3rdparty/zlib/inftrees.c

/* inftrees.c -- generate Huffman trees for efficient decoding
 * Copyright (C) 1995-2010 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

#include "zutil.h"
#include "inftrees.h"

#define MAXBITS 15

const char inflate_copyright[] =
   " inflate 1.2.4 Copyright 1995-2010 Mark Adler ";
/*
  If you use the zlib library in a product, an acknowledgment is welcome
  in the documentation of your product. If for some reason you cannot
  include such an acknowledgment, I would appreciate that you keep this
  copyright string in the executable of your product.
 */

/*
   Build a set of tables to decode the provided canonical Huffman code.
   The code lengths are lens[0..codes-1].  The result starts at *table,
   whose indices are 0..2^bits-1.  work is a writable array of at least
   lens shorts, which is used as a work area.  type is the type of code
   to be generated, CODES, LENS, or DISTS.  On return, zero is success,
   -1 is an invalid code, and +1 means that ENOUGH isn't enough.  table
   on return points to the next available entry's address.  bits is the
   requested root table index bits, and on return it is the actual root
   table index bits.  It will differ if the request is greater than the
   longest code or if it is less than the shortest code.
 */
int inflate_table(type, lens, codes, table, bits, work)
codetype type;
unsigned short FAR *lens;
unsigned codes;
code FAR * FAR *table;
unsigned FAR *bits;
unsigned short FAR *work;
{
    unsigned len;               /* a code's length in bits */
    unsigned sym;               /* index of code symbols */
    unsigned min, max;          /* minimum and maximum code lengths */
    unsigned root;              /* number of index bits for root table */
    unsigned curr;              /* number of index bits for current table */
    unsigned drop;              /* code bits to drop for sub-table */
    int left;                   /* number of prefix codes available */
    unsigned used;              /* code entries in table used */
    unsigned huff;              /* Huffman code */
    unsigned incr;              /* for incrementing code, index */
    unsigned fill;              /* index for replicating entries */
    unsigned low;               /* low bits for current root entry */
    unsigned mask;              /* mask for low root bits */
    code here;                  /* table entry for duplication */
    code FAR *next;             /* next available space in table */
    const unsigned short FAR *base;     /* base value table to use */
    const unsigned short FAR *extra;    /* extra bits table to use */
    int end;                    /* use base and extra for symbol > end */
    unsigned short count[MAXBITS+1];    /* number of codes of each length */
    unsigned short offs[MAXBITS+1];     /* offsets in table for each length */
    static const unsigned short lbase[31] = { /* Length codes 257..285 base */
        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
    static const unsigned short lext[31] = { /* Length codes 257..285 extra */
        16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
        19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 64, 195};
    static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
        8193, 12289, 16385, 24577, 0, 0};
    static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
        16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
        23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
        28, 28, 29, 29, 64, 64};

    /*
       Process a set of code lengths to create a canonical Huffman code.  The
       code lengths are lens[0..codes-1].  Each length corresponds to the
       symbols 0..codes-1.  The Huffman code is generated by first sorting the
       symbols by length from short to long, and retaining the symbol order
       for codes with equal lengths.  Then the code starts with all zero bits
       for the first code of the shortest length, and the codes are integer
       increments for the same length, and zeros are appended as the length
       increases.  For the deflate format, these bits are stored backwards
       from their more natural integer increment ordering, and so when the
       decoding tables are built in the large loop below, the integer codes
       are incremented backwards.

       This routine assumes, but does not check, that all of the entries in
       lens[] are in the range 0..MAXBITS.  The caller must assure this.
       1..MAXBITS is interpreted as that code length.  zero means that that
       symbol does not occur in this code.

       The codes are sorted by computing a count of codes for each length,
       creating from that a table of starting indices for each length in the
       sorted table, and then entering the symbols in order in the sorted
       table.  The sorted table is work[], with that space being provided by
       the caller.

       The length counts are used for other purposes as well, i.e. finding
       the minimum and maximum length codes, determining if there are any
       codes at all, checking for a valid set of lengths, and looking ahead
       at length counts to determine sub-table sizes when building the
       decoding tables.
     */

    /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
    for (len = 0; len <= MAXBITS; len++)
        count[len] = 0;
    for (sym = 0; sym < codes; sym++)
        count[lens[sym]]++;

