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

zoo/decode.c

@@ -0,0 +1,71 @@
+/*$Source: /usr/home/dhesi/zoo/RCS/decode.c,v $*/
+/*$Id: decode.c,v 1.6 91/07/09 01:39:49 dhesi Exp $*/
+/***********************************************************
+    decode.c
+
+Adapted from "ar" archiver written by Haruhiko Okumura.
+***********************************************************/
+// Modified for in-memory decompression by Natalia Portillo, 2025
+
+#include <limits.h>
+#include <stdint.h>
+
+#include "ar.h"
+#include "lzh.h"
+
+extern int decoded; /* from huf.c */
+
+static int j; /* remaining bytes to copy */
+
+void decode_start()
+{
+    huf_decode_start();
+    j       = 0;
+    decoded = 0;
+}
+
+/*
+decodes; returns no. of chars decoded
+*/
+
+int decode(uint32_t count, uint8_t *buffer)
+/* The calling function must keep the number of
+   bytes to be processed.  This function decodes
+   either 'count' bytes or 'DICSIZ' bytes, whichever
+   is smaller, into the array 'buffer[]' of size
+   'DICSIZ' or more.
+   Call decode_start() once for each new file
+   before calling this function. */
+{
+    static uint32_t i;
+    uint32_t        r, c;
+
+    r = 0;
+    while(--j >= 0)
+    {
+        buffer[r] = buffer[i];
+        i         = (i + 1) & (DICSIZ - 1);
+        if(++r == count) return r;
+    }
+    for(;;)
+    {
+        c = decode_c();
+        if(decoded) return r;
+        if(c <= UCHAR_MAX)
+        {
+            buffer[r] = c;
+            if(++r == count) return r;
+        }
+        else
+        {
+            j = c - (UCHAR_MAX + 1 - THRESHOLD);
+            i = (r - decode_p() - 1) & (DICSIZ - 1);
+            while(--j >= 0)
+            {
+                buffer[r] = buffer[i];
+                i         = (i + 1) & (DICSIZ - 1);
+                if(++r == count) return r;
+            }
+        }
+    }
+}