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

zoo/io.c

@@ -0,0 +1,105 @@
+/*$Source: /usr/home/dhesi/zoo/RCS/io.c,v $*/
+/*$Id: io.c,v 1.14 91/07/09 01:39:54 dhesi Exp $*/
+/***********************************************************
+    io.c -- input/output (modified for in-memory I/O)
+
+Adapted from "ar" archiver written by Haruhiko Okumura.
+This version reads compressed bytes from an input buffer
+via mem_getc() and writes output bytes to a buffer via
+mem_putc(), removing all FILE* dependencies for decompression.
+***********************************************************/
+// Modified for in-memory decompression by Natalia Portillo, 2025
+
+#include <limits.h>
+
+#include "ar.h"
+#include "lzh.h"
+
+#include "lh5.h" /* mem_getc(), mem_putc(), in_ptr/in_left, out_ptr/out_left */
+
+uint16_t bitbuf;
+int      unpackable;
+size_t   compsize, origsize;
+uint32_t subbitbuf;
+int      bitcount;
+
+/*
+ * fillbuf(n) -- shift bitbuf left by n bits and read in n new bits
+ * now reads bytes directly from in-memory input buffer
+ */
+void fillbuf(int n) /* Shift bitbuf n bits left, read n bits */
+{
+    bitbuf <<= n;
+    while(n > bitcount)
+    {
+        bitbuf |= subbitbuf << (n -= bitcount);
+
+        /* fetch next compressed byte from in_buf */
+        {
+            int c     = mem_getc();
+            subbitbuf = (c == EOF ? 0 : (uint8_t)c);
+        }
+
+        bitcount = CHAR_BIT;
+    }
+    bitbuf |= subbitbuf >> (bitcount -= n);
+}
+
+/*
+ * getbits(n) -- return next n bits from the bit buffer
+ */
+uint32_t getbits(int n)
+{
+    uint32_t x = bitbuf >> (BITBUFSIZ - n);
+    fillbuf(n);
+    return x;
+}
+
+/*
+ * putbits(n,x) -- write the lowest n bits of x to the bit buffer
+ * now writes bytes directly to in-memory output buffer
+ */
+void putbits(int n, uint32_t x) /* Write rightmost n bits of x */
+{
+    if(n < bitcount) { subbitbuf |= x << (bitcount -= n); }
+    else
+    {
+        /* output first byte */
+        {
+            int w = (int)(subbitbuf | (x >> (n -= bitcount)));
+            mem_putc(w);
+            compsize++;
+        }
+        if(n < CHAR_BIT) { subbitbuf = x << (bitcount = CHAR_BIT - n); }
+        else
+        {
+            /* output second byte */
+            {
+                int w2 = (int)(x >> (n - CHAR_BIT));
+                mem_putc(w2);
+                compsize++;
+            }
+            subbitbuf = x << (bitcount = 2 * CHAR_BIT - n);
+        }
+    }
+}
+
+/*
+ * init_getbits -- initialize bit reader state
+ */
+void init_getbits()
+{
+    bitbuf    = 0;
+    subbitbuf = 0;
+    bitcount  = 0;
+    fillbuf(BITBUFSIZ);
+}
+
+/*
+ * init_putbits -- initialize bit writer state
+ */
+void init_putbits()
+{
+    bitcount  = CHAR_BIT;
+    subbitbuf = 0;
+}