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