/************************************************************************
 *   IRC - Internet Relay Chat, ircd/s_zip.c
 *   Copyright (C) 1996  Christophe Kalt
 *
 *   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.
 */

#ifndef lint
static const volatile char rcsid[] = "@(#)$Id: s_zip.c,v 1.12 2005/02/20 23:09:45 chopin Exp $";
#endif

#include "os.h"
#include "s_defines.h"
#define S_ZIP_C
#include "s_externs.h"
#undef S_ZIP_C

#ifdef	ZIP_LINKS

/*
** Important note:
**	The provided buffers for compression *MUST* be big
**	enough for any operation to complete.
**
**	s_bsd.c current settings are that the biggest packet size is 16k
**	(but socket buffers are set to 8k..)
*/

/*
** size of the buffer holding compressed data
**
** outgoing data:
**	must be enough to hold compressed data resulting of the compression
**	of up to ZIP_MAXIMUM bytes
** incoming data:
**	must be enough to hold what was just read
**	(cptr->zip->inbuf should never hold more than ONE compression block.
**	The biggest block allowed for compression is ZIP_MAXIMUM bytes)
*/
#define	ZIP_BUFFER_SIZE		(MAX(ZIP_MAXIMUM, READBUF_SIZE))

/*
** size of the buffer where zlib puts compressed data
**	should be enough to hold uncompressed data resulting of the
**	uncompression of zipbuffer
**
**	tests show that an average ratio is around 40%,
**	in some very particular cases, ratio can be VERY low, BUT:
**
**	s_bsd.c/read_packet() is now smart enough to detect when uncompression
**	stopped because the buffer is too small, and calls dopacket() again
**	to finish the work (as many times as needed).
*/
#define	UNZIP_BUFFER_SIZE	4*ZIP_BUFFER_SIZE

/* buffers */
static	char	unzipbuf[UNZIP_BUFFER_SIZE];
static	char	zipbuf[ZIP_BUFFER_SIZE];

/*
** zip_init
**	Initialize compression structures for a server.
**	If failed, zip_free() has to be called.
*/
int	zip_init(aClient *cptr)
{
	cptr->zip  = (aZdata *) MyMalloc(sizeof(aZdata));
	cptr->zip->outcount = 0;

	cptr->zip->in  = (z_stream *) MyMalloc(sizeof(z_stream));
	cptr->zip->in->avail_in = 0;
	cptr->zip->in->total_in = 0;
	cptr->zip->in->total_out = 0;
	cptr->zip->in->zalloc = (alloc_func)0;
	cptr->zip->in->zfree = (free_func)0;
	cptr->zip->in->data_type = Z_ASCII;
	if (inflateInit(cptr->zip->in) != Z_OK)
	    {
		cptr->zip->out = NULL;
		return -1;
	    }

	cptr->zip->out = (z_stream *) MyMalloc(sizeof(z_stream));
	cptr->zip->out->total_in = 0;
	cptr->zip->out->total_out = 0;
	cptr->zip->out->zalloc = (alloc_func)0;
	cptr->zip->out->zfree = (free_func)0;
	cptr->zip->out->data_type = Z_ASCII;
	if (deflateInit(cptr->zip->out, ZIP_LEVEL) != Z_OK)
		return -1;

	return 0;
}

/*
** zip_free
*/
void	zip_free(aClient *cptr)
{
	cptr->flags &= ~FLAGS_ZIP;
	if (cptr->zip)
	    {
		if (cptr->zip->in)
			inflateEnd(cptr->zip->in);
		MyFree(cptr->zip->in);
		if (cptr->zip->out)
			deflateEnd(cptr->zip->out);
		MyFree(cptr->zip->out);
		MyFree(cptr->zip);
		cptr->zip = NULL;
	    }
}

