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authorRaimo Niskanen <[email protected]>2011-12-08 13:32:09 +0100
committerRaimo Niskanen <[email protected]>2011-12-20 12:07:41 +0100
commitb3db46435e2d32aa4197753bc95a81648f794021 (patch)
treec79295468315656a94f86f816ed914bdd830b312 /erts/emulator/drivers/unix
parentd34e248f0913a337f1662e07b15298f9a082834b (diff)
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erts: rewrite efile_writev to handle partial writes correctly
Diffstat (limited to 'erts/emulator/drivers/unix')
-rw-r--r--erts/emulator/drivers/unix/unix_efile.c97
1 files changed, 38 insertions, 59 deletions
diff --git a/erts/emulator/drivers/unix/unix_efile.c b/erts/emulator/drivers/unix/unix_efile.c
index 7cf0a712ce..e7dd9d2bdb 100644
--- a/erts/emulator/drivers/unix/unix_efile.c
+++ b/erts/emulator/drivers/unix/unix_efile.c
@@ -1004,13 +1004,11 @@ efile_writev(Efile_error* errInfo, /* Where to return error codes */
* opened */
int fd, /* File descriptor to write to */
SysIOVec* iov, /* Vector of buffer structs.
- * The structs are unchanged
- * after the call */
- int iovcnt, /* Number of structs in vector */
- size_t size) /* Number of bytes to write */
+ * The structs may be changed i.e.
+ * due to incomplete writes */
+ int iovcnt) /* Number of structs in vector */
{
int cnt = 0; /* Buffers so far written */
- int p = 0; /* Position in next buffer */
ASSERT(iovcnt >= 0);
@@ -1021,66 +1019,47 @@ efile_writev(Efile_error* errInfo, /* Where to return error codes */
#endif
while (cnt < iovcnt) {
+ if ((! iov[cnt].iov_base) || (iov[cnt].iov_len <= 0)) {
+ /* Empty buffer - skip */
+ cnt++;
+ } else { /* Non-empty buffer */
+ ssize_t w; /* Bytes written in this call */
#ifdef HAVE_WRITEV
- int w; /* Bytes written in this call */
- int b = iovcnt - cnt; /* Buffers to write */
- if (b > MAXIOV)
- b = MAXIOV;
- if (iov[cnt].iov_base && iov[cnt].iov_len > 0) {
- if (b == 1) {
- /* Degenerated io vector */
- do {
- w = write(fd, iov[cnt].iov_base + p, iov[cnt].iov_len - p);
- } while (w < 0 && errno == EINTR);
- } else {
- /* Non-empty vector first.
- * Adjust pos in first buffer in case of
- * previous incomplete writev */
- iov[cnt].iov_base += p;
- iov[cnt].iov_len -= p;
+ int b = iovcnt - cnt; /* Buffers to write */
+ /* Use as many buffers as MAXIOV allows */
+ if (b > MAXIOV)
+ b = MAXIOV;
+ if (b > 1) {
do {
w = writev(fd, &iov[cnt], b);
} while (w < 0 && errno == EINTR);
- iov[cnt].iov_base -= p;
- iov[cnt].iov_len += p;
- }
- if (w < 0)
- return check_error(-1, errInfo);
- } else {
- /* Empty vector first - skip */
- cnt++;
- continue;
- }
- ASSERT(w >= 0);
- /* Move forward to next vector to write */
- for (; cnt < iovcnt; cnt++) {
- if (iov[cnt].iov_base && iov[cnt].iov_len > 0) {
- if (w < iov[cnt].iov_len)
- break;
- else
- w -= iov[cnt].iov_len;
- }
- }
- ASSERT(w >= 0);
- p = w > 0 ? w : 0; /* Skip p bytes next writev */
-#else /* #ifdef HAVE_WRITEV */
- if (iov[cnt].iov_base && iov[cnt].iov_len > 0) {
- /* Non-empty vector */
- int w; /* Bytes written in this call */
- while (p < iov[cnt].iov_len) {
- do {
- w = write(fd, iov[cnt].iov_base + p, iov[cnt].iov_len - p);
- } while (w < 0 && errno == EINTR);
- if (w < 0)
- return check_error(-1, errInfo);
- p += w;
+ } else
+ /* Degenerated io vector - use regular write */
+#endif
+ {
+ do {
+ w = write(fd, iov[cnt].iov_base, iov[cnt].iov_len);
+ } while (w < 0 && errno == EINTR);
+ ASSERT(w <= iov[cnt].iov_len);
+ }
+ if (w < 0) return check_error(-1, errInfo);
+ /* Move forward to next buffer to write */
+ for (; cnt < iovcnt && w > 0; cnt++) {
+ if (iov[cnt].iov_base && iov[cnt].iov_len > 0) {
+ if (w < iov[cnt].iov_len) {
+ /* Adjust the buffer for next write */
+ iov[cnt].iov_len -= w;
+ iov[cnt].iov_base += w;
+ w = 0;
+ break;
+ } else {
+ w -= iov[cnt].iov_len;
+ }
+ }
}
- }
- cnt++;
- p = 0;
-#endif /* #ifdef HAVE_WRITEV */
+ ASSERT(w == 0);
+ } /* else Non-empty buffer */
} /* while (cnt< iovcnt) */
- size = 0; /* Avoid compiler warning */
return 1;
}