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/*
* make-sparse.c --- make a sparse file from stdin
*
* Copyright 2004 by Theodore Ts'o.
*
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
* %End-Header%
*/
#define _LARGEFILE_SOURCE
#define _LARGEFILE64_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
int full_read(int fd, char *buf, size_t count)
{
int got, total = 0;
int pass = 0;
while (count > 0) {
got = read(fd, buf, count);
if (got == -1) {
if ((errno == EINTR) || (errno == EAGAIN))
continue;
return total ? total : -1;
}
if (got == 0) {
if (pass++ >= 3)
return total;
continue;
}
pass = 0;
buf += got;
total += got;
count -= got;
}
return total;
}
int main(int argc, char **argv)
{
int fd, got, i;
int zflag = 0;
char buf[1024];
if (argc != 2) {
fprintf(stderr, "Usage: make-sparse out-file\n");
exit(1);
}
fd = open(argv[1], O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0777);
if (fd < 0) {
perror(argv[1]);
exit(1);
}
while (1) {
got = full_read(0, buf, sizeof(buf));
if (got == 0)
break;
if (got == sizeof(buf)) {
for (i=0; i < sizeof(buf); i++)
if (buf[i])
break;
if (i == sizeof(buf)) {
lseek(fd, sizeof(buf), SEEK_CUR);
zflag = 1;
continue;
}
}
zflag = 0;
write(fd, buf, got);
}
if (zflag) {
lseek(fd, -1, SEEK_CUR);
buf[0] = 0;
write(fd, buf, 1);
}
return 0;
}
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