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/*
* Copyright (C) 2004-2019 Anders Gavare. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*
* This program copies a file, but only those blocks that are not zero-
* filled. Typical usage would be if you have a harddisk image stored
* as a file, which has all its zeroed blocks explicitly saved on disk,
* and would like to save space.
*
* Example: You download a file called diskimage.gz from somewhere,
* run gunzip on it, and the resulting file diskimage is
* 1 GB large. ls -l reports the file size as 1 GB, and
* so does 'du -k diskimage'. If a lot of the space used
* by diskimage is actually zeroes, those parts do not need
* to actually be saved. By running this program on diskimage:
*
* ./cp_removeblocks diskimage diskimage_compact
*
* you will get a file with the same functionality, but possibly
* using less disk space. ('ls -l diskimage_compact' should
* return the same size as for diskimage, but 'du -k' will
* print only how many kb the file takes up on your disk.)
*
* You don't even need to gunzip the file to be 1 GB first,
* you can pipe it through cp_removeblocks directly.
*
* gunzip -c file.img.gz | ./cp_removeblocks - file.img
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#define BSIZE 512
int main(int argc, char *argv[])
{
FILE *f1, *f2;
unsigned char buf[BSIZE];
off_t len;
off_t in_pos = 0;
int i, res, wrote_last = 0;
if (argc != 3) {
fprintf(stderr, "usage: %s infile outfile\n", argv[0]);
fprintf(stderr, "if infile is \"-\", then stdin is used.\n");
fprintf(stderr, "if outfile is \"-\", then stdout is used.\n");
exit(1);
}
if (strcmp(argv[1], "-") == 0)
f1 = stdin;
else
f1 = fopen(argv[1], "r");
if (f1 == NULL) {
perror(argv[1]);
exit(1);
}
if (strcmp(argv[2], "-") == 0)
f2 = stdout;
else
f2 = fopen(argv[2], "w");
if (f2 == NULL) {
perror(argv[2]);
exit(1);
}
while (!feof(f1)) {
len = fread(buf, 1, BSIZE, f1);
if (len > 0) {
/* Check for data in buf: */
for (i=0; i<len; i++)
if (buf[i])
break;
if (i < len) {
fseeko(f2, in_pos, SEEK_SET);
fwrite(buf, 1, len, f2);
wrote_last = 1;
} else
wrote_last = 0;
in_pos += len;
}
}
/*
* Copy the last byte explicitly, if necessary.
* (This causes f2 to get the correct file size.)
*/
if (!wrote_last && in_pos > 0) {
res = fseeko(f2, in_pos - 1, SEEK_SET);
if (res != 0)
perror("fseeko(f2)");
buf[0] = '\0';
fwrite(&buf[0], 1, 1, f2);
}
fclose(f1);
fclose(f2);
return 0;
}
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