At least for me, this improves the readability of xread and
xwrite; hopefully allowing missing "continue" statements to
be spotted more easily.
Signed-off-by: Eric Wong <e@xxxxxxxxx>
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
Jeff King <peff@xxxxxxxx> 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
--
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