memb.h

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.h,v 1.1 2006/06/12 08:21:43 adam Exp $
00034  */
00035 
00036 /**
00037  * \defgroup memb Memory block management functions
00038  *
00039  * The memory block allocation routines provide a simple yet powerful
00040  * set of functions for managing a set of memory blocks of fixed
00041  * size. A set of memory blocks is statically declared with the
00042  * MEMB() macro. Memory blocks are allocated from the declared
00043  * memory by the memb_alloc() function, and are deallocated with the
00044  * memb_free() function.
00045  *
00046  * \note Because of namespace clashes only one MEMB() can be
00047  * declared per C module, and the name scope of a MEMB() memory
00048  * block is local to each C module.
00049  *
00050  * The following example shows how to declare and use a memory block
00051  * called "cmem" which has 8 chunks of memory with each memory chunk
00052  * being 20 bytes large.
00053  *
00054  * @{
00055  */
00056 
00057 
00058 /**
00059  * \file
00060  *         Memory block allocation routines.
00061  * \author
00062  *         Adam Dunkels <adam@sics.se>
00063  *
00064  */
00065 
00066 #ifndef __MEMB_H__
00067 #define __MEMB_H__
00068 
00069 /*
00070  * Here we define a C preprocessing macro for concatenating to
00071  * strings. We need use two macros in order to allow concatenation of
00072  * two #defined macros.
00073  */
00074 #define MEMB_CONCAT2(s1, s2) s1##s2
00075 #define MEMB_CONCAT(s1, s2) MEMB_CONCAT2(s1, s2)
00076 
00077 /**
00078  * Declare a memory block.
00079  *
00080  * This macro is used to staticall declare a block of memory that can
00081  * be used by the block allocation functions. The macro statically
00082  * declares a C array with a size that matches the specified number of
00083  * blocks and their individual sizes.
00084  *
00085  * Example:
00086  \code
00087 MEMB(connections, sizeof(struct connection), 16);
00088  \endcode
00089  *
00090  * \param name The name of the memory block (later used with
00091  * memb_init(), memb_alloc() and memb_free()).
00092  *
00093  * \param size The size of each memory chunk, in bytes.
00094  *
00095  * \param num The total number of memory chunks in the block.
00096  *
00097  */
00098 #define MEMB(name, structure, num) \
00099         static char MEMB_CONCAT(name,_memb_count)[num]; \
00100         static structure MEMB_CONCAT(name,_memb_mem)[num]; \
00101         static struct memb_blocks name = {sizeof(structure), num, \
00102                                           MEMB_CONCAT(name,_memb_count), \
00103                                           (void *)MEMB_CONCAT(name,_memb_mem)}
00104 
00105 struct memb_blocks {
00106   unsigned short size;
00107   unsigned short num;
00108   char *count;
00109   void *mem;
00110 };
00111 
00112 /**
00113  * Initialize a memory block that was declared with MEMB().
00114  *
00115  * \param m A memory block previosly declared with MEMB().
00116  */
00117 void  memb_init(struct memb_blocks *m);
00118 
00119 /**
00120  * Allocate a memory block from a block of memory declared with MEMB().
00121  *
00122  * \param m A memory block previosly declared with MEMB().
00123  */
00124 void *memb_alloc(struct memb_blocks *m);
00125 
00126 /**
00127  * Deallocate a memory block from a memory block previously declared
00128  * with MEMB().
00129  *
00130  * \param m m A memory block previosly declared with MEMB().
00131  *
00132  * \param ptr A pointer to the memory block that is to be deallocated.
00133  *
00134  * \return The new reference count for the memory block (should be 0
00135  * if successfully deallocated) or -1 if the pointer "ptr" did not
00136  * point to a legal memory block.
00137  */
00138 char  memb_free(struct memb_blocks *m, void *ptr);
00139 
00140 /** @} */
00141 
00142 #endif /* __MEMB_H__ */