["Peter Johansson" <Peter.Johansson@xxxxxxxxxxxx>]

ronnie sahlberg said:
> List
>
> Attached are two new files with a new FAST api to provide memory
> allocation and automatic garbage collection with an allocation
> lifetime of
> either    until-next-packet
> or until-next-capture-file

I had a quick look at the source and have comments on the function
emem_capture_alloc:
1) Why is the size parameter to emem_capture_alloc signed? Why is it
*only* 32-bit? Should perhaps size_t be used instead?
2) Why is the size rounded to the nearest higher 4-byte boundary. This
assumes a 32-bit platform, right? Why not round to an 8 byte boundary
instead to make this work on 64-bit platforms too!?

I took the liberty of changing the implementation a bit as can be seen in
the attached modified_emem.c file. There I have made changes for my
questions in 1) and 2) above as well as rewriting it a bit to be a bit (in
my personal oppinion) more generic for future enhancements.

Regards, Peter

/* emem.c
 * Ethereal memory management and garbage collection functions
 *
 * $Id: emem.c 14510 2005-05-31 21:17:54Z ulfl $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@xxxxxxxxxxxx>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#include "emem.h"

/* When required, allocate more memory from the OS in this size chunks */
#define EMEM_PACKET_CHUNK_SIZE 1048576

typedef struct _emem_chunk_t {
	struct _emem_chunk_t *next;
	int	amount_free;
	int	free_offset;
	char *buf;
} emem_chunk_t;

static emem_chunk_t *emem_packet_chunk=NULL;
static emem_chunk_t *emem_capture_chunk=NULL;

/* Initialize the packet-lifetime memory allocation pool.
 * This function should be called only once when Etehreal or Tethereal starts
 * up.
 */
void
emem_init_chunk(emem_chunk_t **chunk)
{
	*chunk=g_malloc(sizeof(emem_chunk_t));
	*chunk->next=NULL;
	*chunk->amount_free=EMEM_PACKET_CHUNK_SIZE;
	*chunk->free_offset=0;
	*chunk->g_malloc(*EMEM_PACKET_CHUNK_SIZE);
}

/* allocate 'size' amount of memory with an allocation lifetime until the
 * next packet.
 */
char *
emem_alloc(emem_chunk_t **chunk, size_t size)
{
	char *buf;

	/* round up to an 8 byte boundary */
	if(size&0x08){
		size=(size+8)&0xfffffff0;
	}

	/* make sure we dont try to allocate too much */
	g_assert(size<(EMEM_PACKET_CHUNK_SIZE>>2));

	/* oops, we need to allocate more memory to serve this request */
	if(size>chunk->amount_free){
		emem_chunk_t *npc;
		npc=g_malloc(sizeof(emem_chunk_t));
		npc->next=(*chunk);
		(*chunk)=npc;
		(*chunk)->amount_free=EMEM_PACKET_CHUNK_SIZE;
		(*chunk)->free_offset=0;
		(*chunk)->g_malloc(EMEM_PACKET_CHUNK_SIZE);
	}

	buf=(*chunk)->data+(*chunk)->free_offset;

	(*chunk)->amount_free-=size;
	(*chunk)->free_offset+=size;

	return buf;
}

/* release all allocated memory back to the pool.
 */
void
emem_free_all(emem_chunk_t *chunk)
{
	emem_chunk_t *tmp;

	for(tmp=chunk;tmp;tmp=tmp->next){
		chunk->amount_free=EMEM_PACKET_CHUNK_SIZE;
		chunk->free_offset=0;
	}
}

/* Initialize the packet-lifetime memory allocation pool.
 * This function should be called only once when Etehreal or Tethereal starts
 * up.
 */
void
emem_packet_init_chunk(void)
{
	emem_init_chunk(&emem_packet_chunk);
}

/* allocate 'size' amount of memory with an allocation lifetime until the
 * next packet.
 */
char *
emem_packet_alloc(size_t size)
{
	return emem_alloc(&emem_packet_chunk, size);
}

/* release all allocated memory back to the pool.
 */
void
emem_packet_free_all(void)
{
	emem_free_all(emem_packet_chunk);
}


/* Initialize the capture-lifetime memory allocation pool.
 * This function should be called only once when Etehreal or Tethereal starts
 * up.
 */
void
emem_capture_init_chunk(void)
{
	emem_init_chunk(&emem_capture_chunk);
}

/* allocate 'size' amount of memory with an allocation lifetime until the
 * next capture file.
 */
char *
emem_capture_alloc(size_t size)
{
	return emem_alloc(&emem_capture_chunk, size);
}

/* release all allocated memory back to the pool.
 */
void
emem_capture_free_all(void)
{
	emem_free_all(emem_capture_chunk);
}