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https://github.com/RGBCube/serenity
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LibGfx/JPEG: Encapsulate operations on HuffmanStream
Advantages of encapsulation are really obvious here: - Put related code together - Prevent external functions to modify the object - Abstract the implementation No functional changes intended.
This commit is contained in:
Lucas CHOLLET
Andreas Kling
parent
66108d102e
commit
86ce9cc30f
1 changed files with 121 additions and 100 deletions
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@ -187,10 +187,115 @@ struct HuffmanTableSpec {
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Vector<u16> codes;
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};
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struct HuffmanStream {
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Vector<u8> stream;
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u8 bit_offset { 0 };
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size_t byte_offset { 0 };
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class HuffmanStream {
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public:
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static ErrorOr<HuffmanStream> create(SeekableStream& stream)
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{
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HuffmanStream huffman {};
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u8 last_byte {};
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u8 current_byte = TRY(stream.read_value<u8>());
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for (;;) {
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last_byte = current_byte;
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current_byte = TRY(stream.read_value<u8>());
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if (last_byte == 0xFF) {
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if (current_byte == 0xFF)
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continue;
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if (current_byte == 0x00) {
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current_byte = TRY(stream.read_value<u8>());
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huffman.m_stream.append(last_byte);
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continue;
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}
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Marker marker = 0xFF00 | current_byte;
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if (marker >= JPEG_RST0 && marker <= JPEG_RST7) {
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huffman.m_stream.append(marker);
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current_byte = TRY(stream.read_value<u8>());
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continue;
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}
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// Rollback the marker we just read
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TRY(stream.seek(-2, AK::SeekMode::FromCurrentPosition));
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return huffman;
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}
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huffman.m_stream.append(last_byte);
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}
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VERIFY_NOT_REACHED();
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}
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ErrorOr<u8> next_symbol(HuffmanTableSpec const& table)
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{
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unsigned code = 0;
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u64 code_cursor = 0;
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for (int i = 0; i < 16; i++) { // Codes can't be longer than 16 bits.
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auto result = TRY(read_bits());
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code = (code << 1) | result;
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for (int j = 0; j < table.code_counts[i]; j++) {
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if (code == table.codes[code_cursor])
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return table.symbols[code_cursor];
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code_cursor++;
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}
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}
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dbgln_if(JPEG_DEBUG, "If you're seeing this...the jpeg decoder needs to support more kinds of JPEGs!");
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return Error::from_string_literal("This kind of JPEG is not yet supported by the decoder");
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}
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ErrorOr<u16> read_bits(u8 count = 1)
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{
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if (count > NumericLimits<u16>::digits()) {
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dbgln_if(JPEG_DEBUG, "Can't read {} bits at once!", count);
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return Error::from_string_literal("Reading too much huffman bits at once");
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}
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u16 value = 0;
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while (count--) {
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if (m_byte_offset >= m_stream.size()) {
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dbgln_if(JPEG_DEBUG, "Huffman stream exhausted. This could be an error!");
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return Error::from_string_literal("Huffman stream exhausted.");
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}
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u8 const current_byte = m_stream[m_byte_offset];
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u8 const current_bit = 1u & (current_byte >> (7 - m_bit_offset)); // MSB first.
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m_bit_offset++;
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value = (value << 1) | current_bit;
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if (m_bit_offset == 8) {
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m_byte_offset++;
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m_bit_offset = 0;
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}
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}
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return value;
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}
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void advance_to_byte_boundary()
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{
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if (m_bit_offset > 0) {
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m_bit_offset = 0;
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m_byte_offset++;
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}
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}
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void skip_byte()
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{
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m_byte_offset++;
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}
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u64 byte_offset() const
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{
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return m_byte_offset;
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}
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private:
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Vector<u8> m_stream;
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u8 m_bit_offset { 0 };
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u64 m_byte_offset { 0 };
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};
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struct ICCMultiChunkState {
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@ -270,48 +375,6 @@ static void generate_huffman_codes(HuffmanTableSpec& table)
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}
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}
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static ErrorOr<size_t> read_huffman_bits(HuffmanStream& hstream, size_t count = 1)
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{
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if (count > (8 * sizeof(size_t))) {
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dbgln_if(JPEG_DEBUG, "Can't read {} bits at once!", count);
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return Error::from_string_literal("Reading too much huffman bits at once");
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}
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size_t value = 0;
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while (count--) {
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if (hstream.byte_offset >= hstream.stream.size()) {
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dbgln_if(JPEG_DEBUG, "Huffman stream exhausted. This could be an error!");
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return Error::from_string_literal("Huffman stream exhausted.");
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}
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u8 current_byte = hstream.stream[hstream.byte_offset];
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u8 current_bit = 1u & (u32)(current_byte >> (7 - hstream.bit_offset)); // MSB first.
