88 lines
2.6 KiB
C
88 lines
2.6 KiB
C
/*
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* Copyright (c) 2014
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Create a sparse file by writing one byte to the end of it.
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*
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* Should work on emufs (emu0:) once the basic system calls are done,
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* and should work on SFS when the file system assignment is
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* done. Sufficiently small files should work on SFS even before that
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* assignment.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <err.h>
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int
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main(int argc, char *argv[])
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{
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const char *filename;
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int size;
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int fd;
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int r;
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char byte;
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if (argc != 3) {
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errx(1, "Usage: sparsefile <filename> <size>");
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}
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filename = argv[1];
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size = atoi(argv[2]);
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byte = '\n';
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if (size == 0) {
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err(1, "Sparse files of length zero are not meaningful");
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}
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printf("Creating a sparse file of size %d\n", size);
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fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC);
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if (fd < 0) {
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err(1, "%s: create", filename);
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}
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if (lseek(fd, size-1, SEEK_SET) == -1) {
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err(1, "%s: lseek", filename);
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}
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r = write(fd, &byte, 1);
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if (r < 0) {
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err(1, "%s: write", filename);
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}
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else if (r != 1) {
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errx(1, "%s: write: Unexpected result count %d", filename, r);
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}
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close(fd);
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return 0;
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}
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