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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [zlib/] [contrib/] [infback9/] [inftree9.c] - Blame information for rev 745

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1 745 jeremybenn
/* inftree9.c -- generate Huffman trees for efficient decoding
2
 * Copyright (C) 1995-2005 Mark Adler
3
 * For conditions of distribution and use, see copyright notice in zlib.h
4
 */
5
 
6
#include "zutil.h"
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#include "inftree9.h"
8
 
9
#define MAXBITS 15
10
 
11
const char inflate9_copyright[] =
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   " inflate9 1.2.3 Copyright 1995-2005 Mark Adler ";
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/*
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  If you use the zlib library in a product, an acknowledgment is welcome
15
  in the documentation of your product. If for some reason you cannot
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  include such an acknowledgment, I would appreciate that you keep this
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  copyright string in the executable of your product.
18
 */
19
 
20
/*
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   Build a set of tables to decode the provided canonical Huffman code.
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   The code lengths are lens[0..codes-1].  The result starts at *table,
23
   whose indices are 0..2^bits-1.  work is a writable array of at least
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   lens shorts, which is used as a work area.  type is the type of code
25
   to be generated, CODES, LENS, or DISTS.  On return, zero is success,
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   -1 is an invalid code, and +1 means that ENOUGH isn't enough.  table
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   on return points to the next available entry's address.  bits is the
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   requested root table index bits, and on return it is the actual root
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   table index bits.  It will differ if the request is greater than the
30
   longest code or if it is less than the shortest code.
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 */
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int inflate_table9(type, lens, codes, table, bits, work)
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codetype type;
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unsigned short FAR *lens;
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unsigned codes;
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code FAR * FAR *table;
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unsigned FAR *bits;
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unsigned short FAR *work;
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{
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    unsigned len;               /* a code's length in bits */
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    unsigned sym;               /* index of code symbols */
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    unsigned min, max;          /* minimum and maximum code lengths */
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    unsigned root;              /* number of index bits for root table */
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    unsigned curr;              /* number of index bits for current table */
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    unsigned drop;              /* code bits to drop for sub-table */
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    int left;                   /* number of prefix codes available */
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    unsigned used;              /* code entries in table used */
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    unsigned huff;              /* Huffman code */
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    unsigned incr;              /* for incrementing code, index */
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    unsigned fill;              /* index for replicating entries */
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    unsigned low;               /* low bits for current root entry */
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    unsigned mask;              /* mask for low root bits */
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    code this;                  /* table entry for duplication */
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    code FAR *next;             /* next available space in table */
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    const unsigned short FAR *base;     /* base value table to use */
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    const unsigned short FAR *extra;    /* extra bits table to use */
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    int end;                    /* use base and extra for symbol > end */
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    unsigned short count[MAXBITS+1];    /* number of codes of each length */
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    unsigned short offs[MAXBITS+1];     /* offsets in table for each length */
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    static const unsigned short lbase[31] = { /* Length codes 257..285 base */
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        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17,
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        19, 23, 27, 31, 35, 43, 51, 59, 67, 83, 99, 115,
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        131, 163, 195, 227, 3, 0, 0};
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    static const unsigned short lext[31] = { /* Length codes 257..285 extra */
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        128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129,
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        130, 130, 130, 130, 131, 131, 131, 131, 132, 132, 132, 132,
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        133, 133, 133, 133, 144, 201, 196};
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    static const unsigned short dbase[32] = { /* Distance codes 0..31 base */
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        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49,
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        65, 97, 129, 193, 257, 385, 513, 769, 1025, 1537, 2049, 3073,
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        4097, 6145, 8193, 12289, 16385, 24577, 32769, 49153};
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    static const unsigned short dext[32] = { /* Distance codes 0..31 extra */
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        128, 128, 128, 128, 129, 129, 130, 130, 131, 131, 132, 132,
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        133, 133, 134, 134, 135, 135, 136, 136, 137, 137, 138, 138,
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        139, 139, 140, 140, 141, 141, 142, 142};
76
 
77
    /*
78
       Process a set of code lengths to create a canonical Huffman code.  The
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       code lengths are lens[0..codes-1].  Each length corresponds to the
80
       symbols 0..codes-1.  The Huffman code is generated by first sorting the
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       symbols by length from short to long, and retaining the symbol order
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       for codes with equal lengths.  Then the code starts with all zero bits
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       for the first code of the shortest length, and the codes are integer
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       increments for the same length, and zeros are appended as the length
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       increases.  For the deflate format, these bits are stored backwards
86
       from their more natural integer increment ordering, and so when the
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       decoding tables are built in the large loop below, the integer codes
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       are incremented backwards.
89
 
