forked from madler/zlib
-
Notifications
You must be signed in to change notification settings - Fork 0
/
deflate_stored.c
187 lines (170 loc) · 8.23 KB
/
deflate_stored.c
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
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
/* deflate_stored.c -- store data without compression using deflation algorithm
*
* Copyright (C) 1995-2022 Jean-loup Gailly and Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*/
#include "zbuild.h"
#include "zutil.h"
#include "deflate.h"
#include "deflate_p.h"
#include "functable.h"
/* ===========================================================================
* Copy without compression as much as possible from the input stream, return
* the current block state.
*
* In case deflateParams() is used to later switch to a non-zero compression
* level, s->matches (otherwise unused when storing) keeps track of the number
* of hash table slides to perform. If s->matches is 1, then one hash table
* slide will be done when switching. If s->matches is 2, the maximum value
* allowed here, then the hash table will be cleared, since two or more slides
* is the same as a clear.
*
* deflate_stored() is written to minimize the number of times an input byte is
* copied. It is most efficient with large input and output buffers, which
* maximizes the opportunites to have a single copy from next_in to next_out.
*/
Z_INTERNAL block_state deflate_stored(deflate_state *s, int flush) {
/* Smallest worthy block size when not flushing or finishing. By default
* this is 32K. This can be as small as 507 bytes for memLevel == 1. For
* large input and output buffers, the stored block size will be larger.
*/
unsigned min_block = MIN(s->pending_buf_size - 5, s->w_size);
/* Copy as many min_block or larger stored blocks directly to next_out as
* possible. If flushing, copy the remaining available input to next_out as
* stored blocks, if there is enough space.
*/
unsigned len, left, have, last = 0;
unsigned used = s->strm->avail_in;
do {
/* Set len to the maximum size block that we can copy directly with the
* available input data and output space. Set left to how much of that
* would be copied from what's left in the window.
*/
len = MAX_STORED; /* maximum deflate stored block length */
have = (s->bi_valid + 42) >> 3; /* number of header bytes */
if (s->strm->avail_out < have) /* need room for header */
break;
/* maximum stored block length that will fit in avail_out: */
have = s->strm->avail_out - have;
left = (int)s->strstart - s->block_start; /* bytes left in window */
if (len > (unsigned long)left + s->strm->avail_in)
len = left + s->strm->avail_in; /* limit len to the input */
len = MIN(len, have); /* limit len to the output */
/* If the stored block would be less than min_block in length, or if
* unable to copy all of the available input when flushing, then try
* copying to the window and the pending buffer instead. Also don't
* write an empty block when flushing -- deflate() does that.
*/
if (len < min_block && ((len == 0 && flush != Z_FINISH) || flush == Z_NO_FLUSH || len != left + s->strm->avail_in))
break;
/* Make a dummy stored block in pending to get the header bytes,
* including any pending bits. This also updates the debugging counts.
*/
last = flush == Z_FINISH && len == left + s->strm->avail_in ? 1 : 0;
zng_tr_stored_block(s, (char *)0, 0L, last);
/* Replace the lengths in the dummy stored block with len. */
s->pending -= 4;
put_short(s, (uint16_t)len);
put_short(s, (uint16_t)~len);
/* Write the stored block header bytes. */
PREFIX(flush_pending)(s->strm);
/* Update debugging counts for the data about to be copied. */
cmpr_bits_add(s, len << 3);
sent_bits_add(s, len << 3);
/* Copy uncompressed bytes from the window to next_out. */
if (left) {
left = MIN(left, len);
memcpy(s->strm->next_out, s->window + s->block_start, left);
s->strm->next_out += left;
s->strm->avail_out -= left;
s->strm->total_out += left;
s->block_start += (int)left;
len -= left;
}
/* Copy uncompressed bytes directly from next_in to next_out, updating
* the check value.
*/
if (len) {
read_buf(s->strm, s->strm->next_out, len);
s->strm->next_out += len;
s->strm->avail_out -= len;
s->strm->total_out += len;
}
} while (last == 0);
/* Update the sliding window with the last s->w_size bytes of the copied
* data, or append all of the copied data to the existing window if less
* than s->w_size bytes were copied. Also update the number of bytes to
* insert in the hash tables, in the event that deflateParams() switches to
* a non-zero compression level.
*/
used -= s->strm->avail_in; /* number of input bytes directly copied */
if (used) {
/* If any input was used, then no unused input remains in the window,
* therefore s->block_start == s->strstart.
*/
if (used >= s->w_size) { /* supplant the previous history */
s->matches = 2; /* clear hash */
memcpy(s->window, s->strm->next_in - s->w_size, s->w_size);
s->strstart = s->w_size;
s->insert = s->strstart;
} else {
if (s->window_size - s->strstart <= used) {
/* Slide the window down. */
s->strstart -= s->w_size;
memcpy(s->window, s->window + s->w_size, s->strstart);
if (s->matches < 2)
s->matches++; /* add a pending slide_hash() */
s->insert = MIN(s->insert, s->strstart);
}
memcpy(s->window + s->strstart, s->strm->next_in - used, used);
s->strstart += used;
s->insert += MIN(used, s->w_size - s->insert);
}
s->block_start = (int)s->strstart;
}
s->high_water = MAX(s->high_water, s->strstart);
/* If the last block was written to next_out, then done. */
if (last)
return finish_done;
/* If flushing and all input has been consumed, then done. */
if (flush != Z_NO_FLUSH && flush != Z_FINISH && s->strm->avail_in == 0 && (int)s->strstart == s->block_start)
return block_done;
/* Fill the window with any remaining input. */
have = s->window_size - s->strstart;
if (s->strm->avail_in > have && s->block_start >= (int)s->w_size) {
/* Slide the window down. */
s->block_start -= (int)s->w_size;
s->strstart -= s->w_size;
memcpy(s->window, s->window + s->w_size, s->strstart);
if (s->matches < 2)
s->matches++; /* add a pending slide_hash() */
have += s->w_size; /* more space now */
s->insert = MIN(s->insert, s->strstart);
}
have = MIN(have, s->strm->avail_in);
if (have) {
read_buf(s->strm, s->window + s->strstart, have);
s->strstart += have;
s->insert += MIN(have, s->w_size - s->insert);
}
s->high_water = MAX(s->high_water, s->strstart);
/* There was not enough avail_out to write a complete worthy or flushed
* stored block to next_out. Write a stored block to pending instead, if we
* have enough input for a worthy block, or if flushing and there is enough
* room for the remaining input as a stored block in the pending buffer.
*/
have = (s->bi_valid + 42) >> 3; /* number of header bytes */
/* maximum stored block length that will fit in pending: */
have = MIN(s->pending_buf_size - have, MAX_STORED);
min_block = MIN(have, s->w_size);
left = (int)s->strstart - s->block_start;
if (left >= min_block || ((left || flush == Z_FINISH) && flush != Z_NO_FLUSH && s->strm->avail_in == 0 && left <= have)) {
len = MIN(left, have);
last = flush == Z_FINISH && s->strm->avail_in == 0 && len == left ? 1 : 0;
zng_tr_stored_block(s, (char *)s->window + s->block_start, len, last);
s->block_start += (int)len;
PREFIX(flush_pending)(s->strm);
}
/* We've done all we can with the available input and output. */
return last ? finish_started : need_more;
}