Initial commit

engines/awe/pak.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 "awe/pak.h"
+#include "awe/detection.h"
+
+namespace Awe {
+
+// static const uint32 XOR_KEY1 = 0x31111612;
+// static const uint32 CHECKSUM = 0x20202020;
+
+static const uint32 XOR_KEY2 = 0x22683297;
+
+static uint8 *decode_toodc(uint8 *p, int count) {
+	uint32 key = XOR_KEY2;
+	uint32 acc = 0;
+	for (int i = 0; i < count; ++i) {
+		uint8 *q = p + i * 4;
+		const uint32 data = READ_LE_UINT32(q) ^ key;
+		uint32 r = (q[2] + q[1] + q[0]) ^ q[3];
+		r += acc;
+		key += r;
+		acc += 0x4D;
+		WRITE_LE_UINT32(q, data);
+	}
+	return p + 4;
+}
+
+const char *Pak::FILENAME = "Pak01.pak";
+
+Pak::Pak()
+	: _entries(nullptr), _entriesCount(0) {
+}
+
+Pak::~Pak() {
+	close();
+}
+
+void Pak::open(const char *dataPath) {
+	_f.open(Common::Path(FILENAME));
+}
+
+void Pak::close() {
+	free(_entries);
+	_entries = nullptr;
+	_entriesCount = 0;
+}
+
+static int comparePakEntry(const void *a, const void *b) {
+	return scumm_stricmp(((const PakEntry *)a)->name, ((const PakEntry *)b)->name);
+}
+
+void Pak::readEntries() {
+	uint8 header[12];
+
+	memset(header, 0, sizeof(header));
+	_f.read(header, sizeof(header));
+	if (_f.err() || memcmp(header, "PACK", 4) != 0) {
+		return;
+	}
+	const uint32 entriesOffset = READ_LE_UINT32(header + 4);
+	_f.seek(entriesOffset);
+	const uint32 entriesSize = READ_LE_UINT32(header + 8);
+	_entriesCount = entriesSize / 0x40;
+	debugC(kDebugPak, "Pak::readEntries() entries count %d", _entriesCount);
+	_entries = (PakEntry *)calloc(_entriesCount, sizeof(PakEntry));
+	if (!_entries) {
+		_entriesCount = 0;
+		return;
+	}
+	for (int i = 0; i < _entriesCount; ++i) {
+		uint8 buf[0x40];
+		_f.read(buf, sizeof(buf));
+		if (_f.err()) {
+			break;
+		}
+		const char *name = (const char *)buf;
+		if (strncmp(name, "dlx/", 4) != 0) {
+			continue;
+		}
+		PakEntry *e = &_entries[i];
+		Common::strcpy_s(e->name, name + 4);
+		e->offset = READ_LE_UINT32(buf + 0x38);
+		e->size = READ_LE_UINT32(buf + 0x3C);
+		debugC(kDebugPak, "Pak::readEntries() buf '%s' size %d", e->name, e->size);
+	}
+	qsort(_entries, _entriesCount, sizeof(PakEntry), comparePakEntry);
+
+#if 0
+	// the original executable descrambles the (ke)y.txt file and check the last 4 bytes.
+	// this has been disabled in later re-releases and a key is bundled in the data files
+	uint8 buf[128];
+	const PakEntry *e = find("check.txt");
+	if (e && e->size <= sizeof(buf)) {
+		uint32 size = 0;
+		loadData(e, buf, &size);
+		assert(size >= 4);
+		const uint32 num = READ_LE_UINT32(buf + size - 4);
+		assert(num == CHECKSUM);
+	}
+#endif
+}
+
+const PakEntry *Pak::find(const char *name) {
+	debugC(kDebugPak, "Pak::find() '%s'", name);
+	PakEntry tmp;
+	Common::strcpy_s(tmp.name, name);
+	return (const PakEntry *)bsearch(&tmp, _entries, _entriesCount, sizeof(PakEntry), comparePakEntry);
+}
+
+void Pak::loadData(const PakEntry *e, uint8 *buf, uint32 *size) {
+	debugC(kDebugPak, "Pak::loadData() %d bytes from 0x%x", e->size, e->offset);
+	_f.seek(e->offset);
+	if (_f.err()) {
+		*size = 0;
+		return;
+	}
+	_f.read(buf, e->size);
+	if (e->size > 5 && memcmp(buf, "TooDC", 5) == 0) {
+		const int dataSize = e->size - 6;
+		debugC(kDebugPak, "Pak::loadData() encoded TooDC data, size %d", dataSize);
+		if ((dataSize & 3) != 0) {
+			// descrambler operates on uint32
+			warning("Unexpected size %d for encoded TooDC data '%s'", dataSize, e->name);
+		}
+		*size = dataSize - 4;
+		decode_toodc(buf + 6, (dataSize + 3) / 4);
+		memmove(buf, buf + 10, dataSize - 4);
+	} else {
+		*size = e->size;
+	}
+}
+
+} // namespace Awe