/*--------------------------------------------------------------------------- unshrink.c version 1.21 23 Nov 95 Shrinking is basically a dynamic LZW algorithm with allowed code sizes of up to 13 bits; in addition, there is provision for partial clearing of leaf nodes. PKWARE uses the special code 256 (decimal) to indicate a change in code size or a partial clear of the code tree: 256,1 for the former and 256,2 for the latter. [Note that partial clearing can "orphan" nodes: the parent-to-be can be cleared before its new child is added, but the child is added anyway (as an orphan, as though the parent still exists). When the tree fills up to the point where the parent node is reused, the orphan is effectively "adopted." Versions prior to 1.05 were more affected due to their use of more pointers (to children and siblings as well as parents).] This replacement version of unshrink.c was written from scratch. It is based only on the algorithms described in Mark Nelson's _The Data Compres- sion Book_ and in Terry Welch's original paper in the June 1984 issue of IEEE _Computer_; no existing source code, including any in Nelson's book, was used. Memory requirements have been reduced in this version and are now no more than the original Sam Smith code. This is still larger than any of the other algorithms: at a minimum, 8K+8K+16K (stack+values+parents) assuming 16-bit short ints, and this does not even include the output buffer (the other algorithms leave the uncompressed data in the work area, typically called slide[]). For machines with a 64KB data space this is a problem, particularly when text conversion is required and line endings have more than one character. UnZip's solution is to use two roughly equal halves of outbuf for the ASCII conversion in such a case; the "unshrink" argument to flush() signals that this is the case. For large-memory machines, a second outbuf is allocated for translations, but only if unshrinking and only if translations are required. | binary mode | text mode --------------------------------------------------- big mem | big outbuf | big outbuf + big outbuf2 <- malloc'd here small mem | small outbuf | half + half small outbuf Copyright 1994, 1995 Greg Roelofs. See the accompanying file "COPYING" in UnZip 5.20 (or later) source or binary distributions. ---------------------------------------------------------------------------*/ #define UNZIP_INTERNAL #include "unzip.h" static void partial_clear OF((__GPRO)); #ifdef DEBUG # define OUTDBG(c) \ if ((c)<32 || (c)>=127) fprintf(stderr,"\\x%02x",(c)); else putc((c),stderr); #else # define OUTDBG(c) #endif /* HSIZE is defined as 2^13 (8192) in unzip.h */ #define BOGUSCODE 256 #define FLAG_BITS parent /* upper bits of parent[] used as flag bits */ #define CODE_MASK (HSIZE - 1) /* 0x1fff (lower bits are parent's index) */ #define FREE_CODE HSIZE /* 0x2000 (code is unused or was cleared) */ #define HAS_CHILD (HSIZE << 1) /* 0x4000 (code has a child--do not clear) */ #define parent G.area.shrink.Parent #define Value G.area.shrink.value /* "value" conflicts with Pyramid ioctl.h */ #define stack G.area.shrink.Stack /***********************/ /* Function unshrink() */ /***********************/ int unshrink(__G) __GDEF { #if 0 static uch *stacktop = NULL; #else uch *stacktop = stack + (HSIZE - 1); #endif register uch *newstr; int codesize=9, len, KwKwK, error; shrint code, oldcode, freecode, curcode; shrint lastfreecode; unsigned int outbufsiz; /*--------------------------------------------------------------------------- Initialize various variables. ---------------------------------------------------------------------------*/ #if 0 /* SPC: no longer needed, stacktop is now an automatic variable that * is initialized on every unshrink() entry. */ /* this is required for MACOS, but performance hit is minuscule */ if (stacktop == NULL) stacktop = stack + (HSIZE - 1); #endif lastfreecode = BOGUSCODE; #ifndef VMS /* VMS uses its own buffer scheme for textmode flush(). */ #ifndef SMALL_MEM /* non-memory-limited machines: allocate second (large) buffer for * textmode conversion in flush(), but only if needed */ if (G.pInfo->textmode && !G.outbuf2 && (G.outbuf2 = (uch *)malloc(TRANSBUFSIZ)) == (uch *)NULL) return PK_MEM3; #endif #endif /* !VMS */ for (code = 0; code < BOGUSCODE; ++code) { Value[code] = (uch)code; parent[code] = BOGUSCODE; } for (code = BOGUSCODE+1; code < HSIZE; ++code) parent[code] = FREE_CODE; G.realbuf = G.outbuf; /* use normal outbuf unless we're a DLL routine */ #ifdef DLL if (G.redirect_data) { G.realbuf = G.redirect_buffer; outbufsiz = G.redirect_size; } else #endif if (G.pInfo->textmode) outbufsiz = RAWBUFSIZ; else outbufsiz = OUTBUFSIZ; G.outptr = G.realbuf; G.outcnt = 0L; /*--------------------------------------------------------------------------- Get and output first code, then loop over remaining ones. ---------------------------------------------------------------------------*/ READBITS(codesize, oldcode) if (!G.zipeof) { *G.outptr++ = (uch)oldcode; OUTDBG((uch)oldcode) ++G.outcnt; } do { READBITS(codesize, code) if (G.zipeof) break; if (code == BOGUSCODE) { /* possible to have consecutive escapes? */ READBITS(codesize, code) if (code == 1) { ++codesize; Trace((stderr, " (codesize now %d bits)\n", codesize)); } else if (code == 2) { Trace((stderr, " (partial clear code)\n")); partial_clear(__G); /* clear leafs (nodes with no children) */ Trace((stderr, " (done with partial clear)\n")); lastfreecode = BOGUSCODE; /* reset start of free-node search */ } continue; } /*----------------------------------------------------------------------- Translate code: traverse tree from leaf back to root. -----------------------------------------------------------------------*/ newstr = stacktop; curcode = code; if (parent[curcode] == FREE_CODE) { /* or (FLAG_BITS[curcode] & FREE_CODE)? */ KwKwK = TRUE; Trace((stderr, " (found a KwKwK code %d; oldcode = %d)\n", code, oldcode)); --newstr; /* last character will be same as first character */ curcode = oldcode; } else KwKwK = FALSE; do { *newstr-- = Value[curcode]; curcode = (shrint)(parent[curcode] & CODE_MASK); } while (curcode != BOGUSCODE); len = (int)(stacktop - newstr++); if (KwKwK) *stacktop = *newstr; /*----------------------------------------------------------------------- Write expanded string in reverse order to output buffer. -----------------------------------------------------------------------*/ Trace((stderr, "code %4d; oldcode %4d; char %3d (%c); string [", code, oldcode, (int)(*newstr), (*newstr<32 || *newstr>=127)? ' ':*newstr)); { register uch *p; for (p = newstr; p < newstr+len; ++p) { *G.outptr++ = *p; OUTDBG(*p) if (++G.outcnt == outbufsiz) { Trace((stderr, "doing flush(), outcnt = %lu\n", G.outcnt)); if ((error = flush(__G__ G.realbuf, G.outcnt, TRUE)) != 0) fprintf(stderr, "unshrink: flush() error (%d)\n", error); Trace((stderr, "done with flush()\n")); G.outptr = G.realbuf; G.outcnt = 0L; } } } /*----------------------------------------------------------------------- Add new leaf (first character of newstr) to tree as child of oldcode. -----------------------------------------------------------------------*/ /* search for freecode */ freecode = (shrint)(lastfreecode + 1); /* add if-test before loop for speed? */ while (parent[freecode] != FREE_CODE) ++freecode; lastfreecode = freecode; Trace((stderr, "]; newcode %d\n", freecode)); Value[freecode] = *newstr; parent[freecode] = oldcode; oldcode = code; } while (!G.zipeof); /*--------------------------------------------------------------------------- Flush any remaining data and return to sender... ---------------------------------------------------------------------------*/ if (G.outcnt > 0L) { Trace((stderr, "doing final flush(), outcnt = %lu\n", G.outcnt)); if ((error = flush(__G__ G.realbuf, G.outcnt, TRUE)) != 0) fprintf(stderr, "unshrink: flush() error (%d)\n", error); Trace((stderr, "done with flush()\n")); } return PK_OK; } /* end function unshrink() */ /****************************/ /* Function partial_clear() */ /* no longer recursive... */ /****************************/ static void partial_clear(__G) __GDEF { register shrint code; /* clear all nodes which have no children (i.e., leaf nodes only) */ /* first loop: mark each parent as such */ for (code = BOGUSCODE+1; code < HSIZE; ++code) { register shrint cparent = (shrint)(parent[code] & CODE_MASK); if (cparent > BOGUSCODE && cparent != FREE_CODE) FLAG_BITS[cparent] |= HAS_CHILD; /* set parent's child-bit */ } /* second loop: clear all nodes *not* marked as parents; reset flag bits */ for (code = BOGUSCODE+1; code < HSIZE; ++code) { if (FLAG_BITS[code] & HAS_CHILD) /* just clear child-bit */ FLAG_BITS[code] &= ~HAS_CHILD; else { /* leaf: lose it */ Trace((stderr, "%d\n", code)); parent[code] = FREE_CODE; } } return; }