* the BeBook documents WriteAt() and Write() to differ analogous to

ReadAt() and Read() with regards to the file position. Ie, WriteAt()
  is not supposed to modify the data pointer.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@23830 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/storage/File.cpp

@@ -398,7 +398,13 @@ BFile::WriteAt(off_t location, const void *buffer, size_t size)
 		return InitCheck();
 	if (location < 0)
 		return B_BAD_VALUE;
-	return _kern_write(get_fd(), location, buffer, size);
+
+	// WriteAt() is not supposed to move the current position on the file.
+	off_t curPos = Position(); // Cache current position.
+	ssize_t result = _kern_write(get_fd(), location, buffer, size);
+	Seek(curPos, SEEK_SET); // Resets file position.
+
+	return result;
 }
 
 // Seek