+static int cpio_mkfile_csum(int fd, unsigned long size, uint32_t *csum)
+{
+ while (size) {
+ unsigned char filebuf[65536];
+ ssize_t this_read;
+ size_t i, this_size = MIN(size, sizeof(filebuf));
+
+ this_read = read(fd, filebuf, this_size);
+ if (this_read <= 0 || this_read > this_size)
+ return -1;
+
+ for (i = 0; i < this_read; i++)
+ *csum += filebuf[i];
+
+ size -= this_read;
+ }
+ /* seek back to the start for data segment I/O */
+ if (lseek(fd, 0, SEEK_SET) < 0)
+ return -1;
+
+ return 0;
+}
+