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hstream.bit_offset++;
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value = (value << 1) | (size_t)current_bit;
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if (hstream.bit_offset == 8) {
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hstream.byte_offset++;
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hstream.bit_offset = 0;
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}
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}
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return value;
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}
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static ErrorOr<u8> get_next_symbol(HuffmanStream& hstream, HuffmanTableSpec const& table)
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{
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unsigned code = 0;
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size_t code_cursor = 0;
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for (int i = 0; i < 16; i++) { // Codes can't be longer than 16 bits.
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auto result = TRY(read_huffman_bits(hstream));
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code = (code << 1) | (i32)result;
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for (int j = 0; j < table.code_counts[i]; j++) {
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if (code == table.codes[code_cursor])
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return table.symbols[code_cursor];
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code_cursor++;
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}
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}
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dbgln_if(JPEG_DEBUG, "If you're seeing this...the jpeg decoder needs to support more kinds of JPEGs!");
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return Error::from_string_literal("This kind of JPEG is not yet supported by the decoder");
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}
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static inline auto* get_component(Macroblock& block, unsigned component)
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{
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switch (component) {
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@ -332,7 +395,7 @@ static ErrorOr<void> refine_coefficient(Scan& scan, auto& coefficient)
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{
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// G.1.2.3 - Coding model for subsequent scans of successive approximation
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// See the correction bit from rule b.
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u8 const bit = TRY(read_huffman_bits(scan.huffman_stream, 1));
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u8 const bit = TRY(scan.huffman_stream.read_bits(1));
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if (bit == 1)
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coefficient |= 1 << scan.successive_approximation_low;
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@ -359,14 +422,14 @@ static ErrorOr<void> add_dc(JPEGLoadingContext& context, Macroblock& macroblock,
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}
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// For DC coefficients, symbol encodes the length of the coefficient.
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auto dc_length = TRY(get_next_symbol(scan.huffman_stream, dc_table));
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auto dc_length = TRY(scan.huffman_stream.next_symbol(dc_table));
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if (dc_length > 11) {
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dbgln_if(JPEG_DEBUG, "DC coefficient too long: {}!", dc_length);
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return Error::from_string_literal("DC coefficient too long");
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}
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// DC coefficients are encoded as the difference between previous and current DC values.
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i16 dc_diff = TRY(read_huffman_bits(scan.huffman_stream, dc_length));
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i16 dc_diff = TRY(scan.huffman_stream.read_bits(dc_length));
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// If MSB in diff is 0, the difference is -ve. Otherwise +ve.
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if (dc_length != 0 && dc_diff < (1 << (dc_length - 1)))
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@ -387,7 +450,7 @@ static ErrorOr<bool> read_eob(Scan& scan, u32 symbol)
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if (auto const eob = symbol & 0x0F; eob == 0 && symbol != JPEG_ZRL) {
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// We encountered an EOB marker
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auto const eob_base = symbol >> 4;
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auto const additional_value = TRY(read_huffman_bits(scan.huffman_stream, eob_base));
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auto const additional_value = TRY(scan.huffman_stream.read_bits(eob_base));
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scan.end_of_bands_run_count = additional_value + (1 << eob_base) - 1;
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@ -439,7 +502,7 @@ static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock,
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// number of zeroes to be stuffed before reading the coefficient. Low 4
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// bits represent the magnitude of the coefficient.
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if (!in_zrl && scan.end_of_bands_run_count == 0 && !saved_symbol.has_value()) {
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saved_symbol = TRY(get_next_symbol(scan.huffman_stream, ac_table));
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saved_symbol = TRY(scan.huffman_stream.next_symbol(ac_table));
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if (!TRY(read_eob(scan, *saved_symbol))) {
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to_skip = *saved_symbol >> 4;
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@ -453,7 +516,7 @@ static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock,
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if (!in_zrl && is_progressive(context.frame.type) && scan.successive_approximation_high != 0) {
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// G.1.2.3 - Coding model for subsequent scans of successive approximation
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// Bit sign from rule a
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saved_bit_for_rule_a = TRY(read_huffman_bits(scan.huffman_stream, 1));
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saved_bit_for_rule_a = TRY(scan.huffman_stream.read_bits(1));
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}
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}
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}
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@ -492,7 +555,7 @@ static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock,
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}
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if (coeff_length != 0) {
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i32 ac_coefficient = TRY(read_huffman_bits(scan.huffman_stream, coeff_length));
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i32 ac_coefficient = TRY(scan.huffman_stream.read_bits(coeff_length));
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if (ac_coefficient < (1 << (coeff_length - 1)))
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ac_coefficient -= (1 << coeff_length) - 1;
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@ -614,23 +677,17 @@ static ErrorOr<void> decode_huffman_stream(JPEGLoadingContext& context, Vector<M
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// Restart markers are stored in byte boundaries. Advance the huffman stream cursor to
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// the 0th bit of the next byte.
