Making stateless file IO platform-agnostic.

src/xenia/base/filesystem.h

@@ -11,14 +11,12 @@
 #define XENIA_BASE_FILESYSTEM_H_
 
 #include <iterator>
+#include <memory>
 #include <string>
 #include <vector>
 
 #include "xenia/base/string.h"
 
-// TOODO(benvanik): remove windows headers.
-#undef DeleteFile
-
 namespace xe {
 namespace filesystem {
 
@@ -33,6 +31,50 @@ bool IsFolder(const std::wstring& path);
 FILE* OpenFile(const std::wstring& path, const char* mode);
 bool DeleteFile(const std::wstring& path);
 
+struct FileAccess {
+  // Implies kFileReadData.
+  static const uint32_t kGenericRead = 0x80000000;
+  // Implies kFileWriteData.
+  static const uint32_t kGenericWrite = 0x40000000;
+  static const uint32_t kGenericExecute = 0x20000000;
+  static const uint32_t kGenericAll = 0x10000000;
+  static const uint32_t kFileReadData = 0x00000001;
+  static const uint32_t kFileWriteData = 0x00000002;
+  static const uint32_t kFileAppendData = 0x00000004;
+};
+
+class FileHandle {
+ public:
+  // Opens the file, failing if it doesn't exist.
+  // The desired_access bitmask denotes the permissions on the file.
+  static std::unique_ptr<FileHandle> OpenExisting(std::wstring path,
+                                                  uint32_t desired_access);
+
+  virtual ~FileHandle() = default;
+
+  std::wstring path() const { return path_; }
+
+  // Reads the requested number of bytes from the file starting at the given
+  // offset. The total number of bytes read is returned only if the complete
+  // read succeeds.
+  virtual bool Read(size_t file_offset, void* buffer, size_t buffer_length,
+                    size_t* out_bytes_read) = 0;
+
+  // Writes the given buffer to the file starting at the given offset.
+  // The total number of bytes written is returned only if the complete
+  // write succeeds.
+  virtual bool Write(size_t file_offset, const void* buffer,
+                     size_t buffer_length, size_t* out_bytes_written) = 0;
+
+  // Flushes any pending write buffers to the underlying filesystem.
+  virtual void Flush() = 0;
+
+ protected:
+  FileHandle(std::wstring path) : path_(std::move(path)) {}
+
+  std::wstring path_;
+};
+
 struct FileInfo {
   enum class Type {
     kFile,