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engines/got/utils/compression.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 "got/utils/compression.h"
+#include "common/algorithm.h"
+#include "common/endian.h"
+
+namespace Got {
+
+void decompressLzss(const byte *src, byte *dest, const size_t destSize) {
+	byte *endP = dest + destSize;
+
+	for (;;) {
+		byte v = *src++;
+
+		for (int bits = 8; bits > 0; --bits) {
+			if (endP == dest)
+				return;
+
+			const bool bit = (v & 1) != 0;
+			v >>= 1;
+			if (bit) {
+				*dest++ = *src++;
+			} else {
+				uint16 offset = READ_LE_UINT16(src);
+				src += 2;
+				const int count = (offset >> 12) + 2;
+				offset &= 0xfff;
+
+				Common::copy(dest - offset, dest - offset + count, dest);
+				dest += count;
+			}
+		}
+	}
+}
+
+void decompressRle(const byte *src, byte *dest, const size_t destSize) {
+	byte *endP = dest + destSize;
+
+	for (;;) {
+		byte val = *src++;
+
+		if ((val & 0x80) != 0) {
+			const byte rep = *src++;
+			val &= 0x7f;
+			Common::fill(dest, dest + val, rep);
+			dest += val;
+		} else if (val > 0) {
+			Common::copy(src, src + val, dest);
+			src += val;
+			dest += val;
+		} else {
+			break;
+		}
+	}
+
+	assert(dest == endP);
+}
+
+} // namespace Got