bin/unzip/unshrink.c

14        NOTE:  This code may or may not infringe on the so-called "Welch
19        whatever license(s) may be required for legal use of this code.
25   Shrinking is basically a dynamic LZW algorithm with allowed code sizes of
27   leaf nodes.  PKWARE uses the special code 256 (decimal) to indicate a
28   change in code size or a partial clear of the code tree:  256,1 for the
40   IEEE _Computer_; no existing source code, including any in Nelson's book,
44   than the original Sam Smith code.  This is still larger than any of the
88 #define FREE_CODE  HSIZE         /* 0x2000 (code is unused or was cleared) */
89 #define HAS_CHILD  (HSIZE << 1)  /* 0x4000 (code has a child--do not clear) */
107     shrint code, oldcode, freecode, curcode;
137     for (code = 0;  code < BOGUSCODE;  ++code) {
138         Value[code] = (uch)code;
139         parent[code] = BOGUSCODE;
141     for (code = BOGUSCODE+1;  code < HSIZE;  ++code)
142         parent[code] = FREE_CODE;
162     Get and output first code, then loop over remaining ones.
173         READBITS(codesize, code)
176         if (code == BOGUSCODE) {   /* possible to have consecutive escapes? */
177             READBITS(codesize, code)
178             if (code == 1) {
181             } else if (code == 2) {
182                 Trace((stderr, " (partial clear code)\n"));
191         Translate code:  traverse tree from leaf back to root.
195         curcode = code;
200             Trace((stderr, " (found a KwKwK code %d; oldcode = %d)\n", code,
220         Trace((stderr, "code %4d; oldcode %4d; char %3d (%c); string [", code,
257         oldcode = code;
289     register shrint code;
294     for (code = BOGUSCODE+1;  code < HSIZE;  ++code) {
295         register shrint cparent = (shrint)(parent[code] & CODE_MASK);
302     for (code = BOGUSCODE+1;  code < HSIZE;  ++code) {
303         if (FLAG_BITS[code] & HAS_CHILD)    /* just clear child-bit */
304             FLAG_BITS[code] &= ~HAS_CHILD;
306             Trace((stderr, "%d\n", code));
307             parent[code] = FREE_CODE;