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/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
* checksum.c
*
* Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
*/
#include "config.h"
#include "internal.h"
static unsigned int get_checksum(const tar_header_t *hdr)
{
const unsigned char *header_start = (const unsigned char *)hdr;
const unsigned char *chksum_start = (const unsigned char *)hdr->chksum;
const unsigned char *header_end = header_start + sizeof(*hdr);
const unsigned char *chksum_end = chksum_start + sizeof(hdr->chksum);
const unsigned char *p;
unsigned int chksum = 0;
for (p = header_start; p < chksum_start; p++)
chksum += *p;
for (; p < chksum_end; p++)
chksum += ' ';
for (; p < header_end; p++)
chksum += *p;
return chksum;
}
void update_checksum(tar_header_t *hdr)
{
unsigned int chksum = get_checksum(hdr);
sprintf(hdr->chksum, "%06o", chksum);
hdr->chksum[6] = '\0';
hdr->chksum[7] = ' ';
}
bool is_checksum_valid(const tar_header_t *hdr)
{
unsigned int calculated_chksum = get_checksum(hdr);
uint64_t read_chksum;
if (read_octal(hdr->chksum, sizeof(hdr->chksum), &read_chksum))
return 0;
return read_chksum == calculated_chksum;
}
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