From 7dbd2cecd86f4e3ecbac4163dbdebd2a9b547a22 Mon Sep 17 00:00:00 2001
From: "Unknown W. Brackets" <checkins@unknownbrackets.org>
Date: Sun, 8 Apr 2018 08:14:07 -0700
Subject: [PATCH] Android: Avoid pread64 for > 2GB offsets.

Appears to not actually work as advertised.  See #10862.
---
 Core/FileLoaders/LocalFileLoader.cpp | 14 ++++++++++++--
 Core/FileLoaders/LocalFileLoader.h   |  2 ++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Core/FileLoaders/LocalFileLoader.cpp b/Core/FileLoaders/LocalFileLoader.cpp
index d720bf61cf..389f47d652 100644
--- a/Core/FileLoaders/LocalFileLoader.cpp
+++ b/Core/FileLoaders/LocalFileLoader.cpp
@@ -37,7 +37,7 @@ LocalFileLoader::LocalFileLoader(const std::string &filename)
 	if (fd_ == -1) {
 		return;
 	}
-#if defined(__ANDROID__) || (defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS < 64)
+#if PPSSPP_PLATFORM(ANDROID) || (defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS < 64)
 	off64_t off = lseek64(fd_, 0, SEEK_END);
 	filesize_ = off;
 	lseek64(fd_, 0, SEEK_SET);
@@ -112,7 +112,17 @@ std::string LocalFileLoader::Path() const {
 }
 
 size_t LocalFileLoader::ReadAt(s64 absolutePos, size_t bytes, size_t count, void *data, Flags flags) {
-#ifndef _WIN32
+#if PPSSPP_PLATFORM(ANDROID)
+	// pread64 doesn't appear to actually be 64-bit safe, though such ISOs are uncommon.  See #10862.
+	if (absolutePos <= 0x7FFFFFFF) {
+		return pread64(fd_, data, bytes * count, absolutePos) / bytes;
+	} else {
+		// Since pread64 doesn't change the file offset, it should be safe to avoid the lock in the common case.
+		std::lock_guard<std::mutex> guard(readLock_);
+		lseek64(fd_, absolutePos, SEEK_SET);
+		return read(fd_, data, bytes * count) / bytes;
+	}
+#elif !defined(_WIN32)
 #if defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS < 64
 	return pread64(fd_, data, bytes * count, absolutePos) / bytes;
 #else
diff --git a/Core/FileLoaders/LocalFileLoader.h b/Core/FileLoaders/LocalFileLoader.h
index d5203656ea..bb5910494f 100644
--- a/Core/FileLoaders/LocalFileLoader.h
+++ b/Core/FileLoaders/LocalFileLoader.h
@@ -17,6 +17,7 @@
 
 #pragma once
 
+#include <mutex>
 #include "Common/CommonTypes.h"
 #include "Core/Loaders.h"
 #ifdef _WIN32
@@ -42,4 +43,5 @@ private:
 #endif
 	u64 filesize_;
 	std::string filename_;
+	std::mutex readLock_;
 };