6 files changed, 236 insertions, 9 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 13ed68b3f..aecb46872 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -155,6 +155,14 @@ if (WIN32)
   target_link_libraries(common PRIVATE ntdll)
 endif()
 
+if(ANDROID)
+    target_sources(common
+        PRIVATE
+            fs/fs_android.cpp
+            fs/fs_android.h
+    )
+endif()
+
 if(ARCHITECTURE_x86_64)
     target_sources(common
         PRIVATE
diff --git a/src/common/fs/file.cpp b/src/common/fs/file.cpp
index 656b03cc5..b0b25eb43 100644
--- a/src/common/fs/file.cpp
+++ b/src/common/fs/file.cpp
@@ -5,6 +5,9 @@
 
 #include "common/fs/file.h"
 #include "common/fs/fs.h"
+#ifdef ANDROID
+#include "common/fs/fs_android.h"
+#endif
 #include "common/logging/log.h"
 
 #ifdef _WIN32
@@ -252,6 +255,23 @@ void IOFile::Open(const fs::path& path, FileAccessMode mode, FileType type, File
     } else {
         _wfopen_s(&file, path.c_str(), AccessModeToWStr(mode, type));
     }
+#elif ANDROID
+    if (Android::IsContentUri(path)) {
+        ASSERT_MSG(mode == FileAccessMode::Read, "Content URI file access is for read-only!");
+        const auto fd = Android::OpenContentUri(path, Android::OpenMode::Read);
+        if (fd != -1) {
+            file = fdopen(fd, "r");
+            const auto error_num = errno;
+            if (error_num != 0 && file == nullptr) {
+                LOG_ERROR(Common_Filesystem, "Error opening file: {}, error: {}", path.c_str(),
+                          strerror(error_num));
+            }
+        } else {
+            LOG_ERROR(Common_Filesystem, "Error opening file: {}", path.c_str());
+        }
+    } else {
+        file = std::fopen(path.c_str(), AccessModeToStr(mode, type));
+    }
 #else
     file = std::fopen(path.c_str(), AccessModeToStr(mode, type));
 #endif
@@ -372,6 +392,23 @@ u64 IOFile::GetSize() const {
     // Flush any unwritten buffered data into the file prior to retrieving the file size.
     std::fflush(file);
 
+#if ANDROID
+    u64 file_size = 0;
+    if (Android::IsContentUri(file_path)) {
+        file_size = Android::GetSize(file_path);
+    } else {
+        std::error_code ec;
+
+        file_size = fs::file_size(file_path, ec);
+
+        if (ec) {
+            LOG_ERROR(Common_Filesystem,
+                      "Failed to retrieve the file size of path={}, ec_message={}",
+                      PathToUTF8String(file_path), ec.message());
+            return 0;
+        }
+    }
+#else
     std::error_code ec;
 
     const auto file_size = fs::file_size(file_path, ec);
@@ -381,6 +418,7 @@ u64 IOFile::GetSize() const {
                   PathToUTF8String(file_path), ec.message());
         return 0;
     }
+#endif
 
