inffast.c
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上传日期:2007-06-13
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- /*
- * ===========================================================================
- * PRODUCTION $Log: inffast.c,v $
- * PRODUCTION Revision 1000.0 2003/10/29 15:49:04 gouriano
- * PRODUCTION PRODUCTION: IMPORTED [ORIGINAL] Dev-tree R1.1
- * PRODUCTION
- * ===========================================================================
- */
- /* inffast.c -- process literals and length/distance pairs fast
- * Copyright (C) 1995-2002 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%02xn", 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 %un", 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 %un", d));
- /* do the copy */
- m -= c;
- r = q - d;
- if (r < s->window) /* wrap if needed */
- {
- do {
- r += s->end - s->window; /* force pointer in window */
- } while (r < s->window); /* covers invalid distances */
- e = s->end - r;
- if (c > e)
- {
- c -= e; /* wrapped copy */
- do {
- *q++ = *r++;
- } while (--e);
- r = s->window;
- do {
- *q++ = *r++;
- } while (--c);
- }
- else /* normal copy */
- {
- *q++ = *r++; c--;
- *q++ = *r++; c--;
- do {
- *q++ = *r++;
- } while (--c);
- }
- }
- else /* normal copy */
- {
- *q++ = *r++; c--;
- *q++ = *r++; c--;
- do {
- *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%02xn", t->base));
- *q++ = (Byte)t->base;
- m--;
- break;
- }
- }
- else if (e & 32)
- {
- Tracevv((stderr, "inflate: * end of blockn"));
- 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;
- }