337 lines
12 KiB
C
337 lines
12 KiB
C
/*
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Copyright (c) 1990-2008 Info-ZIP. All rights reserved.
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See the accompanying file LICENSE, version 2000-Apr-09 or later
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(the contents of which are also included in unzip.h) for terms of use.
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If, for some reason, all these files are missing, the Info-ZIP license
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also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
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*/
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/*---------------------------------------------------------------------------
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unshrink.c version 1.22 19 Mar 2008
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NOTE: This code may or may not infringe on the so-called "Welch
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patent" owned by Unisys. (From reading the patent, it appears
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that a pure LZW decompressor is *not* covered, but this claim has
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not been tested in court, and Unisys is reported to believe other-
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wise.) It is therefore the responsibility of the user to acquire
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whatever license(s) may be required for legal use of this code.
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THE INFO-ZIP GROUP DISCLAIMS ALL LIABILITY FOR USE OF THIS CODE
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IN VIOLATION OF APPLICABLE PATENT LAW.
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Shrinking is basically a dynamic LZW algorithm with allowed code sizes of
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up to 13 bits; in addition, there is provision for partial clearing of
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leaf nodes. PKWARE uses the special code 256 (decimal) to indicate a
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change in code size or a partial clear of the code tree: 256,1 for the
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former and 256,2 for the latter. [Note that partial clearing can "orphan"
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nodes: the parent-to-be can be cleared before its new child is added,
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but the child is added anyway (as an orphan, as though the parent still
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existed). When the tree fills up to the point where the parent node is
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reused, the orphan is effectively "adopted." Versions prior to 1.05 were
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affected more due to greater use of pointers (to children and siblings
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as well as parents).]
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This replacement version of unshrink.c was written from scratch. It is
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based only on the algorithms described in Mark Nelson's _The Data Compres-
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sion Book_ and in Terry Welch's original paper in the June 1984 issue of
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IEEE _Computer_; no existing source code, including any in Nelson's book,
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was used.
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Memory requirements have been reduced in this version and are now no more
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than the original Sam Smith code. This is still larger than any of the
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other algorithms: at a minimum, 8K+8K+16K (stack+values+parents) assuming
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16-bit short ints, and this does not even include the output buffer (the
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other algorithms leave the uncompressed data in the work area, typically
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called slide[]). For machines with a 64KB data space this is a problem,
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particularly when text conversion is required and line endings have more
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than one character. UnZip's solution is to use two roughly equal halves
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of outbuf for the ASCII conversion in such a case; the "unshrink" argument
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to flush() signals that this is the case.
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For large-memory machines, a second outbuf is allocated for translations,
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but only if unshrinking and only if translations are required.
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| binary mode | text mode
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---------------------------------------------------
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big mem | big outbuf | big outbuf + big outbuf2 <- malloc'd here
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small mem | small outbuf | half + half small outbuf
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Copyright 1994, 1995 Greg Roelofs. See the accompanying file "COPYING"
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in UnZip 5.20 (or later) source or binary distributions.
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---------------------------------------------------------------------------*/
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#define __UNSHRINK_C /* identifies this source module */
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#define UNZIP_INTERNAL
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#include "unzip.h"
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#ifndef LZW_CLEAN
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static void partial_clear OF((__GPRO__ int lastcodeused));
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#ifdef DEBUG
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# define OUTDBG(c) \
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if ((c)<32 || (c)>=127) fprintf(stderr,"\\x%02x",(c)); else putc((c),stderr);
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#else
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# define OUTDBG(c)
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#endif
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/* HSIZE is defined as 2^13 (8192) in unzip.h (resp. unzpriv.h */
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#define BOGUSCODE 256
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#define FLAG_BITS parent /* upper bits of parent[] used as flag bits */
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#define CODE_MASK (HSIZE - 1) /* 0x1fff (lower bits are parent's index) */
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#define FREE_CODE HSIZE /* 0x2000 (code is unused or was cleared) */
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#define HAS_CHILD (HSIZE << 1) /* 0x4000 (code has a child--do not clear) */
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#define parent G.area.shrink.Parent
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#define Value G.area.shrink.value /* "value" conflicts with Pyramid ioctl.h */
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#define stack G.area.shrink.Stack
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/***********************/
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/* Function unshrink() */
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/***********************/
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int unshrink(__G)
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__GDEF
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{
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uch *stacktop = stack + (HSIZE - 1);
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register uch *newstr;
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uch finalval;
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int codesize=9, len, error;
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shrint code, oldcode, curcode;
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shrint lastfreecode;
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unsigned int outbufsiz;
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#if (defined(DLL) && !defined(NO_SLIDE_REDIR))
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/* Normally realbuf and outbuf will be the same. However, if the data
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* are redirected to a large memory buffer, realbuf will point to the
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* new location while outbuf will remain pointing to the malloc'd
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* memory buffer. */
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uch *realbuf = G.outbuf;
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#else
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# define realbuf G.outbuf
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#endif
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/*---------------------------------------------------------------------------
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Initialize various variables.
