The Sacred Tears: TRUE uses a modified map tree

Detect this and apply a shift of 1 to all bytes in the map tree to make it work.

CMakeLists.txt

@@ -123,6 +123,8 @@ add_library(${PROJECT_NAME} OBJECT
 	src/fileext_guesser.h
 	src/filesystem.cpp
 	src/filesystem.h
+	src/filesystem_hook.cpp
+	src/filesystem_hook.h
 	src/filesystem_lzh.cpp
 	src/filesystem_lzh.h
 	src/filesystem_native.cpp

Makefile.am

@@ -103,6 +103,8 @@ libeasyrpg_player_a_SOURCES = \
 	src/fileext_guesser.h \
 	src/filesystem.cpp \
 	src/filesystem.h \
+	src/filesystem_hook.cpp \
+	src/filesystem_hook.h \
 	src/filesystem_lzh.cpp \
 	src/filesystem_lzh.h \
 	src/filesystem_native.cpp \

src/filesystem_hook.cpp

@@ -0,0 +1,145 @@
+/*
+ * This file is part of EasyRPG Player.
+ *
+ * EasyRPG Player 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.
+ *
+ * EasyRPG Player 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 EasyRPG Player. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "filesystem_hook.h"
+#include "filesystem_stream.h"
+#include "options.h"
+
+#include <cassert>
+#include <cstdio>
+#include <streambuf>
+
+class CaesarStreamBuf : public std::streambuf {
+public:
+	CaesarStreamBuf(std::streambuf* parent_sb, int n) : parent_sb(parent_sb), n(n) {
+		setg(&buf, &buf + 1, &buf + 1);
+	}
+	CaesarStreamBuf(CaesarStreamBuf const& other) = delete;
+	CaesarStreamBuf const& operator=(CaesarStreamBuf const& other) = delete;
+	~CaesarStreamBuf() {
+		delete parent_sb;
+	}
+
+protected:
+	int_type underflow() override {
+		auto byte = parent_sb->sbumpc();
+
+		if (byte == traits_type::eof()) {
+			return byte;
+		}
+
+		buf = traits_type::to_char_type(byte);
+		buf -= n;
+
+		setg(&buf, &buf, &buf + 1);
+
+		return byte;
+	}
+
+	std::streambuf::pos_type seekoff(std::streambuf::off_type offset, std::ios_base::seekdir dir, std::ios_base::openmode) override {
+		return parent_sb->pubseekoff(offset, dir);
+	}
+
+	std::streambuf::pos_type seekpos(std::streambuf::pos_type pos, std::ios_base::openmode) override {
+		return parent_sb->pubseekpos(pos);
+	}
+
+private:
+	std::streambuf* parent_sb;
+
+	char buf;
+	int n;
+};
+
+
+HookFilesystem::HookFilesystem(FilesystemView parent_fs, Hook hook) : Filesystem("", parent_fs), active_hook(hook) {
+	// no-op
+}
+
+FilesystemView HookFilesystem::Detect(FilesystemView fs) {
+	auto lmt = fs.OpenInputStream(TREEMAP_NAME);
+	std::array<char, 11> buf;
+
+	lmt.ReadIntoObj(buf);
+
+	if (!memcmp(buf.data(), "\xbMdgNbqUsff", 11)) {
+		auto hook_fs = std::make_shared<HookFilesystem>(fs, Hook::SacredTears);
+		return hook_fs->Subtree("");
+	}
+
+	return fs;
+}
+
+bool HookFilesystem::IsFile(StringView path) const {
+	return GetParent().IsFile(path);
+}
+
+bool HookFilesystem::IsDirectory(StringView path, bool follow_symlinks) const {
+	return GetParent().IsDirectory(path, follow_symlinks);
+}
+
+bool HookFilesystem::Exists(StringView path) const {
+	return GetParent().Exists(path);
+}
+
+int64_t HookFilesystem::GetFilesize(StringView path) const {
+	return GetParent().GetFilesize(path);
+}
+
+bool HookFilesystem::MakeDirectory(StringView dir, bool follow_symlinks) const {
+	return GetParent().MakeDirectory(dir, follow_symlinks);
+}
+
+bool HookFilesystem::IsFeatureSupported(Feature f) const {
+	return GetParent().IsFeatureSupported(f);
+}
+
+std::streambuf* HookFilesystem::CreateInputStreambuffer(StringView path, std::ios_base::openmode mode) const {
+	auto parent_sb = GetParent().CreateInputStreambuffer(path, mode);
+
+	if (active_hook == Hook::SacredTears) {
+		if (path == TREEMAP_NAME) {
+			return new CaesarStreamBuf(parent_sb, 1);
+		}
+	}
+
+	return parent_sb;
+}
+
+std::streambuf* HookFilesystem::CreateOutputStreambuffer(StringView path, std::ios_base::openmode mode) const {
+	return GetParent().CreateOutputStreambuffer(path, mode);
+}
+
+bool HookFilesystem::GetDirectoryContent(StringView path, std::vector<DirectoryTree::Entry>& tree) const {
+	auto dir_tree = GetParent().ListDirectory(path);
+
+	if (!dir_tree) {
+		return false;
+	}
+
+	for (auto& item: *dir_tree) {
+		tree.push_back(item.second);
+	}
+
+	return true;
+}
+
+std::string HookFilesystem::Describe() const {
+	assert(active_hook == Hook::SacredTears);
+
+	return fmt::format("[Hook] ({})", "Sacred Tears");
+}

