Initial commit

engines/chamber/decompr.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 "chamber/chamber.h"
+
+namespace Chamber {
+
+
+static struct {
+	byte codes[256];
+	byte prefix[256];
+	byte suffix[256];
+	byte coddict[256];
+	byte codlink[256];
+	byte stackpos;
+} DecompCtx;
+
+byte decode_string(byte code, byte prev_n, byte *stack) {
+	byte n;
+	while ((n = DecompCtx.coddict[code]) != 0) {
+		while (n >= prev_n) {
+			n = DecompCtx.codlink[n];
+			if (n == 0)
+				return code;
+		}
+		/*if(DecompCtx.stackpos == 255) exit("stack exploded");*/
+		stack[DecompCtx.stackpos++] = prev_n = n;
+		code = DecompCtx.prefix[n];
+	}
+	return code;
+}
+
+uint32 decompress(byte *data, byte *result) {
+	byte dict_size, more;
+	uint16 compsize;
+	uint16 i;
+	byte code, n, suffix;
+	byte stack[256];
+	uint32 decompsize = 0;
+
+	do {
+		dict_size = *data++;
+		more = *data++;
+		compsize = *data++;
+		compsize |= (*data++) << 8;
+
+		if (dict_size == 0) {
+			/* uncompressed block */
+			decompsize += compsize;
+			while (compsize--)
+				*result++ = *data++;
+		} else {
+			/* compressed block */
+			/*
+			memcpy(DecompCtx.codes + 1, data, dict_size); data += dict_size;
+			memcpy(DecompCtx.prefix + 1, data, dict_size); data += dict_size;
+			memcpy(DecompCtx.suffix + 1, data, dict_size); data += dict_size;
+			*/
+			for (n = 1, i = 0; i < dict_size; n++, i++) DecompCtx.codes[n] = *data++;
+			for (n = 1, i = 0; i < dict_size; n++, i++) DecompCtx.prefix[n] = *data++;
+			for (n = 1, i = 0; i < dict_size; n++, i++) DecompCtx.suffix[n] = *data++;
+
+			memset(DecompCtx.coddict, 0, 256);
+			for (n = 1, i = 0; i < dict_size; n++, i++) {
+				code = DecompCtx.codes[n];
+				DecompCtx.codlink[n] = DecompCtx.coddict[code];
+				DecompCtx.coddict[code] = n;
+			}
+
+			while (compsize-- > 0) {
+				code = *data++;
+
+				if (DecompCtx.coddict[code] == 0) {
+					/* literal */
+					*result++ = code;
+					decompsize += 1;
+				} else {
+					/* string */
+					DecompCtx.stackpos = 0;
+
+					n = DecompCtx.coddict[code];
+
+					stack[DecompCtx.stackpos++] = n;
+
+					for (code = DecompCtx.prefix[n];; code = DecompCtx.suffix[n]) {
+						suffix = decode_string(code, n, stack);
+						*result++ = suffix;
+						decompsize += 1;
+						if (DecompCtx.stackpos == 0)
+							break;
+						n = stack[--DecompCtx.stackpos];
+					}
+				}
+			}
+		}
+	} while (more != 0);
+
+	return decompsize;
+}
+
+} // End of namespace Chamber