/* open a compressed file, filtering it thru zcat.

18 Jan 1990 tps@chem.ucsd.edu (Tom Stockfisch) posted to comp.sys.sgi
13 Jan 1993  added mode argument.   Eric Grosse <ehg@research.att.com>
	 (and changed name to copen(), to protect the innocent.)
26 Nov 1993 (ehg)  added -f; provided for gzip; converted to POSIX
16 Mar 1995 (ehg)  gzcat name
 2 May 2000 (rsc)  posix include fixes
*/

/*
#define COMPRESS		execlp("compress", "compress","-f",0)
#define UNCOMPRESS	execlp("zcat", "zcat",name,0)
/**/
#define COMPRESS		execlp("gzip","gzip","-f",0)
#define UNCOMPRESS	execlp("gzcat","gzcat",name,0)
/**/

#define _POSIX_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
extern FILE *fdopen();
#define READ	0
#define WRITE	1

static void
defaultErrHndlr(char *diagnostic)
{
	fprintf( stderr, "copen(): %s\n", diagnostic );
	exit(1);
}
void (*zopenErrHndlr)(char *) = defaultErrHndlr;

FILE *
zopen(char *name)
{
	FILE	*stream;
	int	piped[2];

	if ( pipe(piped) == -1 )
		(*zopenErrHndlr)( "pipe failure\n" );
	switch ( fork() )
	{
	case -1:
		(*zopenErrHndlr)( "fork failure\n" );
	case 0:	/* child */
		close( piped[READ] );
		close(1);
		if ( dup( piped[WRITE] ) != 1 )
			(*zopenErrHndlr)( "dup screwup\n" );
		close( piped[WRITE] );
		UNCOMPRESS;
		(*zopenErrHndlr)( "cannot start uncompression" );
	default:	/* parent */
		close( piped[WRITE] );
		stream = fdopen( piped[READ], "r" );
		if (stream == NULL)
			(*zopenErrHndlr)( "cannot open pipe\n" );
		break;
	}
	return	stream;
}

FILE *
copen(char *name, char *mode)
{
	FILE	*stream;
	int	piped[2], out;

	if(strcmp(mode,"r")==0) return zopen(name);
	if(strcmp(mode,"w")!=0) (*zopenErrHndlr)( "mode must be r or w\n" );

	if ( pipe(piped) == -1 )
		(*zopenErrHndlr)( "pipe failure\n" );
	switch ( fork() )
	{
	case -1:
		(*zopenErrHndlr)( "fork failure\n" );
	case 0:	/* child */
		close( piped[WRITE] );
		close(0);
		if ( dup( piped[READ] ) != 0 )
			(*zopenErrHndlr)( "dup screwup\n" );
		close( piped[READ] );
		close(1);
		out = creat(name,0666);
		if ( out < 0 )
			(*zopenErrHndlr)( "can't create file\n" );
		if ( out != 1 )
			(*zopenErrHndlr)( "expected fd=1\n" );
		COMPRESS;
		(*zopenErrHndlr)( "cannot start compression" );
	default:	/* parent */
		close( piped[READ] );
		stream = fdopen( piped[WRITE], "w" );
		if (stream == NULL)
			(*zopenErrHndlr)( "cannot open pipe\n" );
		break;
	}
	return	stream;
}