Name
relay_file_read_start_pos — 
     find the first available byte to read
 
Synopsis
| size_t relay_file_read_start_pos ( | size_t read_pos, | 
|  | struct rchan_buf * buf ); | 
 
Arguments
- read_pos
- 
     file read position
     
- buf
- 
     relay channel buffer
     
Description
   If the read_pos is in the middle of padding, return the
   position of the first actually available byte, otherwise
   return the original value.