PRead.c

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#include "syshdrs.h"
 
#if !defined(NO_SIGNALS) && defined(SIGPIPE)
extern volatile Sjmp_buf gPipeJmp;
#endif
 
/* Read up to "size" bytes on sfd.
 *
 * If "retry" is on, after a successful read of less than "size"
 * bytes, it will attempt to read more, upto "size."
 *
 * Although "retry" would seem to indicate you may want to always
 * read "size" bytes or else it is an error, even with that on you
 * may get back a value < size.  Set "retry" to 0 when you want to
 * return as soon as there is a chunk of data whose size is <= "size".
 */
 
int
PRead(int sfd, char *const buf0, size_t size, int retry)
{
    int nread;
    volatile int nleft;
    char *volatile buf = buf0;
#if !defined(NO_SIGNALS) && defined(SIGPIPE)
    vsio_sigproc_t sigpipe;
 
    if (SSetjmp(gPipeJmp) != 0) {
        (void) SSignal(SIGPIPE, (sio_sigproc_t) sigpipe);
        nread = size - nleft;
        if (nread > 0)
            return (nread);
        errno = EPIPE;
        return (kBrokenPipeErr);
    }
 
    sigpipe = (vsio_sigproc_t) SSignal(SIGPIPE, SIOHandler);
#endif
    errno = 0;
 
    nleft = (int) size;
    forever {
        nread = read(sfd, buf, nleft);
        if (nread <= 0) {
            if (nread == 0) {
                /* EOF */
                nread = size - nleft;
                goto done;
            } else if (errno != EINTR) {
                nread = size - nleft;
                if (nread == 0)
                    nread = -1;
                goto done;
            } else {
                errno = 0;
                nread = 0;
                /* Try again. */
            }
        }
        nleft -= nread;
        if ((nleft <= 0) || (retry == 0))
            break;
        buf += nread;
    }
    nread = size - nleft;
 
done:
#if !defined(NO_SIGNALS) && defined(SIGPIPE)
    (void) SSignal(SIGPIPE, (sio_sigproc_t) sigpipe);
#endif
    return (nread);
}   /* PRead */