    /* bound code lengths, force root to be within code lengths */
    root = *bits;
    for (max = MAXBITS; max >= 1; max--)
        if (count[max] != 0) break;
    if (root > max) root = max;
    if (max == 0) {                     /* no symbols to code at all */
        here.op = (unsigned char)64;    /* invalid code marker */
        here.bits = (unsigned char)1;
        here.val = (unsigned short)0;
        *(*table)++ = here;             /* make a table to force an error */
        *(*table)++ = here;
        *bits = 1;
        return 0;     /* no symbols, but wait for decoding to report error */
    }
    for (min = 1; min < max; min++)
        if (count[min] != 0) break;
    if (root < min) root = min;

    /* check for an over-subscribed or incomplete set of lengths */
    left = 1;
    for (len = 1; len <= MAXBITS; len++) {
        left <<= 1;
        left -= count[len];
        if (left < 0) return -1;        /* over-subscribed */
    }
    if (left > 0 && (type == CODES || max != 1))
        return -1;                      /* incomplete set */

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

    /* sort symbols by length, by symbol order within each length */
    for (sym = 0; sym < codes; sym++)
        if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;

    /*
       Create and fill in decoding tables.  In this loop, the table being
       filled is at next and has curr index bits.  The code being used is huff
       with length len.  That code is converted to an index by dropping drop
       bits off of the bottom.  For codes where len is less than drop + curr,
       those top drop + curr - len bits are incremented through all values to
       fill the table with replicated entries.

       root is the number of index bits for the root table.  When len exceeds
       root, sub-tables are created pointed to by the root entry with an index
       of the low root bits of huff.  This is saved in low to check for when a
       new sub-table should be started.  drop is zero when the root table is
       being filled, and drop is root when sub-tables are being filled.

       When a new sub-table is needed, it is necessary to look ahead in the
       code lengths to determine what size sub-table is needed.  The length
       counts are used for this, and so count[] is decremented as codes are
       entered in the tables.

       used keeps track of how many table entries have been allocated from the
       provided *table space.  It is checked for LENS and DIST tables against
       the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
       the initial root table size constants.  See the comments in inftrees.h
       for more information.

       sym increments through all symbols, and the loop terminates when
       all codes of length max, i.e. all codes, have been processed.  This
       routine permits incomplete codes, so another loop after this one fills
       in the rest of the decoding tables with invalid code markers.
     */

    /* set up for code type */
    switch (type) {
    case CODES:
        base = extra = work;    /* dummy value--not used */
        end = 19;
        break;
    case LENS:
        base = lbase;
        base -= 257;
        extra = lext;
        extra -= 257;
        end = 256;
        break;
    default:            /* DISTS */
        base = dbase;
        extra = dext;
        end = -1;
    }

    /* initialize state for loop */
    huff = 0;                   /* starting code */
    sym = 0;                    /* starting code symbol */
    len = min;                  /* starting code length */
    next = *table;              /* current table to fill in */
    curr = root;                /* current table index bits */
    drop = 0;                   /* current bits to drop from code for index */
    low = (unsigned)(-1);       /* trigger new sub-table when len > root */
    used = 1U << root;          /* use root table entries */
    mask = used - 1;            /* mask for comparing low */

    /* check available table space */
    if ((type == LENS && used >= ENOUGH_LENS) ||
        (type == DISTS && used >= ENOUGH_DISTS))
        return 1;

    /* process all codes and make table entries */
    for (;;) {
        /* create table entry */
        here.bits = (unsigned char)(len - drop);
        if ((int)(work[sym]) < end) {
            here.op = (unsigned char)0;
            here.val = work[sym];
        }
        else if ((int)(work[sym]) > end) {
            here.op = (unsigned char)(extra[work[sym]]);
            here.val = base[work[sym]];
        }
        else {
            here.op = (unsigned char)(32 + 64);         /* end of block */
            here.val = 0;
        }

        /* replicate for those indices with low len bits equal to huff */
        incr = 1U << (len - drop);
        fill = 1U << curr;
        min = fill;                 /* save offset to next table */
        do {
            fill -= incr;
            next[(huff >> drop) + fill] = here;
        } while (fill != 0);

        /* backwards increment the len-bit code huff */
        incr = 1U << (len - 1);
        while (huff & incr)
            incr >>= 1;
        if (incr != 0) {
            huff &= incr - 1;
            huff += incr;
        }
        else
            huff = 0;

        /* go to next symbol, update count, len */
        sym++;
        if (--(count[len]) == 0) {
            if (len == max) break;
            len = lens[work[sym]];
        }

        /* create new sub-table if needed */
        if (len > root && (huff & mask) != low) {
            /* if first time, transition to sub-tables */
            if (drop == 0)
                drop = root;

            /* increment past last table */
            next += min;            /* here min is 1 << curr */

