archive-logs

 1#include <unistd.h>
 2#include <sys/types.h>
 3
 4static ssize_t
 5sendfile(int out, int in, off_t *offset, size_t count)
 6{
 7	off_t start;
 8	char buf[4096];
 9	ssize_t rw, rr;
10	size_t c, max, written;
11
12	/* XXX: Technically, sendfile should not modify the file offset if
13	 * offset is not NULL, this implementation ignore this requirement. */
14
15	if (offset) {
16		start = *offset;
17		if (lseek(in, start, SEEK_SET) == -1)
18			return -1;
19	}
20
21	written = 0;
22	for (c = count; c > 0; c -= rw) {
23		if ((max = sizeof(buf)) > c)
24			max = c;
25
26		rr = read(in, buf, max);
27		if (rr == 0)
28			break;
29		else if (rr == -1)
30			return -1;
31
32		if ((rw = write(out, buf, rr)) == -1)
33			return -1;
34		written += rw;
35
36		/* If a short write occured, seek back and return */
37		if (rw < rr) {
38			if (lseek(in, rw - rr, SEEK_CUR) == -1)
39				return -1;
40			break;
41		}
42	}
43
44	if (offset)
45		*offset = start + written;
46	return written;
47}