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---------------------------------------------------------------------------*/
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lastfreecode = BOGUSCODE;
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#ifndef VMS /* VMS uses its own buffer scheme for textmode flush(). */
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#ifndef SMALL_MEM
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/* non-memory-limited machines: allocate second (large) buffer for
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* textmode conversion in flush(), but only if needed */
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if (G.pInfo->textmode && !G.outbuf2 &&
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(G.outbuf2 = (uch *)malloc(TRANSBUFSIZ)) == (uch *)NULL)
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return PK_MEM3;
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#endif
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#endif /* !VMS */
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for (code = 0; code < BOGUSCODE; ++code) {
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Value[code] = (uch)code;
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parent[code] = BOGUSCODE;
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}
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for (code = BOGUSCODE+1; code < HSIZE; ++code)
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parent[code] = FREE_CODE;
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#if (defined(DLL) && !defined(NO_SLIDE_REDIR))
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if (G.redirect_slide) { /* use normal outbuf unless we're a DLL routine */
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realbuf = G.redirect_buffer;
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outbufsiz = (unsigned)G.redirect_size;
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} else
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#endif
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#ifdef DLL
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if (G.pInfo->textmode && !G.redirect_data)
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#else
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if (G.pInfo->textmode)
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#endif
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outbufsiz = RAWBUFSIZ;
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else
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outbufsiz = OUTBUFSIZ;
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G.outptr = realbuf;
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G.outcnt = 0L;
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/*---------------------------------------------------------------------------
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Get and output first code, then loop over remaining ones.
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---------------------------------------------------------------------------*/
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READBITS(codesize, oldcode)
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if (G.zipeof)
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return PK_OK;
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finalval = (uch)oldcode;
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OUTDBG(finalval)
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*G.outptr++ = finalval;
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++G.outcnt;
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while (TRUE) {
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READBITS(codesize, code)
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if (G.zipeof)
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break;
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if (code == BOGUSCODE) { /* possible to have consecutive escapes? */
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READBITS(codesize, code)
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if (G.zipeof)
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break;
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if (code == 1) {
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++codesize;
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Trace((stderr, " (codesize now %d bits)\n", codesize));
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if (codesize > MAX_BITS) return PK_ERR;
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} else if (code == 2) {
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Trace((stderr, " (partial clear code)\n"));
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/* clear leafs (nodes with no children) */
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partial_clear(__G__ lastfreecode);
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Trace((stderr, " (done with partial clear)\n"));
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lastfreecode = BOGUSCODE; /* reset start of free-node search */
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}
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continue;
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}
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/*-----------------------------------------------------------------------
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Translate code: traverse tree from leaf back to root.
