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
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
|
// SPDX-License-Identifier: LGPL-3.0-or-later
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <errno.h>
#include <string.h>
static ssize_t read_data(FILE *in, uint8_t **pdata) {
size_t alloc = 4096;
uint8_t *data = malloc(alloc);
if(!data) return -1;
size_t len = 0;
while(1) {
size_t n = fread_unlocked(data + len, 1, alloc - len, in);
if(n == 0) break;
len += n;
size_t want_min = len + (len >> 2);
if(alloc < want_min) {
size_t a2 = len + (len >> 1);
uint8_t *r = realloc(data, a2);
if(!r) goto fail;
data = r;
alloc = a2;
}
}
if(ferror_unlocked(in)) goto fail;
uint8_t *r = realloc(data, len);
if(r) data = r;
*pdata = data;
return len;
fail:;
int e = errno;
free(data);
errno = e;
return -1;
}
struct backref {
size_t cost;
uint8_t mlen, moff;
};
struct node {
size_t off, len;
struct node *next[256];
};
static void free_nodes(struct node **p) {
for(size_t i = 0; i < 256; i++) {
struct node *n = p[i];
if(!n) continue;
free_nodes(n->next);
free(n);
}
}
inline static void init_nodes(struct node **p) {
memset(p, 0, 256 * sizeof(*p));
}
static struct backref *compress_data(const uint8_t *data, size_t len) {
struct node *root[256];
init_nodes(root);
if(len >= (size_t)-1 / sizeof(struct backref) - 1) {
errno = ENOMEM;
return NULL;
}
struct backref *best = malloc((len + 1) * sizeof(struct backref));
if(!best) {
return NULL;
}
best[0] = (struct backref){
.cost = 0,
};
for(size_t suff_len = 1; suff_len <= len; suff_len++) {
size_t min_cost = best[suff_len - 1].cost + 9;
uint8_t min_mlen = 0;
uint8_t min_moff = 0;
size_t at = suff_len;
size_t bound = at < 256 ? 0 : at - 256;
struct node **p = root;
while(at > bound) {
size_t left = at - bound;
p += data[at - 1];
struct node *n = *p;
size_t mlen;
if(!n) {
n = calloc(1, sizeof(struct node));
if(!n) goto fail;
mlen = left;
*p = n;
} else {
assert(n->len > 0);
assert(n->off < at);
size_t moff = at - n->off;
if(moff > 256) {
free_nodes(n->next);
init_nodes(n->next);
mlen = left;
} else {
const uint8_t *cmp1 = data + at;
const uint8_t *cmp2 = data + n->off;
if(n->len < left) left = n->len;
mlen = 0;
while(mlen < left) {
if(*--cmp1 != *--cmp2) break;
mlen++;
}
assert(mlen > 0);
for(size_t i = mlen; i > 0; i--) {
size_t base = at - i;
size_t cost = best[base].cost + 17;
assert(suff_len - base <= 256);
if(cost < min_cost) {
assert(suff_len - base > 1);
min_cost = cost;
min_mlen = suff_len - base - 1;
min_moff = moff - 1;
}
}
if(mlen != n->len) {
n->len -= mlen;
n->off -= mlen;
struct node *n2 = calloc(1, sizeof(struct node));
if(!n2) goto fail;
n2->next[*cmp2] = n;
n = n2;
*p = n;
}
}
}
n->off = at;
n->len = mlen;
p = n->next;
at -= mlen;
}
best[suff_len] = (struct backref){
.cost = min_cost,
.mlen = min_mlen,
.moff = min_moff,
};
}
free_nodes(root);
return best;
fail:;
int e = errno;
free_nodes(root);
errno = e;
return NULL;
}
static int reconstruct(FILE *out, const uint8_t *data, size_t len, struct backref *back) {
size_t cost = back[len].cost;
size_t bytes = (cost + 7) / 8;
uint8_t *buf = malloc(bytes);
if(!buf) return -1;
uint8_t *at = buf + bytes;
uint8_t cmd = 0;
while(len) {
assert(cost == back[len].cost);
cmd <<= 1;
if(back[len].mlen == 0) {
cost -= 9;
*--at = data[--len];
} else {
cmd |= 1;
cost -= 17;
*--at = back[len].mlen;
*--at = back[len].moff;
len -= (size_t)back[len].mlen + 1;
}
if(cost % 8 == 0) {
*--at = cmd;
cmd = 0;
}
}
assert(cost == 0);
assert(at == buf);
at = buf;
while(bytes) {
size_t n = fwrite_unlocked(buf, 1, bytes, out);
if(n == 0) {
int e = errno;
free(buf);
errno = e;
return -1;
}
at += n;
bytes -= n;
}
free(buf);
return 0;
}
int main() {
uint8_t *data;
ssize_t n = read_data(stdin, &data);
if(n < 0) {
fprintf(stderr, "Read Error: %m\n");
return 1;
}
struct backref *best = compress_data(data, n);
int r = reconstruct(stdout, data, n, best);
if(r < 0) {
fprintf(stderr, "Write Error: %m\n");
return 1;
}
free(best);
free(data);
return 0;
}
|
