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engines/ultima/ultima4/filesys/rle.cpp

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "ultima/ultima4/filesys/rle.h"
+
+namespace Ultima {
+namespace Ultima4 {
+
+/**
+ * Decompress an RLE encoded file.
+ */
+long rleDecompressFile(Common::ReadStream *in, long inlen, void **out) {
+	void *indata;
+	long outlen;
+
+	/* input file should be longer than 0 bytes */
+	if (inlen <= 0)
+		return -1;
+
+	/* load compressed file into memory */
+	indata = malloc(inlen);
+	in->read(indata, inlen);
+
+	outlen = rleDecompressMemory(indata, inlen, out);
+
+	free(indata);
+
+	return outlen;
+}
+
+long rleDecompressMemory(void *in, long inlen, void **out) {
+	byte *indata, *outdata;
+	long outlen;
+
+	/* input should be longer than 0 bytes */
+	if (inlen <= 0)
+		return -1;
+
+	indata = (byte *)in;
+
+	/* determine decompressed file size */
+	outlen = rleGetDecompressedSize(indata, inlen);
+
+	if (outlen <= 0)
+		return -1;
+
+	/* decompress file from inlen to outlen */
+	outdata = (byte *) malloc(outlen);
+	rleDecompress(indata, inlen, outdata, outlen);
+
+	*out = outdata;
+
+	return outlen;
+}
+
+/**
+ * Determine the uncompressed size of RLE compressed data.
+ */
+long rleGetDecompressedSize(byte *indata, long inlen) {
+	byte *p;
+	byte ch, count;
+	long len = 0;
+
+	p = indata;
+	while ((p - indata) < inlen) {
+		ch = *p++;
+		if (ch == RLE_RUNSTART) {
+			count = *p++;
+			p++;
+			len += count;
+		} else
+			len++;
+	}
+
+	return len;
+}
+
+/**
+ * Decompress a block of RLE encoded memory.
+ */
+long rleDecompress(byte *indata, long inlen, byte *outdata, long outlen) {
+	int i;
+	byte *p, *q;
+	byte ch, count, val;
+
+	p = indata;
+	q = outdata;
+	while ((p - indata) < inlen) {
+		ch = *p++;
+		if (ch == RLE_RUNSTART) {
+			count = *p++;
+			val = *p++;
+			for (i = 0; i < count; i++) {
+				*q++ = val;
+				if ((q - outdata) >= outlen)
+					break;
+			}
+		} else {
+			*q++ = ch;
+			if ((q - outdata) >= outlen)
+				break;
+		}
+	}
+
+	return q - outdata;
+}
+
+} // End of namespace Ultima4
+} // End of namespace Ultima