long osdFileRead(OSD_File *file, char *buffer,unsigned long len)
The memory pointed to by buffer should be large enough to hold
len bytes.
After the osdFileRead() the file pointer location is incremented by the actual
number of bytes read.
Returns the actual number of bytes read. This may be less than len
if the end of the file has been reached, and any subsequent calls will return
0. On failure -1 is returned.
| file | the file to be read |
| buffer | a pointer where read data will be placed |
| len | the number of bytes to read |