Android: Add content provider support to File::OpenFStream

Source/Android/jni/AndroidCommon/AndroidCommon.cpp

@@ -4,6 +4,7 @@
 
 #include "jni/AndroidCommon/AndroidCommon.h"
 
+#include <ios>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -66,6 +67,28 @@ std::string OpenModeToAndroid(std::string mode)
   return mode;
 }
 
+std::string OpenModeToAndroid(std::ios_base::openmode mode)
+{
+  std::string result;
+
+  if (mode & std::ios_base::in)
+    result += 'r';
+
+  if (mode & (std::ios_base::out | std::ios_base::app))
+    result += 'w';
+
+  if (mode & std::ios_base::app)
+    result += 'a';
+
+  constexpr std::ios_base::openmode t = std::ios_base::in | std::ios_base::trunc;
+  if ((mode & t) == t)
+    result += 't';
+
+  // The 'b' specifier is not supported. Since we're on POSIX, it's fine to just skip it.
+
+  return result;
+}
+
 int OpenAndroidContent(const std::string& uri, const std::string& mode)
 {
   JNIEnv* env = IDCache::GetEnvForThread();

Source/Android/jni/AndroidCommon/AndroidCommon.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <ios>
 #include <string>
 
 #include <jni.h>
@@ -17,6 +18,7 @@ bool IsPathAndroidContent(const std::string& uri);
 
 // Turns a C/C++ style mode (e.g. "rb") into one which can be used with OpenAndroidContent.
 std::string OpenModeToAndroid(std::string mode);
+std::string OpenModeToAndroid(std::ios_base::openmode mode);
 
 // Opens a given file and returns a file descriptor.
 int OpenAndroidContent(const std::string& uri, const std::string& mode);

Source/Core/Common/FileUtil.h

@@ -18,6 +18,11 @@
 #include "Common/StringUtil.h"
 #endif
 
+#ifdef ANDROID
+#include "Common/StringUtil.h"
+#include "jni/AndroidCommon/AndroidCommon.h"
+#endif
+
 // User directory indices for GetUserPath
 enum
 {
@@ -213,14 +218,20 @@ std::string GetExeDirectory();
 bool WriteStringToFile(const std::string& filename, std::string_view str);
 bool ReadFileToString(const std::string& filename, std::string& str);
 
-// To deal with Windows being dumb at unicode:
+// To deal with Windows not fully supporting UTF-8 and Android not fully supporting paths.
 template <typename T>
 void OpenFStream(T& fstream, const std::string& filename, std::ios_base::openmode openmode)
 {
 #ifdef _WIN32
   fstream.open(UTF8ToTStr(filename).c_str(), openmode);
 #else
-  fstream.open(filename.c_str(), openmode);
+#ifdef ANDROID
+  // Unfortunately it seems like the non-standard __open is the only way to use a file descriptor
+  if (IsPathAndroidContent(filename))
+    fstream.__open(OpenAndroidContent(filename, OpenModeToAndroid(openmode)), openmode);
+  else
+#endif
+    fstream.open(filename.c_str(), openmode);
 #endif
 }