1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
|
/*
* This file is part of NetSurf's LibNSGIF, http://www.netsurf-browser.org/
* Licensed under the MIT License,
* 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_
#define LZW_H_
/**
* \file
* \brief LZW decompression (interface)
*
* 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 */
LZW_OK_EOD, /**< Success; reached zero-length sub-block */
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.
*
* \param[out] ctx Returns an LZW decompression context. Caller owned,
* free with lzw_context_destroy().
* \return LZW_OK on success, or appropriate error code otherwise.
*/
lzw_result lzw_context_create(
struct lzw_ctx **ctx);
/**
* Destroy an LZW decompression context.
*
* \param[in] ctx The LZW decompression context to destroy.
*/
void lzw_context_destroy(
struct lzw_ctx *ctx);
/**
* Initialise an LZW decompression context for decoding.
*
* \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,
uint8_t minimum_code_size,
const uint8_t *input_data,
uint32_t input_length,
uint32_t input_pos);
/**
* 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.
*
* \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.
*
* 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 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_init_map(
struct lzw_ctx *ctx,
uint8_t minimum_code_size,
uint32_t transparency_idx,
const uint32_t *colour_table,
const uint8_t *input_data,
uint32_t input_length,
uint32_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
|