     return file_size;
 }
diff --git a/src/common/fs/fs_android.cpp b/src/common/fs/fs_android.cpp
new file mode 100644
index 000000000..298a79bac
--- /dev/null
+++ b/src/common/fs/fs_android.cpp
@@ -0,0 +1,98 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/fs/fs_android.h"
+
+namespace Common::FS::Android {
+
+JNIEnv* GetEnvForThread() {
+    thread_local static struct OwnedEnv {
+        OwnedEnv() {
+            status = g_jvm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6);
+            if (status == JNI_EDETACHED)
+                g_jvm->AttachCurrentThread(&env, nullptr);
+        }
+
+        ~OwnedEnv() {
+            if (status == JNI_EDETACHED)
+                g_jvm->DetachCurrentThread();
+        }
+
+        int status;
+        JNIEnv* env = nullptr;
+    } owned;
+    return owned.env;
+}
+
+void RegisterCallbacks(JNIEnv* env, jclass clazz) {
+    env->GetJavaVM(&g_jvm);
+    native_library = clazz;
+
+#define FR(FunctionName, ReturnValue, JMethodID, Caller, JMethodName, Signature)                   \
+    F(JMethodID, JMethodName, Signature)
+#define FS(FunctionName, ReturnValue, Parameters, JMethodID, JMethodName, Signature)               \
+    F(JMethodID, JMethodName, Signature)
+#define F(JMethodID, JMethodName, Signature)                                                       \
+    JMethodID = env->GetStaticMethodID(native_library, JMethodName, Signature);
+    ANDROID_SINGLE_PATH_DETERMINE_FUNCTIONS(FR)
+    ANDROID_STORAGE_FUNCTIONS(FS)
+#undef F
+#undef FS
+#undef FR
+}
+
+void UnRegisterCallbacks() {
+#define FR(FunctionName, ReturnValue, JMethodID, Caller, JMethodName, Signature) F(JMethodID)
+#define FS(FunctionName, ReturnValue, Parameters, JMethodID, JMethodName, Signature) F(JMethodID)
+#define F(JMethodID) JMethodID = nullptr;
+    ANDROID_SINGLE_PATH_DETERMINE_FUNCTIONS(FR)
+    ANDROID_STORAGE_FUNCTIONS(FS)
+#undef F
+#undef FS
+#undef FR
+}
+
+bool IsContentUri(const std::string& path) {
+    constexpr std::string_view prefix = "content://";
+    if (path.size() < prefix.size()) [[unlikely]] {
+        return false;
+    }
+
+    return path.find(prefix) == 0;
+}
+
+int OpenContentUri(const std::string& filepath, OpenMode openmode) {
+    if (open_content_uri == nullptr)
+        return -1;
+
+    const char* mode = "";
+    switch (openmode) {
+    case OpenMode::Read:
+        mode = "r";
+        break;
+    default:
+        UNIMPLEMENTED();
+        return -1;
+    }
+    auto env = GetEnvForThread();
+    jstring j_filepath = env->NewStringUTF(filepath.c_str());
+    jstring j_mode = env->NewStringUTF(mode);
+    return env->CallStaticIntMethod(native_library, open_content_uri, j_filepath, j_mode);
+}
+
+#define FR(FunctionName, ReturnValue, JMethodID, Caller, JMethodName, Signature)                   \
+    F(FunctionName, ReturnValue, JMethodID, Caller)
+#define F(FunctionName, ReturnValue, JMethodID, Caller)                                            \
+    ReturnValue FunctionName(const std::string& filepath) {                                        \
+        if (JMethodID == nullptr) {                                                                \
+            return 0;                                                                              \
+        }                                                                                          \
+        auto env = GetEnvForThread();                                                              \
+        jstring j_filepath = env->NewStringUTF(filepath.c_str());                                  \
+        return env->Caller(native_library, JMethodID, j_filepath);                                 \
+    }
+ANDROID_SINGLE_PATH_DETERMINE_FUNCTIONS(FR)
+#undef F
+#undef FR
+
+} // namespace Common::FS::Android
diff --git a/src/common/fs/fs_android.h b/src/common/fs/fs_android.h
new file mode 100644
index 000000000..bb8a52648
--- /dev/null
+++ b/src/common/fs/fs_android.h
@@ -0,0 +1,62 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <string>
+#include <vector>
+#include <jni.h>
+
+#define ANDROID_STORAGE_FUNCTIONS(V)                                                               \
+    V(OpenContentUri, int, (const std::string& filepath, OpenMode openmode), open_content_uri,     \
+      "openContentUri", "(Ljava/lang/String;Ljava/lang/String;)I")
+
+#define ANDROID_SINGLE_PATH_DETERMINE_FUNCTIONS(V)                                                 \
+    V(GetSize, std::uint64_t, get_size, CallStaticLongMethod, "getSize", "(Ljava/lang/String;)J")
+
+namespace Common::FS::Android {
+
+static JavaVM* g_jvm = nullptr;
+static jclass native_library = nullptr;
+
+#define FR(FunctionName, ReturnValue, JMethodID, Caller, JMethodName, Signature) F(JMethodID)
+#define FS(FunctionName, ReturnValue, Parameters, JMethodID, JMethodName, Signature) F(JMethodID)
+#define F(JMethodID) static jmethodID JMethodID = nullptr;
+ANDROID_SINGLE_PATH_DETERMINE_FUNCTIONS(FR)
+ANDROID_STORAGE_FUNCTIONS(FS)
+#undef F
+#undef FS
+#undef FR
+
+enum class OpenMode {
+    Read,
+    Write,
+    ReadWrite,
+    WriteAppend,
+    WriteTruncate,
+    ReadWriteAppend,
+    ReadWriteTruncate,
+    Never
+};
+
+void RegisterCallbacks(JNIEnv* env, jclass clazz);
+
+void UnRegisterCallbacks();
+
+bool IsContentUri(const std::string& path);
+
+#define FS(FunctionName, ReturnValue, Parameters, JMethodID, JMethodName, Signature)               \
+    F(FunctionName, Parameters, ReturnValue)
+#define F(FunctionName, Parameters, ReturnValue) ReturnValue FunctionName Parameters;
+ANDROID_STORAGE_FUNCTIONS(FS)
+#undef F
+#undef FS
+
+#define FR(FunctionName, ReturnValue, JMethodID, Caller, JMethodName, Signature)                   \
+    F(FunctionName, ReturnValue)
+#define F(FunctionName, ReturnValue) ReturnValue FunctionName(const std::string& filepath);
+ANDROID_SINGLE_PATH_DETERMINE_FUNCTIONS(FR)
+#undef F
+#undef FR
+
+} // namespace Common::FS::Android
diff --git a/src/common/fs/path_util.cpp b/src/common/fs/path_util.cpp
index ca755b053..e026a13d9 100644
--- a/src/common/fs/path_util.cpp
+++ b/src/common/fs/path_util.cpp
@@ -6,6 +6,9 @@
 #include <unordered_map>
 