90
       This routine assumes, but does not check, that all of the entries in
91
       lens[] are in the range 0..MAXBITS.  The caller must assure this.
92
       1..MAXBITS is interpreted as that code length.  zero means that that
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       symbol does not occur in this code.
94
 
95
       The codes are sorted by computing a count of codes for each length,
96
       creating from that a table of starting indices for each length in the
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       sorted table, and then entering the symbols in order in the sorted
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       table.  The sorted table is work[], with that space being provided by
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       the caller.
100
 
101
       The length counts are used for other purposes as well, i.e. finding
102
       the minimum and maximum length codes, determining if there are any
103
       codes at all, checking for a valid set of lengths, and looking ahead
104
       at length counts to determine sub-table sizes when building the
105
       decoding tables.
106
     */
107
 
108
    /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
109
    for (len = 0; len <= MAXBITS; len++)
110
        count[len] = 0;
111
    for (sym = 0; sym < codes; sym++)
112
        count[lens[sym]]++;
113
 
114
    /* bound code lengths, force root to be within code lengths */
115
    root = *bits;
116
    for (max = MAXBITS; max >= 1; max--)
117
        if (count[max] != 0) break;
118
    if (root > max) root = max;
119
    if (max == 0) return -1;            /* no codes! */
120
    for (min = 1; min <= MAXBITS; min++)
121
        if (count[min] != 0) break;
122
    if (root < min) root = min;
123
 
124
    /* check for an over-subscribed or incomplete set of lengths */
125
    left = 1;
126
    for (len = 1; len <= MAXBITS; len++) {
127
        left <<= 1;
128
        left -= count[len];
129
        if (left < 0) return -1;        /* over-subscribed */
130
    }
131
    if (left > 0 && (type == CODES || max != 1))
132
        return -1;                      /* incomplete set */
133
 
134
    /* generate offsets into symbol table for each length for sorting */
135
    offs[1] = 0;
136
    for (len = 1; len < MAXBITS; len++)
137
        offs[len + 1] = offs[len] + count[len];
138
 
139
    /* sort symbols by length, by symbol order within each length */
140
    for (sym = 0; sym < codes; sym++)
141
        if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;
142
 
143
    /*
144
       Create and fill in decoding tables.  In this loop, the table being
145
       filled is at next and has curr index bits.  The code being used is huff
146
       with length len.  That code is converted to an index by dropping drop
147
       bits off of the bottom.  For codes where len is less than drop + curr,
148
       those top drop + curr - len bits are incremented through all values to
149
       fill the table with replicated entries.
150
 
151
       root is the number of index bits for the root table.  When len exceeds
152
       root, sub-tables are created pointed to by the root entry with an index
153
       of the low root bits of huff.  This is saved in low to check for when a
154
       new sub-table should be started.  drop is zero when the root table is
155
       being filled, and drop is root when sub-tables are being filled.
156
 
157
       When a new sub-table is needed, it is necessary to look ahead in the
158
       code lengths to determine what size sub-table is needed.  The length
159
       counts are used for this, and so count[] is decremented as codes are
160
       entered in the tables.
161
 
162
       used keeps track of how many table entries have been allocated from the
163
       provided *table space.  It is checked when a LENS table is being made
164
       against the space in *table, ENOUGH, minus the maximum space needed by
165
       the worst case distance code, MAXD.  This should never happen, but the
166
       sufficiency of ENOUGH has not been proven exhaustively, hence the check.
167
       This assumes that when type == LENS, bits == 9.
168
 
169
       sym increments through all symbols, and the loop terminates when
170
       all codes of length max, i.e. all codes, have been processed.  This
171
       routine permits incomplete codes, so another loop after this one fills
172
       in the rest of the decoding tables with invalid code markers.
173
     */
174
 
175
    /* set up for code type */
176
    switch (type) {
177
    case CODES:
178
        base = extra = work;    /* dummy value--not used */
179
        end = 19;
180
        break;
181
    case LENS:
182
        base = lbase;
183
        base -= 257;
184
        extra = lext;
185
        extra -= 257;
186
        end = 256;
187
        break;
188
    default:            /* DISTS */
189
        base = dbase;
190
        extra = dext;
191
        end = -1;
192
    }
193
 
