1 /*
2 * revoutput.c --- Provide an output wrapper that reverses lines.
3 *
4 * Arnold Robbins
5 * arnold@skeeve.com
6 * Written 8/2012
7 */
8
9 /*
10 * Copyright (C) 2012, 2013, 2015, 2018 the Free Software Foundation, Inc.
11 *
12 * This file is part of GAWK, the GNU implementation of the
13 * AWK Programming Language.
14 *
15 * GAWK is free software; you can redistribute it and/or modify
16 * it under the terms of the GNU General Public License as published by
17 * the Free Software Foundation; either version 3 of the License, or
18 * (at your option) any later version.
19 *
20 * GAWK is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 * GNU General Public License for more details.
24 *
25 * You should have received a copy of the GNU General Public License
26 * along with this program; if not, write to the Free Software
27 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
28 */
29
30 #ifdef HAVE_CONFIG_H
31 #include <config.h>
32 #endif
33
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <unistd.h>
38
39 #include <sys/types.h>
40 #include <sys/stat.h>
41
42 #include "gawkapi.h"
43
44 #include "gettext.h"
45 #define _(msgid) gettext(msgid)
46 #define N_(msgid) msgid
47
48 static const gawk_api_t *api; /* for convenience macros to work */
49 static awk_ext_id_t ext_id;
50 static const char *ext_version = "revoutput extension: version 1.1";
51
52 static awk_bool_t init_revoutput(void);
53 static awk_bool_t (*init_func)(void) = init_revoutput;
54
55 int plugin_is_GPL_compatible;
56
57 /* rev_fwrite --- write out characters in reverse order */
58
59 static size_t
rev_fwrite(const void * buf,size_t size,size_t count,FILE * fp,void * opaque)60 rev_fwrite(const void *buf, size_t size, size_t count, FILE *fp, void *opaque)
61 {
62 const char *cp = buf;
63 int nbytes = size * count;
64
65 (void) opaque;
66
67 for (; nbytes >= 1; nbytes--)
68 putc(cp[nbytes-1], fp);
69
70 return (size * count);
71 }
72
73
74 /* revoutput_can_take_file --- return true if we want the file */
75
76 static awk_bool_t
revoutput_can_take_file(const awk_output_buf_t * outbuf)77 revoutput_can_take_file(const awk_output_buf_t *outbuf)
78 {
79 awk_value_t value;
80
81 if (outbuf == NULL)
82 return awk_false;
83
84 if (! sym_lookup("REVOUT", AWK_NUMBER, & value))
85 return awk_false;
86
87 return (value.num_value != 0);
88 }
89
90 /*
91 * revoutput_take_control_of --- set up output wrapper.
92 * We can assume that revoutput_can_take_file just returned true,
93 * and no state has changed since then.
94 */
95
96 static awk_bool_t
revoutput_take_control_of(awk_output_buf_t * outbuf)97 revoutput_take_control_of(awk_output_buf_t *outbuf)
98 {
99 if (outbuf == NULL)
100 return awk_false;
101
102 outbuf->gawk_fwrite = rev_fwrite;
103 outbuf->redirected = awk_true;
104 return awk_true;
105 }
106
107 static awk_output_wrapper_t output_wrapper = {
108 "revoutput",
109 revoutput_can_take_file,
110 revoutput_take_control_of,
111 NULL
112 };
113
114 /* init_revoutput --- set things ups */
115
116 static awk_bool_t
init_revoutput()117 init_revoutput()
118 {
119 awk_value_t value;
120
121 register_output_wrapper(& output_wrapper);
122
123 if (! sym_lookup("REVOUT", AWK_SCALAR, & value)) {
124 /* only install it if not there, e.g. -v REVOUT=1 */
125 make_number(0.0, & value); /* init to false */
126 if (! sym_update("REVOUT", & value)) {
127 warning(ext_id, _("revoutput: could not initialize REVOUT variable"));
128
129 return awk_false;
130 }
131 }
132
133 return awk_true;
134 }
135
136 static awk_ext_func_t func_table[] = {
137 { NULL, NULL, 0, 0, awk_false, NULL }
138 };
139
140 /* define the dl_load function using the boilerplate macro */
141
142 dl_load_func(func_table, revoutput, "")
143