hw/bsp/native/src/sbrk.c

/**
 * Copyright (c) 2015 Runtime Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <sys/mman.h>
#include <unistd.h>
#include <errno.h>

extern int getpagesize(void);

static void *cont;
static int sys_pagesize;
static int cont_left;

void *
_sbrk(int incr)
{
    void *result;

    if (!sys_pagesize) {
        sys_pagesize = getpagesize();
    }
    if (cont && incr <= cont_left) {
        result = cont;
        cont_left -= incr;
        if (cont_left) {
            cont = (char *)cont + incr;
        } else {
            cont = NULL;
        }
        return result;
    }
    result = mmap(NULL, incr, PROT_READ | PROT_WRITE, MAP_ANON | MAP_SHARED,
      -1, 0);
    if (result) {
        cont_left = sys_pagesize - (incr % sys_pagesize);
        if (cont_left) {
            cont = (char *)result + incr;
        } else {
            cont = NULL;
        }
    }
    return result;
}