varnish-cache/lib/libvgz/inftrees.c
1
/* inftrees.c -- generate Huffman trees for efficient decoding
2
 * Copyright (C) 1995-2017 Mark Adler
3
 * For conditions of distribution and use, see copyright notice in zlib.h
4
 */
5
6
#include "zutil.h"
7
#include "inftrees.h"
8
9
#define MAXBITS 15
10
11
extern const char inflate_copyright[];
12
const char inflate_copyright[] =
13
   " inflate 1.2.11 Copyright 1995-2017 Mark Adler ";
14
/*
15
  If you use the zlib library in a product, an acknowledgment is welcome
16
  in the documentation of your product. If for some reason you cannot
17
  include such an acknowledgment, I would appreciate that you keep this
18
  copyright string in the executable of your product.
19
 */
20
21
/*
22
   Build a set of tables to decode the provided canonical Huffman code.
23
   The code lengths are lens[0..codes-1].  The result starts at *table,
24
   whose indices are 0..2^bits-1.  work is a writable array of at least
25
   lens shorts, which is used as a work area.  type is the type of code
26
   to be generated, CODES, LENS, or DISTS.  On return, zero is success,
27
   -1 is an invalid code, and +1 means that ENOUGH isn't enough.  table
28
   on return points to the next available entry's address.  bits is the
29
   requested root table index bits, and on return it is the actual root
30
   table index bits.  It will differ if the request is greater than the
31
   longest code or if it is less than the shortest code.
32
 */
33 55890
int ZLIB_INTERNAL inflate_table(type, lens, codes, table, bits, work)
34
codetype type;
35
unsigned short FAR *lens;
36
unsigned codes;
37
code FAR * FAR *table;
38
unsigned FAR *bits;
39
unsigned short FAR *work;
40
{
41
    unsigned len;               /* a code's length in bits */
42
    unsigned sym;               /* index of code symbols */
43
    unsigned min, max;          /* minimum and maximum code lengths */
44
    unsigned root;              /* number of index bits for root table */
45
    unsigned curr;              /* number of index bits for current table */
46
    unsigned drop;              /* code bits to drop for sub-table */
47
    int left;                   /* number of prefix codes available */
48
    unsigned used;              /* code entries in table used */
49
    unsigned huff;              /* Huffman code */
50
    unsigned incr;              /* for incrementing code, index */
51
    unsigned fill;              /* index for replicating entries */
52
    unsigned low;               /* low bits for current root entry */
53
    unsigned mask;              /* mask for low root bits */
54
    code here;                  /* table entry for duplication */
55
    code FAR *next;             /* next available space in table */
56
    const unsigned short FAR *base;     /* base value table to use */
57
    const unsigned short FAR *extra;    /* extra bits table to use */
58
    unsigned match;             /* use base and extra for symbol >= match */
59
    unsigned short count[MAXBITS+1];    /* number of codes of each length */
60
    unsigned short offs[MAXBITS+1];     /* offsets in table for each length */
61
    static const unsigned short lbase[31] = { /* Length codes 257..285 base */
62
        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
63
        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
64
    static const unsigned short lext[31] = { /* Length codes 257..285 extra */
65
        16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
66
        19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 77, 202};
67
    static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
68
        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
69
        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
70
        8193, 12289, 16385, 24577, 0, 0};
71
    static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
72
        16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
73
        23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
74
        28, 28, 29, 29, 64, 64};
75
76
    /*
77
       Process a set of code lengths to create a canonical Huffman code.  The
78
       code lengths are lens[0..codes-1].  Each length corresponds to the
79
       symbols 0..codes-1.  The Huffman code is generated by first sorting the
80
       symbols by length from short to long, and retaining the symbol order
81
       for codes with equal lengths.  Then the code starts with all zero bits
82
       for the first code of the shortest length, and the codes are integer
83
       increments for the same length, and zeros are appended as the length
84
       increases.  For the deflate format, these bits are stored backwards
85
       from their more natural integer increment ordering, and so when the
86
       decoding tables are built in the large loop below, the integer codes
87
       are incremented backwards.
88
89
       This routine assumes, but does not check, that all of the entries in
90
       lens[] are in the range 0..MAXBITS.  The caller must assure this.
91
       1..MAXBITS is interpreted as that code length.  zero means that that
92
       symbol does not occur in this code.
