+/**
+ * Write a buffer to a file descriptor, re-write on short writes.
+ *
+ * \param fd The file descriptor.
+ * \param buf The buffer to be sent.
+ * \param len The length of \a buf.
+ *
+ * \return Standard. In any case, the number of bytes that have been written is
+ * stored in \a len.
+ */
+int write_all(int fd, const char *buf, size_t *len)
+{
+ size_t total = *len;
+
+ assert(total);
+ *len = 0;
+ while (*len < total) {
+ int ret = write(fd, buf + *len, total - *len);
+ if (ret == -1)
+ return -ERRNO_TO_PARA_ERROR(errno);
+ *len += ret;
+ }
+ return 1;
+}
+