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
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
#ifndef AWS_COMPRESSION_HUFFMAN_H
#define AWS_COMPRESSION_HUFFMAN_H
/**
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0.
*/
#include <aws/compression/compression.h>
#include <aws/common/byte_buf.h>
AWS_PUSH_SANE_WARNING_LEVEL
/**
* Represents an encoded code
*/
struct aws_huffman_code {
/**
* The value of the code
* \note The pattern is stored in the least significant bits
*/
uint32_t pattern;
/** The number of bits in pattern to use */
uint8_t num_bits;
};
/**
* Function used to encode a single symbol to an aws_huffman_code
*
* \param[in] symbol The symbol to encode
* \param[in] userdata Optional userdata (aws_huffman_symbol_coder.userdata)
*
* \returns The code representing the symbol. If this symbol is not recognized,
* return a code with num_bits set to 0.
*/
typedef struct aws_huffman_code(aws_huffman_symbol_encoder_fn)(uint8_t symbol, void *userdata);
/**
* Function used to decode a code into a symbol
*
* \param[in] bits The bits to attept to decode a symbol from
* \param[out] symbol The symbol found. Do not write to if no valid symbol
* found \param[in] userdata Optional userdata
* (aws_huffman_symbol_coder.userdata)
*
* \returns The number of bits read from bits
*/
typedef uint8_t(aws_huffman_symbol_decoder_fn)(uint32_t bits, uint8_t *symbol, void *userdata);
/**
* Structure used to define how symbols are encoded and decoded
*/
struct aws_huffman_symbol_coder {
aws_huffman_symbol_encoder_fn *encode;
aws_huffman_symbol_decoder_fn *decode;
void *userdata;
};
/**
* Structure used for persistent encoding.
* Allows for reading from or writing to incomplete buffers.
*/
struct aws_huffman_encoder {
/* Params */
struct aws_huffman_symbol_coder *coder;
uint8_t eos_padding;
/* State */
struct aws_huffman_code overflow_bits;
};
/**
* Structure used for persistent decoding.
* Allows for reading from or writing to incomplete buffers.
*/
struct aws_huffman_decoder {
/* Param */
struct aws_huffman_symbol_coder *coder;
bool allow_growth;
/* State */
uint64_t working_bits;
uint8_t num_bits;
};
AWS_EXTERN_C_BEGIN
/**
* Initialize a encoder object with a symbol coder.
*/
AWS_COMPRESSION_API
void aws_huffman_encoder_init(struct aws_huffman_encoder *encoder, struct aws_huffman_symbol_coder *coder);
/**
* Resets a decoder for use with a new binary stream
*/
AWS_COMPRESSION_API
void aws_huffman_encoder_reset(struct aws_huffman_encoder *encoder);
/**
* Initialize a decoder object with a symbol coder.
*/
AWS_COMPRESSION_API
void aws_huffman_decoder_init(struct aws_huffman_decoder *decoder, struct aws_huffman_symbol_coder *coder);
/**
* Resets a decoder for use with a new binary stream
*/
AWS_COMPRESSION_API
void aws_huffman_decoder_reset(struct aws_huffman_decoder *decoder);
/**
* Get the byte length of to_encode post-encoding.
*
* \param[in] encoder The encoder object to use
* \param[in] to_encode The symbol buffer to encode
*
* \return The length of the encoded string.
*/
AWS_COMPRESSION_API
size_t aws_huffman_get_encoded_length(struct aws_huffman_encoder *encoder, struct aws_byte_cursor to_encode);
/**
* Encode a symbol buffer into the output buffer.
*
* \param[in] encoder The encoder object to use
* \param[in] to_encode The symbol buffer to encode
* \param[in] output The buffer to write encoded bytes to
*
* \return AWS_OP_SUCCESS if encoding is successful, AWS_OP_ERR otherwise
*/
AWS_COMPRESSION_API
int aws_huffman_encode(
struct aws_huffman_encoder *encoder,
struct aws_byte_cursor *to_encode,
struct aws_byte_buf *output);
/**
* Decodes a byte buffer into the provided symbol array.
*
* \param[in] decoder The decoder object to use
* \param[in] to_decode The encoded byte buffer to read from
* \param[in] output The buffer to write decoded symbols to.
* If decoder is set to allow growth, capacity will be increased when necessary.
*
* \return AWS_OP_SUCCESS if encoding is successful, AWS_OP_ERR otherwise
*/
AWS_COMPRESSION_API
int aws_huffman_decode(
struct aws_huffman_decoder *decoder,
struct aws_byte_cursor *to_decode,
struct aws_byte_buf *output);
/**
* Set whether or not to increase capacity when the output buffer fills up while decoding.
* This is false by default.
*/
AWS_COMPRESSION_API
void aws_huffman_decoder_allow_growth(struct aws_huffman_decoder *decoder, bool allow_growth);
AWS_EXTERN_C_END
AWS_POP_SANE_WARNING_LEVEL
#endif /* AWS_COMPRESSION_HUFFMAN_H */
|
