IO buffer structure.
Source position: ostypes.inc line 478
| type iovec = record | ||
| iov_base: pointer; | 
 | Location of the buffer. | 
| iov_len: size_t; | 
 | Length of the buffer. | 
| end; | 
iovec is used in fpreadv for IO to multiple buffers to describe a buffer location.
| 
 | Vector read: Read into multiple buffers. | |
| 
 | Vector write: Write from multiple buffers to a file descriptor. |