/*
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright © 2019 Keith Packard
 *
 * 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 copyright holder 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
 * COPYRIGHT HOLDER 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.
 */

#define _DEFAULT_SOURCE
#include <unistd.h>
#include <errno.h>
#include <stdint.h>

#if __INTERNAL_HEAP > 0
char __heap_start[__INTERNAL_HEAP] __aligned(sizeof(double));
#define __heap_end (&__heap_start[__INTERNAL_HEAP])
#else
extern char __heap_start[];
extern char __heap_end[];
#endif

static char *__brk = __heap_start;

#ifndef __weak_reference
#define __fallback_sbrk sbrk
#endif

void *
__fallback_sbrk(ptrdiff_t incr)
{
    if (incr < 0) {
        if ((size_t)((uintptr_t)__brk - (uintptr_t)__heap_start) < (size_t)(-incr)) {
            errno = ENOMEM;
            return (void *)-1;
        }
    } else {
        if ((size_t)((uintptr_t)__heap_end - (uintptr_t)__brk) < (size_t)incr) {
            errno = ENOMEM;
            return (void *)-1;
        }
    }
    void *ret = __brk;
    __brk = (char *)((uintptr_t)__brk + incr);
    return ret;
}

#ifdef __weak_reference
__weak_reference(__fallback_sbrk, sbrk);
#endif