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-----------------------------------------------------------------------*/
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newstr = stacktop;
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curcode = code;
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if (parent[code] == FREE_CODE) {
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/* or (FLAG_BITS[code] & FREE_CODE)? */
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Trace((stderr, " (found a KwKwK code %d; oldcode = %d)\n", code,
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oldcode));
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*newstr-- = finalval;
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code = oldcode;
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}
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while (code != BOGUSCODE) {
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if (newstr < stack) {
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/* Bogus compression stream caused buffer underflow! */
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Trace((stderr, "unshrink stack overflow!\n"));
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return PK_ERR;
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}
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if (parent[code] == FREE_CODE) {
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/* or (FLAG_BITS[code] & FREE_CODE)? */
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Trace((stderr, " (found a KwKwK code %d; oldcode = %d)\n",
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code, oldcode));
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*newstr-- = finalval;
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code = oldcode;
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} else {
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*newstr-- = Value[code];
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code = (shrint)(parent[code] & CODE_MASK);
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}
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}
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len = (int)(stacktop - newstr++);
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finalval = *newstr;
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/*-----------------------------------------------------------------------
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Write expanded string in reverse order to output buffer.
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-----------------------------------------------------------------------*/
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Trace((stderr,
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"code %4d; oldcode %4d; char %3d (%c); len %d; string [", curcode,
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oldcode, (int)(*newstr), (*newstr<32 || *newstr>=127)? ' ':*newstr,
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len));
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{
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register uch *p;
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for (p = newstr; p < newstr+len; ++p) {
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*G.outptr++ = *p;
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OUTDBG(*p)
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if (++G.outcnt == outbufsiz) {
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Trace((stderr, "doing flush(), outcnt = %lu\n", G.outcnt));
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if ((error = flush(__G__ realbuf, G.outcnt, TRUE)) != 0) {
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Trace((stderr, "unshrink: flush() error (%d)\n",
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error));
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return error;
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}
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G.outptr = realbuf;
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G.outcnt = 0L;
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Trace((stderr, "done with flush()\n"));
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}
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}
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}
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/*-----------------------------------------------------------------------
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Add new leaf (first character of newstr) to tree as child of oldcode.
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-----------------------------------------------------------------------*/
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/* search for freecode */
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code = (shrint)(lastfreecode + 1);
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/* add if-test before loop for speed? */
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while ((code < HSIZE) && (parent[code] != FREE_CODE))
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++code;
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lastfreecode = code;
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Trace((stderr, "]; newcode %d\n", code));
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if (code >= HSIZE)
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/* invalid compressed data caused max-code overflow! */
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return PK_ERR;
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Value[code] = finalval;
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parent[code] = oldcode;
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oldcode = curcode;
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}
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/*---------------------------------------------------------------------------
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Flush any remaining data and return to sender...
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---------------------------------------------------------------------------*/
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if (G.outcnt > 0L) {
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Trace((stderr, "doing final flush(), outcnt = %lu\n", G.outcnt));
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if ((error = flush(__G__ realbuf, G.outcnt, TRUE)) != 0) {
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Trace((stderr, "unshrink: flush() error (%d)\n", error));
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return error;
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}
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Trace((stderr, "done with flush()\n"));
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}
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return PK_OK;
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} /* end function unshrink() */
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/****************************/
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/* Function partial_clear() */ /* no longer recursive... */
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/****************************/
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static void partial_clear(__G__ lastcodeused)
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__GDEF
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int lastcodeused;
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{
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register shrint code;
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/* clear all nodes which have no children (i.e., leaf nodes only) */
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/* first loop: mark each parent as such */
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for (code = BOGUSCODE+1; code <= lastcodeused; ++code) {
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register shrint cparent = (shrint)(parent[code] & CODE_MASK);
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if (cparent > BOGUSCODE)
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FLAG_BITS[cparent] |= HAS_CHILD; /* set parent's child-bit */
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}
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/* second loop: clear all nodes *not* marked as parents; reset flag bits */
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for (code = BOGUSCODE+1; code <= lastcodeused; ++code) {
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if (FLAG_BITS[code] & HAS_CHILD) /* just clear child-bit */
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FLAG_BITS[code] &= ~HAS_CHILD;
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else { /* leaf: lose it */
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Trace((stderr, "%d\n", code));
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parent[code] = FREE_CODE;
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}
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}
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return;
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}
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#endif /* !LZW_CLEAN */
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