93
94
       The codes are sorted by computing a count of codes for each length,
95
       creating from that a table of starting indices for each length in the
96
       sorted table, and then entering the symbols in order in the sorted
97
       table.  The sorted table is work[], with that space being provided by
98
       the caller.
99
100
       The length counts are used for other purposes as well, i.e. finding
101
       the minimum and maximum length codes, determining if there are any
102
       codes at all, checking for a valid set of lengths, and looking ahead
103
       at length counts to determine sub-table sizes when building the
104
       decoding tables.
105
     */
106
107
    /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
108 950130
    for (len = 0; len <= MAXBITS; len++)
109 894240
        count[len] = 0;
110 5981741
    for (sym = 0; sym < codes; sym++)
111 5925851
        count[lens[sym]]++;
112
113
    /* bound code lengths, force root to be within code lengths */
114 55890
    root = *bits;
115 498266
    for (max = MAXBITS; max >= 1; max--)
116 498266
        if (count[max] != 0) break;
117 55890
    if (root > max) root = max;
118 55890
    if (max == 0) {                     /* no symbols to code at all */
119 0
        here.op = (unsigned char)64;    /* invalid code marker */
120 0
        here.bits = (unsigned char)1;
121 0
        here.val = (unsigned short)0;
122 0
        *(*table)++ = here;             /* make a table to force an error */
123 0
        *(*table)++ = here;
124 0
        *bits = 1;
125 0
        return 0;     /* no symbols, but wait for decoding to report error */
126
    }
127 134891
    for (min = 1; min < max; min++)
128 134891
        if (count[min] != 0) break;
129 55890
    if (root < min) root = min;
130
131
    /* check for an over-subscribed or incomplete set of lengths */
132 55890
    left = 1;
133 894240
    for (len = 1; len <= MAXBITS; len++) {
134 838350
        left <<= 1;
135 838350
        left -= count[len];
136 838350
        if (left < 0) return -1;        /* over-subscribed */
137
    }
138 55890
    if (left > 0 && (type == CODES || max != 1))
139 0
        return -1;                      /* incomplete set */
140
141
    /* generate offsets into symbol table for each length for sorting */
142 55890
    offs[1] = 0;
143 838350
    for (len = 1; len < MAXBITS; len++)
144 782460
        offs[len + 1] = offs[len] + count[len];
145
146
    /* sort symbols by length, by symbol order within each length */
147 5981741
    for (sym = 0; sym < codes; sym++)
148 5925851
        if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;
149
150
    /*
151
       Create and fill in decoding tables.  In this loop, the table being
152
       filled is at next and has curr index bits.  The code being used is huff
153
       with length len.  That code is converted to an index by dropping drop
154
       bits off of the bottom.  For codes where len is less than drop + curr,
155
       those top drop + curr - len bits are incremented through all values to
156
       fill the table with replicated entries.
157
158
       root is the number of index bits for the root table.  When len exceeds
159
       root, sub-tables are created pointed to by the root entry with an index
160
       of the low root bits of huff.  This is saved in low to check for when a
161
       new sub-table should be started.  drop is zero when the root table is
162
       being filled, and drop is root when sub-tables are being filled.
163
164
       When a new sub-table is needed, it is necessary to look ahead in the
165
       code lengths to determine what size sub-table is needed.  The length
166
       counts are used for this, and so count[] is decremented as codes are
167
       entered in the tables.
168
169
       used keeps track of how many table entries have been allocated from the
170
       provided *table space.  It is checked for LENS and DIST tables against
171
       the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
172
       the initial root table size constants.  See the comments in inftrees.h
173
       for more information.
174
175
       sym increments through all symbols, and the loop terminates when
176
       all codes of length max, i.e. all codes, have been processed.  This
177
       routine permits incomplete codes, so another loop after this one fills
178
       in the rest of the decoding tables with invalid code markers.
