[PATCH v3 1/5] osdep: make readv_writev() work with partial read/write

[marcandre . lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

With a pipe or other reasons, read/write may return less than the
requested bytes. This happens with the test-io-channel-command test on
Windows. glib spawn code uses a binary pipe of 4096 bytes, and the first
read returns that much (although more are requested), for some unclear
reason...

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 util/osdep.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/util/osdep.c b/util/osdep.c
index 60fcbbaebe..b85715a743 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -544,12 +544,17 @@ readv_writev(int fd, const struct iovec *iov, int 
iov_cnt, bool do_write)
 {
     unsigned i = 0;
     ssize_t ret = 0;
+    ssize_t off = 0;
     while (i < iov_cnt) {
         ssize_t r = do_write
-            ? write(fd, iov[i].iov_base, iov[i].iov_len)
-            : read(fd, iov[i].iov_base, iov[i].iov_len);
+            ? write(fd, iov[i].iov_base + off, iov[i].iov_len - off)
+            : read(fd, iov[i].iov_base + off, iov[i].iov_len - off);
         if (r > 0) {
             ret += r;
+            off += r;
+            if (off < iov[i].iov_len) {
+                continue;
+            }
         } else if (!r) {
             break;
         } else if (errno == EINTR) {
@@ -562,6 +567,7 @@ readv_writev(int fd, const struct iovec *iov, int iov_cnt, 
bool do_write)
             }
             break;
         }
+        off = 0;
         i++;
     }
     return ret;
-- 
2.37.3