From 371b264bddbe53f1312a97dc8f328a3261abd1e6 Mon Sep 17 00:00:00 2001
From: Daveo <daveo@localhost>
Date: Wed, 4 Jul 2001 15:34:35 +0000
Subject: [PATCH]

---
 source/utils/lznp.H   |  1 +
 source/utils/lznp.cpp | 93 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+)
 create mode 100644 source/utils/lznp.H
 create mode 100644 source/utils/lznp.cpp

diff --git a/source/utils/lznp.H b/source/utils/lznp.H
new file mode 100644
index 000000000..32465f1ba
--- /dev/null
+++ b/source/utils/lznp.H
@@ -0,0 +1 @@
+int LZNP_Decode(unsigned char *in, unsigned char *out);
diff --git a/source/utils/lznp.cpp b/source/utils/lznp.cpp
new file mode 100644
index 000000000..13a245b5e
--- /dev/null
+++ b/source/utils/lznp.cpp
@@ -0,0 +1,93 @@
+/*
+	Program:		unlznp.c
+	Author:		Nick Pelling
+	Function:	Decompresses an LZNP-compressed file
+	Note:			Copyright (c) 1993-1994 Nick Pelling. All rights reserved.
+*/
+
+/*
+	Notes:
+
+		The basic procedure is:
+
+		(a)	Read a control byte, and examine each bit in turn, LSB...MSB
+		(b)	if bit is clear, copy a byte from input stream
+		(c)	...else read another byte in.
+				if >= 0x60, this means "copy a pair from nearby"
+		(d)	...else split it up into a length, and high 4 bits of offset
+		(e)	read the low order 8 bits, and merge to form (-ve) offset
+		(f)	if (offset == 0), then exit: this terminates decompression
+		(g)	if length is maximum length, read superlength from next byte
+		(h)	copy length bytes from (-ve) offset. Note: this may overlap!
+		(i)	If no more bits in control byte, read another control byte
+		(j)	Loop.
+
+	...and that's it.
+*/
+
+#include "lznp.h"
+
+#define SMALLEST_LEN	2						/* smallest len usable at all */
+#define MIN_LEN		3						/* smallest short length encodable */
+#define MAX_LEN		(MIN_LEN + 6-2)	/* largest  short length encodable */
+#define MIN_SUPERLEN	(MIN_LEN + 6-1)	/* shortest long length encodable */
+#define MAX_SUPERLEN	(MIN_SUPERLEN + 254)	/* largest  long length encodable */
+#define SUPERLEN_CODE (MIN_SUPERLEN - MIN_LEN)	/* means "read superlength" */
+
+
+typedef unsigned char UBYTE;				/* just for convenience */
+
+
+int LZNP_Decode(UBYTE *in, UBYTE *out)
+{
+	int	i, j;
+	unsigned int flags;								/* now works with 16-bit ints */
+	UBYTE * OriginalOut=out;
+
+	for (flags=0;;)
+	{
+		if (((flags >>= 1) & 0xff00) == 0)
+		{
+			flags = (*in++) | 0xff00;				/* uses higher byte cleverly */
+		}													/* (to count eight) */
+
+		if (!(flags & 1))
+		{
+			*out++ = *in++;
+		}
+		else
+		{
+			i = *in++;
+
+			if (i >= 0x60)
+			{
+				i = 0x100 - i;			/* i = copy offset */
+				j = SMALLEST_LEN;		/* j = copy length */
+			}
+			else
+			{
+				j = i >> 4;
+				i = (i & 0x0F) << 8;
+				i |= *in++;
+
+				if (i == 0)				/* offset of zero terminates LZNP data */
+					break;
+
+				if (j != SUPERLEN_CODE)
+					j += MIN_LEN;
+				else
+					j = MIN_SUPERLEN + (*in++);
+			}
+
+			for (i=-i,j++; --j; out++)
+			{
+				out[0] = out[i];
+			}
+		}
+	}
+
+	/* Return size */
+	return(out-OriginalOut);
+}
+
+