summaryrefslogtreecommitdiff
path: root/win32/zlib/contrib/blast/blast.c
blob: 69ef0fe00e8d883539e88596dadd4ba51e2a5704 (plain)
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
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
/* blast.c
 * Copyright (C) 2003, 2012 Mark Adler
 * For conditions of distribution and use, see copyright notice in blast.h
 * version 1.2, 24 Oct 2012
 *
 * blast.c decompresses data compressed by the PKWare Compression Library.
 * This function provides functionality similar to the explode() function of
 * the PKWare library, hence the name "blast".
 *
 * This decompressor is based on the excellent format description provided by
 * Ben Rudiak-Gould in comp.compression on August 13, 2001.  Interestingly, the
 * example Ben provided in the post is incorrect.  The distance 110001 should
 * instead be 111000.  When corrected, the example byte stream becomes:
 *
 *    00 04 82 24 25 8f 80 7f
 *
 * which decompresses to "AIAIAIAIAIAIA" (without the quotes).
 */

/*
 * Change history:
 *
 * 1.0  12 Feb 2003     - First version
 * 1.1  16 Feb 2003     - Fixed distance check for > 4 GB uncompressed data
 * 1.2  24 Oct 2012     - Add note about using binary mode in stdio
 *                      - Fix comparisons of differently signed integers
 */

#include <setjmp.h>             /* for setjmp(), longjmp(), and jmp_buf */
#include "blast.h"              /* prototype for blast() */

#define local static            /* for local function definitions */
#define MAXBITS 13              /* maximum code length */
#define MAXWIN 4096             /* maximum window size */

/* input and output state */
struct state {
    /* input state */
    blast_in infun;             /* input function provided by user */
    void *inhow;                /* opaque information passed to infun() */
    unsigned char *in;          /* next input location */
    unsigned left;              /* available input at in */
    int bitbuf;                 /* bit buffer */
    int bitcnt;                 /* number of bits in bit buffer */

    /* input limit error return state for bits() and decode() */
    jmp_buf env;

    /* output state */
    blast_out outfun;           /* output function provided by user */
    void *outhow;               /* opaque information passed to outfun() */
    unsigned next;              /* index of next write location in out[] */
    int first;                  /* true to check distances (for first 4K) */
    unsigned char out[MAXWIN];  /* output buffer and sliding window */
};

/*
 * Return need bits from the input stream.  This always leaves less than
 * eight bits in the buffer.  bits() works properly for need == 0.
 *
 * Format notes:
 *
 * - Bits are stored in bytes from the least significant bit to the most
 *   significant bit.  Therefore bits are dropped from the bottom of the bit
 *   buffer, using shift right, and new bytes are appended to the top of the
 *   bit buffer, using shift left.
 */
local int bits(struct state *s, int need)
{
    int val;            /* bit accumulator */

    /* load at least need bits into val */
    val = s->bitbuf;
    while (s->bitcnt < need) {
        if (s->left == 0) {
            s->left = s->infun(s->inhow, &(s->in));
            if (s->left == 0) longjmp(s->env, 1);       /* out of input */
        }
        val |= (int)(*(s->in)++) << s->bitcnt;          /* load eight bits */
        s->left--;
        s->bitcnt += 8;
    }

    /* drop need bits and update buffer, always zero to seven bits left */
    s->bitbuf = val >> need;
    s->bitcnt -= need;

    /* return need bits, zeroing the bits above that */
    return val & ((1 << need) - 1);
}

/*
 * Huffman code decoding tables.  count[1..MAXBITS] is the number of symbols of
 * each length, which for a canonical code are stepped through in order.
 * symbol[] are the symbol values in canonical order, where the number of
 * entries is the sum of the counts in count[].  The decoding process can be
 * seen in the function decode() below.
 */
struct huffman {
    short *count;       /* number of symbols of each length */
    short *symbol;      /* canonically ordered symbols */
};

