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engines/agi/logic.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 "agi/agi.h"
+
+namespace Agi {
+
+/**
+ * Decode logic resource
+ * This function decodes messages from the specified raw logic resource
+ * into a message list.
+ * @param logicNr  The number of the logic resource to decode.
+ */
+int AgiEngine::decodeLogic(int16 logicNr) {
+	AgiLogic &logic = _game.logics[logicNr];
+	AgiDir &dirLogic = _game.dirLogic[logicNr];
+
+	// bytecode section:
+	// u16  bytecode size
+	// u8[] bytecode
+	uint16 bytecodeSize = READ_LE_UINT16(logic.data);
+
+	// message section:
+	// u8       message count
+	// u16      messages size (2 + offsets + strings)
+	// u16[]    string offsets (relative to message section + 1)
+	// string[] strings (null terminated, possibly encrypted)
+	int messageSectionPos = 2 + bytecodeSize;
+	uint8 messageCount = logic.data[messageSectionPos];
+	uint16 messagesSize = READ_LE_UINT16(logic.data + messageSectionPos + 1);
+	int stringOffsetsPos = messageSectionPos + 3;
+	int stringsPos = stringOffsetsPos + (2 * messageCount);
+	int stringsSize = messagesSize - 2 - (2 * messageCount);
+
+	// decrypt the message strings if the logic was not compressed
+	// and the logic has messages.
+	if ((~dirLogic.flags & RES_COMPRESSED) && messageCount > 0) {
+		decrypt(logic.data + stringsPos, stringsSize);
+	}
+
+	// reset logic pointers
+	logic.sIP = 2;
+	logic.cIP = 2;
+	logic.size = messageSectionPos; // exclude messages from logic size
+
+	// allocate list of pointers to message texts. last entry is null.
+	logic.numTexts = messageCount;
+	logic.texts = (const char **)calloc(1 + logic.numTexts, sizeof(char *));
+	if (logic.texts == nullptr) {
+		free(logic.data);
+		logic.data = nullptr;
+		logic.numTexts = 0;
+		return errNotEnoughMemory;
+	}
+
+	// populate list of pointers to message texts
+	for (int i = 0; i < messageCount; i++) {
+		int stringOffset = READ_LE_UINT16(logic.data + stringOffsetsPos + (i * 2));
+		if (stringOffset != 0) {
+			// offset is relative to the message section + 1
+			stringOffset += messageSectionPos + 1;
+			logic.texts[i] = (const char *)(logic.data + stringOffset);
+		} else {
+			// TODO: does this happen? when is a string offset zero?
+			logic.texts[i] = "";
+		}
+	}
+
+	// set loaded flag
+	dirLogic.flags |= RES_LOADED;
+	return errOK;
+}
+
+/**
+ * Unload logic resource
+ * This function unloads the specified logic resource, freeing any
+ * memory chunks allocated for this resource.
+ * @param logicNr  The number of the logic resource to unload
+ */
+void AgiEngine::unloadLogic(int16 logicNr) {
+	AgiLogic &logic = _game.logics[logicNr];
+	AgiDir &dirLogic = _game.dirLogic[logicNr];
+
+	if (dirLogic.flags & RES_LOADED) {
+		free(logic.data);
+		logic.data = nullptr;
+		free(logic.texts);
+		logic.texts = nullptr;
+		logic.numTexts = 0;
+		dirLogic.flags &= ~RES_LOADED;
+	}
+
+	logic.sIP = 2;
+	logic.cIP = 2;
+}
+
+} // End of namespace Agi