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Annotation of src/usr.bin/rsync/hash.c, Revision 1.1

1.1     ! benno       1: /*     $Id$ */
        !             2: /*
        !             3:  * Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv>
        !             4:  *
        !             5:  * Permission to use, copy, modify, and distribute this software for any
        !             6:  * purpose with or without fee is hereby granted, provided that the above
        !             7:  * copyright notice and this permission notice appear in all copies.
        !             8:  *
        !             9:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
        !            10:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
        !            11:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
        !            12:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
        !            13:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
        !            14:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
        !            15:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
        !            16:  */
        !            17: #include <sys/types.h>
        !            18:
        !            19: #include <assert.h>
        !            20: #include <endian.h>
        !            21: #include <stdint.h>
        !            22: #include <stdlib.h>
        !            23:
        !            24: #include "extern.h"
        !            25: #include "md4.h"
        !            26:
        !            27: /*
        !            28:  * A fast 32-bit hash.
        !            29:  * Described in Tridgell's "Efficient Algorithms for Sorting and
        !            30:  * Synchronization" thesis and the "Rolling checksum" document.
        !            31:  */
        !            32: uint32_t
        !            33: hash_fast(const void *buf, size_t len)
        !            34: {
        !            35:        size_t           i = 0;
        !            36:        uint32_t         a = 0, /* part of a(k, l) */
        !            37:                         b = 0; /* b(k, l) */
        !            38:        const signed char *dat = buf;
        !            39:
        !            40:        if (len > 4)
        !            41:                for ( ; i < len - 4; i += 4) {
        !            42:                        b += 4 * (a + dat[i]) +
        !            43:                              3 * dat[i + 1] +
        !            44:                              2 * dat[i + 2] +
        !            45:                                  dat[i + 3];
        !            46:                        a += dat[i + 0] +
        !            47:                              dat[i + 1] +
        !            48:                              dat[i + 2] +
        !            49:                              dat[i + 3];
        !            50:                }
        !            51:
        !            52:        for ( ; i < len; i++) {
        !            53:                a += dat[i];
        !            54:                b += a;
        !            55:        }
        !            56:
        !            57:        /* s(k, l) = (eps % M) + 2^16 b(k, l) % M */
        !            58:
        !            59:        return (a & 0xffff) + (b << 16);
        !            60: }
        !            61:
        !            62: /*
        !            63:  * Slow MD4-based hash with trailing seed.
        !            64:  */
        !            65: void
        !            66: hash_slow(const void *buf, size_t len,
        !            67:        unsigned char *md, const struct sess *sess)
        !            68: {
        !            69:        MD4_CTX          ctx;
        !            70:        int32_t          seed = htole32(sess->seed);
        !            71:
        !            72:        MD4_Init(&ctx);
        !            73:        MD4_Update(&ctx, buf, len);
        !            74:        MD4_Update(&ctx, (unsigned char *)&seed, sizeof(int32_t));
        !            75:        MD4_Final(md, &ctx);
        !            76: }
        !            77:
        !            78: /*
        !            79:  * Hash an entire file.
        !            80:  * This is similar to hash_slow() except the seed is hashed at the end
        !            81:  * of the sequence, not the beginning.
        !            82:  */
        !            83: void
        !            84: hash_file(const void *buf, size_t len,
        !            85:        unsigned char *md, const struct sess *sess)
        !            86: {
        !            87:        MD4_CTX          ctx;
        !            88:        int32_t          seed = htole32(sess->seed);
        !            89:
        !            90:        MD4_Init(&ctx);
        !            91:        MD4_Update(&ctx, (unsigned char *)&seed, sizeof(int32_t));
        !            92:        MD4_Update(&ctx, buf, len);
        !            93:        MD4_Final(md, &ctx);
        !            94: }