Change to arena `realloc' interface, to fix a design bug.

[mLib] / pkbuf.c

/* -*-c-*-
 *
 * $Id: pkbuf.c,v 1.2 2000/07/16 12:29:16 mdw Exp $
 *
 * Simple packet buffering
 *
 * (c) 2000 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of the mLib utilities library.
 *
 * mLib 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.
 * 
 * mLib 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 mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: pkbuf.c,v $
 * Revision 1.2  2000/07/16 12:29:16  mdw
 * Change to arena `realloc' interface, to fix a design bug.
 *
 * Revision 1.1  2000/06/17 10:39:19  mdw
 * Experimental new support for packet buffering.
 *
 */

/*----- Header files ------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "alloc.h"
#include "arena.h"
#include "pkbuf.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @pkbuf_flush@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *              @octet *p@ = pointer to where to start searching
 *              @size_t len@ = length of new material added
 *
 * Returns:     ---
 *
 * Use:         Flushes any complete packets in a packet buffer.  New
 *              material is assumed to have been added starting at @p@.  If
 *              @p@ is null, then the scan starts at the beginning of the
 *              buffer, and the size of data already in the buffer is used in
 *              place of @len@.
 *
 *              It is assumed that the buffer is initially enabled.  You
 *              shouldn't be contributing data to a disabled buffer anyway.
 *              However, the buffer handler may at some point disable itself,
 *              and @pkbuf_flush@ can cope with this eventuality.  Any
 *              pending data is left at the start of the buffer and can be
 *              flushed out by calling @pkbuf_flush(b, 0, 0)@ if the buffer
 *              is ever re-enabled.
 */

void pkbuf_flush(pkbuf *pk, octet *p, size_t len)
{
  size_t l;
  size_t keep;

  /* --- Initialize variables as necessary --- */

  if (!p) {
    p = pk->buf;
    len = pk->len;
  }
  l = p + len - pk->buf;
  p = pk->buf;

  /* --- Now grind through any packets which have accumulated --- */

  while (l > pk->want) {
    size_t sz = pk->want;

    /* --- Pass a packet to the user handler --- */

    keep = 0;
    pk->func(p, sz, pk, &keep, pk->p);

    /* --- Adjust all the pointers for the next packet --- */

    sz -= keep;
    p += sz;
    l -= sz;

    /* --- Abort here if disabled --- */

    if (!(pk->f & PKBUF_ENABLE))
      break;
  }

  /* --- Shunt data around in the buffer --- */

  if (p > pk->buf && l != 0)
    memmove(pk->buf, p, l);
  pk->len = l;
}

/* --- @pkbuf_close@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *
 * Returns:     ---
 *
 * Use:         Informs the client that no more data is likely to arrive.  If
 *              there is a partial packet in the buffer, it is discarded.
 */

void pkbuf_close(pkbuf *pk)
{
  if (pk->buf) {
    fprintf(stderr, "*** destroying buffer, closing down\n");
    x_free(pk->a, pk->buf);
    pk->buf = 0;
  }
  if (pk->f & PKBUF_ENABLE)
    pk->func(0, 0, pk, 0, pk->p);
}

/* --- @pkbuf_free@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *              @octet **p@ = output pointer to free space
 *
 * Returns:     Free buffer size.
 *
 * Use:         Returns the free portion of a packet buffer.  Data can then
 *              be written to this portion, and split out into packets by
 *              calling @pkbuf_flush@.  A buffer is allocated if none
 *              currently exists.
 */

size_t pkbuf_free(pkbuf *pk, octet **p)
{
  if (!pk->buf) {
    fprintf(stderr, "*** allocating new buffer\n");
    pk->buf = x_alloc(pk->a, pk->sz);
  }
  *p = pk->buf + pk->len;
  return (pk->sz - pk->len);
}

/* --- @pkbuf_snarf@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *              @const void *p@ = pointer to input data buffer
 *              @size_t sz@ = size of data in input buffer
 *
 * Returns:     ---
 *
 * Use:         Snarfs the data from the input buffer and spits it out as
 *              packets.  This interface ignores the complexities of dealing
 *              with disablement: you should be using @pkbuf_free@ to
 *              contribute data if you want to cope with that.
 */

void pkbuf_snarf(pkbuf *pk, const void *p, size_t sz)
{
  const octet *pp = p;
  while (sz && (pk->f & PKBUF_ENABLE)) {
    size_t bsz;
    octet *bp;

    bsz = pkbuf_free(pk, &bp);
    if (bsz > sz)
      bsz = sz;
    memcpy(bp, pp, bsz);
    pkbuf_flush(pk, bp, bsz);
    pp += bsz;
    sz -= bsz;
  }
}

/* --- @pkbuf_want@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *              @size_t want@ = how many octets wanted for next packet
 *
 * Returns:     ---
 *
 * Use:         Sets the desired size for the next packet to be read.  If
 *              it's larger than the current buffer, the buffer is extended.
 */

void pkbuf_want(pkbuf *pk, size_t want)
{
  pk->want = want;
  if (want > pk->sz) {
    do pk->sz <<= 1; while (want < pk->sz);
    if (pk->buf) {
      if (pk->len)
        pk->buf = x_realloc(pk->a, pk->buf, pk->sz, pk->len);
      else {
        x_free(pk->a, pk->buf);
        pk->buf = 0;
      }
    }
  }
}

/* --- @pkbuf_init@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *              @void (*func)(octet *b, size_t sz, pkbuf *pk,@
 *                           @size_t *keep, void *p)@ =
 *                      handler function
 *              @void *p@ = argument pointer for @func@
 *
 * Returns:     ---
 *
 * Use:         Initializes a packet buffer block.  Any packets are passed to
 *              the provided function for handling.
 */

void pkbuf_init(pkbuf *pk,
                void (*func)(octet */*b*/, size_t /*sz*/,
                             pkbuf */*pk*/, size_t */*keep*/, void */*p*/),
                void *p)
{
  pk->func = func;
  pk->p = p;
  pk->len = 0;
  pk->f = PKBUF_ENABLE;
  pk->buf = 0;
  pk->sz = 256;
  pk->want = 1;
  pk->a = arena_global;
}

/* --- @pkbuf_destroy@ --- *
 *
 * Arguments:   @pkbuf *pk@ = pointer to buffer block
 *
 * Returns:     ---
 *
 * Use:         Deallocates a line buffer and frees any resources it owned.
 */

void pkbuf_destroy(pkbuf *pk)
{
  if (pk->buf) {
    x_free(pk->a, pk->buf);
    pk->buf = 0;
  }
}

/*----- That's all, folks -------------------------------------------------*/