 #include "common/fs/fs.h"
+#ifdef ANDROID
+#include "common/fs/fs_android.h"
+#endif
 #include "common/fs/fs_paths.h"
 #include "common/fs/path_util.h"
 #include "common/logging/log.h"
@@ -80,9 +83,7 @@ public:
         yuzu_paths.insert_or_assign(yuzu_path, new_path);
     }
 
-private:
-    PathManagerImpl() {
-        fs::path yuzu_path;
+    void Reinitialize(fs::path yuzu_path = {}) {
         fs::path yuzu_path_cache;
         fs::path yuzu_path_config;
 
@@ -96,12 +97,9 @@ private:
         yuzu_path_cache = yuzu_path / CACHE_DIR;
         yuzu_path_config = yuzu_path / CONFIG_DIR;
 #elif ANDROID
-        // On Android internal storage is mounted as "/sdcard"
-        if (Exists("/sdcard")) {
-            yuzu_path = "/sdcard/yuzu-emu";
-            yuzu_path_cache = yuzu_path / CACHE_DIR;
-            yuzu_path_config = yuzu_path / CONFIG_DIR;
-        }
+        ASSERT(!yuzu_path.empty());
+        yuzu_path_cache = yuzu_path / CACHE_DIR;
+        yuzu_path_config = yuzu_path / CONFIG_DIR;
 #else
         yuzu_path = GetCurrentDir() / PORTABLE_DIR;
 
@@ -129,6 +127,11 @@ private:
         GenerateYuzuPath(YuzuPath::TASDir, yuzu_path / TAS_DIR);
     }
 
+private:
+    PathManagerImpl() {
+        Reinitialize();
+    }
+
     ~PathManagerImpl() = default;
 
     void GenerateYuzuPath(YuzuPath yuzu_path, const fs::path& new_path) {
@@ -217,6 +220,10 @@ fs::path RemoveTrailingSeparators(const fs::path& path) {
     return fs::path{string_path};
 }
 
+void SetAppDirectory(const std::string& app_directory) {
+    PathManagerImpl::GetInstance().Reinitialize(app_directory);
+}
+
 const fs::path& GetYuzuPath(YuzuPath yuzu_path) {
     return PathManagerImpl::GetInstance().GetYuzuPathImpl(yuzu_path);
 }
@@ -357,6 +364,12 @@ std::vector<std::string> SplitPathComponents(std::string_view filename) {
 
 std::string SanitizePath(std::string_view path_, DirectorySeparator directory_separator) {
     std::string path(path_);
+#ifdef ANDROID
+    if (Android::IsContentUri(path)) {
+        return path;
+    }
+#endif // ANDROID
+
     char type1 = directory_separator == DirectorySeparator::BackwardSlash ? '/' : '\\';
     char type2 = directory_separator == DirectorySeparator::BackwardSlash ? '\\' : '/';
 
diff --git a/src/common/fs/path_util.h b/src/common/fs/path_util.h
index 13d713f1e..7cfe85b70 100644
--- a/src/common/fs/path_util.h
+++ b/src/common/fs/path_util.h
@@ -181,6 +181,14 @@ template <typename Path>
 #endif
 
 /**
+ * Sets the directory used for application storage. Used on Android where we do not know internal
+ * storage until informed by the frontend.
+ *
+ * @param app_directory Directory to use for application storage.
+ */
+void SetAppDirectory(const std::string& app_directory);
+
+/**
  * Gets the filesystem path associated with the YuzuPath enum.
  *
  * @param yuzu_path YuzuPath enum