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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [zlib/] [inftrees.c] - Blame information for rev 790

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1 745 jeremybenn
/* inftrees.c -- generate Huffman trees for efficient decoding
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 * Copyright (C) 1995-2005 Mark Adler
3
 * For conditions of distribution and use, see copyright notice in zlib.h
4
 */
5
 
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#include "zutil.h"
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#include "inftrees.h"
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9
#define MAXBITS 15
10
 
11
const char inflate_copyright[] =
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   " inflate 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
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  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.
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 */
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,
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   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
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   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
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   longest code or if it is less than the shortest code.
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 */
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int inflate_table(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, 19, 23, 27, 31,
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        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
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    static const unsigned short lext[31] = { /* Length codes 257..285 extra */
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        16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
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        19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 201, 196};
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    static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
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        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
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        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
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        8193, 12289, 16385, 24577, 0, 0};
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    static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
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        16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
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        23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
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        28, 28, 29, 29, 64, 64};
74
 
75
    /*
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       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
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       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
82
       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
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       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.
87
 
88
       This routine assumes, but does not check, that all of the entries in
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       lens[] are in the range 0..MAXBITS.  The caller must assure this.
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       1..MAXBITS is interpreted as that code length.  zero means that that
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       symbol does not occur in this code.
92
 
93
       The codes are sorted by computing a count of codes for each length,
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       creating from that a table of starting indices for each length in the
95
       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.
98
 
99
       The length counts are used for other purposes as well, i.e. finding
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       the minimum and maximum length codes, determining if there are any
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       codes at all, checking for a valid set of lengths, and looking ahead
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       at length counts to determine sub-table sizes when building the
103
       decoding tables.
104
     */
105
 
106
    /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
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    for (len = 0; len <= MAXBITS; len++)
108
        count[len] = 0;
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    for (sym = 0; sym < codes; sym++)
110
        count[lens[sym]]++;
111
 
112
    /* bound code lengths, force root to be within code lengths */
113
    root = *bits;
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    for (max = MAXBITS; max >= 1; max--)
115
        if (count[max] != 0) break;
116
    if (root > max) root = max;
117
    if (max == 0) {                     /* no symbols to code at all */
118
        this.op = (unsigned char)64;    /* invalid code marker */
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        this.bits = (unsigned char)1;
120
        this.val = (unsigned short)0;
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        *(*table)++ = this;             /* make a table to force an error */
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        *(*table)++ = this;
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        *bits = 1;
124
        return 0;     /* no symbols, but wait for decoding to report error */
125
    }
126
    for (min = 1; min <= MAXBITS; min++)
127
        if (count[min] != 0) break;
128
    if (root < min) root = min;
129
 
130
    /* check for an over-subscribed or incomplete set of lengths */
131
    left = 1;
132
    for (len = 1; len <= MAXBITS; len++) {
133
        left <<= 1;
134
        left -= count[len];
135
        if (left < 0) return -1;        /* over-subscribed */
136
    }
137
    if (left > 0 && (type == CODES || max != 1))
138
        return -1;                      /* incomplete set */
139
 
140
    /* generate offsets into symbol table for each length for sorting */
141
    offs[1] = 0;
142
    for (len = 1; len < MAXBITS; len++)
143
        offs[len + 1] = offs[len] + count[len];
144
 
145
    /* sort symbols by length, by symbol order within each length */
146
    for (sym = 0; sym < codes; sym++)
147
        if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;
148
 
149
    /*
150
       Create and fill in decoding tables.  In this loop, the table being
151
       filled is at next and has curr index bits.  The code being used is huff
152
       with length len.  That code is converted to an index by dropping drop
153
       bits off of the bottom.  For codes where len is less than drop + curr,
154
       those top drop + curr - len bits are incremented through all values to
155
       fill the table with replicated entries.
156
 
157
       root is the number of index bits for the root table.  When len exceeds
158
       root, sub-tables are created pointed to by the root entry with an index
159
       of the low root bits of huff.  This is saved in low to check for when a
160
       new sub-table should be started.  drop is zero when the root table is
161
       being filled, and drop is root when sub-tables are being filled.
162
 
163
       When a new sub-table is needed, it is necessary to look ahead in the
164
       code lengths to determine what size sub-table is needed.  The length
165
       counts are used for this, and so count[] is decremented as codes are
166
       entered in the tables.
167
 
168
       used keeps track of how many table entries have been allocated from the
169
       provided *table space.  It is checked when a LENS table is being made
170
       against the space in *table, ENOUGH, minus the maximum space needed by
171
       the worst case distance code, MAXD.  This should never happen, but the
172
       sufficiency of ENOUGH has not been proven exhaustively, hence the check.
173
       This assumes that when type == LENS, bits == 9.
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
    switch (type) {
183
    case CODES:
184
        base = extra = work;    /* dummy value--not used */
185
        end = 19;
186
        break;
187
    case LENS:
188
        base = lbase;
189
        base -= 257;
190
        extra = lext;
191
        extra -= 257;
192
        end = 256;
193
        break;
194
    default:            /* DISTS */
195
        base = dbase;
196
        extra = dext;
197
        end = -1;
198
    }
199
 
