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inftree9.c
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1 /* inftree9.c -- generate Huffman trees for efficient decoding
2  * Copyright (C) 1995-2013 Mark Adler
3  * For conditions of distribution and use, see copyright notice in zlib.h
4  */
5 
6 #include "zutil.h"
7 #include "inftree9.h"
8 
9 #define MAXBITS 15
10 
11 const char inflate9_copyright[] =
12  " inflate9 1.2.8 Copyright 1995-2013 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_table9(type, lens, codes, table, bits, work)
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 this; /* 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,
62  19, 23, 27, 31, 35, 43, 51, 59, 67, 83, 99, 115,
63  131, 163, 195, 227, 3, 0, 0};
64  static const unsigned short lext[31] = { /* Length codes 257..285 extra */
65  128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129,
66  130, 130, 130, 130, 131, 131, 131, 131, 132, 132, 132, 132,
67  133, 133, 133, 133, 144, 72, 78};
68  static const unsigned short dbase[32] = { /* Distance codes 0..31 base */
69  1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49,
70  65, 97, 129, 193, 257, 385, 513, 769, 1025, 1537, 2049, 3073,
71  4097, 6145, 8193, 12289, 16385, 24577, 32769, 49153};
72  static const unsigned short dext[32] = { /* Distance codes 0..31 extra */
73  128, 128, 128, 128, 129, 129, 130, 130, 131, 131, 132, 132,
74  133, 133, 134, 134, 135, 135, 136, 136, 137, 137, 138, 138,
75  139, 139, 140, 140, 141, 141, 142, 142};
76 
77  /*
78  Process a set of code lengths to create a canonical Huffman code. The
79  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
81  symbols by length from short to long, and retaining the symbol order
82  for codes with equal lengths. Then the code starts with all zero bits
83  for the first code of the shortest length, and the codes are integer
84  increments for the same length, and zeros are appended as the length
85  increases. For the deflate format, these bits are stored backwards
86  from their more natural integer increment ordering, and so when the
87  decoding tables are built in the large loop below, the integer codes
88  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
93  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
97  sorted table, and then entering the symbols in order in the sorted
98  table. The sorted table is work[], with that space being provided by
99  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 for LENS and DIST tables against
164  the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
165  the initial root table size constants. See the comments in inftree9.h
166  for more information.
167 
168  sym increments through all symbols, and the loop terminates when
169  all codes of length max, i.e. all codes, have been processed. This
170  routine permits incomplete codes, so another loop after this one fills
171  in the rest of the decoding tables with invalid code markers.
172  */
173 
174  /* set up for code type */
175  switch (type) {
176  case CODES:
177  base = extra = work; /* dummy value--not used */
178  end = 19;
179  break;
180  case LENS:
181  base = lbase;
182  base -= 257;
183  extra = lext;
184  extra -= 257;
185  end = 256;
186  break;
187  default: /* DISTS */
188  base = dbase;
189  extra = dext;
190  end = -1;
191  }
192 
193  /* initialize state for loop */
194  huff = 0; /* starting code */
195  sym = 0; /* starting code symbol */
196  len = min; /* starting code length */
197  next = *table; /* current table to fill in */
198  curr = root; /* current table index bits */
199  drop = 0; /* current bits to drop from code for index */
200  low = (unsigned)(-1); /* trigger new sub-table when len > root */
201  used = 1U << root; /* use root table entries */
202  mask = used - 1; /* mask for comparing low */
203 
204  /* check available table space */
205  if ((type == LENS && used >= ENOUGH_LENS) ||
206  (type == DISTS && used >= ENOUGH_DISTS))
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_LENS) ||
274  (type == DISTS && used >= ENOUGH_DISTS))
275  return 1;
276 
277  /* point entry in root table to sub-table */
278  low = huff & mask;
279  (*table)[low].op = (unsigned char)curr;
280  (*table)[low].bits = (unsigned char)root;
281  (*table)[low].val = (unsigned short)(next - *table);
282  }
283  }
284 
285  /*
286  Fill in rest of table for incomplete codes. This loop is similar to the
287  loop above in incrementing huff for table indices. It is assumed that
288  len is equal to curr + drop, so there is no loop needed to increment
289  through high index bits. When the current sub-table is filled, the loop
290  drops back to the root table to fill in any remaining entries there.
291  */
292  this.op = (unsigned char)64; /* invalid code marker */
293  this.bits = (unsigned char)(len - drop);
294  this.val = (unsigned short)0;
295  while (huff != 0) {
296  /* when done with sub-table, drop back to root table */
297  if (drop != 0 && (huff & mask) != low) {
298  drop = 0;
299  len = root;
300  next = *table;
301  curr = root;
302  this.bits = (unsigned char)len;
303  }
304 
305  /* put invalid code marker in table */
306  next[huff >> drop] = this;
307 
308  /* backwards increment the len-bit code huff */
309  incr = 1U << (len - 1);
310  while (huff & incr)
311  incr >>= 1;
312  if (incr != 0) {
313  huff &= incr - 1;
314  huff += incr;
315  }
316  else
317  huff = 0;
318  }
319 
320  /* set return parameters */
321  *table += used;
322  *bits = root;
323  return 0;
324 }
Definition: infutil.h:16
codetype
Definition: inftree9.h:53
#define ENOUGH_DISTS
Definition: inftree9.h:49
int inflate_table9(codetype type, unsigned short FAR *lens, unsigned codes, code FAR *FAR *table, unsigned FAR *bits, unsigned short FAR *work)
Definition: inftree9.c:32
#define bits
Definition: infblock.c:15
GLenum GLint GLuint mask
GLenum GLsizei len
GLint left
Definition: infutil.h:21
float min(float a, float b)
Definition: Vector2.hpp:307
GLuint GLfloat * val
Definition: inftree9.h:56
local int root
Definition: enough.c:171
#define FAR
Definition: zconf.h:215
GLuint GLuint end
local int max
Definition: enough.c:170
Definition: inftree9.h:24
GLenum type
typedef int
Definition: png.h:978
#define ENOUGH_LENS
Definition: inftree9.h:48
GLuint GLuint GLsizei count
GLenum GLint GLenum GLsizei GLsizei GLsizei GLint GLsizei const GLvoid * bits
local int codes(struct state *s, const struct huffman *lencode, const struct huffman *distcode)
Definition: puff.c:436
GLenum GLsizei GLenum GLenum const GLvoid * table
const char inflate9_copyright[]
Definition: inftree9.c:11
#define MAXBITS
Definition: inftree9.c:9