1 // SPDX-License-Identifier: 0BSD
2
3 ///////////////////////////////////////////////////////////////////////////////
4 //
5 /// \file delta_encoder.c
6 /// \brief Delta filter encoder
7 //
8 // Author: Lasse Collin
9 //
10 ///////////////////////////////////////////////////////////////////////////////
11
12 #include "delta_encoder.h"
13 #include "delta_private.h"
14
15
16 /// Copies and encodes the data at the same time. This is used when Delta
17 /// is the first filter in the chain (and thus the last filter in the
18 /// encoder's filter stack).
19 static void
copy_and_encode(lzma_delta_coder * coder,const uint8_t * restrict in,uint8_t * restrict out,size_t size)20 copy_and_encode(lzma_delta_coder *coder,
21 const uint8_t *restrict in, uint8_t *restrict out, size_t size)
22 {
23 const size_t distance = coder->distance;
24
25 for (size_t i = 0; i < size; ++i) {
26 const uint8_t tmp = coder->history[
27 (distance + coder->pos) & 0xFF];
28 coder->history[coder->pos-- & 0xFF] = in[i];
29 out[i] = in[i] - tmp;
30 }
31 }
32
33
34 /// Encodes the data in place. This is used when we are the last filter
35 /// in the chain (and thus non-last filter in the encoder's filter stack).
36 static void
encode_in_place(lzma_delta_coder * coder,uint8_t * buffer,size_t size)37 encode_in_place(lzma_delta_coder *coder, uint8_t *buffer, size_t size)
38 {
39 const size_t distance = coder->distance;
40
41 for (size_t i = 0; i < size; ++i) {
42 const uint8_t tmp = coder->history[
43 (distance + coder->pos) & 0xFF];
44 coder->history[coder->pos-- & 0xFF] = buffer[i];
45 buffer[i] -= tmp;
46 }
47 }
48
49
50 static lzma_ret
delta_encode(void * coder_ptr,const lzma_allocator * allocator,const uint8_t * restrict in,size_t * restrict in_pos,size_t in_size,uint8_t * restrict out,size_t * restrict out_pos,size_t out_size,lzma_action action)51 delta_encode(void *coder_ptr, const lzma_allocator *allocator,
52 const uint8_t *restrict in, size_t *restrict in_pos,
53 size_t in_size, uint8_t *restrict out,
54 size_t *restrict out_pos, size_t out_size, lzma_action action)
55 {
56 lzma_delta_coder *coder = coder_ptr;
57
58 lzma_ret ret;
59
60 if (coder->next.code == NULL) {
61 const size_t in_avail = in_size - *in_pos;
62 const size_t out_avail = out_size - *out_pos;
63 const size_t size = my_min(in_avail, out_avail);
64
65 // in and out might be NULL. In such cases size == 0.
66 // Null pointer + 0 is undefined behavior so skip
67 // the call in that case as it would do nothing anyway.
68 if (size > 0)
69 copy_and_encode(coder, in + *in_pos, out + *out_pos,
70 size);
71
72 *in_pos += size;
73 *out_pos += size;
74
75 ret = action != LZMA_RUN && *in_pos == in_size
76 ? LZMA_STREAM_END : LZMA_OK;
77
78 } else {
79 const size_t out_start = *out_pos;
80
81 ret = coder->next.code(coder->next.coder, allocator,
82 in, in_pos, in_size, out, out_pos, out_size,
83 action);
84
85 // Like above, avoid null pointer + 0.
86 const size_t size = *out_pos - out_start;
87 if (size > 0)
88 encode_in_place(coder, out + out_start, size);
89 }
90
91 return ret;
92 }
93
94
95 static lzma_ret
delta_encoder_update(void * coder_ptr,const lzma_allocator * allocator,const lzma_filter * filters_null lzma_attribute ((__unused__)),const lzma_filter * reversed_filters)96 delta_encoder_update(void *coder_ptr, const lzma_allocator *allocator,
97 const lzma_filter *filters_null lzma_attribute((__unused__)),
98 const lzma_filter *reversed_filters)
99 {
100 lzma_delta_coder *coder = coder_ptr;
101
102 // Delta doesn't and will never support changing the options in
103 // the middle of encoding. If the app tries to change them, we
104 // simply ignore them.
105 return lzma_next_filter_update(
106 &coder->next, allocator, reversed_filters + 1);
107 }
108
109
110 extern lzma_ret
lzma_delta_encoder_init(lzma_next_coder * next,const lzma_allocator * allocator,const lzma_filter_info * filters)111 lzma_delta_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
112 const lzma_filter_info *filters)
113 {
114 next->code = &delta_encode;
115 next->update = &delta_encoder_update;
116 return lzma_delta_coder_init(next, allocator, filters);
117 }
118
119
120 extern lzma_ret
lzma_delta_props_encode(const void * options,uint8_t * out)121 lzma_delta_props_encode(const void *options, uint8_t *out)
122 {
123 // The caller must have already validated the options, so it's
124 // LZMA_PROG_ERROR if they are invalid.
125 if (lzma_delta_coder_memusage(options) == UINT64_MAX)
126 return LZMA_PROG_ERROR;
127
128 const lzma_options_delta *opt = options;
129 out[0] = opt->dist - LZMA_DELTA_DIST_MIN;
130
131 return LZMA_OK;
132 }
133