/*
 * Decode a code from the stream s using huffman table h.  Return the symbol or
 * a negative value if there is an error.  If all of the lengths are zero, i.e.
 * an empty code, or if the code is incomplete and an invalid code is received,
 * then -9 is returned after reading MAXBITS bits.
 *
 * Format notes:
 *
 * - The codes as stored in the compressed data are bit-reversed relative to
 *   a simple integer ordering of codes of the same lengths.  Hence below the
 *   bits are pulled from the compressed data one at a time and used to
 *   build the code value reversed from what is in the stream in order to
 *   permit simple integer comparisons for decoding.
 *
 * - The first code for the shortest length is all ones.  Subsequent codes of
 *   the same length are simply integer decrements of the previous code.  When
 *   moving up a length, a one bit is appended to the code.  For a complete
 *   code, the last code of the longest length will be all zeros.  To support
 *   this ordering, the bits pulled during decoding are inverted to apply the
 *   more "natural" ordering starting with all zeros and incrementing.
 */
local int decode(struct state *s, struct huffman *h)
{
    int len;            /* current number of bits in code */
    int code;           /* len bits being decoded */
    int first;          /* first code of length len */
    int count;          /* number of codes of length len */
    int index;          /* index of first code of length len in symbol table */
    int bitbuf;         /* bits from stream */
    int left;           /* bits left in next or left to process */
    short *next;        /* next number of codes */

    bitbuf = s->bitbuf;
    left = s->bitcnt;
    code = first = index = 0;
    len = 1;
    next = h->count + 1;
    while (1) {
        while (left--) {
            code |= (bitbuf & 1) ^ 1;   /* invert code */
            bitbuf >>= 1;
            count = *next++;
            if (code < first + count) { /* if length len, return symbol */
                s->bitbuf = bitbuf;
                s->bitcnt = (s->bitcnt - len) & 7;
                return h->symbol[index + (code - first)];
            }
            index += count;             /* else update for next length */
            first += count;
            first <<= 1;
            code <<= 1;
            len++;
        }
        left = (MAXBITS+1) - len;
        if (left == 0) break;
        if (s->left == 0) {
            s->left = s->infun(s->inhow, &(s->in));
            if (s->left == 0) longjmp(s->env, 1);       /* out of input */
        }
        bitbuf = *(s->in)++;
        s->left--;
        if (left > 8) left = 8;
    }
    return -9;                          /* ran out of codes */
}

/*
 * Given a list of repeated code lengths rep[0..n-1], where each byte is a
 * count (high four bits + 1) and a code length (low four bits), generate the
 * list of code lengths.  This compaction reduces the size of the object code.
 * Then given the list of code lengths length[0..n-1] representing a canonical
 * Huffman code for n symbols, construct the tables required to decode those
 * codes.  Those tables are the number of codes of each length, and the symbols
 * sorted by length, retaining their original order within each length.  The
 * return value is zero for a complete code set, negative for an over-
 * subscribed code set, and positive for an incomplete code set.  The tables
 * can be used if the return value is zero or positive, but they cannot be used
 * if the return value is negative.  If the return value is zero, it is not
 * possible for decode() using that table to return an error--any stream of
 * enough bits will resolve to a symbol.  If the return value is positive, then
 * it is possible for decode() using that table to return an error for received
 * codes past the end of the incomplete lengths.
 */
local int construct(struct huffman *h, const unsigned char *rep, int n)
{
    int symbol;         /* current symbol when stepping through length[] */
    int len;            /* current length when stepping through h->count[] */
    int left;           /* number of possible codes left of current length */
    short offs[MAXBITS+1];      /* offsets in symbol table for each length */
    short length[256];  /* code lengths */

    /* convert compact repeat counts into symbol bit length list */
    symbol = 0;
    do {
        len = *rep++;
        left = (len >> 4) + 1;
        len &= 15;
        do {
            length[symbol++] = len;
        } while (--left);
    } while (--n);
    n = symbol;

    /* count number of codes of each length */
    for (len = 0; len <= MAXBITS; len++)
        h->count[len] = 0;
    for (symbol = 0; symbol < n; symbol++)
        (h->count[length[symbol]])++;   /* assumes lengths are within bounds */
    if (h->count[0] == n)               /* no codes! */
        return 0;                       /* complete, but decode() will fail */

