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Diffstat (limited to 'Utilities/cmlibarchive/libarchive/archive_crc32.h')
| -rw-r--r-- | Utilities/cmlibarchive/libarchive/archive_crc32.h | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/Utilities/cmlibarchive/libarchive/archive_crc32.h b/Utilities/cmlibarchive/libarchive/archive_crc32.h new file mode 100644 index 0000000..cd633af --- /dev/null +++ b/Utilities/cmlibarchive/libarchive/archive_crc32.h @@ -0,0 +1,78 @@ +/*- + * Copyright (c) 2009 Joerg Sonnenberger + * 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. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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(S) 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. + * + * $FreeBSD: head/lib/libarchive/archive_crc32.h 201102 2009-12-28 03:11:36Z kientzle $ + */ + +#ifndef __LIBARCHIVE_BUILD +#error This header is only to be used internally to libarchive. +#endif + +/* + * When zlib is unavailable, we should still be able to validate + * uncompressed zip archives. That requires us to be able to compute + * the CRC32 check value. This is a drop-in compatible replacement + * for crc32() from zlib. It's slower than the zlib implementation, + * but still pretty fast: This runs about 300MB/s on my 3GHz P4 + * compared to about 800MB/s for the zlib implementation. + */ +static unsigned long +crc32(unsigned long crc, const void *_p, size_t len) +{ + unsigned long crc2, b, i; + const unsigned char *p = _p; + static volatile int crc_tbl_inited = 0; + static unsigned long crc_tbl[256]; + + if (!crc_tbl_inited) { + for (b = 0; b < 256; ++b) { + crc2 = b; + for (i = 8; i > 0; --i) { + if (crc2 & 1) + crc2 = (crc2 >> 1) ^ 0xedb88320UL; + else + crc2 = (crc2 >> 1); + } + crc_tbl[b] = crc2; + } + crc_tbl_inited = 1; + } + + crc = crc ^ 0xffffffffUL; + /* A use of this loop is about 20% - 30% faster than + * no use version in any optimization option of gcc. */ + for (;len >= 8; len -= 8) { + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + } + while (len--) + crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8); + return (crc ^ 0xffffffffUL); +} |