bufpool.c

基于linux环境的ns2多机并行仿真补丁

/*---------------------------------------------------------------------------*/
/* Buffer pool implementation.                                               */
/* Author(s): Richard Fujimoto.                                              */
/* $Revision: 1.1 $ $Name: v26apr05 $ $Date: 2003/04/11 20:17:37 $ */
/*---------------------------------------------------------------------------*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "bufpool.h"

/* minimum buffer size to hold free list header info */
#define MIN_BUFFER_SIZE (sizeof (struct MB_Buffer))

/************************************************************************
 *
 * MEMORY BUFFER MANAGER
 * Create a pool of fixed size buffers.
 * Interface:
 * Types:
 *   MB_BufferPool: pointer to a buffer pool
 * Procedures:
 *   MB_BufferPool MB_MakePool (int NBuffers, int BufferSize);
 *     create a new buffer pool with NBuffers buffers, each with BufferSize
 *     bytes.  Returns a handle to the buffer pool.  Return NULL if the
 *     allocation failed.
 *   ADDR_TYPE MB_GetBuffer(MB_BufferPool Pool)
 *     Get a buffer from buffer pool Pool.  Return a pointer to the buffer,
 *     or NULL if the pool is empty.
 *   void MB_FreeBuffer (MB_BufferPool Pool, ADDR_TYPE Buffer)
 *     Return buffer pointed to by Buffer to buffer pool Pool
 *
 ***********************************************************************/

#define IAMABUFFERPOOL 1234567
struct MB_Buffer
{
  struct MB_Buffer *Next;	/* pointer to next free buffer in list */
};

struct MB_Header {
  int32 Signature;		/* flag indicating buffer pool header */
  struct MB_Buffer *Free;
};

/************************************************************************
 *
 * MB_BufferPool MB_MakePool (int NBuffers, int BufferSize)
 * create a new buffer pool with NBuffers buffers, each with BufferSize
 * bytes.  Returns a handle to the buffer pool.  Return NULL if the
 * allocation failed.
 *
 ***********************************************************************/
MB_BufferPool MB_MakePool (int NBuffers, int BufferSize)
{
  int i;
  struct MB_Header *head;
  struct MB_Buffer *buf;

  /* adjust buffer size so data part an integer # 32 bit words */
  if (BufferSize < MIN_BUFFER_SIZE)
    BufferSize = MIN_BUFFER_SIZE;
  if (BufferSize%4 != 0) BufferSize = (BufferSize+4) - (BufferSize%4);

  /* allocate a collection of buffers, string them into a free list */
  head = (struct MB_Header *) malloc (sizeof (struct MB_Header));
  if (!head)
  {
    return (NULL);
  }
  head->Signature = IAMABUFFERPOOL;  /* flag type of memory */
  head->Free = NULL;

  for (i=0; i<NBuffers; i++)
  {
    buf = (struct MB_Buffer *) malloc(BufferSize);
    if (!buf)
    {
      /* return memory allocated thus far */
      for (buf=head->Free; buf != NULL; buf=buf->Next)
        free (buf);
      free (head);
      return (NULL);
    }
    buf->Next = head->Free;
    head->Free = buf;
  }

  return (head);
}

/************************************************************************
 *
 * ADDR_TYPE MB_GetBuffer(MB_BufferPool Pool)
 * Get a buffer from buffer pool Pool.  Return a pointer to the buffer,
 * or NULL if the pool is empty.
 *
 ***********************************************************************/
ADDR_TYPE MB_GetBuffer(MB_BufferPool Pool)
{
  struct MB_Buffer *buf;

  if (Pool->Signature != IAMABUFFERPOOL)
  {
    fprintf (stderr, "MB_GetBuffer: illegal buffer pool pointer specified\n");
    exit (1);
  }

  if (Pool->Free == NULL) return (NULL);
  buf = Pool->Free;
  Pool->Free = buf->Next;
  buf->Next = NULL;	/* clear to prevent misuse */
  return ((ADDR_TYPE) buf);
}


/************************************************************************
 *
 * void MB_FreeBuffer (MB_BufferPool Pool, ADDR_TYPE Buffer)
 * Return buffer pointed to by Buffer to buffer pool Pool
 *
 ***********************************************************************/
void MB_FreeBuffer (MB_BufferPool Pool, ADDR_TYPE Buffer)
{
  struct MB_Buffer *buf;

  if( !Buffer )
      return;

  if (!Pool || Pool->Signature != IAMABUFFERPOOL)
  {
    fprintf (stderr, "MB_FreeBuffer: illegal buffer pool pointer specified\n");
    exit (1);
  }
  buf = (struct MB_Buffer *) Buffer;

  buf->Next = Pool->Free;
  Pool->Free = buf;
}