src/filesystem_hook.h

@@ -0,0 +1,60 @@
+/*
+ * This file is part of EasyRPG Player.
+ *
+ * EasyRPG Player 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.
+ *
+ * EasyRPG Player 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 EasyRPG Player. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef EP_FILESYSTEM_HOOK_H
+#define EP_FILESYSTEM_HOOK_H
+
+#include "filesystem.h"
+
+/**
+ * A virtual filesystem that applies modifications to game files
+ */
+class HookFilesystem : public Filesystem {
+public:
+	enum class Hook {
+		// The Sacred Tears: TRUE
+		// Shifts the offset of all bytes in the LMT back by one
+		SacredTears
+	};
+
+	explicit HookFilesystem(FilesystemView parent_fs, Hook hook);
+
+	static FilesystemView Detect(FilesystemView fs);
+
+	/**
+	 * Implementation of abstract methods
+	 */
+	/** @{ */
+	bool IsFile(StringView path) const override;
+	bool IsDirectory(StringView path, bool follow_symlinks) const override;
+	bool Exists(StringView path) const override;
+	int64_t GetFilesize(StringView path) const override;
+	bool MakeDirectory(StringView dir, bool follow_symlinks) const override;
+	bool IsFeatureSupported(Feature f) const override;
+	std::string Describe() const override;
+	/** @} */
+protected:
+	/** @{ */
+	bool GetDirectoryContent(StringView path, std::vector<DirectoryTree::Entry>& entries) const override;
+	std::streambuf* CreateInputStreambuffer(StringView path, std::ios_base::openmode mode) const override;
+	std::streambuf* CreateOutputStreambuffer(StringView path, std::ios_base::openmode mode) const override;
+	/** @} */
+
+	Hook active_hook;
+};
+
+#endif

src/player.cpp

@@ -24,7 +24,6 @@
 #include <iomanip>
 #include <fstream>
 #include <memory>
-#include <thread>
 
 #ifdef _WIN32
 #  include "platform/windows/utils.h"
@@ -42,6 +41,7 @@
 #include "filefinder.h"
 #include "filefinder_rtp.h"
 #include "fileext_guesser.h"
+#include "filesystem_hook.h"
 #include "game_actors.h"
 #include "game_battle.h"
 #include "game_map.h"
@@ -692,6 +692,9 @@ void Player::CreateGameObjects() {
 	}
 	escape_char = Utils::DecodeUTF32(Player::escape_symbol).front();
 
+	// Special handling for games with altered files
+	FileFinder::SetGameFilesystem(HookFilesystem::Detect(FileFinder::Game()));
+
 	// Check for translation-related directories and load language names.
 	translation.InitTranslations();