Implement simple utility functions for reading and writing to fds

src/lxc/utils.c

@@ -281,3 +281,38 @@ again:
 		goto again;
 	return status;
 }
+
+int lxc_write_nointr(int fd, const void* buf, size_t count)
+{
+	int ret;
+again:
+	ret = write(fd, buf, count);
+	if (ret < 0 && errno == EINTR)
+		goto again;
+	return ret;
+}
+
+int lxc_read_nointr(int fd, void* buf, size_t count)
+{
+	int ret;
+again:
+	ret = read(fd, buf, count);
+	if (ret < 0 && errno == EINTR)
+		goto again;
+	return ret;
+}
+
+int lxc_read_nointr_expect(int fd, void* buf, size_t count, const void* expected_buf)
+{
+	int ret;
+	ret = lxc_read_nointr(fd, buf, count);
+	if (ret <= 0)
+		return ret;
+	if (ret != count)
+		return -1;
+	if (expected_buf && memcmp(buf, expected_buf, count) != 0) {
+		errno = EINVAL;
+		return -1;
+	}
+	return ret;
+}

src/lxc/utils.h

@@ -68,4 +68,9 @@ extern int __build_bug_on_failed;
 extern int wait_for_pid(pid_t pid);
 extern int lxc_wait_for_pid_status(pid_t pid);
 
+/* send and receive buffers completely */
+extern int lxc_write_nointr(int fd, const void* buf, size_t count);
+extern int lxc_read_nointr(int fd, void* buf, size_t count);
+extern int lxc_read_nointr_expect(int fd, void* buf, size_t count, const void* expected_buf);
+
 #endif