/************************************************************************
 *   Unreal Internet Relay Chat Daemon, src/dbuf.c
 *   Copyright (C) 1990 Markku Savela
 *
 *   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 1, 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* -- Jto -- 20 Jun 1990
 * extern void free() fixed as suggested by
 * gruner@informatik.tu-muenchen.de
 */

/* -- Jto -- 10 May 1990
 * Changed memcpy into bcopy and removed the declaration of memset
 * because it was unnecessary.
 * Added the #includes for "struct.h" and "sys.h" to get bcopy/memcpy
 * work
 */

/*
** For documentation of the *global* functions implemented here,
** see the header file (dbuf.h).
**
*/

#include <stdio.h>
#include "struct.h"
#include "common.h"
#include "sys.h"
#ifdef USE_DMALLOC
#include "h.h"
#endif
ID_Copyright("(C) 1990 Markku Savela");
ID_Notes("2.17 1/30/94 (C) 1990 Markku Savela");
#if !defined(VALLOC) && !defined(valloc) && !defined(USE_DMALLOC)
# ifndef _WIN32
#  define	valloc malloc
# else
#  define	valloc MyMalloc
# endif
#endif
int  dbufalloc = 0, dbufblocks = 0;
static dbufbuf *freelist = NULL;

/* This is a dangerous define because a broken compiler will set DBUFSIZ
** to 4, which will work but will be very inefficient. However, there
** are other places where the code breaks badly if this is screwed
** up, so... -- Wumpus
*/

#define DBUFSIZ sizeof(((dbufbuf *)0)->data)

/*
** dbuf_alloc - allocates a dbufbuf structure either from freelist or
** creates a new one.
*/
static dbufbuf *dbuf_alloc(void)
{
#if defined(VALLOC) && !defined(DEBUGMODE)
	dbufbuf *dbptr, *db2ptr;
	int  num;
#else
	dbufbuf *dbptr;
#endif

	dbufalloc++;
	if ((dbptr = freelist))
	{
		freelist = freelist->next;
		return dbptr;
	}
	if (dbufalloc * DBUFSIZ > BUFFERPOOL)
	{
		dbufalloc--;
		return NULL;
	}

#if defined(VALLOC) && !defined(DEBUGMODE)
# if defined(_SOLARIS) || defined(_SC_PAGESIZE)
	num = sysconf(_SC_PAGESIZE) / sizeof(dbufbuf);
# else
	num = getpagesize() / sizeof(dbufbuf);
# endif
	if (num < 0)
		num = 1;

	dbufblocks += num;

	dbptr = (dbufbuf *)valloc(num * sizeof(dbufbuf));
	if (!dbptr)
		return (dbufbuf *)NULL;

	num--;
	for (db2ptr = dbptr; num; num--)
	{
		db2ptr = (dbufbuf *)((char *)db2ptr + sizeof(dbufbuf));
		db2ptr->next = freelist;
		freelist = db2ptr;
	}
	return dbptr;
#else
	dbufblocks++;
	return (dbufbuf *)MyMalloc(sizeof(dbufbuf));
#endif
}

/*
** dbuf_free - return a dbufbuf structure to the freelist
*/
static void dbuf_free(dbufbuf *ptr)
{
	dbufalloc--;
	ptr->next = freelist;
	freelist = ptr;
}

/*
** This is called when malloc fails. Scrap the whole content
** of dynamic buffer and return -1. (malloc errors are FATAL,
** there is no reason to continue this buffer...). After this
** the "dbuf" has consistent EMPTY status... ;)
*/
static int dbuf_malloc_error(dbuf *dyn)
{
	dbufbuf *p;

	dyn->length = 0;
	dyn->offset = 0;
	while ((p = dyn->head) != NULL)
	{
		dyn->head = p->next;
		dbuf_free(p);
	}
	dyn->tail = dyn->head;
	return -1;
}


int  dbuf_put(dbuf *dyn, char *buf, int length)
{
	dbufbuf **h, *d;
	int  off;
	int  chunk;

