dt_search.c

/*
 * Copyright (c) 2012-2015 Christian Hansen <chansen@cpan.org>
 * <https://github.com/chansen/c-dt>
 * 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 COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER OR CONTRIBUTORS 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.
 */
#include "dt_core.h"

const dt_t *
dt_lower_bound(dt_t dt, const dt_t *lo, const dt_t *hi) {
    const dt_t *mid;

    while (lo < hi) {
        mid = lo + (hi - lo) / 2;
        if (*mid < dt)
            lo = mid + 1;
        else
            hi = mid;
    }
    return lo;
}

const dt_t *
dt_upper_bound(dt_t dt, const dt_t *lo, const dt_t *hi) {
    const dt_t *mid;

    while (lo < hi) {
        mid = lo + (hi - lo) / 2;
        if (*mid <= dt)
            lo = mid + 1;
        else
            hi = mid;
    }
    return lo;
}

bool
dt_binary_search(dt_t dt, const dt_t *lo, const dt_t *hi) {
    lo = dt_lower_bound(dt, lo, hi);
    return (lo != hi && !(dt < *lo));
}