194
    /* initialize state for loop */
195
    huff = 0;                   /* starting code */
196
    sym = 0;                    /* starting code symbol */
197
    len = min;                  /* starting code length */
198
    next = *table;              /* current table to fill in */
199
    curr = root;                /* current table index bits */
200
    drop = 0;                   /* current bits to drop from code for index */
201
    low = (unsigned)(-1);       /* trigger new sub-table when len > root */
202
    used = 1U << root;          /* use root table entries */
203
    mask = used - 1;            /* mask for comparing low */
204
 
205
    /* check available table space */
206
    if (type == LENS && used >= ENOUGH - MAXD)
207
        return 1;
208
 
209
    /* process all codes and make table entries */
210
    for (;;) {
211
        /* create table entry */
212
        this.bits = (unsigned char)(len - drop);
213
        if ((int)(work[sym]) < end) {
214
            this.op = (unsigned char)0;
215
            this.val = work[sym];
216
        }
217
        else if ((int)(work[sym]) > end) {
218
            this.op = (unsigned char)(extra[work[sym]]);
219
            this.val = base[work[sym]];
220
        }
221
        else {
222
            this.op = (unsigned char)(32 + 64);         /* end of block */
223
            this.val = 0;
224
        }
225
 
226
        /* replicate for those indices with low len bits equal to huff */
227
        incr = 1U << (len - drop);
228
        fill = 1U << curr;
229
        do {
230
            fill -= incr;
231
            next[(huff >> drop) + fill] = this;
232
        } while (fill != 0);
233
 
234
        /* backwards increment the len-bit code huff */
235
        incr = 1U << (len - 1);
236
        while (huff & incr)
237
            incr >>= 1;
238
        if (incr != 0) {
239
            huff &= incr - 1;
240
            huff += incr;
241
        }
242
        else
243
            huff = 0;
244
 
245
        /* go to next symbol, update count, len */
246
        sym++;
247
        if (--(count[len]) == 0) {
248
            if (len == max) break;
249
            len = lens[work[sym]];
250
        }
251
 
252
        /* create new sub-table if needed */
253
        if (len > root && (huff & mask) != low) {
254
            /* if first time, transition to sub-tables */
255
            if (drop == 0)
256
                drop = root;
257
 
258
            /* increment past last table */
259
            next += 1U << curr;
260
 
261
            /* determine length of next table */
262
            curr = len - drop;
263
            left = (int)(1 << curr);
264
            while (curr + drop < max) {
265
                left -= count[curr + drop];
266
                if (left <= 0) break;
267
                curr++;
268
                left <<= 1;
269
            }
270
 
271
            /* check for enough space */
272
            used += 1U << curr;
273
            if (type == LENS && used >= ENOUGH - MAXD)
274
                return 1;
275
 
276
            /* point entry in root table to sub-table */
277
            low = huff & mask;
278
            (*table)[low].op = (unsigned char)curr;
279
            (*table)[low].bits = (unsigned char)root;
280
            (*table)[low].val = (unsigned short)(next - *table);
281
        }
282
    }
283
 
284
    /*
285
       Fill in rest of table for incomplete codes.  This loop is similar to the
286
       loop above in incrementing huff for table indices.  It is assumed that
287
       len is equal to curr + drop, so there is no loop needed to increment
288
       through high index bits.  When the current sub-table is filled, the loop
289
       drops back to the root table to fill in any remaining entries there.
290
     */
291
    this.op = (unsigned char)64;                /* invalid code marker */
292
    this.bits = (unsigned char)(len - drop);
293
    this.val = (unsigned short)0;
294
    while (huff != 0) {
295
        /* when done with sub-table, drop back to root table */
296
        if (drop != 0 && (huff & mask) != low) {
297
            drop = 0;
298
            len = root;
299
            next = *table;
300
            curr = root;
301
            this.bits = (unsigned char)len;
302
        }
303
 
304
        /* put invalid code marker in table */
305
        next[huff >> drop] = this;
306
 
307
        /* backwards increment the len-bit code huff */
308
        incr = 1U << (len - 1);
309
        while (huff & incr)
310
            incr >>= 1;
311
        if (incr != 0) {
312
            huff &= incr - 1;
313
            huff += incr;
314
        }
315
        else
316
            huff = 0;
317
    }
318
 
319
    /* set return parameters */
320
    *table += used;
321
    *bits = root;
322
    return 0;
323
}

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