            /* determine length of next table */
            curr = len - drop;
            left = (int)(1 << curr);
            while (curr + drop < max) {
                left -= count[curr + drop];
                if (left <= 0) break;
                curr++;
                left <<= 1;
            }

            /* check for enough space */
            used += 1U << curr;
            if ((type == LENS && used >= ENOUGH_LENS) ||
                (type == DISTS && used >= ENOUGH_DISTS))
                return 1;

            /* point entry in root table to sub-table */
            low = huff & mask;
            (*table)[low].op = (unsigned char)curr;
            (*table)[low].bits = (unsigned char)root;
            (*table)[low].val = (unsigned short)(next - *table);
        }
    }

    /*
       Fill in rest of table for incomplete codes.  This loop is similar to the
       loop above in incrementing huff for table indices.  It is assumed that
       len is equal to curr + drop, so there is no loop needed to increment
       through high index bits.  When the current sub-table is filled, the loop
       drops back to the root table to fill in any remaining entries there.
     */
    here.op = (unsigned char)64;                /* invalid code marker */
    here.bits = (unsigned char)(len - drop);
    here.val = (unsigned short)0;
    while (huff != 0) {
        /* when done with sub-table, drop back to root table */
        if (drop != 0 && (huff & mask) != low) {
            drop = 0;
            len = root;
            next = *table;
            here.bits = (unsigned char)len;
        }

        /* put invalid code marker in table */
        next[huff >> drop] = here;

        /* backwards increment the len-bit code huff */
        incr = 1U << (len - 1);
        while (huff & incr)
            incr >>= 1;
        if (incr != 0) {
            huff &= incr - 1;
            huff += incr;
        }
        else
            huff = 0;
    }

