Add support for decompressing Lempel-Ziv-Huffman, LH5 variant.

2025-12-16 19:24:31 +00:00 · 2025-08-26 01:02:06 +01:00
parent 0068268c65
commit 057d0c0242
15 changed files with 793 additions and 4 deletions
--- a/zoo/maketbl.c
+++ b/zoo/maketbl.c
@@ -0,0 +1,77 @@
+/*$Source: /usr/home/dhesi/zoo/RCS/maketbl.c,v $*/
+/*$Id: maketbl.c,v 1.8 91/07/09 01:39:52 dhesi Exp $*/
+/***********************************************************
+    maketbl.c -- make table for decoding
+
+Adapted from "ar" archiver written by Haruhiko Okumura.
+***********************************************************/
+// Modified for in-memory decompression by Natalia Portillo, 2025
+
+#include "ar.h"
+#include "lzh.h"
+
+void make_table(int nchar, uint8_t *bitlen, int tablebits, uint16_t *table)
+{
+    uint16_t count[17], weight[17], start[18], *p;
+    uint32_t i, k, len, ch, jutbits, avail, nextcode, mask;
+
+    for(i = 1; i <= 16; i++) count[i] = 0;
+    for(i = 0; i < nchar; i++) count[bitlen[i]]++;
+
+    start[1] = 0;
+    for(i = 1; i <= 16; i++) start[i + 1] = start[i] + (count[i] << (16 - i));
+    if(start[17] != (uint16_t)((unsigned)1 << 16)) fprintf(stderr, "Bad decode table\n");
+
+    jutbits = 16 - tablebits;
+    for(i = 1; i <= tablebits; i++)
+    {
+        start[i] >>= jutbits;
+        weight[i] = (unsigned)1 << (tablebits - i);
+    }
+    while(i <= 16)
+    {
+        weight[i] = (unsigned)1 << (16 - i);
+        i++;
+    }
+
+    i = start[tablebits + 1] >> jutbits;
+    if(i != (uint16_t)((unsigned)1 << 16))
+    {
+        k = 1 << tablebits;
+        while(i != k) table[i++] = 0;
+    }
+
+    avail = nchar;
+    mask  = (unsigned)1 << (15 - tablebits);
+    for(ch = 0; ch < nchar; ch++)
+    {
+        if((len = bitlen[ch]) == 0) continue;
+        nextcode = start[len] + weight[len];
+        if(len <= tablebits)
+        {
+            for(i = start[len]; i < nextcode; i++) table[i] = ch;
+        }
+        else
+        {
+            k = start[len];
+            p = &table[k >> jutbits];
+            i = len - tablebits;
+            while(i != 0)
+            {
+                if(*p == 0)
+                {
+                    right[avail] = left[avail] = 0;
+                    *p                         = avail++;
+                }
+                if(k & mask)
+                    p = &right[*p];
+                else
+                    p = &left[*p];
+                k <<= 1;
+                i--;
+            }
+            *p = ch;
+        }
+        start[len] = nextcode;
+    }
+}