[PATCH 3/2] hoist out handle_nonblock function for xread and xwrite

From

EWEric Wong <e@80x24.org>

Date

Jul 10, 2016, 08:20 UTC

Message-ID

<20160710082046.GB29312@whir>

In-Reply-To

<20160710044529.GA10777@sigill.intra.peff.net>

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Jeff King <peff@peff.net>
---
  Jeff King <peff@peff.net> wrote:
  > On Sun, Jul 10, 2016 at 03:47:36AM +0000, Eric Wong wrote:
  > > Yes, I'm fine with either, but I'm slightly thrown off by
  > > a function relying on errno being set by the caller, even if it
  > > is errno.  So maybe localizing it is better (see below)
  > 
  > Yeah, I had a similar reservation, but didn't want to clutter the
  > interface. However, just passing errno isn't too bad (as you showed
  > below), and is much less magical.
  > 
  > Do you want to squash that and re-send the whole patch to make Junio's
  > life easier?

  Done, also updated the subject to match the new function name.

  I wasn't attached to the "io_wait" name, either, as it could
  be confused with "I/O wait" commonly associated with disk I/O
  and not often with socket/pipe I/O that poll gets used for.

 wrapper.c | 48 ++++++++++++++++++++----------------------------
 1 file changed, 20 insertions(+), 28 deletions(-)

diff --git a/wrapper.c b/wrapper.c
index 0b920f1..78f6431 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -227,6 +227,24 @@ int xopen(const char *path, int oflag, ...)
 	}
 }
 
+static int handle_nonblock(int fd, short poll_events, int err)
+{
+	struct pollfd pfd;
+
+	if (err != EAGAIN && err != EWOULDBLOCK)
+		return 0;
+
+	pfd.fd = fd;
+	pfd.events = poll_events;
+
+	/*
+	 * no need to check for errors, here;
+	 * a subsequent read/write will detect unrecoverable errors
+	 */
+	poll(&pfd, 1, -1);
+	return 1;
+}
+
 /*
  * xread() is the same a read(), but it automatically restarts read()
  * operations with a recoverable error (EAGAIN and EINTR). xread()
@@ -242,21 +260,8 @@ ssize_t xread(int fd, void *buf, size_t len)
 		if (nr < 0) {
 			if (errno == EINTR)
 				continue;
-			if (errno == EAGAIN || errno == EWOULDBLOCK) {
-				struct pollfd pfd;
-				pfd.events = POLLIN;
-				pfd.fd = fd;
-				/*
-				 * it is OK if this poll() failed; we
-				 * want to leave this infinite loop
-				 * only when read() returns with
-				 * success, or an expected failure,
-				 * which would be checked by the next
-				 * call to read(2).
-				 */
-				poll(&pfd, 1, -1);
+			if (handle_nonblock(fd, POLLIN, errno))
 				continue;
-			}
 		}
 		return nr;
 	}
@@ -277,21 +282,8 @@ ssize_t xwrite(int fd, const void *buf, size_t len)
 		if (nr < 0) {
 			if (errno == EINTR)
 				continue;
-			if (errno == EAGAIN || errno == EWOULDBLOCK) {
-				struct pollfd pfd;
-				pfd.events = POLLOUT;
-				pfd.fd = fd;
-				/*
-				 * it is OK if this poll() failed; we
-				 * want to leave this infinite loop
-				 * only when write() returns with
-				 * success, or an expected failure,
-				 * which would be checked by the next
-				 * call to write(2).
-				 */
-				poll(&pfd, 1, -1);
+			if (handle_nonblock(fd, POLLOUT, errno))
 				continue;
-			}
 		}
 
 		return nr;

-- 
EW