/*

 * revoutput.c --- Provide an output wrapper that reverses lines.

 *

 * Arnold Robbins

 * arnold@skeeve.com

 * Written 8/2012

 */

/*

 * Copyright (C) 2012, 2013, 2015 the Free Software Foundation, Inc.

 *

 * This file is part of GAWK, the GNU implementation of the

 * AWK Programming Language.

 *

 * GAWK 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 3 of the License, or

 * (at your option) any later version.

 *

 * GAWK 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

 */

#ifdef HAVE_CONFIG_H

#include <config.h>

#endif

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include "gawkapi.h"

#include "gettext.h"

#define _(msgid)  gettext(msgid)

#define N_(msgid) msgid

static const gawk_api_t *api;	/* for convenience macros to work */

static awk_ext_id_t ext_id;

static const char *ext_version = "revoutput extension: version 1.1";

static awk_bool_t init_revoutput(void);

static awk_bool_t (*init_func)(void) = init_revoutput;

int plugin_is_GPL_compatible;

/* rev_fwrite --- write out characters in reverse order */

static size_t

rev_fwrite(const void *buf, size_t size, size_t count, FILE *fp, void *opaque)

{

	const char *cp = buf;

	int nbytes = size * count;

	(void) opaque;

	for (; nbytes >= 1; nbytes--)

		putc(cp[nbytes-1], fp);

	return (size * count);

}

/* revoutput_can_take_file --- return true if we want the file */

static awk_bool_t

revoutput_can_take_file(const awk_output_buf_t *outbuf)

{

	awk_value_t value;

	if (outbuf == NULL)

		return awk_false;

	if (! sym_lookup("REVOUT", AWK_NUMBER, & value))

		return awk_false;

	return (value.num_value != 0);

}

/*

 * revoutput_take_control_of --- set up output wrapper.

 * We can assume that revoutput_can_take_file just returned true,

 * and no state has changed since then.

 */

static awk_bool_t

revoutput_take_control_of(awk_output_buf_t *outbuf)

{

	if (outbuf == NULL)

		return awk_false;

	outbuf->gawk_fwrite = rev_fwrite;

	outbuf->redirected = awk_true;

	return awk_true;

}

static awk_output_wrapper_t output_wrapper = {

	"revoutput",

	revoutput_can_take_file,

	revoutput_take_control_of,

	NULL

};

/* init_revoutput --- set things ups */

static awk_bool_t

init_revoutput()

{

	awk_value_t value;

	register_output_wrapper(& output_wrapper);

	if (! sym_lookup("REVOUT", AWK_SCALAR, & value)) {

		/* only install it if not there, e.g. -v REVOUT=1 */

		make_number(0.0, & value);	/* init to false */

		if (! sym_update("REVOUT", & value)) {

			warning(ext_id, _("revoutput: could not initialize REVOUT variable"));

			return awk_false;

		}

	}

	return awk_true;

}

static awk_ext_func_t func_table[] = {

	{ NULL, NULL, 0, 0, awk_false, NULL }

};

/* define the dl_load function using the boilerplate macro */

dl_load_func(func_table, revoutput, "")