    /* check for an over-subscribed or incomplete set of lengths */
    left = 1;                           /* one possible code of zero length */
    for (len = 1; len <= MAXBITS; len++) {
        left <<= 1;                     /* one more bit, double codes left */
        left -= h->count[len];          /* deduct count from possible codes */
        if (left < 0) return left;      /* over-subscribed--return negative */
    }                                   /* left > 0 means incomplete */

    /* generate offsets into symbol table for each length for sorting */
    offs[1] = 0;
    for (len = 1; len < MAXBITS; len++)
        offs[len + 1] = offs[len] + h->count[len];

    /*
     * put symbols in table sorted by length, by symbol order within each
     * length
     */
    for (symbol = 0; symbol < n; symbol++)
        if (length[symbol] != 0)
            h->symbol[offs[length[symbol]]++] = symbol;

    /* return zero for complete set, positive for incomplete set */
    return left;
}

/*
 * Decode PKWare Compression Library stream.
 *
 * Format notes:
 *
 * - First byte is 0 if literals are uncoded or 1 if they are coded.  Second
 *   byte is 4, 5, or 6 for the number of extra bits in the distance code.
 *   This is the base-2 logarithm of the dictionary size minus six.
 *
 * - Compressed data is a combination of literals and length/distance pairs
 *   terminated by an end code.  Literals are either Huffman coded or
 *   uncoded bytes.  A length/distance pair is a coded length followed by a
 *   coded distance to represent a string that occurs earlier in the
 *   uncompressed data that occurs again at the current location.
 *
 * - A bit preceding a literal or length/distance pair indicates which comes
 *   next, 0 for literals, 1 for length/distance.
 *
 * - If literals are uncoded, then the next eight bits are the literal, in the
 *   normal bit order in th stream, i.e. no bit-reversal is needed. Similarly,
 *   no bit reversal is needed for either the length extra bits or the distance
 *   extra bits.
 *
 * - Literal bytes are simply written to the output.  A length/distance pair is
 *   an instruction to copy previously uncompressed bytes to the output.  The
 *   copy is from distance bytes back in the output stream, copying for length
 *   bytes.
 *
 * - Distances pointing before the beginning of the output data are not
 *   permitted.
 *
 * - Overlapped copies, where the length is greater than the distance, are
 *   allowed and common.  For example, a distance of one and a length of 518
 *   simply copies the last byte 518 times.  A distance of four and a length of
 *   twelve copies the last four bytes three times.  A simple forward copy
 *   ignoring whether the length is greater than the distance or not implements
 *   this correctly.
 */
local int decomp(struct state *s)
{
    int lit;            /* true if literals are coded */
    int dict;           /* log2(dictionary size) - 6 */
    int symbol;         /* decoded symbol, extra bits for distance */
    int len;            /* length for copy */
    unsigned dist;      /* distance for copy */
    int copy;           /* copy counter */
    unsigned char *from, *to;   /* copy pointers */
    static int virgin = 1;                              /* build tables once */
    static short litcnt[MAXBITS+1], litsym[256];        /* litcode memory */
    static short lencnt[MAXBITS+1], lensym[16];         /* lencode memory */
    static short distcnt[MAXBITS+1], distsym[64];       /* distcode memory */
    static struct huffman litcode = {litcnt, litsym};   /* length code */
    static struct huffman lencode = {lencnt, lensym};   /* length code */
    static struct huffman distcode = {distcnt, distsym};/* distance code */
        /* bit lengths of literal codes */
    static const unsigned char litlen[] = {
        11, 124, 8, 7, 28, 7, 188, 13, 76, 4, 10, 8, 12, 10, 12, 10, 8, 23, 8,
        9, 7, 6, 7, 8, 7, 6, 55, 8, 23, 24, 12, 11, 7, 9, 11, 12, 6, 7, 22, 5,
        7, 24, 6, 11, 9, 6, 7, 22, 7, 11, 38, 7, 9, 8, 25, 11, 8, 11, 9, 12,
        8, 12, 5, 38, 5, 38, 5, 11, 7, 5, 6, 21, 6, 10, 53, 8, 7, 24, 10, 27,
        44, 253, 253, 253, 252, 252, 252, 13, 12, 45, 12, 45, 12, 61, 12, 45,
        44, 173};
        /* bit lengths of length codes 0..15 */
    static const unsigned char lenlen[] = {2, 35, 36, 53, 38, 23};
        /* bit lengths of distance codes 0..63 */
    static const unsigned char distlen[] = {2, 20, 53, 230, 247, 151, 248};
    static const short base[16] = {     /* base for length codes */
        3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 136, 264};
    static const char extra[16] = {     /* extra bits for length codes */
        0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8};