/*
** unzip_packet
** 	Unzip the content of the buffer, don't worry about any leftover.
**
**	will return the uncompressed buffer, length will be updated.
**	if a fatal error occurs, length will be set to -1
*/
char	*unzip_packet(aClient *cptr, char *buffer, int *length)
{
	Reg	z_stream *zin = cptr->zip->in;
	int	r;

	if (*length != 0 && zin->avail_in != 0)
	    {
		sendto_flag(SCH_ERROR,
			    "assertion failed in unzip_packet(): %d %d",
			    *length, zin->avail_in);
		sendto_flag(SCH_ERROR, "Please report to ircd-bugs@irc.org");
		*length = -1;
		return NULL;
	    }
	if (*length)
	    {
		zin->next_in = (Bytef *) buffer;
		zin->avail_in = *length;
	    }
	zin->next_out = (Bytef *) unzipbuf;
	zin->avail_out = UNZIP_BUFFER_SIZE;
	switch (r = inflate(zin, Z_SYNC_FLUSH))
	  {
	  case Z_OK:
		cptr->flags &= ~FLAGS_ZIPRQ;
		*length = UNZIP_BUFFER_SIZE - zin->avail_out;
		return unzipbuf;

	  case Z_BUF_ERROR: /*no progress possible or output buffer too small*/
		if (zin->avail_out == 0)
		    {
			sendto_flag(SCH_ERROR,
				    "inflate() returned Z_BUF_ERROR: %s",
				    (zin->msg) ? zin->msg : "?");
			*length = -1;
		    }
		break;

	  case Z_DATA_ERROR: /* the buffer might not be compressed.. */
		if ((cptr->flags & FLAGS_ZIPRQ) &&
		    !strncmp("ERROR ", buffer, 6))
		    {
			cptr->flags &= ~(FLAGS_ZIP | FLAGS_ZIPRQ);
			/*
			 * This is not sane at all.  But if other server
			 * has sent an error now, it is probably closing
			 * the link as well.
			 */
			return buffer;
		    }

		/* no break */

	  default: /* error ! */
		/* should probably mark link as dead or something... */
		sendto_flag(SCH_ERROR, "inflate() error(%d): %s", r,
			    (zin->msg) ? zin->msg : "?");
		*length = -1; /* report error condition */
		break;
	  }
	return NULL;
}

/*
** zip_buffer
** 	Zip the content of cptr->zip->outbuf and of the buffer,
**	put anything left in cptr->zip->outbuf, update cptr->zip->outcount
**
**	if flush is set, then all available data will be compressed,
**	otherwise, compression only occurs if there's enough to compress,
**	or if we are reaching the maximum allowed size during a connect burst.
**
**	will return the uncompressed buffer, length will be updated.
**	if a fatal error occurs, length will be set to -1
*/
char	*zip_buffer(aClient *cptr, char *buffer, int *length, int flush)
{
	Reg	z_stream *zout = cptr->zip->out;
	int	r;

	if (buffer)
	    {
		/* concatenate buffer in cptr->zip->outbuf */
		bcopy(buffer, cptr->zip->outbuf + cptr->zip->outcount,*length);
		cptr->zip->outcount += *length;
	    }
	*length = 0;

	if (!flush && ((cptr->zip->outcount < ZIP_MINIMUM) ||
		       ((cptr->zip->outcount < (ZIP_MAXIMUM - BUFSIZE)) &&
			CBurst(cptr))))
		return NULL;

	zout->next_in = cptr->zip->outbuf;
	zout->avail_in = cptr->zip->outcount;
	zout->next_out = (Bytef *) zipbuf;
	zout->avail_out = ZIP_BUFFER_SIZE;

	switch (r = deflate(zout, Z_SYNC_FLUSH))
	  {
	  case Z_OK:
	    if (zout->avail_in)
	      {
		/* can this occur?? I hope not... */
		sendto_flag(SCH_ERROR,
			    "deflate() didn't process all available data!");
	      }
	    cptr->zip->outcount = 0;
	    *length = ZIP_BUFFER_SIZE - zout->avail_out;
	    return zipbuf;

	  default: /* error ! */
	    sendto_flag(SCH_ERROR, "deflate() error(%d): %s", r,
			(zout->msg) ? zout->msg : "?");
	    *length = -1;
	    break;
	  }
	return NULL;
}

#endif	/* ZIP_LINKS */