	if (!length)
		return 1;	/* Nothing to do */

	off = (dyn->offset + dyn->length) % DBUFSIZ;
	/*
	   ** Locate the last non-empty buffer. If the last buffer is
	   ** full, the loop will terminate with 'd==NULL'. This loop
	   ** assumes that the 'dyn->length' field is correctly
	   ** maintained, as it should--no other check really needed.
	 */
	if (!dyn->length)
		h = &(dyn->head);
	else
	{
		if (off)
			h = &(dyn->tail);
		else
			h = &(dyn->tail->next);
	}
	/*
	   ** Append users data to buffer, allocating buffers as needed
	 */
	chunk = DBUFSIZ - off;
	dyn->length += length;
	for (; length > 0; h = &(d->next))
	{
		if ((d = *h) == NULL)
		{
			if ((d = (dbufbuf *)dbuf_alloc()) == NULL)
				return dbuf_malloc_error(dyn);
			dyn->tail = d;
			*h = d;
			d->next = NULL;
		}
		if (chunk > length)
			chunk = length;
		bcopy(buf, d->data + off, chunk);
		length -= chunk;
		buf += chunk;
		off = 0;
		chunk = DBUFSIZ;
	}
	return 1;
}


char *dbuf_map(dbuf *dyn, int *length)
{
	if (dyn->head == NULL)
	{
		dyn->tail = NULL;
		*length = 0;
		return NULL;
	}
	*length = DBUFSIZ - dyn->offset;
	if (*length > dyn->length)
		*length = dyn->length;
	return (dyn->head->data + dyn->offset);
}

int  dbuf_delete(dbuf *dyn, int length)
{
	dbufbuf *d;
	int  chunk;

	if (length > dyn->length)
		length = dyn->length;
	chunk = DBUFSIZ - dyn->offset;
	while (length > 0)
	{
		if (chunk > length)
			chunk = length;
		length -= chunk;
		dyn->offset += chunk;
		dyn->length -= chunk;
		if (dyn->offset == DBUFSIZ || dyn->length == 0)
		{
			d = dyn->head;
			dyn->head = d->next;
			dyn->offset = 0;
			dbuf_free(d);
		}
		chunk = DBUFSIZ;
	}
	if (dyn->head == (dbufbuf *)NULL)
	{
		dyn->length = 0;
		dyn->tail = 0;
	}
	return 0;
}

int  dbuf_get(dbuf *dyn, char *buf, int length)
{
	int  moved = 0;
	int  chunk;
	char *b;

	while (length > 0 && (b = dbuf_map(dyn, &chunk)) != NULL)
	{
		if (chunk > length)
			chunk = length;
		bcopy(b, buf, (int)chunk);
		(void)dbuf_delete(dyn, chunk);
		buf += chunk;
		length -= chunk;
		moved += chunk;
	}
	return moved;
}

/*
** dbuf_getmsg
**
** Check the buffers to see if there is a string which is terminted with
** either a \r or \n prsent.  If so, copy as much as possible (determined by
** length) into buf and return the amount copied - else return 0.
*/
int  dbuf_getmsg(dbuf *dyn, char *buf, int length)
{
	dbufbuf *d;
	char *s;
	int  dlen;
	int  i;
	int  copy;

      getmsg_init:
	d = dyn->head;
	dlen = dyn->length;
	i = DBUFSIZ - dyn->offset;
	if (i <= 0)
		return -1;
	copy = 0;
	if (d && dlen)
		s = dyn->offset + d->data;
	else
		return 0;

	if (i > dlen)
		i = dlen;
	while (length > 0 && dlen > 0)
	{
		dlen--;
		if (*s == '\n' || *s == '\r' )
		{
			copy = dyn->length - dlen;
			/*
			   ** Shortcut this case here to save time elsewhere.
			   ** -avalon
			 */
			if (copy == 1)
			{
				(void)dbuf_delete(dyn, 1);
				goto getmsg_init;
			}
			break;
		}
		length--;
		if (!--i)
		{
			if ((d = d->next))
			{
				s = d->data;
				i = MIN(DBUFSIZ, dlen);
			}
		}
		else
			s++;
	}

	if (copy <= 0)
		return 0;

	/*
	   ** copy as much of the message as wanted into parse buffer
	 */
	i = dbuf_get(dyn, buf, MIN(copy, length));
	/*
	   ** and delete the rest of it!
	 */
	if (copy - i > 0)
		(void)dbuf_delete(dyn, copy - i);
	if (i >= 0)
		*(buf + i) = '\0';	/* mark end of messsage */

	return i;
}