1 files changed, 74 insertions, 0 deletions
diff --git a/lzss.h b/lzss.h
new file mode 100644
index 0000000..5753ba9
--- /dev/null
+++ b/lzss.h
@@ -0,0 +1,74 @@
+/* LZSS encoder-decoder (Haruhiko Okumura; public domain) */
+/* Modified by Clyne Sullivan to focus on streamed decompression. */
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+#define EI 8  /* typically 10..13 */
+#define EJ  3  /* typically 4..5 */
+#define N (1 << EI)  /* buffer size */
+#define F ((1 << EJ) + 1)  /* lookahead buffer size */
+
+static unsigned char buffer[N * 2];
+static const unsigned char *inbuffer;
+static unsigned int insize, inidx;
+static int buf, mask;
+
+/* Prepares decode() to decompress the given data. */
+void lzssinit(const unsigned char *inb, unsigned int ins)
+{
+    inbuffer = inb;
+    insize = ins;
+    inidx = 0;
+    buf = 0;
+    mask = 0;
+}
+
+int getbit(int n) /* get n bits */
+{
+    int i, x;
+
+    x = 0;
+    for (i = 0; i < n; i++) {
+        if (mask == 0) {
+            if (inidx >= insize)
+                return EOF;
+            buf = inbuffer[inidx++];
+            mask = 128;
+        }
+        x <<= 1;
+        if (buf & mask) x++;
+        mask >>= 1;
+    }
+    return x;
+}
+
+/* handleoutput() receives each decompressed byte, return zero if want more. */
+int decode(int (*handleoutput)(int))
+{
+    int i, j, k, r, c, ret;
+
+    for (i = 0; i < N - F; i++) buffer[i] = ' ';
+    r = N - F;
+    while ((c = getbit(1)) != EOF) {
+        if (c) {
+            if ((c = getbit(8)) == EOF) break;
+            if ((ret = handleoutput(c)))
+                return ret;
+            buffer[r++] =(unsigned char) c;  r &= (N - 1);
+        } else {
+            if ((i = getbit(EI)) == EOF) break;
+            if ((j = getbit(EJ)) == EOF) break;
+            for (k = 0; k <= j + 1; k++) {
+                c = buffer[(i + k) & (N - 1)];
+                if ((ret = handleoutput(c)))
+                    return ret;
+                buffer[r++] = (unsigned char)c;  r &= (N - 1);
+            }
+        }
+    }
+
+    return EOF;
+}
+