179
     */
180
181
    /* set up for code type */
182 55890
    switch (type) {
183
    case CODES:
184 18630
        base = extra = work;    /* dummy value--not used */
185 18630
        match = 20;
186 18630
        break;
187
    case LENS:
188 18630
        base = lbase;
189 18630
        extra = lext;
190 18630
        match = 257;
191 18630
        break;
192
    default:    /* DISTS */
193 18630
        base = dbase;
194 18630
        extra = dext;
195 18630
        match = 0;
196
    }
197
198
    /* initialize state for loop */
199 55890
    huff = 0;                   /* starting code */
200 55890
    sym = 0;                    /* starting code symbol */
201 55890
    len = min;                  /* starting code length */
202 55890
    next = *table;              /* current table to fill in */
203 55890
    curr = root;                /* current table index bits */
204 55890
    drop = 0;                   /* current bits to drop from code for index */
205 55890
    low = (unsigned)(-1);       /* trigger new sub-table when len > root */
206 55890
    used = 1U << root;          /* use root table entries */
207 55890
    mask = used - 1;            /* mask for comparing low */
208
209
    /* check available table space */
210 55890
    if ((type == LENS && used > ENOUGH_LENS) ||
211 18630
        (type == DISTS && used > ENOUGH_DISTS))
212 0
        return 1;
213
214
    /* process all codes and make table entries */
215
    for (;;) {
216
        /* create table entry */
217 1737637
        here.bits = (unsigned char)(len - drop);
218 1737637
        if (work[sym] + 1U < match) {
219 1144829
            here.op = (unsigned char)0;
220 1144829
            here.val = work[sym];
221
        }
222 592808
        else if (work[sym] >= match) {
223 574178
            here.op = (unsigned char)(extra[work[sym] - match]);
224 574178
            here.val = base[work[sym] - match];
225
        }
226
        else {
227 18630
            here.op = (unsigned char)(32 + 64);         /* end of block */
228 18630
            here.val = 0;
229
        }
230
231
        /* replicate for those indices with low len bits equal to huff */
232 1737637
        incr = 1U << (len - drop);
233 1737637
        fill = 1U << curr;
234 1737637
        min = fill;                 /* save offset to next table */
235
        do {
236 8483388
            fill -= incr;
237 8483388
            next[(huff >> drop) + fill] = here;
238 8483388
        } while (fill != 0);
239
240
        /* backwards increment the len-bit code huff */
241 1737637
        incr = 1U << (len - 1);
242 5157021
        while (huff & incr)
243 1681747
            incr >>= 1;
244 1737637
        if (incr != 0) {
245 1681747
            huff &= incr - 1;
246 1681747
            huff += incr;
247
        }
248
        else
249 55890
            huff = 0;
250
251
        /* go to next symbol, update count, len */
252 1737637
        sym++;
253 1737637
        if (--(count[len]) == 0) {
254 311275
            if (len == max) break;
255 255385
            len = lens[work[sym]];
256
        }
257
258
        /* create new sub-table if needed */
259 1681747
        if (len > root && (huff & mask) != low) {
260
            /* if first time, transition to sub-tables */
261 12256
            if (drop == 0)
262 4288
                drop = root;
263
264
            /* increment past last table */
265 12256
            next += min;            /* here min is 1 << curr */
266
267
            /* determine length of next table */
268 12256
            curr = len - drop;
269 12256
            left = (int)(1 << curr);
270 26968
            while (curr + drop < max) {
271 7368
                left -= count[curr + drop];
272 7368
                if (left <= 0) break;
273 2456
                curr++;
274 2456
                left <<= 1;
275
            }
276
277
            /* check for enough space */
278 12256
            used += 1U << curr;
279 12256
            if ((type == LENS && used > ENOUGH_LENS) ||
280 7344
                (type == DISTS && used > ENOUGH_DISTS))
281 0
                return 1;
282
283
            /* point entry in root table to sub-table */
284 12256
            low = huff & mask;
285 12256
            (*table)[low].op = (unsigned char)curr;
286 12256
            (*table)[low].bits = (unsigned char)root;
287 12256
            (*table)[low].val = (unsigned short)(next - *table);
288
        }
289 1681747
    }
290
291
    /* fill in remaining table entry if code is incomplete (guaranteed to have
292
       at most one remaining entry, since if the code is incomplete, the
293
       maximum code length that was allowed to get this far is one bit) */
294 55890
    if (huff != 0) {
295 0
        here.op = (unsigned char)64;            /* invalid code marker */
296 0
        here.bits = (unsigned char)(len - drop);
297 0
        here.val = (unsigned short)0;
298 0
        next[huff] = here;
299
    }
300
301
    /* set return parameters */
302 55890
    *table += used;
303 55890
    *bits = root;
304 55890
    return 0;
305
}