An index into |m_data| representing how much we've already decoded.
    // Note that this only tracks data _this_ class decodes; once the
    // BMPImageReader takes over this will not be updated further.
    size_t m_decodedOffset;

    // Which type of file (ICO/CUR) this is.
    FileType m_fileType;

    // The headers for the ICO.
    typedef Vector<IconDirectoryEntry> IconDirectoryEntries;
    IconDirectoryEntries m_dirEntries;

    // Count of directory entries is parsed from header before initializing
    // m_dirEntries. m_dirEntries is populated only when full header
    // information including directory entries is available.
    size_t m_dirEntriesCount;

    // The image decoders for the various frames.
    typedef Vector<std::unique_ptr<BMPImageReader>> BMPReaders;
    BMPReaders m_bmpReaders;
    typedef Vector<std::unique_ptr<PNGImageDecoder>> PNGDecoders;
    PNGDecoders m_pngDecoders;

    // Valid only while a BMPImageReader is decoding, this holds the size
    // for the particular entry being decoded.
    IntSize m_frameSize;

    // Used to pass on to an internally created PNG decoder.
    const GammaAndColorProfileOption m_gammaAndColorProfileOption;
};

} // namespace blink

#endif