diff options
Diffstat (limited to 'zlib/inffast.c')
| -rw-r--r-- | zlib/inffast.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/zlib/inffast.c b/zlib/inffast.c new file mode 100644 index 000000000..61a78ee93 --- /dev/null +++ b/zlib/inffast.c @@ -0,0 +1,170 @@ +/* inffast.c -- process literals and length/distance pairs fast + * Copyright (C) 1995-1998 Mark Adler + * For conditions of distribution and use, see copyright notice in zlib.h + */ + +#include "zutil.h" +#include "inftrees.h" +#include "infblock.h" +#include "infcodes.h" +#include "infutil.h" +#include "inffast.h" + +struct inflate_codes_state {int dummy;}; /* for buggy compilers */ + +/* simplify the use of the inflate_huft type with some defines */ +#define exop word.what.Exop +#define bits word.what.Bits + +/* macros for bit input with no checking and for returning unused bytes */ +#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}} +#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;} + +/* Called with number of bytes left to write in window at least 258 + (the maximum string length) and number of input bytes available + at least ten. The ten bytes are six bytes for the longest length/ + distance pair plus four bytes for overloading the bit buffer. */ + +int inflate_fast(bl, bd, tl, td, s, z) +uInt bl, bd; +inflate_huft *tl; +inflate_huft *td; /* need separate declaration for Borland C++ */ +inflate_blocks_statef *s; +z_streamp z; +{ + inflate_huft *t; /* temporary pointer */ + uInt e; /* extra bits or operation */ + uLong b; /* bit buffer */ + uInt k; /* bits in bit buffer */ + Bytef *p; /* input data pointer */ + uInt n; /* bytes available there */ + Bytef *q; /* output window write pointer */ + uInt m; /* bytes to end of window or read pointer */ + uInt ml; /* mask for literal/length tree */ + uInt md; /* mask for distance tree */ + uInt c; /* bytes to copy */ + uInt d; /* distance back to copy from */ + Bytef *r; /* copy source pointer */ + + /* load input, output, bit values */ + LOAD + + /* initialize masks */ + ml = inflate_mask[bl]; + md = inflate_mask[bd]; + + /* do until not enough input or output space for fast loop */ + do { /* assume called with m >= 258 && n >= 10 */ + /* get literal/length code */ + GRABBITS(20) /* max bits for literal/length code */ + if ((e = (t = tl + ((uInt)b & ml))->exop) == 0) + { + DUMPBITS(t->bits) + Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? + "inflate: * literal '%c'\n" : + "inflate: * literal 0x%02x\n", t->base)); + *q++ = (Byte)t->base; + m--; + continue; + } + do { + DUMPBITS(t->bits) + if (e & 16) + { + /* get extra bits for length */ + e &= 15; + c = t->base + ((uInt)b & inflate_mask[e]); + DUMPBITS(e) + Tracevv((stderr, "inflate: * length %u\n", c)); + + /* decode distance base of block to copy */ + GRABBITS(15); /* max bits for distance code */ + e = (t = td + ((uInt)b & md))->exop; + do { + DUMPBITS(t->bits) + if (e & 16) + { + /* get extra bits to add to distance base */ + e &= 15; + GRABBITS(e) /* get extra bits (up to 13) */ + d = t->base + ((uInt)b & inflate_mask[e]); + DUMPBITS(e) + Tracevv((stderr, "inflate: * distance %u\n", d)); + + /* do the copy */ + m -= c; + if ((uInt)(q - s->window) >= d) /* offset before dest */ + { /* just copy */ + r = q - d; + *q++ = *r++; c--; /* minimum count is three, */ + *q++ = *r++; c--; /* so unroll loop a little */ + } + else /* else offset after destination */ + { + e = d - (uInt)(q - s->window); /* bytes from offset to end */ + r = s->end - e; /* pointer to offset */ + if (c > e) /* if source crosses, */ + { + c -= e; /* copy to end of window */ + do { + *q++ = *r++; + } while (--e); + r = s->window; /* copy rest from start of window */ + } + } + do { /* copy all or what's left */ + *q++ = *r++; + } while (--c); + break; + } + else if ((e & 64) == 0) + { + t += t->base; + e = (t += ((uInt)b & inflate_mask[e]))->exop; + } + else + { + z->msg = (char*)"invalid distance code"; + UNGRAB + UPDATE + return Z_DATA_ERROR; + } + } while (1); + break; + } + if ((e & 64) == 0) + { + t += t->base; + if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0) + { + DUMPBITS(t->bits) + Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? + "inflate: * literal '%c'\n" : + "inflate: * literal 0x%02x\n", t->base)); + *q++ = (Byte)t->base; + m--; + break; + } + } + else if (e & 32) + { + Tracevv((stderr, "inflate: * end of block\n")); + UNGRAB + UPDATE + return Z_STREAM_END; + } + else + { + z->msg = (char*)"invalid literal/length code"; + UNGRAB + UPDATE + return Z_DATA_ERROR; + } + } while (1); + } while (m >= 258 && n >= 10); + + /* not enough input or output--restore pointers and return */ + UNGRAB + UPDATE + return Z_OK; +} |