First pass of ImageWriter

Change-Id: I4f189587a2e3cc1c265200b8fa64321b299947eb
diff --git a/src/os.h b/src/os.h
new file mode 100644
index 0000000..440c997
--- /dev/null
+++ b/src/os.h
@@ -0,0 +1,28 @@
+// Copyright 2009 Google Inc. All Rights Reserved.
+
+#ifndef ART_SRC_OS_H_
+#define ART_SRC_OS_H_
+
+namespace art {
+
+// Interface to the underlying OS platform.
+
+class File;
+
+class OS {
+ public:
+
+  // Open a file. The returned file must be deleted by the caller.
+  static File* OpenBinaryFile(const char* name, bool writable);
+  static File* OpenTextFile(const char* name, bool writable);
+
+  // Create a file from an already open file descriptor
+  static File* FileFromFd(const char* name, int fd);
+
+  // Check if a file exists.
+  static bool FileExists(const char* name);
+};
+
+}  // namespace art
+
+#endif  // ART_SRC_OS_H_