36 lines
1.1 KiB
C
36 lines
1.1 KiB
C
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/*
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* Copyright (C) 2021 Denys Vlasenko <vda.linux@googlemail.com>
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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//kbuild:lib-$(CONFIG_FEATURE_TAR_CREATE) += chksum_and_xwrite_tar_header.o
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//kbuild:lib-$(CONFIG_SMEMCAP) += chksum_and_xwrite_tar_header.o
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#include "libbb.h"
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#include "bb_archive.h"
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void FAST_FUNC chksum_and_xwrite_tar_header(int fd, struct tar_header_t *hp)
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{
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/* POSIX says that checksum is done on unsigned bytes
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* (Sun and HP-UX gets it wrong... more details in
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* GNU tar source) */
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const unsigned char *cp;
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int chksum, size;
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strcpy(hp->magic, "ustar ");
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/* Calculate and store the checksum (the sum of all of the bytes of
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* the header). The checksum field must be filled with blanks for the
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* calculation. The checksum field is formatted differently from the
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* other fields: it has 6 digits, a NUL, then a space -- rather than
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* digits, followed by a NUL like the other fields... */
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memset(hp->chksum, ' ', sizeof(hp->chksum));
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cp = (const unsigned char *) hp;
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chksum = 0;
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size = sizeof(*hp);
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do { chksum += *cp++; } while (--size);
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sprintf(hp->chksum, "%06o", chksum);
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xwrite(fd, hp, sizeof(*hp));
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}
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