-ssize_t sendfile_full(int out_fd, const char *fn) {
- _cleanup_fclose_ FILE *f;
- struct stat st;
- int r;
- ssize_t s;
-
- size_t n, l;
- _cleanup_free_ char *buf = NULL;
-
- assert(out_fd > 0);
- assert(fn);
-
- f = fopen(fn, "re");
- if (!f)
- return -errno;
-
- r = fstat(fileno(f), &st);
- if (r < 0)
- return -errno;
-
- s = sendfile(out_fd, fileno(f), NULL, st.st_size);
- if (s < 0)
- if (errno == EINVAL || errno == ENOSYS) {
- /* continue below */
- } else
- return -errno;
- else
- return s;
-
- /* sendfile() failed, fall back to read/write */
-
- /* Safety check */
- if (st.st_size > 4*1024*1024)
- return -E2BIG;
-
- n = st.st_size > 0 ? st.st_size : LINE_MAX;
- l = 0;
-
- while (true) {
- char *t;
- size_t k;
-
- t = realloc(buf, n);
- if (!t)
- return -ENOMEM;
-
- buf = t;
- k = fread(buf + l, 1, n - l, f);
-
- if (k <= 0) {
- if (ferror(f))
- return -errno;
-
- break;
- }
-
- l += k;
- n *= 2;
-
- /* Safety check */
- if (n > 4*1024*1024)
- return -E2BIG;
- }
-
- r = write(out_fd, buf, l);
- if (r < 0)
- return -errno;
-
- return (ssize_t) l;
-}
-