143 lines
3.3 KiB
C
143 lines
3.3 KiB
C
/*
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* revoutput.c --- Provide an output wrapper that reverses lines.
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*
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* Arnold Robbins
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* arnold@skeeve.com
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* Written 8/2012
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*/
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/*
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* Copyright (C) 2012, 2013, 2015, 2018 the Free Software Foundation, Inc.
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*
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* This file is part of GAWK, the GNU implementation of the
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* AWK Programming Language.
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*
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* GAWK is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GAWK is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include "gawkapi.h"
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#include "gettext.h"
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#define _(msgid) gettext(msgid)
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#define N_(msgid) msgid
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static const gawk_api_t *api; /* for convenience macros to work */
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static awk_ext_id_t ext_id;
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static const char *ext_version = "revoutput extension: version 1.1";
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static awk_bool_t init_revoutput(void);
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static awk_bool_t (*init_func)(void) = init_revoutput;
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int plugin_is_GPL_compatible;
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/* rev_fwrite --- write out characters in reverse order */
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static size_t
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rev_fwrite(const void *buf, size_t size, size_t count, FILE *fp, void *opaque)
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{
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const char *cp = buf;
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int nbytes = size * count;
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(void) opaque;
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for (; nbytes >= 1; nbytes--)
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putc(cp[nbytes-1], fp);
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return (size * count);
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}
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/* revoutput_can_take_file --- return true if we want the file */
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static awk_bool_t
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revoutput_can_take_file(const awk_output_buf_t *outbuf)
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{
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awk_value_t value;
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if (outbuf == NULL)
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return awk_false;
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if (! sym_lookup("REVOUT", AWK_NUMBER, & value))
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return awk_false;
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return (value.num_value != 0);
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}
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/*
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* revoutput_take_control_of --- set up output wrapper.
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* We can assume that revoutput_can_take_file just returned true,
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* and no state has changed since then.
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*/
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static awk_bool_t
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revoutput_take_control_of(awk_output_buf_t *outbuf)
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{
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if (outbuf == NULL)
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return awk_false;
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outbuf->gawk_fwrite = rev_fwrite;
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outbuf->redirected = awk_true;
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return awk_true;
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}
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static awk_output_wrapper_t output_wrapper = {
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"revoutput",
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revoutput_can_take_file,
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revoutput_take_control_of,
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NULL
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};
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/* init_revoutput --- set things ups */
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static awk_bool_t
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init_revoutput()
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{
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awk_value_t value;
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register_output_wrapper(& output_wrapper);
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if (! sym_lookup("REVOUT", AWK_SCALAR, & value)) {
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/* only install it if not there, e.g. -v REVOUT=1 */
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make_number(0.0, & value); /* init to false */
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if (! sym_update("REVOUT", & value)) {
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warning(ext_id, _("revoutput: could not initialize REVOUT variable"));
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return awk_false;
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}
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}
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return awk_true;
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}
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static awk_ext_func_t func_table[] = {
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{ NULL, NULL, 0, 0, awk_false, NULL }
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};
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/* define the dl_load function using the boilerplate macro */
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dl_load_func(func_table, revoutput, "")
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