first commit

1 files changed, 177 insertions, 0 deletions

diff --git a/source/unzip/unshrink.c b/source/unzip/unshrink.c
new file mode 100644
index 0000000..6deb4d4
--- /dev/null
+++ b/source/unzip/unshrink.c
@@ -0,0 +1,177 @@
+/*---------------------------------------------------------------------------
+
+  unshrink.c
+
+  Shrinking is a Dynamic Lempel-Ziv-Welch compression algorithm with partial
+  clearing.
+
+  ---------------------------------------------------------------------------*/
+
+
+#include "unz.h"
+void flush_stack (int);
+
+/*************************************/
+/*  UnShrink Defines, Globals, etc.  */
+/*************************************/
+
+/*      MAX_BITS        13   (in unzip.h; defines size of global work area)  */
+#define INIT_BITS       9
+#define FIRST_ENT       257
+#define CLEAR           256
+#define GetCode(dest)   READBIT(codesize,dest)
+
+static void partial_clear ();
+
+int codesize, maxcode, maxcodemax, free_ent;
+
+
+
+
+/*************************/
+/*  Function unShrink()  */
+/*************************/
+
+void unShrink()
+{
+    register int code;
+    register int stackp;
+    int finchar;
+    int oldcode;
+    int incode;
+
+
+    /* decompress the file */
+    codesize = INIT_BITS;
+    maxcode = (1 << codesize) - 1;
+    maxcodemax = HSIZE;         /* (1 << MAX_BITS) */
+    free_ent = FIRST_ENT;
+
+    code = maxcodemax;
+    do {
+        prefix_of[code] = -1;
+    } while (--code > 255);
+/*
+    OvdL: -Ox with SCO's 3.2.0 cc gives
+    a. warning: overflow in constant multiplication
+    b. segmentation fault (core dumped) when using the executable
+    for (code = maxcodemax; code > 255; code--)
+        prefix_of[code] = -1;
+ */
+
+    for (code = 255; code >= 0; code--) {
+        prefix_of[code] = 0;
+        suffix_of[code] = (byte) code;
+    }
+
+    GetCode(oldcode);
+    if (zipeof)
+        return;
+    finchar = oldcode;
+
+    stack[0] = finchar;
+    flush_stack (1);
+
+    stackp = HSIZE;
+
+    while (!zipeof) {
+        GetCode(code);
+        if (zipeof)
+            return;
+
+        while (code == CLEAR) {
+            GetCode(code);
+            switch (code) {
+                case 1:
+                    codesize++;
+                    if (codesize == MAX_BITS)
+                        maxcode = maxcodemax;
+                    else
+                        maxcode = (1 << codesize) - 1;
+                    break;
+
+                case 2:
+                    partial_clear();
+                    break;
+            }
+
+            GetCode(code);
+            if (zipeof)
+                return;
+        }
+
+
+        /* special case for KwKwK string */
+        incode = code;
+        if (prefix_of[code] == -1) {
+            stack[--stackp] = (byte) finchar;
+            code = oldcode;
+        }
+        /* generate output characters in reverse order */
+        while (code >= FIRST_ENT) {
+            if (prefix_of[code] == -1) {
+                stack[--stackp] = (byte) finchar;
+                code = oldcode;
+            } else {
+                stack[--stackp] = suffix_of[code];
+                code = prefix_of[code];
+            }
+        }
+
+        finchar = suffix_of[code];
+        stack[--stackp] = (byte) finchar;
+
+        /* and put them out in forward order, block copy */
+	flush_stack (HSIZE - stackp);
+	stackp = HSIZE;
+
+        /* generate new entry */
+        code = free_ent;
+        if (code < maxcodemax) {
+            prefix_of[code] = oldcode;
+            suffix_of[code] = (byte) finchar;
+
+            do
+                code++;
+            while ((code < maxcodemax) && (prefix_of[code] != -1));
+
+            free_ent = code;
+        }
+        /* remember previous code */
+        oldcode = incode;
+    }
+}
+
+
+
+/******************************/
+/*  Function partial_clear()  */
+/******************************/
+
+static void partial_clear()
+{
+    register int pr;
+    register int cd;
+
+    /* mark all nodes as potentially unused */
+    for (cd = FIRST_ENT; cd < free_ent; cd++)
+        prefix_of[cd] |= 0x8000;
+
+    /* unmark those that are used by other nodes */
+    for (cd = FIRST_ENT; cd < free_ent; cd++) {
+        pr = prefix_of[cd] & 0x7fff;    /* reference to another node? */
+        if (pr >= FIRST_ENT)    /* flag node as referenced */
+            prefix_of[pr] &= 0x7fff;
+    }
+
+    /* clear the ones that are still marked */
+    for (cd = FIRST_ENT; cd < free_ent; cd++)
+        if ((prefix_of[cd] & 0x8000) != 0)
+            prefix_of[cd] = -1;
+
+    /* find first cleared node as next free_ent */
+    cd = FIRST_ENT;
+    while ((cd < maxcodemax) && (prefix_of[cd] != -1))
+        cd++;
+    free_ent = cd;
+}