    /* set return parameters */
    *table += used;
    *bits = root;
    return 0;
}
1	/* inftrees.c -- generate Huffman trees for efficient decoding
2	* Copyright (C) 1995-2010 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	const char inflate_copyright[] =
12	" inflate 1.2.4 Copyright 1995-2010 Mark Adler ";
13	/*
14	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
16	include such an acknowledgment, I would appreciate that you keep this
17	copyright string in the executable of your product.
18	*/
19
20	/*
21	Build a set of tables to decode the provided canonical Huffman code.
22	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
24	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,
26	-1 is an invalid code, and +1 means that ENOUGH isn't enough. table
27	on return points to the next available entry's address. bits is the
28	requested root table index bits, and on return it is the actual root
29	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.
31	*/
32	int inflate_table(type, lens, codes, table, bits, work)
33	codetype type;
34	unsigned short FAR *lens;
35	unsigned codes;
36	code FAR * FAR *table;
37	unsigned FAR *bits;
38	unsigned short FAR *work;
39	{
40	unsigned len; /* a code's length in bits */
41	unsigned sym; /* index of code symbols */
42	unsigned min, max; /* minimum and maximum code lengths */
43	unsigned root; /* number of index bits for root table */
44	unsigned curr; /* number of index bits for current table */
45	unsigned drop; /* code bits to drop for sub-table */
46	int left; /* number of prefix codes available */
47	unsigned used; /* code entries in table used */
48	unsigned huff; /* Huffman code */
49	unsigned incr; /* for incrementing code, index */
50	unsigned fill; /* index for replicating entries */
51	unsigned low; /* low bits for current root entry */
52	unsigned mask; /* mask for low root bits */
53	code here; /* table entry for duplication */
54	code FAR next; / next available space in table */
55	const unsigned short FAR base; / base value table to use */
56	const unsigned short FAR extra; / extra bits table to use */
57	int end; /* use base and extra for symbol > end */
58	unsigned short count[MAXBITS+1]; /* number of codes of each length */
59	unsigned short offs[MAXBITS+1]; /* offsets in table for each length */
60	static const unsigned short lbase[31] = { /* Length codes 257..285 base */
61	3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
62	35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
63	static const unsigned short lext[31] = { /* Length codes 257..285 extra */
64	16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
65	19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 64, 195};
66	static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
67	1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
68	257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
69	8193, 12289, 16385, 24577, 0, 0};
70	static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
71	16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
72	23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
73	28, 28, 29, 29, 64, 64};
74
75	/*
76	Process a set of code lengths to create a canonical Huffman code. The
77	code lengths are lens[0..codes-1]. Each length corresponds to the
78	symbols 0..codes-1. The Huffman code is generated by first sorting the
79	symbols by length from short to long, and retaining the symbol order
80	for codes with equal lengths. Then the code starts with all zero bits
81	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
83	increases. For the deflate format, these bits are stored backwards
84	from their more natural integer increment ordering, and so when the
85	decoding tables are built in the large loop below, the integer codes
86	are incremented backwards.
87
88	This routine assumes, but does not check, that all of the entries in
89	lens[] are in the range 0..MAXBITS. The caller must assure this.
90	1..MAXBITS is interpreted as that code length. zero means that that
91	symbol does not occur in this code.
92
93	The codes are sorted by computing a count of codes for each length,
94	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
96	table. The sorted table is work[], with that space being provided by
97	the caller.
98
99	The length counts are used for other purposes as well, i.e. finding
100	the minimum and maximum length codes, determining if there are any
101	codes at all, checking for a valid set of lengths, and looking ahead
102	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) */
107	for (len = 0; len <= MAXBITS; len++)
108	count[len] = 0;
109	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;
114	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	here.op = (unsigned char)64; /* invalid code marker */
119	here.bits = (unsigned char)1;
120	here.val = (unsigned short)0;
121	(table)++ = here; /* make a table to force an error */
122	(table)++ = here;
123	*bits = 1;
124	return 0; /* no symbols, but wait for decoding to report error */
125	}
126	for (min = 1; min < max; 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 for LENS and DIST tables against
170	the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
171	the initial root table size constants. See the comments in inftrees.h
172	for more information.
173
174	sym increments through all symbols, and the loop terminates when
175	all codes of length max, i.e. all codes, have been processed. This
176	routine permits incomplete codes, so another loop after this one fills
177	in the rest of the decoding tables with invalid code markers.
178	*/
179
180	/* set up for code type */
181	switch (type) {
182	case CODES:
183	base = extra = work; /* dummy value--not used */
184	end = 19;
185	break;
186	case LENS:
187	base = lbase;
188	base -= 257;
189	extra = lext;
190	extra -= 257;
191	end = 256;
192	break;
193	default: /* DISTS */
194	base = dbase;
195	extra = dext;
196	end = -1;
197	}
198
199	/* initialize state for loop */
200	huff = 0; /* starting code */
201	sym = 0; /* starting code symbol */
202	len = min; /* starting code length */
203	next = table; / current table to fill in */
204	curr = root; /* current table index bits */
205	drop = 0; /* current bits to drop from code for index */
206	low = (unsigned)(-1); /* trigger new sub-table when len > root */
207	used = 1U << root; /* use root table entries */
208	mask = used - 1; /* mask for comparing low */
209
210	/* check available table space */
211	if ((type == LENS && used >= ENOUGH_LENS) \|\|
212	(type == DISTS && used >= ENOUGH_DISTS))
213	return 1;
214
215	/* process all codes and make table entries */
216	for (;;) {
217	/* create table entry */
218	here.bits = (unsigned char)(len - drop);
219	if ((int)(work[sym]) < end) {
220	here.op = (unsigned char)0;
221	here.val = work[sym];
222	}
223	else if ((int)(work[sym]) > end) {
224	here.op = (unsigned char)(extra[work[sym]]);
225	here.val = base[work[sym]];
226	}
227	else {
228	here.op = (unsigned char)(32 + 64); /* end of block */
229	here.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] = here;
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_LENS) \|\|
281	(type == DISTS && used >= ENOUGH_DISTS))
282	return 1;
283
284	/* point entry in root table to sub-table */
285	low = huff & mask;
286	(*table)[low].op = (unsigned char)curr;
287	(*table)[low].bits = (unsigned char)root;
288	(table)[low].val = (unsigned short)(next - table);
289	}
290	}
291
292	/*
293	Fill in rest of table for incomplete codes. This loop is similar to the
294	loop above in incrementing huff for table indices. It is assumed that
295	len is equal to curr + drop, so there is no loop needed to increment
296	through high index bits. When the current sub-table is filled, the loop
297	drops back to the root table to fill in any remaining entries there.
298	*/
299	here.op = (unsigned char)64; /* invalid code marker */
300	here.bits = (unsigned char)(len - drop);
301	here.val = (unsigned short)0;
302	while (huff != 0) {
303	/* when done with sub-table, drop back to root table */
304	if (drop != 0 && (huff & mask) != low) {
305	drop = 0;
306	len = root;
307	next = *table;
308	here.bits = (unsigned char)len;
309	}
310
311	/* put invalid code marker in table */
312	next[huff >> drop] = here;
313
314	/* backwards increment the len-bit code huff */
315	incr = 1U << (len - 1);
316	while (huff & incr)
317	incr >>= 1;
318	if (incr != 0) {
319	huff &= incr - 1;
320	huff += incr;
321	}
322	else
323	huff = 0;
324	}
325
326	/* set return parameters */
327	*table += used;
328	*bits = root;
329	return 0;
330	}