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1.1 |
NAME |
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String::CRC32C - Castagnoli CRC |
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SYNOPSIS |
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use String::CRC32C; # does not export anything by default |
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use String::CRC32C 'crc32c'; |
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$crc = crc32 "some string"; |
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$crc = crc32 "some string", $initvalue; |
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DESCRIPTION |
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This module calculates the Castagnoli CRC32 variant (polynomial |
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0x11EDC6F41). |
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It is used by iSCSI, SCTP, BTRFS, ext4, leveldb, x86 CPUs and others. |
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This module uses an optimized implementation for SSE 4.2 targets (GCC |
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and compatible supported, SSE 4.2 must be enabled in your Perl) and the |
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SlicingBy8 algorithm for anything else. |
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$crc32c = crc32c $string[, $initvalue] |
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Calculates the CRC32C value of the given $string and returns it as a |
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32 bit unsigned integer. |
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To get the common hex form, use one of: |
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sprintf "%08x", crc32c $string |
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unpack "H*", pack "L>", crc32c $string |
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A seed/initial crc value can be given as second argument. Note that |
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both the initial value and the result value are inverted |
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(pre-inversion and post-inversion), e.g. a common init value of -1 |
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from other descriptions needs to be given as 0 (or "~-1"). |
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This allows easy chaining, e.g. |
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(crc32c "abcdefghi") eq (crc32 "ghi", crc32 "def", crc32 "abc") |
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$String::CRC32C::IMPL |
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Contains a string indicating the implementation that will be used. |
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Currently either "SlicingBy8" for the portable implementation or |
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"IntelCSSE42" for the SSE 4.2 optimized intel version. |
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PERLMULTICORE SUPPORT |
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This module supports the perl multicore spoecification |
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(<http://perlmulticore.schmorp.de/>): the "crc32c" function will |
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relinquish the current thread for crc32c lengths larger than 64k (the |
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break-even point on my machine is around 128k), so multiprocessing makes |
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only sense for very long blocks. |
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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CRC32C code by various sources, ported from |
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https://github.com/htot/crc32c, see sources for details. |
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