106 lines
3.2 KiB
C
106 lines
3.2 KiB
C
/*
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* This file is part of NetSurf's LibNSGIF, http://www.netsurf-browser.org/
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* Licensed under the MIT License,
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* http://www.opensource.org/licenses/mit-license.php
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*
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* Copyright 2017 Michael Drake <michael.drake@codethink.co.uk>
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*/
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#ifndef LZW_H_
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#define LZW_H_
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/**
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* \file
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* \brief LZW decompression (interface)
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*
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* Decoder for GIF LZW data.
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*/
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/** Maximum LZW code size in bits */
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#define LZW_CODE_MAX 12
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/* Declare lzw internal context structure */
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struct lzw_ctx;
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/** LZW decoding response codes */
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typedef enum lzw_result {
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LZW_OK, /**< Success */
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LZW_OK_EOD, /**< Success; reached zero-length sub-block */
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LZW_NO_MEM, /**< Error: Out of memory */
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LZW_NO_DATA, /**< Error: Out of data */
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LZW_EOI_CODE, /**< Error: End of Information code */
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LZW_BAD_ICODE, /**< Error: Bad initial LZW code */
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LZW_BAD_CODE, /**< Error: Bad LZW code */
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} lzw_result;
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/**
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* Create an LZW decompression context.
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*
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* \param[out] ctx Returns an LZW decompression context. Caller owned,
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* free with lzw_context_destroy().
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* \return LZW_OK on success, or appropriate error code otherwise.
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*/
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lzw_result lzw_context_create(
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struct lzw_ctx **ctx);
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/**
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* Destroy an LZW decompression context.
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*
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* \param[in] ctx The LZW decompression context to destroy.
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*/
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void lzw_context_destroy(
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struct lzw_ctx *ctx);
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/**
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* Initialise an LZW decompression context for decoding.
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*
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* Caller owns neither `stack_base_out` or `stack_pos_out`.
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*
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* \param[in] ctx The LZW decompression context to initialise.
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* \param[in] compressed_data The compressed data.
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* \param[in] compressed_data_len Byte length of compressed data.
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* \param[in] compressed_data_pos Start position in data. Must be position
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* of a size byte at sub-block start.
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* \param[in] code_size The initial LZW code size to use.
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* \param[out] stack_base_out Returns base of decompressed data stack.
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* \param[out] stack_pos_out Returns current stack position.
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* There are `stack_pos_out - stack_base_out`
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* current stack entries.
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* \return LZW_OK on success, or appropriate error code otherwise.
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*/
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lzw_result lzw_decode_init(
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struct lzw_ctx *ctx,
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const uint8_t *compressed_data,
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uint32_t compressed_data_len,
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uint32_t compressed_data_pos,
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uint8_t code_size,
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const uint8_t ** const stack_base_out,
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const uint8_t ** const stack_pos_out);
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/**
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* Fill the LZW stack with decompressed data
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*
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* Ensure anything on the stack is used before calling this, as anything
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* on the stack before this call will be trampled.
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*
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* Caller does not own `stack_pos_out`.
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*
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* \param[in] ctx LZW reading context, updated.
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* \param[out] stack_pos_out Returns current stack position.
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* Use with `stack_base_out` value from previous
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* lzw_decode_init() call.
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* There are `stack_pos_out - stack_base_out`
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* current stack entries.
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* \return LZW_OK on success, or appropriate error code otherwise.
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*/
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lzw_result lzw_decode(
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struct lzw_ctx *ctx,
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const uint8_t ** const stack_pos_out);
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#endif
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