source: trunk/third/zlib/inffast.c @ 15211

Revision 15211, 5.5 KB checked in by ghudson, 24 years ago (diff)
This commit was generated by cvs2svn to compensate for changes in r15210, which included commits to RCS files with non-trunk default branches.
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1/* inffast.c -- process literals and length/distance pairs fast
2 * Copyright (C) 1995-1998 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#include "infblock.h"
9#include "infcodes.h"
10#include "infutil.h"
11#include "inffast.h"
12
13struct inflate_codes_state {int dummy;}; /* for buggy compilers */
14
15/* simplify the use of the inflate_huft type with some defines */
16#define exop word.what.Exop
17#define bits word.what.Bits
18
19/* macros for bit input with no checking and for returning unused bytes */
20#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
21#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}
22
23/* Called with number of bytes left to write in window at least 258
24   (the maximum string length) and number of input bytes available
25   at least ten.  The ten bytes are six bytes for the longest length/
26   distance pair plus four bytes for overloading the bit buffer. */
27
28int inflate_fast(bl, bd, tl, td, s, z)
29uInt bl, bd;
30inflate_huft *tl;
31inflate_huft *td; /* need separate declaration for Borland C++ */
32inflate_blocks_statef *s;
33z_streamp z;
34{
35  inflate_huft *t;      /* temporary pointer */
36  uInt e;               /* extra bits or operation */
37  uLong b;              /* bit buffer */
38  uInt k;               /* bits in bit buffer */
39  Bytef *p;             /* input data pointer */
40  uInt n;               /* bytes available there */
41  Bytef *q;             /* output window write pointer */
42  uInt m;               /* bytes to end of window or read pointer */
43  uInt ml;              /* mask for literal/length tree */
44  uInt md;              /* mask for distance tree */
45  uInt c;               /* bytes to copy */
46  uInt d;               /* distance back to copy from */
47  Bytef *r;             /* copy source pointer */
48
49  /* load input, output, bit values */
50  LOAD
51
52  /* initialize masks */
53  ml = inflate_mask[bl];
54  md = inflate_mask[bd];
55
56  /* do until not enough input or output space for fast loop */
57  do {                          /* assume called with m >= 258 && n >= 10 */
58    /* get literal/length code */
59    GRABBITS(20)                /* max bits for literal/length code */
60    if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
61    {
62      DUMPBITS(t->bits)
63      Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
64                "inflate:         * literal '%c'\n" :
65                "inflate:         * literal 0x%02x\n", t->base));
66      *q++ = (Byte)t->base;
67      m--;
68      continue;
69    }
70    do {
71      DUMPBITS(t->bits)
72      if (e & 16)
73      {
74        /* get extra bits for length */
75        e &= 15;
76        c = t->base + ((uInt)b & inflate_mask[e]);
77        DUMPBITS(e)
78        Tracevv((stderr, "inflate:         * length %u\n", c));
79
80        /* decode distance base of block to copy */
81        GRABBITS(15);           /* max bits for distance code */
82        e = (t = td + ((uInt)b & md))->exop;
83        do {
84          DUMPBITS(t->bits)
85          if (e & 16)
86          {
87            /* get extra bits to add to distance base */
88            e &= 15;
89            GRABBITS(e)         /* get extra bits (up to 13) */
90            d = t->base + ((uInt)b & inflate_mask[e]);
91            DUMPBITS(e)
92            Tracevv((stderr, "inflate:         * distance %u\n", d));
93
94            /* do the copy */
95            m -= c;
96            if ((uInt)(q - s->window) >= d)     /* offset before dest */
97            {                                   /*  just copy */
98              r = q - d;
99              *q++ = *r++;  c--;        /* minimum count is three, */
100              *q++ = *r++;  c--;        /*  so unroll loop a little */
101            }
102            else                        /* else offset after destination */
103            {
104              e = d - (uInt)(q - s->window); /* bytes from offset to end */
105              r = s->end - e;           /* pointer to offset */
106              if (c > e)                /* if source crosses, */
107              {
108                c -= e;                 /* copy to end of window */
109                do {
110                  *q++ = *r++;
111                } while (--e);
112                r = s->window;          /* copy rest from start of window */
113              }
114            }
115            do {                        /* copy all or what's left */
116              *q++ = *r++;
117            } while (--c);
118            break;
119          }
120          else if ((e & 64) == 0)
121          {
122            t += t->base;
123            e = (t += ((uInt)b & inflate_mask[e]))->exop;
124          }
125          else
126          {
127            z->msg = (char*)"invalid distance code";
128            UNGRAB
129            UPDATE
130            return Z_DATA_ERROR;
131          }
132        } while (1);
133        break;
134      }
135      if ((e & 64) == 0)
136      {
137        t += t->base;
138        if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
139        {
140          DUMPBITS(t->bits)
141          Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
142                    "inflate:         * literal '%c'\n" :
143                    "inflate:         * literal 0x%02x\n", t->base));
144          *q++ = (Byte)t->base;
145          m--;
146          break;
147        }
148      }
149      else if (e & 32)
150      {
151        Tracevv((stderr, "inflate:         * end of block\n"));
152        UNGRAB
153        UPDATE
154        return Z_STREAM_END;
155      }
156      else
157      {
158        z->msg = (char*)"invalid literal/length code";
159        UNGRAB
160        UPDATE
161        return Z_DATA_ERROR;
162      }
163    } while (1);
164  } while (m >= 258 && n >= 10);
165
166  /* not enough input or output--restore pointers and return */
167  UNGRAB
168  UPDATE
169  return Z_OK;
170}
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