1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file delta_encoder.c
4 /// \brief Delta filter encoder
5 //
6 // Author: Lasse Collin
7 //
8 // This file has been put into the public domain.
9 // You can do whatever you want with this file.
10 //
11 ///////////////////////////////////////////////////////////////////////////////
12
13 #include "delta_encoder.h"
14 #include "delta_private.h"
15
16
17 /// Copies and encodes the data at the same time. This is used when Delta
18 /// is the first filter in the chain (and thus the last filter in the
19 /// encoder's filter stack).
20 static void
copy_and_encode(lzma_delta_coder * coder,const uint8_t * restrict in,uint8_t * restrict out,size_t size)21 copy_and_encode(lzma_delta_coder *coder,
22 const uint8_t *restrict in, uint8_t *restrict out, size_t size)
23 {
24 const size_t distance = coder->distance;
25
26 for (size_t i = 0; i < size; ++i) {
27 const uint8_t tmp = coder->history[
28 (distance + coder->pos) & 0xFF];
29 coder->history[coder->pos-- & 0xFF] = in[i];
30 out[i] = in[i] - tmp;
31 }
32 }
33
34
35 /// Encodes the data in place. This is used when we are the last filter
36 /// in the chain (and thus non-last filter in the encoder's filter stack).
37 static void
encode_in_place(lzma_delta_coder * coder,uint8_t * buffer,size_t size)38 encode_in_place(lzma_delta_coder *coder, uint8_t *buffer, size_t size)
39 {
40 const size_t distance = coder->distance;
41
42 for (size_t i = 0; i < size; ++i) {
43 const uint8_t tmp = coder->history[
44 (distance + coder->pos) & 0xFF];
45 coder->history[coder->pos-- & 0xFF] = buffer[i];
46 buffer[i] -= tmp;
47 }
48 }
49
50
51 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)52 delta_encode(void *coder_ptr, const lzma_allocator *allocator,
53 const uint8_t *restrict in, size_t *restrict in_pos,
54 size_t in_size, uint8_t *restrict out,
55 size_t *restrict out_pos, size_t out_size, lzma_action action)
56 {
57 lzma_delta_coder *coder = coder_ptr;
58
59 lzma_ret ret;
60
61 if (coder->next.code == NULL) {
62 const size_t in_avail = in_size - *in_pos;
63 const size_t out_avail = out_size - *out_pos;
64 const size_t size = my_min(in_avail, out_avail);
65
66 copy_and_encode(coder, in + *in_pos, out + *out_pos, size);
67
68 *in_pos += size;
69 *out_pos += size;
70
71 ret = action != LZMA_RUN && *in_pos == in_size
72 ? LZMA_STREAM_END : LZMA_OK;
73
74 } else {
75 const size_t out_start = *out_pos;
76
77 ret = coder->next.code(coder->next.coder, allocator,
78 in, in_pos, in_size, out, out_pos, out_size,
79 action);
80
81 encode_in_place(coder, out + out_start, *out_pos - out_start);
82 }
83
84 return ret;
85 }
86
87
88 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)89 delta_encoder_update(void *coder_ptr, const lzma_allocator *allocator,
90 const lzma_filter *filters_null lzma_attribute((__unused__)),
91 const lzma_filter *reversed_filters)
92 {
93 lzma_delta_coder *coder = coder_ptr;
94
95 // Delta doesn't and will never support changing the options in
96 // the middle of encoding. If the app tries to change them, we
97 // simply ignore them.
98 return lzma_next_filter_update(
99 &coder->next, allocator, reversed_filters + 1);
100 }
101
102
103 extern lzma_ret
lzma_delta_encoder_init(lzma_next_coder * next,const lzma_allocator * allocator,const lzma_filter_info * filters)104 lzma_delta_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
105 const lzma_filter_info *filters)
106 {
107 next->code = &delta_encode;
108 next->update = &delta_encoder_update;
109 return lzma_delta_coder_init(next, allocator, filters);
110 }
111
112
113 extern lzma_ret
lzma_delta_props_encode(const void * options,uint8_t * out)114 lzma_delta_props_encode(const void *options, uint8_t *out)
115 {
116 // The caller must have already validated the options, so it's
117 // LZMA_PROG_ERROR if they are invalid.
118 if (lzma_delta_coder_memusage(options) == UINT64_MAX)
119 return LZMA_PROG_ERROR;
120
121 const lzma_options_delta *opt = options;
122 out[0] = opt->dist - LZMA_DELTA_DIST_MIN;
123
124 return LZMA_OK;
125 }
126