cmd/mandoc/man_hash.c

	man_hash.c revision 260e9a87725c090ba5835b1f9f0b62fa2f96036f
/*  $Id: man_hash.c,v 1.29 2014/12/01 08:05:52 schwarze Exp $ */
/*
 * Copyright (c) 2008, 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include "config.h"

#include <sys/types.h>

#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <string.h>

#include "man.h"
#include "libman.h"

#define HASH_DEPTH   6

#define HASH_ROW(x) do { \
        if (isupper((unsigned char)(x))) \
            (x) -= 65; \
        else \
            (x) -= 97; \
        (x) *= HASH_DEPTH; \
    } while (/* CONSTCOND */ 0)

/*
 * Lookup table is indexed first by lower-case first letter (plus one
 * for the period, which is stored in the last row), then by lower or
 * uppercase second letter.  Buckets correspond to the index of the
 * macro (the integer value of the enum stored as a char to save a bit
 * of space).
 */
static  unsigned char    table[26 * HASH_DEPTH];


/*
 * XXX - this hash has global scope, so if intended for use as a library
 * with multiple callers, it will need re-invocation protection.
 */
void
man_hash_init(void)
{
    int      i, j, x;

    memset(table, UCHAR_MAX, sizeof(table));

    assert(MAN_MAX < UCHAR_MAX);

    for (i = 0; i < (int)MAN_MAX; i++) {
        x = man_macronames[i][0];

        assert(isalpha((unsigned char)x));

        HASH_ROW(x);

        for (j = 0; j < HASH_DEPTH; j++)
            if (UCHAR_MAX == table[x + j]) {
                table[x + j] = (unsigned char)i;
                break;
            }

        assert(j < HASH_DEPTH);
    }
}

enum mant
man_hash_find(const char *tmp)
{
    int      x, y, i;
    enum mant    tok;

    if ('\0' == (x = tmp[0]))
        return(MAN_MAX);
    if ( ! (isalpha((unsigned char)x)))
        return(MAN_MAX);

    HASH_ROW(x);

    for (i = 0; i < HASH_DEPTH; i++) {
        if (UCHAR_MAX == (y = table[x + i]))
            return(MAN_MAX);

        tok = (enum mant)y;
        if (0 == strcmp(tmp, man_macronames[tok]))
            return(tok);
    }

    return(MAN_MAX);
}