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zrle.c (5726B)
1
2 #include "libsheepyObject.h"
3 #include "zrle.h"
4
5 zrlebuft zrle(void *buf, size_t len) {
6 zrlebuft r;
7
8 // allocate compressed buffer, twice bigger than b
9 // initialize state
10 // copy bytes
11 // replace anchors with 0xfc+anchor
12 // copy
13 // zero is found, count zeros
14 // check for buffer overflow, error when overflow
15 // zero is found again, count zeros
16 // check if the zero count exceeds the max count (0xfb)
17 // zero count exceeded max, write 0xfc 0xfb in compressed buffer and start a new zero count
18 // non zero is found
19 // when count is less 3, write 0 in compressed buffer
20 // when count is 3, write 0xfe in compressed buffer
21 // when count is 7, write 0xfd in compressed buffer
22 // write 0xfc zcount-4 in compressed buffer
23 // copy byte
24 // when state is ZCOUNT at the end, write last zero string
25 // realloc to fit compress buffer size to data
26
27 if (!buf || len < 3) {
28 // buffer too small
29 r.buf = NULL;
30 return r;
31 }
32
33 u8 *b = buf;
34
35 // allocate compressed buffer, twice bigger than b
36 // (compressed buffer should be smaller than source)
37 r.buf = malloc(len*2);
38
39 // initialize state
40 enum {COPY, ZCOUNT};
41 u8 state = COPY;
42
43 // offset of first zero in b in current zero string
44 u32 src;
45 // offset in compressed buffer
46 u32 dst = 0;
47 // zero count in current zero string
48 u8 zcount;
49 range(i, len) {
50 if (state == ZCOUNT) {
51 if (!b[i]) {
52 // zero is found again, count zeros
53 zcount++;
54 // check if the zero count exceeds the max count (0xfb)
55 if (zcount-4 == 0xfc) {
56 // zero count exceeded max, write 0xfc 0xfb in compressed buffer and start a new zero count
57 r.buf[dst++] = 0xfc;
58 r.buf[dst++] = 0xfb;
59 zcount = 1;
60 }
61 goto next;
62 }
63 else {
64 // when count is less 3, write 0 in compressed buffer
65 if (zcount < 3) {
66 range(j, zcount)
67 r.buf[dst++] = 0;
68 }
69 // when count is 3, write 0xfe in compressed buffer
70 else if (zcount == 3)
71 r.buf[dst++] = 0xfe;
72 // when count is 7, write 0xfd in compressed buffer
73 else if (zcount == 7)
74 r.buf[dst++] = 0xfd;
75 // write 0xfc zcount-4 in compressed buffer
76 else {
77 r.buf[dst++] = 0xfc;
78 r.buf[dst++] = zcount-4;
79 }
80 // copy byte
81 r.buf[dst++] = b[i];
82 state = COPY;
83 goto next;
84 }
85 }
86 if (state == COPY) {
87 // copy bytes
88 if (b[i]) {
89 switch (b[i]) {
90 case 0xfe:
91 case 0xfd:
92 case 0xfc:
93 // replace anchors with 0xfc+anchor
94 r.buf[dst++] = 0xfc;
95 r.buf[dst++] = b[i];
96 break;
97 default:
98 // copy
99 r.buf[dst++] = b[i];
100 }
101 }
102 else {
103 // zero is found, count zeros
104 zcount = 1;
105 src = i;
106 state = ZCOUNT;
107 }
108 }
109
110 next:
111 // check for buffer overflow
112 if (dst > 2*len-2) {
113 // end of buffer - stop error
114 free(r.buf);
115 r.buf = NULL;
116 break;
117 }
118 }
119
120 // when state is ZCOUNT at the end, write last zero string
121 if (state == ZCOUNT) {
122 // when count is less 3, write 0 in compressed buffer
123 if (zcount < 3) {
124 range(j, zcount)
125 r.buf[dst++] = 0;
126 }
127 // when count is 3, write 0xfe in compressed buffer
128 else if (zcount == 3)
129 r.buf[dst++] = 0xfe;
130 // when count is 7, write 0xfd in compressed buffer
131 else if (zcount == 7)
132 r.buf[dst++] = 0xfd;
133 // write 0xfc zcount-4 in compressed buffer
134 else {
135 r.buf[dst++] = 0xfc;
136 r.buf[dst++] = zcount-4;
137 }
138 }
139
140 r.count = dst;
141 // realloc to fit compress buffer size to data
142 r.buf = realloc(r.buf, dst);
143
144 return r;
145 }
146
147 zrlebuft dezrle(void *buf, size_t len) {
148 zrlebuft r;
149
150 // initialize state
151 // not an anchor, copy byte
152 // expand anchors
153 // reallocate when there is buffer overflow
154 // when count >= 0xfc, copy count as a byte
155 // check for buffer overflow when expanding
156 // realloc to fit buffer size to data
157
158 // initialize state
159 u8 *b = buf;
160 r.buf = malloc(len*2);
161 u32 blen = len*2;
162 u32 dst = 0;
163 enum {COPY, EXPAND};
164 u8 state = COPY;
165
166 range(i, len) {
167 // expand anchors
168 if (state == EXPAND) {
169 // when count >= 0xfc, copy count as a byte
170 if (b[i] >= 0xfc)
171 r.buf[dst++] = b[i];
172 else {
173 // check for buffer overflow when expanding
174 if (dst+(u16)(b[i])+4 >= blen) {
175 r.buf = realloc(r.buf, 2*blen + (u16)(b[i])+4);
176 blen = 2*blen + (u16)(b[i])+4;
177 }
178 range(j, (u16)(b[i])+4)
179 r.buf[dst++] = 0;
180 }
181 state = COPY;
182 goto next;
183 }
184 // not an anchor, copy byte
185 if ((b[i] != 0xfe) and (b[i] != 0xfd) and (b[i] != 0xfc)) {
186 r.buf[dst++] = b[i];
187 }
188 // expand anchors
189 if (b[i] == 0xfe) {
190 if (dst+3 >= blen) {
191 r.buf = realloc(r.buf, 2*blen + 3);
192 blen = 2*blen + 3;
193 }
194 range(j, 3)
195 r.buf[dst++] = 0;
196 }
197 if (b[i] == 0xfd) {
198 if (dst+7 >= blen) {
199 r.buf = realloc(r.buf, 2*blen + 7);
200 blen = 2*blen + 7;
201 }
202 range(j, 7)
203 r.buf[dst++] = 0;
204 }
205 if (b[i] == 0xfc) {
206 state = EXPAND;
207 }
208 next:
209 // reallocate when there is buffer overflow
210 if (dst >= blen) {
211 r.buf = realloc(r.buf, 2*blen);
212 blen = 2*blen;
213 }
214 }
215
216 r.count = dst;
217 // realloc to fit buffer size to data
218 r.buf = realloc(r.buf, dst);
219
220 return r;
221 }
222
223 bool checkLibsheepyVersionZrle(const char *currentLibsheepyVersion) {
224 return eqG(currentLibsheepyVersion, LIBSHEEPY_VERSION);
225 }
226