Android: Make the handling of SAF open modes more robust

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/ContentHandler.java

@@ -17,7 +17,9 @@ public class ContentHandler
       return DolphinApplication.getAppContext().getContentResolver()
               .openFileDescriptor(Uri.parse(uri), mode).detachFd();
     }
-    catch (FileNotFoundException | NullPointerException e)
+    // Some content providers throw IllegalArgumentException for invalid modes,
+    // despite the documentation saying that invalid modes result in a FileNotFoundException
+    catch (FileNotFoundException | IllegalArgumentException | NullPointerException e)
     {
       return -1;
     }

Source/Android/jni/AndroidCommon/AndroidCommon.cpp

@@ -10,6 +10,7 @@
 
 #include <jni.h>
 
+#include "Common/Assert.h"
 #include "Common/StringUtil.h"
 #include "jni/AndroidCommon/IDCache.h"
 
@@ -42,21 +43,35 @@ std::vector<std::string> JStringArrayToVector(JNIEnv* env, jobjectArray array)
   return result;
 }
 
+bool IsPathAndroidContent(const std::string& uri)
+{
+  return StringBeginsWith(uri, "content://");
+}
+
+std::string OpenModeToAndroid(std::string mode)
+{
+  // The 'b' specifier is not supported. Since we're on POSIX, it's fine to just skip it.
+  if (!mode.empty() && mode.back() == 'b')
+    mode.pop_back();
+
+  if (mode == "r+")
+    mode = "rw";
+  else if (mode == "w+")
+    mode = "rwt";
+  else if (mode == "a+")
+    mode = "rwa";
+  else if (mode == "a")
+    mode = "wa";
+
+  return mode;
+}
+
 int OpenAndroidContent(const std::string& uri, const std::string& mode)
 {
   JNIEnv* env = IDCache::GetEnvForThread();
-  const jint fd = env->CallStaticIntMethod(IDCache::GetContentHandlerClass(),
-                                           IDCache::GetContentHandlerOpenFd(), ToJString(env, uri),
-                                           ToJString(env, mode));
-
-  // We can get an IllegalArgumentException when passing an invalid mode
-  if (env->ExceptionCheck())
-  {
-    env->ExceptionDescribe();
-    abort();
-  }
-
-  return fd;
+  return env->CallStaticIntMethod(IDCache::GetContentHandlerClass(),
+                                  IDCache::GetContentHandlerOpenFd(), ToJString(env, uri),
+                                  ToJString(env, mode));
 }
 
 bool DeleteAndroidContent(const std::string& uri)

Source/Android/jni/AndroidCommon/AndroidCommon.h

@@ -12,5 +12,14 @@ std::string GetJString(JNIEnv* env, jstring jstr);
 jstring ToJString(JNIEnv* env, const std::string& str);
 std::vector<std::string> JStringArrayToVector(JNIEnv* env, jobjectArray array);
 
+// Returns true if the given path should be opened as Android content instead of a normal file.
+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);
+
+// Opens a given file and returns a file descriptor.
 int OpenAndroidContent(const std::string& uri, const std::string& mode);
+
+// Deletes a given file.
 bool DeleteAndroidContent(const std::string& uri);