path: root/runtime/zlib/inflate.c

/* inflate.c -- zlib decompression
 * Copyright (C) 1995-2003 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/*
 * Change history:
 *
 * 1.2.beta0    24 Nov 2002
 * - First version -- complete rewrite of inflate to simplify code, avoid
 *   creation of window when not needed, minimize use of window when it is
 *   needed, make inffast.c even faster, implement gzip decoding, and to
 *   improve code readability and style over the previous zlib inflate code
 *
 * 1.2.beta1    25 Nov 2002
 * - Use pointers for available input and output checking in inffast.c
 * - Remove input and output counters in inffast.c
 * - Change inffast.c entry and loop from avail_in >= 7 to >= 6
 * - Remove unnecessary second byte pull from length extra in inffast.c
 * - Unroll direct copy to three copies per loop in inffast.c
 *
 * 1.2.beta2    4 Dec 2002
 * - Change external routine names to reduce potential conflicts
 * - Correct filename to inffixed.h for fixed tables in inflate.c
 * - Make hbuf[] unsigned char to match parameter type in inflate.c
 * - Change strm->next_out[-state->offset] to *(strm->next_out - state->offset)
 *   to avoid negation problem on Alphas (64 bit) in inflate.c
 *
 * 1.2.beta3    22 Dec 2002
 * - Add comments on state->bits assertion in inffast.c
 * - Add comments on op field in inftrees.h
 * - Fix bug in reuse of allocated window after inflateReset()
 * - Remove bit fields--back to byte structure for speed
 * - Remove distance extra == 0 check in inflate_fast()--only helps for lengths
 * - Change post-increments to pre-increments in inflate_fast(), PPC biased?
 * - Add compile time option, POSTINC, to use post-increments instead (Intel?)
 * - Make MATCH copy in inflate() much faster for when inflate_fast() not used
 * - Use local copies of stream next and avail values, as well as local bit
 *   buffer and bit count in inflate()--for speed when inflate_fast() not used
 *
 * 1.2.beta4    1 Jan 2003
 * - Split ptr - 257 statements in inflate_table() to avoid compiler warnings
 * - Move a comment on output buffer sizes from inffast.c to inflate.c
 * - Add comments in inffast.c to introduce the inflate_fast() routine
 * - Rearrange window copies in inflate_fast() for speed and simplification
 * - Unroll last copy for window match in inflate_fast()
 * - Use local copies of window variables in inflate_fast() for speed
 * - Pull out common write == 0 case for speed in inflate_fast()
 * - Make op and len in inflate_fast() unsigned for consistency
 * - Add FAR to lcode and dcode declarations in inflate_fast()
 * - Simplified bad distance check in inflate_fast()
 * - Added inflateBackInit(), inflateBack(), and inflateBackEnd() in new
 *   source file infback.c to provide a call-back interface to inflate for
 *   programs like gzip and unzip -- uses window as output buffer to avoid
 *   window copying
 *
 * 1.2.beta5    1 Jan 2003
 * - Improved inflateBack() interface to allow the caller to provide initial
 *   input in strm.
 * - Fixed stored blocks bug in inflateBack()
 *
 * 1.2.beta6    4 Jan 2003
 * - Added comments in inffast.c on effectiveness of POSTINC
 * - Typecasting all around to reduce compiler warnings
 * - Changed loops from while (1) or do {} while (1) to for (;;), again to
 *   make compilers happy
 * - Changed type of window in inflateBackInit() to unsigned char *
 *
 * 1.2.beta7    27 Jan 2003
 * - Changed many types to unsigned or unsigned short to avoid warnings
 * - Added inflateCopy() function
 *
 * 1.2.0        9 Mar 2003
 * - Changed inflateBack() interface to provide separate opaque descriptors
 *   for the in() and out() functions
 * - Changed inflateBack() argument and in_func typedef to swap the length
 *   and buffer address return values for the input function
 * - Check next_in and next_out for Z_NULL on entry to inflate()
 *
 * The history for versions after 1.2.0 are in ChangeLog in zlib distribution.
 */

#include "zutil.h"
#include "inftrees.h"
#include "inflate.h"
#include "inffast.h"

#ifdef MAKEFIXED
#  ifndef BUILDFIXED
#    define BUILDFIXED
#  endif
#endif

/* function prototypes */
local void fixedtables OF((struct inflate_state FAR *state));
local int updatewindow OF((z_streamp strm, unsigned out));
#ifdef BUILDFIXED
   void makefixed OF((void));
#endif
local unsigned syncsearch OF((unsigned FAR *have, unsigned char FAR *buf,
                              unsigned len));

int ZEXPORT inflateReset(strm)
z_streamp strm;
{
    struct inflate_state FAR *state;

    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
    state = (struct inflate_state FAR *)strm->state;
    strm->total_in = strm->total_out = state->total = 0;
    strm->msg = Z_NULL;
    state->mode = HEAD;
    state->last = 0;
    state->havedict = 0;
    state-&g