From d4dedeeeb87e213a75d07b85114b028d70fd10b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Sat, 30 Apr 2022 17:47:17 +0200
Subject: [PATCH] Detect ISO files from file contents if extensions are wrong.

On older Android versions (that still support Android Storage
Framework), filenames are not always preserved in Content URIs, they can
look like .../msf:342 and things like that. So identify a few more file
types by content if filename identification fails.
---
 Core/Loaders.cpp     | 24 ++++++++++++++++++++++++
 Core/Loaders.h       |  1 +
 UI/GameInfoCache.cpp |  1 +
 3 files changed, 26 insertions(+)

diff --git a/Core/Loaders.cpp b/Core/Loaders.cpp
index c39900061e..09ac48f47f 100644
--- a/Core/Loaders.cpp
+++ b/Core/Loaders.cpp
@@ -126,6 +126,9 @@ IdentifiedFileType Identify_File(FileLoader *fileLoader, std::string *errorStrin
 		return IdentifiedFileType::NORMAL_DIRECTORY;
 	}
 
+	// OK, quick methods of identification for common types failed. Moving on to more expensive methods,
+	// starting by reading the first few bytes.
+
 	u32_le id;
 
 	size_t readSize = fileLoader->ReadAt(0, 4, 1, &id);
@@ -141,8 +144,28 @@ IdentifiedFileType Identify_File(FileLoader *fileLoader, std::string *errorStrin
 	} else if (!memcmp(&_id, "\x00PBP", 4)) {
 		fileLoader->ReadAt(0x24, 4, 1, &psar_offset);
 		fileLoader->ReadAt(psar_offset, 4, 1, &psar_id);
+		// Fall through to the below if chain.
 	} else if (!memcmp(&_id, "Rar!", 4)) {
 		return IdentifiedFileType::ARCHIVE_RAR;
+	} else if (!memcmp(&_id, "\x37\x7A\xBC\xAF", 4)) {
+		return IdentifiedFileType::ARCHIVE_7Z;
+	} else if (!memcmp(&_id, "\0\0\0\0", 4)) {
+		// All zeroes. ISO files start like this but their 16th 2048-byte sector contains metadata.
+		if (fileLoader->FileSize() > 0x8100) {
+			char buffer[16];
+			fileLoader->ReadAt(0x8000, sizeof(buffer), buffer);
+			if (!memcmp(buffer + 1, "CD001", 5)) {
+				// It's an ISO file.
+				if (!memcmp(buffer + 8, "PSP GAME", 8)) {
+					return IdentifiedFileType::PSP_ISO;
+				}
+				return IdentifiedFileType::UNKNOWN_ISO;
+			}
+		}
+	} else if (!memcmp(&_id, "CISO", 4)) {
+		// CISO are not used for many other kinds of ISO so let's just guess it's a PSP one and let it
+		// fail later...
+		return IdentifiedFileType::PSP_ISO;
 	}
 
 	if (id == 'FLE\x7F') {
@@ -337,6 +360,7 @@ bool LoadFile(FileLoader **fileLoaderPtr, std::string *error_string) {
 
 	case IdentifiedFileType::UNKNOWN_BIN:
 	case IdentifiedFileType::UNKNOWN_ELF:
+	case IdentifiedFileType::UNKNOWN_ISO:
 	case IdentifiedFileType::UNKNOWN:
 		ERROR_LOG(LOADER, "Unknown file type: %s (%s)", fileLoader->GetPath().c_str(), error_string->c_str());
 		*error_string = "Unknown file type: " + fileLoader->GetPath().ToString();
diff --git a/Core/Loaders.h b/Core/Loaders.h
index 131c82451b..fa6c637d9e 100644
--- a/Core/Loaders.h
+++ b/Core/Loaders.h
@@ -37,6 +37,7 @@ enum class IdentifiedFileType {
 
 	UNKNOWN_BIN,
 	UNKNOWN_ELF,
+	UNKNOWN_ISO,
 
 	// Try to reduce support emails...
 	ARCHIVE_RAR,
diff --git a/UI/GameInfoCache.cpp b/UI/GameInfoCache.cpp
index 91a5e209c5..ec4ea77700 100644
--- a/UI/GameInfoCache.cpp
+++ b/UI/GameInfoCache.cpp
@@ -83,6 +83,7 @@ bool GameInfo::Delete() {
 	case IdentifiedFileType::PSP_ELF:
 	case IdentifiedFileType::UNKNOWN_BIN:
 	case IdentifiedFileType::UNKNOWN_ELF:
+	case IdentifiedFileType::UNKNOWN_ISO:
 	case IdentifiedFileType::ARCHIVE_RAR:
 	case IdentifiedFileType::ARCHIVE_ZIP:
 	case IdentifiedFileType::ARCHIVE_7Z: