diff options
Diffstat (limited to 'src/lzw.h')
| -rw-r--r-- | src/lzw.h | 100 |
1 files changed, 66 insertions, 34 deletions
@@ -4,6 +4,7 @@ * http://www.opensource.org/licenses/mit-license.php * * Copyright 2017 Michael Drake <michael.drake@codethink.co.uk> + * Copyright 2021 Michael Drake <tlsa@netsurf-browser.org> */ #ifndef LZW_H_ @@ -16,15 +17,12 @@ * Decoder for GIF LZW data. */ - /** Maximum LZW code size in bits */ #define LZW_CODE_MAX 12 - /* Declare lzw internal context structure */ struct lzw_ctx; - /** LZW decoding response codes */ typedef enum lzw_result { LZW_OK, /**< Success */ @@ -32,11 +30,12 @@ typedef enum lzw_result { LZW_NO_MEM, /**< Error: Out of memory */ LZW_NO_DATA, /**< Error: Out of data */ LZW_EOI_CODE, /**< Error: End of Information code */ + LZW_NO_COLOUR, /**< Error: No colour map provided. */ LZW_BAD_ICODE, /**< Error: Bad initial LZW code */ + LZW_BAD_PARAM, /**< Error: Bad function parameter. */ LZW_BAD_CODE, /**< Error: Bad LZW code */ } lzw_result; - /** * Create an LZW decompression context. * @@ -58,48 +57,81 @@ void lzw_context_destroy( /** * Initialise an LZW decompression context for decoding. * - * Caller owns neither `stack_base_out` or `stack_pos_out`. - * - * \param[in] ctx The LZW decompression context to initialise. - * \param[in] compressed_data The compressed data. - * \param[in] compressed_data_len Byte length of compressed data. - * \param[in] compressed_data_pos Start position in data. Must be position - * of a size byte at sub-block start. - * \param[in] code_size The initial LZW code size to use. - * \param[out] stack_base_out Returns base of decompressed data stack. - * \param[out] stack_pos_out Returns current stack position. - * There are `stack_pos_out - stack_base_out` - * current stack entries. + * \param[in] ctx The LZW decompression context to initialise. + * \param[in] minimum_code_size The LZW Minimum Code Size. + * \param[in] input_data The compressed data. + * \param[in] input_length Byte length of compressed data. + * \param[in] input_pos Start position in data. Must be position + * of a size byte at sub-block start. * \return LZW_OK on success, or appropriate error code otherwise. */ lzw_result lzw_decode_init( struct lzw_ctx *ctx, - const uint8_t *compressed_data, - uint32_t compressed_data_len, - uint32_t compressed_data_pos, - uint8_t code_size, - const uint8_t ** const stack_base_out, - const uint8_t ** const stack_pos_out); + uint8_t minimum_code_size, + const uint8_t *input_data, + size_t input_length, + size_t input_pos); /** - * Fill the LZW stack with decompressed data + * Read input codes until end of LZW context owned output buffer. + * + * Ensure anything in output is used before calling this, as anything + * there before this call will be trampled. * - * Ensure anything on the stack is used before calling this, as anything - * on the stack before this call will be trampled. + * \param[in] ctx LZW reading context, updated. + * \param[out] output_data Returns pointer to array of output values. + * \param[out] output_written Returns the number of values written to data. + * \return LZW_OK on success, or appropriate error code otherwise. + */ +lzw_result lzw_decode(struct lzw_ctx *ctx, + const uint8_t *restrict *const restrict output_data, + uint32_t *restrict output_written); + +/** + * Initialise an LZW decompression context for decoding to colour map values. * - * Caller does not own `stack_pos_out`. + * For transparency to work correctly, the given client buffer must have + * the values from the previous frame. The transparency_idx should be a value + * of 256 or above, if the frame does not have transparency. * - * \param[in] ctx LZW reading context, updated. - * \param[out] stack_pos_out Returns current stack position. - * Use with `stack_base_out` value from previous - * lzw_decode_init() call. - * There are `stack_pos_out - stack_base_out` - * current stack entries. + * \param[in] ctx The LZW decompression context to initialise. + * \param[in] minimum_code_size The LZW Minimum Code Size. + * \param[in] transparency_idx Index representing transparency. + * \param[in] colour_table Index to pixel colour mapping. + * \param[in] input_data The compressed data. + * \param[in] input_length Byte length of compressed data. + * \param[in] input_pos Start position in data. Must be position + * of a size byte at sub-block start. * \return LZW_OK on success, or appropriate error code otherwise. */ -lzw_result lzw_decode( +lzw_result lzw_decode_init_map( struct lzw_ctx *ctx, - const uint8_t ** const stack_pos_out); + uint8_t minimum_code_size, + uint32_t transparency_idx, + const uint32_t *colour_table, + const uint8_t *input_data, + size_t input_length, + size_t input_pos); +/** + * Read LZW codes into client buffer, mapping output to colours. + * + * The context must have been initialised using \ref lzw_decode_init_map + * before calling this function, in order to provide the colour mapping table + * and any transparency index. + * + * Ensure anything in output is used before calling this, as anything + * there before this call will be trampled. + * + * \param[in] ctx LZW reading context, updated. + * \param[in] output_data Client buffer to fill with colour mapped values. + * \param[in] output_length Size of output array. + * \param[out] output_written Returns the number of values written to data. + * \return LZW_OK on success, or appropriate error code otherwise. + */ +lzw_result lzw_decode_map(struct lzw_ctx *ctx, + uint32_t *restrict output_data, + uint32_t output_length, + uint32_t *restrict output_written); #endif |