Update SAF handling

src/Common/android/FilesystemAndroid.cpp

@@ -0,0 +1,58 @@
+#include "FilesystemAndroid.h"
+
+#include <boost/iostreams/device/file_descriptor.hpp>
+#include <boost/iostreams/stream_buffer.hpp>
+
+using namespace boost::iostreams;
+
+namespace FilesystemAndroid
+{
+std::shared_ptr<FilesystemCallbacks> g_filesystemCallbacks = nullptr;
+
+void SetFilesystemCallbacks(const std::shared_ptr<FilesystemCallbacks> &filesystemCallbacks)
+{
+    g_filesystemCallbacks = filesystemCallbacks;
+}
+
+int OpenContentUri(const fs::path &uri)
+{
+    if (g_filesystemCallbacks)
+        return g_filesystemCallbacks->OpenContentUri(uri);
+    return -1;
+}
+
+std::vector<fs::path> ListFiles(const fs::path &uri)
+{
+    if (g_filesystemCallbacks)
+        return g_filesystemCallbacks->ListFiles(uri);
+    return {};
+}
+
+bool IsDirectory(const fs::path &uri)
+{
+    if (g_filesystemCallbacks)
+        return g_filesystemCallbacks->IsDirectory(uri);
+    return false;
+}
+
+bool IsFile(const fs::path &uri)
+{
+    if (g_filesystemCallbacks)
+        return g_filesystemCallbacks->IsFile(uri);
+    return false;
+}
+
+bool Exists(const fs::path &uri)
+{
+    if (g_filesystemCallbacks)
+        return g_filesystemCallbacks->Exists(uri);
+    return false;
+}
+
+bool IsContentUri(const std::string &uri)
+{
+    static constexpr auto content = "content://";
+    return uri.starts_with(content);
+}
+
+}  // namespace FilesystemAndroid