    /* set up decoding tables (once--might not be thread-safe) */
    if (virgin) {
        construct(&litcode, litlen, sizeof(litlen));
        construct(&lencode, lenlen, sizeof(lenlen));
        construct(&distcode, distlen, sizeof(distlen));
        virgin = 0;
    }

    /* read header */
    lit = bits(s, 8);
    if (lit > 1) return -1;
    dict = bits(s, 8);
    if (dict < 4 || dict > 6) return -2;

    /* decode literals and length/distance pairs */
    do {
        if (bits(s, 1)) {
            /* get length */
            symbol = decode(s, &lencode);
            len = base[symbol] + bits(s, extra[symbol]);
            if (len == 519) break;              /* end code */

            /* get distance */
            symbol = len == 2 ? 2 : dict;
            dist = decode(s, &distcode) << symbol;
            dist += bits(s, symbol);
            dist++;
            if (s->first && dist > s->next)
                return -3;              /* distance too far back */

            /* copy length bytes from distance bytes back */
            do {
                to = s->out + s->next;
                from = to - dist;
                copy = MAXWIN;
                if (s->next < dist) {
                    from += copy;
                    copy = dist;
                }
                copy -= s->next;
                if (copy > len) copy = len;
                len -= copy;
                s->next += copy;
                do {
                    *to++ = *from++;
                } while (--copy);
                if (s->next == MAXWIN) {
                    if (s->outfun(s->outhow, s->out, s->next)) return 1;
                    s->next = 0;
                    s->first = 0;
                }
            } while (len != 0);
        }
        else {
            /* get literal and write it */
            symbol = lit ? decode(s, &litcode) : bits(s, 8);
            s->out[s->next++] = symbol;
            if (s->next == MAXWIN) {
                if (s->outfun(s->outhow, s->out, s->next)) return 1;
                s->next = 0;
                s->first = 0;
            }
        }
    } while (1);
    return 0;
}

/* See comments in blast.h */
int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow)
{
    struct state s;             /* input/output state */
    int err;                    /* return value */

    /* initialize input state */
    s.infun = infun;
    s.inhow = inhow;
    s.left = 0;
    s.bitbuf = 0;
    s.bitcnt = 0;

    /* initialize output state */
    s.outfun = outfun;
    s.outhow = outhow;
    s.next = 0;
    s.first = 1;

    /* return if bits() or decode() tries to read past available input */
    if (setjmp(s.env) != 0)             /* if came back here via longjmp(), */
        err = 2;                        /*  then skip decomp(), return error */
    else
        err = decomp(&s);               /* decompress */

    /* write any leftover output and update the error code if needed */
    if (err != 1 && s.next && s.outfun(s.outhow, s.out, s.next) && err == 0)
        err = 1;
    return err;
}

#ifdef TEST
/* Example of how to use blast() */
#include <stdio.h>
#include <stdlib.h>

#define CHUNK 16384

local unsigned inf(void *how, unsigned char **buf)
{
    static unsigned char hold[CHUNK];

    *buf = hold;
    return fread(hold, 1, CHUNK, (FILE *)how);
}

local int outf(void *how, unsigned char *buf, unsigned len)
{
    return fwrite(buf, 1, len, (FILE *)how) != len;
}

/* Decompress a PKWare Compression Library stream from stdin to stdout */
int main(void)
{
    int ret, n;

    /* decompress to stdout */
    ret = blast(inf, stdin, outf, stdout);
    if (ret != 0) fprintf(stderr, "blast error: %d\n", ret);

    /* see if there are any leftover bytes */
    n = 0;
    while (getchar() != EOF) n++;
    if (n) fprintf(stderr, "blast warning: %d unused bytes of input\n", n);

    /* return blast() error code */
    return ret;
}
#endif