io_waitread - read from a descriptor
#include <libowfat/io.h>
int io_waitread(int64 fd,char* buf,int64 len);
io_waitread tries to read len bytes of data from descriptor
fd into buf[0], buf[1], ..., buf[len-1]. (The effects are undefined
if len is 0 or smaller.) There are several possible results:
- •
- o_waitread returns an integer between 1 and len: This number of
bytes was available for immediate reading; the bytes were read into the
beginning of buf. Note that this number can be, and often is,
smaller than len; you must not assume that io_waitread always
succeeds in reading exactly len bytes.
- •
- io_waitread returns 0: No bytes were read, because the descriptor is at
end of file. For example, this descriptor has reached the end of a disk
file, or is reading an empty pipe that has been closed by all
writers.
- •
- io_waitread returns -3, setting errno to something other than
EAGAIN: No bytes were read, because the read attempt encountered a
persistent error, such as a serious disk failure (EIO), an unreachable
network (ENETUNREACH), or an invalid descriptor number (EBADF).