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engines/sci/resource/resource_patcher.h

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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/>.
+ *
+ */
+
+#ifndef SCI_RESOURCE_RESOURCE_PATCHER_H
+#define SCI_RESOURCE_RESOURCE_PATCHER_H
+
+#include "common/language.h"
+#include "sci/sci.h"
+#include "sci/resource/resource.h"
+#include "sci/resource/resource_intern.h"
+
+namespace Sci {
+
+enum ResourcePatchOp {
+	// Using high bytes to make it less likely that accidental raw data will be
+	// treated like an operator instead of an error
+	kSkipBytes = 0xF0,
+	kReplaceBytes,
+	kInsertBytes,
+	kReplaceNumber,
+	kAdjustNumber,
+	kInsertNumber,
+	kReplaceFill,
+	kInsertFill,
+	kEndOfPatch
+};
+
+enum SciMedia : uint;
+
+struct GameResourcePatch {
+	/**
+	 * The game to patch.
+	 */
+	SciGameId gameId;
+
+	/**
+	 * The media to patch. Use SCI_MEDIA_ALL for all.
+	 */
+	SciMedia media;
+
+	/**
+	 * The language to patch. Use `Common::UNK_LANG` to apply the patch to all
+	 * languages.
+	 */
+	Common::Language gameLanguage;
+
+	/**
+	 * The resource type to patch.
+	 */
+	ResourceType resourceType;
+
+	/**
+	 * The resource number to patch.
+	 */
+	uint16 resourceNumber;
+
+	/**
+	 * Patch instructions to apply to the resource.
+	 */
+	const byte *patchData;
+
+	/**
+	 * Set to true if the patch resource is actually a new resource, rather than
+	 * a patch for an existing resource.
+	 */
+	bool isNewResource;
+};
+
+/**
+ * A basic class for generating patched resource data at runtime.
+ */
+class ResourcePatcher : public ResourceSource {
+public:
+	ResourcePatcher(const SciGameId gameId, const bool isCD, const Common::Platform platform, const Common::Language gameLanguage);
+
+	~ResourcePatcher() override {}
+
+	/**
+	 * Finds and applies a patch to the given resource.
+	 *
+	 * @returns true if a patch was applied.
+	 */
+	bool applyPatch(Resource &resource) const;
+
+	/**
+	 * Adds new resources from the patch table to the resource manager. This
+	 * is needed since otherwise tests for these resources via `kResCheck`
+	 * would fail, and so they would never actually be loaded.
+	 */
+	void scanSource(ResourceManager *resMan) override;
+
+	/**
+	 * Load a resource. Since resources using this source are patched explicitly
+	 * after they get loaded by any other resource source, this method does
+	 * nothing.
+	 */
+	void loadResource(ResourceManager *resMan, Resource *res) override {}
+
+private:
+	struct PatchSizes {
+		/**
+		 * The minimum number of bytes required in the source data.
+		 */
+		uint32 expected;
+
+		/**
+		 * The difference in size between the original data and the patched
+		 * data.
+		 */
+		int32 delta;
+	};
+
+	typedef Common::Array<GameResourcePatch> PatchList;
+
+	/**
+	 * The list of patches that should apply to the currently loaded game.
+	 */
+	PatchList _patches;
+
+	/**
+	 * Patches the given Resource using patch data from the given
+	 * GameResourcePatch.
+	 */
+	void patchResource(Resource &resource, const GameResourcePatch &patch) const;
+
+	/**
+	 * Calculates expected and extra data sizes from the patch data.
+	 */
+	PatchSizes calculatePatchSizes(const byte *patchData) const;
+
+	/**
+	 * Reads a block size from the patch data, validates it, and advances the
+	 * patch data pointer.
+	 */
+	int32 readBlockSize(const byte * &patchData) const;
+};
+} // End of namespace Sci
+
+#endif	// SCI_RESOURCE_RESOURCE_PATCHER_H