sbrk.c

debug source code under unix platform.

/*
 * mpatrol
 * A library for controlling and tracing dynamic memory allocations.
 * Copyright (C) 1997-2002 Graeme S. Roy <[e-mail]>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307, USA.
 */


/*
 * Simulated UNIX heap.  This implements the brk() and sbrk() functions on
 * non-UNIX platforms by allocating a single block of memory for a simulated
 * heap from the low-level memory allocator.  These functions are not normally
 * used by the mpatrol library and are only defined to resolve any references
 * to them from user code.
 */


#include "sbrk.h"
#include "memory.h"
#include "utils.h"
#include <stdlib.h>
#include <errno.h>


#if MP_IDENT_SUPPORT
#ident "$Id: sbrk.c,v 1.13 2002/01/08 20:13:59 graeme Exp $"
#else /* MP_IDENT_SUPPORT */
static MP_CONST MP_VOLATILE char *sbrk_id = "$Id: sbrk.c,v 1.13 2002/01/08 20:13:59 graeme Exp $";
#endif /* MP_IDENT_SUPPORT */


/* The brkinfo structure contains information about the simulated heap.
 */

typedef struct brkinfo
{
    meminfo memory; /* memory details */
    void *block;    /* pointer to block of memory */
    size_t size;    /* size of block of memory */
    size_t len;     /* current break length */
}
brkinfo;


#ifdef __cplusplus
extern "C"
{
#endif /* __cplusplus */


/* The break header structure used to contain information about the heap.
 */

static brkinfo brkhead;


/* Finalise the break header structure so that the heap becomes empty.
 */

static
void
finibrk(void)
{
    if (brkhead.block != NULL)
        __mp_memfree(&brkhead.memory, brkhead.block, brkhead.size);
    __mp_endmemory(&brkhead.memory);
    brkhead.block = NULL;
    brkhead.size = 0;
    brkhead.len = 0;
}


/* Initialise the fields of the break header structure so that the heap
 * becomes empty.
 */

static
int
initbrk(void)
{
    size_t l;

    l = MP_BREAK_SIZE;
    __mp_newmemory(&brkhead.memory);
    if ((brkhead.block = __mp_memalloc(&brkhead.memory, &l,
          brkhead.memory.align, 1)) == NULL)
        return 0;
    brkhead.size = l;
    brkhead.len = 0;
#if MP_DELETEHEAP
    atexit(finibrk);
#endif /* MP_DELETEHEAP */
    return 1;
}


/* Set the address of the first byte beyond the end of the heap.
 */

MP_API
int
brk(void *p)
{
    if ((brkhead.block != NULL) || initbrk())
    {
        p = (void *) __mp_roundup((unsigned long) p, brkhead.memory.align);
        if ((p >= brkhead.block) &&
            ((char *) p <= (char *) brkhead.block + brkhead.size))
        {
            brkhead.len = (char *) p - (char *) brkhead.block;
            return 0;
        }
    }
    errno = ENOMEM;
    return -1;
}


/* Increase or decrease the amount of available heap space.
 */

MP_API
void *
sbrk(long l)
{
    void *p;
    unsigned long s;

    p = (void *) -1;
    if ((brkhead.block != NULL) || initbrk())
        if (l > 0)
        {
            s = __mp_roundup((unsigned long) l, brkhead.memory.align);
            if (brkhead.len + s <= brkhead.size)
            {
                p = (char *) brkhead.block + brkhead.len;
                brkhead.len += s;
            }
        }
        else if (l < 0)
        {
            s = __mp_roundup((unsigned long) -l, brkhead.memory.align);
            if (brkhead.len >= s)
            {
                p = (char *) brkhead.block + brkhead.len;
                brkhead.len -= s;
            }
        }
        else
            p = (char *) brkhead.block + brkhead.len;
    if (p == (void *) -1)
        errno = ENOMEM;
    return p;
}


#ifdef __cplusplus
}
#endif /* __cplusplus */