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if (huffman_stream.byte_offset < huffman_stream.stream.size()) {
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if (huffman_stream.bit_offset > 0) {
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huffman_stream.bit_offset = 0;
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huffman_stream.byte_offset++;
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}
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huffman_stream.advance_to_byte_boundary();
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// Skip the restart marker (RSTn).
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huffman_stream.byte_offset++;
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}
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// Skip the restart marker (RSTn).
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huffman_stream.skip_byte();
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}
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}
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if (auto result = build_macroblocks(context, macroblocks, hcursor, vcursor); result.is_error()) {
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if constexpr (JPEG_DEBUG) {
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dbgln("Failed to build Macroblock {}: {}", i, result.error());
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dbgln("Huffman stream byte offset {}", huffman_stream.byte_offset);
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dbgln("Huffman stream bit offset {}", huffman_stream.bit_offset);
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dbgln("Huffman stream byte offset {}", huffman_stream.byte_offset());
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}
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return result.release_error();
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}
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@ -720,7 +777,6 @@ static ErrorOr<void> read_start_of_scan(Stream& stream, JPEGLoadingContext& cont
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u8 const component_count = TRY(stream.read_value<u8>());
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Scan current_scan;
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current_scan.huffman_stream.stream.ensure_capacity(50 * KiB);
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Optional<u8> last_read;
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u8 component_read = 0;
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@ -775,6 +831,7 @@ static ErrorOr<void> read_start_of_scan(Stream& stream, JPEGLoadingContext& cont
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return Error::from_string_literal("Spectral selection is not [0,63] or successive approximation is not null");
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}
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current_scan.huffman_stream = TRY(HuffmanStream::create(*context.stream));
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context.current_scan = move(current_scan);
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return {};
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@ -1640,41 +1697,6 @@ static ErrorOr<void> parse_header(Stream& stream, JPEGLoadingContext& context)
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VERIFY_NOT_REACHED();
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}
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static ErrorOr<void> scan_huffman_stream(AK::SeekableStream& stream, HuffmanStream& huffman_stream)
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{
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u8 last_byte;
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u8 current_byte = TRY(stream.read_value<u8>());
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for (;;) {
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last_byte = current_byte;
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current_byte = TRY(stream.read_value<u8>());
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if (last_byte == 0xFF) {
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if (current_byte == 0xFF)
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continue;
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if (current_byte == 0x00) {
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current_byte = TRY(stream.read_value<u8>());
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huffman_stream.stream.append(last_byte);
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continue;
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}
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Marker marker = 0xFF00 | current_byte;
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if (marker >= JPEG_RST0 && marker <= JPEG_RST7) {
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huffman_stream.stream.append(marker);
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current_byte = TRY(stream.read_value<u8>());
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continue;
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}
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// Rollback the marker we just read
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TRY(stream.seek(-2, AK::SeekMode::FromCurrentPosition));
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return {};
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} else {
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huffman_stream.stream.append(last_byte);
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}
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}
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VERIFY_NOT_REACHED();
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}
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static ErrorOr<void> decode_header(JPEGLoadingContext& context)
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{
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if (context.state < JPEGLoadingContext::State::HeaderDecoded) {
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@ -1711,7 +1733,6 @@ static ErrorOr<Vector<Macroblock>> construct_macroblocks(JPEGLoadingContext& con
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TRY(handle_miscellaneous_or_table(*context.stream, context, marker));
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} else if (marker == JPEG_SOS) {
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TRY(read_start_of_scan(*context.stream, context));
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TRY(scan_huffman_stream(*context.stream, context.current_scan.huffman_stream));
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TRY(decode_huffman_stream(context, macroblocks));
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} else if (marker == JPEG_EOI) {
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return macroblocks;
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