200
    /* initialize state for loop */
201
    huff = 0;                   /* starting code */
202
    sym = 0;                    /* starting code symbol */
203
    len = min;                  /* starting code length */
204
    next = *table;              /* current table to fill in */
205
    curr = root;                /* current table index bits */
206
    drop = 0;                   /* current bits to drop from code for index */
207
    low = (unsigned)(-1);       /* trigger new sub-table when len > root */
208
    used = 1U << root;          /* use root table entries */
209
    mask = used - 1;            /* mask for comparing low */
210
 
211
    /* check available table space */
212
    if (type == LENS && used >= ENOUGH - MAXD)
213
        return 1;
214
 
215
    /* process all codes and make table entries */
216
    for (;;) {
217
        /* create table entry */
218
        this.bits = (unsigned char)(len - drop);
219
        if ((int)(work[sym]) < end) {
220
            this.op = (unsigned char)0;
221
            this.val = work[sym];
222
        }
223
        else if ((int)(work[sym]) > end) {
224
            this.op = (unsigned char)(extra[work[sym]]);
225
            this.val = base[work[sym]];
226
        }
227
        else {
228
            this.op = (unsigned char)(32 + 64);         /* end of block */
229
            this.val = 0;
230
        }
231
 
232
        /* replicate for those indices with low len bits equal to huff */
233
        incr = 1U << (len - drop);
234
        fill = 1U << curr;
235
        min = fill;                 /* save offset to next table */
236
        do {
237
            fill -= incr;
238
            next[(huff >> drop) + fill] = this;
239
        } while (fill != 0);
240
 
241
        /* backwards increment the len-bit code huff */
242
        incr = 1U << (len - 1);
243
        while (huff & incr)
244
            incr >>= 1;
245
        if (incr != 0) {
246
            huff &= incr - 1;
247
            huff += incr;
248
        }
249
        else
250
            huff = 0;
251
 
252
        /* go to next symbol, update count, len */
253
        sym++;
254
        if (--(count[len]) == 0) {
255
            if (len == max) break;
256
            len = lens[work[sym]];
257
        }
258
 
259
        /* create new sub-table if needed */
260
        if (len > root && (huff & mask) != low) {
261
            /* if first time, transition to sub-tables */
262
            if (drop == 0)
263
                drop = root;
264
 
265
            /* increment past last table */
266
            next += min;            /* here min is 1 << curr */
267
 
268
            /* determine length of next table */
269
            curr = len - drop;
270
            left = (int)(1 << curr);
271
            while (curr + drop < max) {
272
                left -= count[curr + drop];
273
                if (left <= 0) break;
274
                curr++;
275
                left <<= 1;
276
            }
277
 
278
            /* check for enough space */
279
            used += 1U << curr;
280
            if (type == LENS && used >= ENOUGH - MAXD)
281
                return 1;
282
 
283
            /* point entry in root table to sub-table */
284
            low = huff & mask;
285
            (*table)[low].op = (unsigned char)curr;
286
            (*table)[low].bits = (unsigned char)root;
287
            (*table)[low].val = (unsigned short)(next - *table);
288
        }
289
    }
290
 
291
    /*
292
       Fill in rest of table for incomplete codes.  This loop is similar to the
293
       loop above in incrementing huff for table indices.  It is assumed that
294
       len is equal to curr + drop, so there is no loop needed to increment
295
       through high index bits.  When the current sub-table is filled, the loop
296
       drops back to the root table to fill in any remaining entries there.
297
     */
298
    this.op = (unsigned char)64;                /* invalid code marker */
299
    this.bits = (unsigned char)(len - drop);
300
    this.val = (unsigned short)0;
301
    while (huff != 0) {
302
        /* when done with sub-table, drop back to root table */
303
        if (drop != 0 && (huff & mask) != low) {
304
            drop = 0;
305
            len = root;
306
            next = *table;
307
            this.bits = (unsigned char)len;
308
        }
309
 
310
        /* put invalid code marker in table */
311
        next[huff >> drop] = this;
312
 
313
        /* backwards increment the len-bit code huff */
314
        incr = 1U << (len - 1);
315
        while (huff & incr)
316
            incr >>= 1;
317
        if (incr != 0) {
318
            huff &= incr - 1;
319
            huff += incr;
320
        }
321
        else
322
            huff = 0;
323
    }
324
 
325
    /* set return parameters */
326
    *table += used;
327
    *bits = root;
328
    return 0;
329
}

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