sfdcfilter.c

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/* Copyright (c) Colorado School of Mines, 2006.*/
/* All rights reserved.                       */

#include	"sfdchdr.h"

/*	Discipline to invoke UNIX processes as data filters.
**	These processes must be able to fit in pipelines.
**
**	Written by Kiem-Phong Vo, [e-mail], 03/18/1998.
*/

typedef struct _filter_s
{	Sfdisc_t	disc;		/* discipline structure	*/
	Sfio_t*		filter;		/* the filter stream	*/
	char*		next;		/* data unwritten 	*/
	char*		endb;		/* end of data		*/
	char		raw[4096];	/* raw data buffer	*/
} Filter_t;

/* read data from the filter */
#if __STD_C
static ssize_t filterread(Sfio_t* f, Void_t* buf, size_t n, Sfdisc_t* disc)
#else
static ssize_t filterread(f, buf, n, disc)
Sfio_t*		f;	/* stream reading from */
Void_t*		buf;	/* buffer to read into */
size_t		n;	/* number of bytes requested */
Sfdisc_t*	disc;	/* discipline */
#endif
{
	Filter_t*	fi;
	ssize_t		r, w;

	fi = (Filter_t*)disc;
	for(;;)
	{	
		/* get some raw data to stuff down the pipe */
		if(fi->next && fi->next >= fi->endb )
		{	if((r = sfrd(f,fi->raw,sizeof(fi->raw),disc)) > 0)
			{	fi->next = fi->raw;
				fi->endb = fi->raw+r;
			}
			else
			{	/* eof, close write end of pipes */
				sfset(fi->filter,SF_READ,0);
				close(sffileno(fi->filter));
				sfset(fi->filter,SF_READ,1);
				fi->next = fi->endb = NIL(char*);
			}
		}

		if(fi->next && (w = fi->endb - fi->next) > 0 )
		{	/* see if pipe is ready for write */
			sfset(fi->filter, SF_READ, 0);
			r = sfpoll(&fi->filter, 1, 1);
			sfset(fi->filter, SF_READ, 1);

			if(r == 1) /* non-blocking write */
			{	errno = 0;
				if((w = sfwr(fi->filter, fi->next, w, 0)) > 0)
					fi->next += w;
				else if(errno != EAGAIN)
					return 0;
			}
		}

		/* see if pipe is ready for read */
		sfset(fi->filter, SF_WRITE, 0);
		w = sfpoll(&fi->filter, 1, fi->next ? 1 : -1);
		sfset(fi->filter, SF_WRITE, 1);

		if(!fi->next || w == 1) /* non-blocking read */
		{	errno = 0;
			if((r = sfrd(fi->filter, buf, n, 0)) > 0)
				return r;
			if(errno != EAGAIN)
				return 0;
		}
	}
}

#if __STD_C
static ssize_t filterwrite(Sfio_t* f, const Void_t* buf, size_t n, Sfdisc_t* disc)
#else
static ssize_t filterwrite(f, buf, n, disc)
Sfio_t*		f;	/* stream writing to */
Void_t*		buf;	/* buffer to write into */
size_t		n;	/* number of bytes requested */
Sfdisc_t*	disc;	/* discipline */
#endif
{
	return -1;
}

/* for the duration of this discipline, the stream is unseekable */
#if __STD_C
static Sfoff_t filterseek(Sfio_t* f, Sfoff_t addr, int offset, Sfdisc_t* disc)
#else
static Sfoff_t filterseek(f, addr, offset, disc)
Sfio_t*		f;
Sfoff_t		addr;
int		offset;
Sfdisc_t*	disc;
#endif
{	f = NIL(Sfio_t*);
	addr = 0;
	offset = 0;
	disc = NIL(Sfdisc_t*);
	return (Sfoff_t)(-1);
}

/* on close, remove the discipline */
#if __STD_C
static int filterexcept(Sfio_t* f, int type, Void_t* data, Sfdisc_t* disc)
#else
static int filterexcept(f,type,data,disc)
Sfio_t*		f;
int		type;
Void_t*		data;
Sfdisc_t*	disc;
#endif
{
	if(type == SF_FINAL || type == SF_DPOP)
	{	sfclose(((Filter_t*)disc)->filter);
		free(disc);
	}

	return 0;
}

#if __STD_C
int sfdcfilter(Sfio_t* f, const char* cmd)
#else
int sfdcfilter(f, cmd)
Sfio_t*	f;	/* stream to filter data	*/
char*	cmd;	/* program to run as a filter	*/
#endif
{
	reg Filter_t*	fi;
	reg Sfio_t*	filter;

	/* open filter for read&write */
	if(!(filter = sfpopen(NIL(Sfio_t*),cmd,"r+")) )
		return -1;

	/* unbuffered stream */
	sfsetbuf(filter,NIL(Void_t*),0);

	if(!(fi = (Filter_t*)malloc(sizeof(Filter_t))) )
	{	sfclose(filter);
		return -1;
	}

	fi->disc.readf = filterread;
	fi->disc.writef = filterwrite;
	fi->disc.seekf = filterseek;
	fi->disc.exceptf = filterexcept;
	fi->filter = filter;
	fi->next = fi->endb = fi->raw;

	if(sfdisc(f,(Sfdisc_t*)fi) != (Sfdisc_t*)fi)
	{	sfclose(filter);
		free(fi);
		return -1;
	}

	return 0;
}