1 files changed, 136 insertions, 0 deletions
diff --git a/extension/revoutput.c b/extension/revoutput.c
new file mode 100644
index 00000000..c1ea1ddc
--- /dev/null
+++ b/extension/revoutput.c
@@ -0,0 +1,136 @@
+/*
+ * revoutput.c --- Provide an output wrapper that reverses lines.
+ *
+ * Arnold Robbins
+ * arnold@skeeve.com
+ * Written 8/2012
+ */
+
+/*
+ * Copyright (C) 2012 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
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "config.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 awk_bool_t init_revout(void);
+static awk_bool_t (*init_func)(void) = init_revout;
+
+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);
+}
+
+
+/* revout_can_take_file --- return true if we want the file */
+
+static int
+revout_can_take_file(const awk_output_buf_t *outbuf)
+{
+	awk_value_t value;
+
+	if (outbuf == NULL)
+		return 0;
+
+	if (! sym_lookup("REVOUT", AWK_NUMBER, & value))
+		return 0;
+
+	return (value.num_value != 0);
+}
+
+/*
+ * revout_take_control_of --- set up output wrapper.
+ * We can assume that revout_can_take_file just returned true,
+ * and no state has changed since then.
+ */
+
+static int
+revout_take_control_of(awk_output_buf_t *outbuf)
+{
+	if (outbuf == NULL)
+		return 0;
+
+	outbuf->gawk_fwrite = rev_fwrite;
+	outbuf->redirected = 1;
+	return 1;
+}
+
+static awk_output_wrapper_t output_wrapper = {
+	"revout",
+	revout_can_take_file,
+	revout_take_control_of,
+	NULL
+};
+
+/* init_revout --- set things ups */
+
+static awk_bool_t
+init_revout()
+{
+	awk_value_t value;
+
+	register_output_wrapper(& output_wrapper);
+
+	make_number(0.0, & value);	/* init to false */
+	if (! sym_update("REVOUT", & value)) {
+		warning(ext_id, _("revout: could not initialize REVOUT variable"));
+
+		return 0;
+	}
+
+	return 1;
+}
+
+static awk_ext_func_t func_table[] = {
+	{ NULL, NULL, 0 }
+};
+
+/* define the dl_load function using the boilerplate macro */
+
+dl_load_func(func_table, revout, "")