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authorDavid Gibson <david@gibson.dropbear.id.au>2024-02-28 12:52:03 +1100
committerStefano Brivio <sbrivio@redhat.com>2024-02-29 06:25:17 +0100
commit8bdb0883b441441590589aac46f991c80e4f80f3 (patch)
tree202c4a946b3ea9d365a5056d1bf044b873dfad6e
parent24410b37a44e819877bdb4449a3147567a866ffa (diff)
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util: Add write_remainder() helper
We have several places where we want to write(2) a buffer or buffers and we handle short write()s by retrying until everything is successfully written. Add a helper for this in util.c. This version has some differences from the typical write_all() function. First, take an IO vector rather than a single buffer, because that will be useful for some of our cases. Second, allow it to take an parameter to skip the first n bytes of the given buffers. This will be useful for some of the cases we want, and also falls out quite naturally from the implementation. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> [sbrivio: Minor formatting fixes in write_remainder()] Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
-rw-r--r--util.c35
-rw-r--r--util.h1
2 files changed, 36 insertions, 0 deletions
diff --git a/util.c b/util.c
index 8acce23..81449b7 100644
--- a/util.c
+++ b/util.c
@@ -19,6 +19,7 @@
#include <arpa/inet.h>
#include <net/ethernet.h>
#include <sys/epoll.h>
+#include <sys/uio.h>
#include <fcntl.h>
#include <string.h>
#include <time.h>
@@ -26,6 +27,7 @@
#include <stdbool.h>
#include "util.h"
+#include "iov.h"
#include "passt.h"
#include "packet.h"
#include "log.h"
@@ -574,3 +576,36 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
return clone(fn, stack_area + stack_size / 2, flags, arg);
#endif
}
+
+/* write_remainder() - write the tail of an IO vector to an fd
+ * @fd: File descriptor
+ * @iov: IO vector
+ * @iovcnt: Number of entries in @iov
+ * @skip: Number of bytes of the vector to skip writing
+ *
+ * Return: 0 on success, -1 on error (with errno set)
+ *
+ * #syscalls write writev
+ */
+int write_remainder(int fd, const struct iovec *iov, int iovcnt, size_t skip)
+{
+ int i;
+
+ while ((i = iov_skip_bytes(iov, iovcnt, skip, &skip)) < iovcnt) {
+ ssize_t rc;
+
+ if (skip) {
+ rc = write(fd, (char *)iov[i].iov_base + skip,
+ iov[i].iov_len - skip);
+ } else {
+ rc = writev(fd, &iov[i], iovcnt - i);
+ }
+
+ if (rc < 0)
+ return -1;
+
+ skip += rc;
+ }
+
+ return 0;
+}
diff --git a/util.h b/util.h
index e0df26c..de6816a 100644
--- a/util.h
+++ b/util.h
@@ -229,6 +229,7 @@ void write_pidfile(int fd, pid_t pid);
int __daemon(int pidfile_fd, int devnull_fd);
int fls(unsigned long x);
int write_file(const char *path, const char *buf);
+int write_remainder(int fd, const struct iovec *iov, int iovcnt, size_t skip);
/**
* mod_sub() - Modular arithmetic subtraction