ReactOS  0.4.13-dev-73-gcfe54aa
inftrees.c File Reference
#include "zutil.h"
#include "inftrees.h"
Include dependency graph for inftrees.c:

Go to the source code of this file.

Macros

#define MAXBITS   15
 

Functions

int ZLIB_INTERNAL inflate_table (codetype type, unsigned short FAR *lens, unsigned codes, code FAR *FAR *table, unsigned FAR *bits, unsigned short FAR *work)
 

Variables

const char inflate_copyright []
 

Macro Definition Documentation

◆ MAXBITS

#define MAXBITS   15

Definition at line 9 of file inftrees.c.

Function Documentation

◆ inflate_table()

int ZLIB_INTERNAL inflate_table ( codetype  type,
unsigned short FAR lens,
unsigned  codes,
code FAR * FAR table,
unsigned FAR bits,
unsigned short FAR work 
)

Definition at line 32 of file inftrees.c.

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  unsigned match; /* use base and extra for symbol >= match */
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, 77, 202};
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  match = 20;
185  break;
186  case LENS:
187  base = lbase;
188  extra = lext;
189  match = 257;
190  break;
191  default: /* DISTS */
192  base = dbase;
193  extra = dext;
194  match = 0;
195  }
196 
197  /* initialize state for loop */
198  huff = 0; /* starting code */
199  sym = 0; /* starting code symbol */
200  len = min; /* starting code length */
201  next = *table; /* current table to fill in */
202  curr = root; /* current table index bits */
203  drop = 0; /* current bits to drop from code for index */
204  low = (unsigned)(-1); /* trigger new sub-table when len > root */
205  used = 1U << root; /* use root table entries */
206  mask = used - 1; /* mask for comparing low */
207 
208  /* check available table space */
209  if ((type == LENS && used > ENOUGH_LENS) ||
210  (type == DISTS && used > ENOUGH_DISTS))
211  return 1;
212 
213  /* process all codes and make table entries */
214  for (;;) {
215  /* create table entry */
216  here.bits = (unsigned char)(len - drop);
217  if (work[sym] + 1U < match) {
218  here.op = (unsigned char)0;
219  here.val = work[sym];
220  }
221  else if (work[sym] >= match) {
222  here.op = (unsigned char)(extra[work[sym] - match]);
223  here.val = base[work[sym] - match];
224  }
225  else {
226  here.op = (unsigned char)(32 + 64); /* end of block */
227  here.val = 0;
228  }
229 
230  /* replicate for those indices with low len bits equal to huff */
231  incr = 1U << (len - drop);
232  fill = 1U << curr;
233  min = fill; /* save offset to next table */
234  do {
235  fill -= incr;
236  next[(huff >> drop) + fill] = here;
237  } while (fill != 0);
238 
239  /* backwards increment the len-bit code huff */
240  incr = 1U << (len - 1);
241  while (huff & incr)
242  incr >>= 1;
243  if (incr != 0) {
244  huff &= incr - 1;
245  huff += incr;
246  }
247  else
248  huff = 0;
249 
250  /* go to next symbol, update count, len */
251  sym++;
252  if (--(count[len]) == 0) {
253  if (len == max) break;
254  len = lens[work[sym]];
255  }
256 
257  /* create new sub-table if needed */
258  if (len > root && (huff & mask) != low) {
259  /* if first time, transition to sub-tables */
260  if (drop == 0)
261  drop = root;
262 
263  /* increment past last table */
264  next += min; /* here min is 1 << curr */
265 
266  /* determine length of next table */
267  curr = len - drop;
268  left = (int)(1 << curr);
269  while (curr + drop < max) {
270  left -= count[curr + drop];
271  if (left <= 0) break;
272  curr++;
273  left <<= 1;
274  }
275 
276  /* check for enough space */
277  used += 1U << curr;
278  if ((type == LENS && used > ENOUGH_LENS) ||
279  (type == DISTS && used > ENOUGH_DISTS))
280  return 1;
281 
282  /* point entry in root table to sub-table */
283  low = huff & mask;
284  (*table)[low].op = (unsigned char)curr;
285  (*table)[low].bits = (unsigned char)root;
286  (*table)[low].val = (unsigned short)(next - *table);
287  }
288  }
289 
290  /* fill in remaining table entry if code is incomplete (guaranteed to have
291  at most one remaining entry, since if the code is incomplete, the
292  maximum code length that was allowed to get this far is one bit) */
293  if (huff != 0) {
294  here.op = (unsigned char)64; /* invalid code marker */
295  here.bits = (unsigned char)(len - drop);
296  here.val = (unsigned short)0;
297  next[huff] = here;
298  }
299 
300  /* set return parameters */
301  *table += used;
302  *bits = root;
303  return 0;
304 }
Definition: infutil.h:16
unsigned short val
Definition: inftrees.h:27
#define max(a, b)
Definition: svc.c:63
Definition: match.c:28
GLuint GLuint GLsizei count
Definition: gl.h:1545
struct _root root
#define U(x)
Definition: wordpad.c:44
GLuint GLuint GLsizei GLenum type
Definition: gl.h:1545
GLenum GLsizei GLenum GLenum const GLvoid * table
Definition: glext.h:5644
GLenum GLint GLenum GLsizei GLsizei GLsizei GLint GLsizei const GLvoid * bits
Definition: glext.h:10929
unsigned char op
Definition: inftrees.h:25
unsigned short(__cdecl typeof(TIFFCurrentDirectory))(struct tiff *)
Definition: typeof.h:93
GLenum GLint GLuint mask
Definition: glext.h:6028
GLuint base
Definition: 3dtext.c:35
#define FAR
Definition: guiddef.h:36
unsigned char
Definition: typeof.h:29
struct match match
Definition: match.c:33
#define ENOUGH_DISTS
Definition: inftrees.h:50
Definition: infutil.h:21
c used
Definition: write.c:2885
Definition: id3.c:18
_STLP_MOVE_TO_STD_NAMESPACE void fill(_ForwardIter __first, _ForwardIter __last, const _Tp &__val)
Definition: _algobase.h:449
GLint left
Definition: glext.h:7726
unsigned char bits
Definition: inftrees.h:26
GLenum GLsizei len
Definition: glext.h:6722
#define MAXBITS
Definition: inftrees.c:9
static unsigned __int64 next
Definition: rand_nt.c:6
#define min(a, b)
Definition: monoChain.cc:55
#define ENOUGH_LENS
Definition: inftrees.h:49
Definition: inftrees.h:57
unsigned int(__cdecl typeof(jpeg_read_scanlines))(struct jpeg_decompress_struct *
Definition: typeof.h:31

Referenced by fixedtables(), inflate(), and inflateBack().

Variable Documentation

◆ inflate_copyright

const char inflate_copyright[]
Initial value:
=
" inflate 1.2.11 Copyright 1995-2017 Mark Adler "

Definition at line 11 of file inftrees.c.