+
+int
+do_copy_size (const char *src, const char *dest, int64_t size)
+{
+ char *buf;
+ int src_fd, dest_fd;
+
+ if (STRPREFIX (src, "/dev/"))
+ src_fd = open (src, O_RDONLY);
+ else {
+ buf = sysroot_path (src);
+ if (!buf) {
+ reply_with_perror ("malloc");
+ return -1;
+ }
+ src_fd = open (buf, O_RDONLY);
+ free (buf);
+ }
+ if (src_fd == -1) {
+ reply_with_perror ("%s", src);
+ return -1;
+ }
+
+ if (STRPREFIX (dest, "/dev/"))
+ dest_fd = open (dest, O_WRONLY);
+ else {
+ buf = sysroot_path (dest);
+ if (!buf) {
+ reply_with_perror ("malloc");
+ close (src_fd);
+ return -1;
+ }
+ dest_fd = open (buf, O_WRONLY|O_CREAT|O_TRUNC|O_NOCTTY, 0666);
+ free (buf);
+ }
+ if (dest_fd == -1) {
+ reply_with_perror ("%s", dest);
+ close (src_fd);
+ return -1;
+ }
+
+ while (size > 0) {
+ char buf[1024*1024];
+ size_t n = size > (int64_t) (sizeof buf) ? sizeof buf : (size_t) size;
+ ssize_t r = read (src_fd, buf, n);
+ if (r == -1) {
+ reply_with_perror ("%s: read", src);
+ close (src_fd);
+ close (dest_fd);
+ return -1;
+ }
+ if (r == 0) {
+ reply_with_error ("%s: input file too short", src);
+ close (src_fd);
+ close (dest_fd);
+ return -1;
+ }
+
+ if (xwrite (dest_fd, buf, r) == -1) {
+ reply_with_perror ("%s: write", dest);
+ close (src_fd);
+ close (dest_fd);
+ return -1;
+ }
+
+ size -= r;
+ }
+
+ if (close (src_fd) == -1) {
+ reply_with_perror ("%s: close", src);
+ close (dest_fd);
+ return -1;
+ }
+ if (close (dest_fd) == -1) {
+ reply_with_perror ("%s: close", dest);
+ return -1;
+ }
+
+ return 0;
+}