1 /* 2 * make-sparse.c --- make a sparse file from stdin 3 * 4 * Copyright 2004 by Theodore Ts'o. 5 * 6 * %Begin-Header% 7 * This file may be redistributed under the terms of the GNU Public 8 * License. 9 * %End-Header% 10 */ 11 12 #define _LARGEFILE_SOURCE 13 #define _LARGEFILE64_SOURCE 14 15 #include <stdio.h> 16 #include <unistd.h> 17 #include <stdlib.h> 18 #include <sys/types.h> 19 #include <sys/stat.h> 20 #include <fcntl.h> 21 #include <errno.h> 22 23 int full_read(int fd, char *buf, size_t count) 24 { 25 int got, total = 0; 26 int pass = 0; 27 28 while (count > 0) { 29 got = read(fd, buf, count); 30 if (got == -1) { 31 if ((errno == EINTR) || (errno == EAGAIN)) 32 continue; 33 return total ? total : -1; 34 } 35 if (got == 0) { 36 if (pass++ >= 3) 37 return total; 38 continue; 39 } 40 pass = 0; 41 buf += got; 42 total += got; 43 count -= got; 44 } 45 return total; 46 } 47 48 int main(int argc, char **argv) 49 { 50 int fd, got, i; 51 int zflag = 0; 52 char buf[1024]; 53 54 if (argc != 2) { 55 fprintf(stderr, "Usage: make-sparse out-file\n"); 56 exit(1); 57 } 58 fd = open(argv[1], O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0777); 59 if (fd < 0) { 60 perror(argv[1]); 61 exit(1); 62 } 63 while (1) { 64 got = full_read(0, buf, sizeof(buf)); 65 if (got == 0) 66 break; 67 if (got == sizeof(buf)) { 68 for (i=0; i < sizeof(buf); i++) 69 if (buf[i]) 70 break; 71 if (i == sizeof(buf)) { 72 lseek(fd, sizeof(buf), SEEK_CUR); 73 zflag = 1; 74 continue; 75 } 76 } 77 zflag = 0; 78 write(fd, buf, got); 79 } 80 if (zflag) { 81 lseek(fd, -1, SEEK_CUR); 82 buf[0] = 0; 83 write(fd, buf, 1); 84 } 85 return 0; 86 } 87 88
