badvpn/misc/bsize.h

/**
 * @file bsize.h
 * @author Ambroz Bizjak <ambrop7@gmail.com>
 * 
 * @section LICENSE
 * 
 * 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.
 * 3. Neither the name of the author nor the
 *    names of its contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 * 
 * 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 AUTHOR 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.
 * 
 * @section DESCRIPTION
 * 
 * Arithmetic with overflow detection.
 */

#ifndef BADVPN_MISC_BSIZE_H
#define BADVPN_MISC_BSIZE_H

#include <stddef.h>
#include <limits.h>
#include <stdint.h>

typedef struct {
    int is_overflow;
    size_t value;
} bsize_t;

static bsize_t bsize_fromsize (size_t v);
static bsize_t bsize_fromint (int v);
static bsize_t bsize_overflow (void);
static int bsize_tosize (bsize_t s, size_t *out);
static int bsize_toint (bsize_t s, int *out);
static bsize_t bsize_add (bsize_t s1, bsize_t s2);
static bsize_t bsize_max (bsize_t s1, bsize_t s2);
static bsize_t bsize_mul (bsize_t s1, bsize_t s2);

bsize_t bsize_fromsize (size_t v)
{
    bsize_t s;
    s.is_overflow = 0;
    s.value = v;
    return s;
}

bsize_t bsize_fromint (int v)
{
    bsize_t s;
    
    if (v < 0 || v > SIZE_MAX) {
        s.is_overflow = 1;
    } else {
        s.is_overflow = 0;
        s.value = v;
    }
    
    return s;
}

static bsize_t bsize_overflow (void)
{
    bsize_t s;
    
    s.is_overflow = 1;
    
    return s;
}

int bsize_tosize (bsize_t s, size_t *out)
{
    if (s.is_overflow) {
        return 0;
    }
    
    if (out) {
        *out = s.value;
    }
    
    return 1;
}

int bsize_toint (bsize_t s, int *out)
{
    if (s.is_overflow || s.value > INT_MAX) {
        return 0;
    }
    
    if (out) {
        *out = s.value;
    }
    
    return 1;
}

bsize_t bsize_add (bsize_t s1, bsize_t s2)
{
    bsize_t s;
    
    if (s1.is_overflow || s2.is_overflow || s2.value > SIZE_MAX - s1.value) {
        s.is_overflow = 1;
    } else {
        s.is_overflow = 0;
        s.value = s1.value + s2.value;
    }
    
    return s;
}

bsize_t bsize_max (bsize_t s1, bsize_t s2)
{
    bsize_t s;
    
    if (s1.is_overflow || s2.is_overflow) {
        s.is_overflow = 1;
    } else {
        s.is_overflow = 0;
        s.value = s1.value;
        if (s.value < s2.value) {
            s.value = s2.value;
        }
    }
    
    return s;
}

bsize_t bsize_mul (bsize_t s1, bsize_t s2)
{
    bsize_t s;
    
    if (s1.is_overflow || s2.is_overflow || (s1.value != 0 && s2.value > SIZE_MAX / s1.value)) {
        s.is_overflow = 1;
    } else {
        s.is_overflow = 0;
        s.value = s1.value * s2.value;
    }
    
    return s;
}

#endif