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# lib/memb.c

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    00001 /*
    00002  * Copyright (c) 2004, Swedish Institute of Computer Science.
    00003  * All rights reserved.
    00004  *
    00005  * Redistribution and use in source and binary forms, with or without
    00006  * modification, are permitted provided that the following conditions
    00007  * are met:
    00008  * 1. Redistributions of source code must retain the above copyright
    00009  *    notice, this list of conditions and the following disclaimer.
    00010  * 2. Redistributions in binary form must reproduce the above copyright
    00011  *    notice, this list of conditions and the following disclaimer in the
    00012  *    documentation and/or other materials provided with the distribution.
    00013  * 3. Neither the name of the Institute nor the names of its contributors
    00014  *    may be used to endorse or promote products derived from this software
    00015  *    without specific prior written permission.
    00016  *
    00017  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
    00018  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    00019  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    00020  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
    00021  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    00022  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    00023  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    00024  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    00025  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    00026  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    00027  * SUCH DAMAGE.
    00028  *
    00029  * This file is part of the uIP TCP/IP stack
    00030  *
    00031  * Author: Adam Dunkels <adam@sics.se>
    00032  *
    00033  * $Id: memb.c,v 1.1 2006/06/12 08:21:43 adam Exp $
    00034  */
    00035
    00036 /**
    00037  * \addtogroup memb
    00038  * @{
    00039  */
    00040
    00041  /**
    00042  * \file
    00043  * Memory block allocation routines.
    00044  * \author Adam Dunkels <adam@sics.se>
    00045  */
    00046 #include <string.h>
    00047
    00048 #include "memb.h"
    00049
    00050 /*---------------------------------------------------------------------------*/
    00051 void
    00052 memb_init(struct memb_blocks *m)
    00053 {
    00054   memset(m->count, 0, m->num);
    00055   memset(m->mem, 0, m->size * m->num);
    00056 }
    00057 /*---------------------------------------------------------------------------*/
    00058 void *
    00059 memb_alloc(struct memb_blocks *m)
    00060 {
    00061   int i;
    00062
    00063   for(i = 0; i < m->num; ++i) {
    00064     if(m->count[i] == 0) {
    00065       /* If this block was unused, we increase the reference count to
    00066          indicate that it now is used and return a pointer to the
    00067          memory block. */
    00068       ++(m->count[i]);
    00069       return (void *)((char *)m->mem + (i * m->size));
    00070     }
    00071   }
    00072
    00073   /* No free block was found, so we return NULL to indicate failure to
    00074      allocate block. */
    00075   return NULL;
    00076 }
    00077 /*---------------------------------------------------------------------------*/
    00078 char
    00079 memb_free(struct memb_blocks *m, void *ptr)
    00080 {
    00081   int i;
    00082   char *ptr2;
    00083
    00084   /* Walk through the list of blocks and try to find the block to
    00085      which the pointer "ptr" points to. */
    00086   ptr2 = (char *)m->mem;
    00087   for(i = 0; i < m->num; ++i) {
    00088
    00089     if(ptr2 == (char *)ptr) {
    00090       /* We've found to block to which "ptr" points so we decrease the
    00091          reference count and return the new value of it. */
    00092       if(m->count[i] > 0) {
    00093         /* Make sure that we don't deallocate free memory. */
    00094         --(m->count[i]);
    00095       }
    00096       return m->count[i];
    00097     }
    00098     ptr2 += m->size;
    00099   }
    00100   return -1;
    00101 }
    00102 /*---------------------------------------------------------------------------*/
    00103
    00104 /** @} */