lttng: Add add-trigger command
[lttng-tools.git] / src / common / argpar / argpar.h
1 /*
2 * SPDX-License-Identifier: MIT
3 *
4 * Copyright 2019 Philippe Proulx <pproulx@efficios.com>
5 */
6
7 #ifndef BABELTRACE_ARGPAR_H
8 #define BABELTRACE_ARGPAR_H
9
10 #include <stdbool.h>
11
12 /*
13 * argpar is a library that provides facilities for argument parsing.
14 *
15 * Two APIs are available:
16 *
17 * - The iterator-style API, where you initialize a state object with
18 * `argpar_state_create`, then repeatedly call `argpar_state_parse_next` to
19 * get the arguments, until (1) there are no more arguments, (2) the parser
20 * encounters an error (e.g. unknown option) or (3) you get bored. This
21 * API gives you more control on when to stop parsing the arguments.
22 *
23 * - The parse-everything-in-one-shot-API, where you call `argpar_parse`,
24 * which parses the arguments until (1) there are not more arguments or
25 * (2) it encounters a parser error. It returns you a list of all the
26 * arguments it was able to parse, which you can consult at your leisure.
27 *
28 * The following describes how arguments are parsed, and applies to both APIs.
29 *
30 * argpar parses the arguments `argv` of which the count is `argc` using the
31 * sentinel-terminated (use `ARGPAR_OPT_DESCR_SENTINEL`) option
32 * descriptor array `descrs`.
33 *
34 * argpar considers ALL the elements of `argv`, including the* first one, so
35 * that you would typically pass `argc - 1` and `&argv[1]` from what main()
36 * receives.
37 *
38 * This argument parser supports:
39 *
40 * * Short options without an argument, possibly tied together:
41 *
42 * -f -auf -n
43 *
44 * * Short options with argument:
45 *
46 * -b 45 -f/mein/file -xyzhello
47 *
48 * * Long options without an argument:
49 *
50 * --five-guys --burger-king --pizza-hut --subway
51 *
52 * * Long options with arguments:
53 *
54 * --security enable --time=18.56
55 *
56 * * Non-option arguments (anything else).
57 *
58 * This parser does not accept `-` or `--` as arguments. The latter
59 * means "end of options" for many command-line tools, but this function
60 * is all about keeping the order of the arguments, so it does not mean
61 * much to put them at the end. This has the side effect that a
62 * non-option argument cannot have the form of an option, for example if
63 * you need to pass the exact relative path `--component`. In that case,
64 * you would need to pass `./--component`. There's no generic way to
65 * escape `-` for the moment.
66 *
67 * This parser accepts duplicate options (it will output one item for each
68 * instance).
69 *
70 * The returned items are of the type `struct argpar_item *`. Each item
71 * is to be casted to the appropriate type (`struct argpar_item_opt *` or
72 * `struct argpar_item_non_opt *`) depending on its type.
73 *
74 * The items are returned in the same order that the arguments were parsed,
75 * including non-option arguments. This means, for example, that for
76 *
77 * --hello --meow=23 /path/to/file -b
78 *
79 * found items are returned in this order: option item (--hello), option item
80 * (--meow=23), non-option item (/path/to/file) and option item (-b).
81 */
82
83 /* Sentinel for an option descriptor array */
84 #define ARGPAR_OPT_DESCR_SENTINEL { -1, '\0', NULL, false }
85
86 /*
87 * ARGPAR_HIDDEN: if argpar is used in some shared library, we don't want them
88 * to be exported by that library, so mark them as "hidden".
89 *
90 * On Windows, symbols are local unless explicitly exported,
91 * see https://gcc.gnu.org/wiki/Visibility
92 */
93 #if defined(_WIN32) || defined(__CYGWIN__)
94 #define ARGPAR_HIDDEN
95 #else
96 #define ARGPAR_HIDDEN __attribute__((visibility("hidden")))
97 #endif
98
99 /* Forward-declaration for the opaque type. */
100 struct argpar_state;
101
102 /* Option descriptor */
103 struct argpar_opt_descr {
104 /* Numeric ID for this option */
105 const int id;
106
107 /* Short option character, or `\0` */
108 const char short_name;
109
110 /* Long option name (without `--`), or `NULL` */
111 const char * const long_name;
112
113 /* True if this option has an argument */
114 const bool with_arg;
115 };
116
117 /* Item type */
118 enum argpar_item_type {
119 /* Option */
120 ARGPAR_ITEM_TYPE_OPT,
121
122 /* Non-option */
123 ARGPAR_ITEM_TYPE_NON_OPT,
124 };
125
126 /* Base item */
127 struct argpar_item {
128 enum argpar_item_type type;
129 };
130
131 /* Option item */
132 struct argpar_item_opt {
133 struct argpar_item base;
134
135 /* Corresponding descriptor */
136 const struct argpar_opt_descr *descr;
137
138 /* Argument, or `NULL` if none */
139 const char *arg;
140 };
141
142 /* Non-option item */
143 struct argpar_item_non_opt {
144 struct argpar_item base;
145
146 /*
147 * Complete argument, pointing to one of the entries of the
148 * original arguments (`argv`).
149 */
150 const char *arg;
151
152 /* Index of this argument amongst all original arguments (`argv`) */
153 unsigned int orig_index;
154
155 /* Index of this argument amongst other non-option arguments */
156 unsigned int non_opt_index;
157 };
158
159 struct argpar_item_array {
160 /* Array of `struct argpar_item *`, or `NULL` on error */
161 struct argpar_item **items;
162
163 /* Number of used slots in `items`. */
164 unsigned int n_items;
165
166 /* Number of allocated slots in `items`. */
167 unsigned int n_alloc;
168 };
169
170 /* What is returned by argpar_parse() */
171 struct argpar_parse_ret {
172 /* Array of `struct argpar_item *`, or `NULL` on error */
173 struct argpar_item_array *items;
174
175 /* Error string, or `NULL` if none */
176 char *error;
177
178 /* Number of original arguments (`argv`) ingested */
179 unsigned int ingested_orig_args;
180 };
181
182 /*
183 * Parses arguments in `argv` until the end is reached or an error is
184 * encountered.
185 *
186 * On success, this function returns an array of items
187 * (field `items` of `struct argpar_parse_ret`) corresponding to each parsed
188 * argument.
189 *
190 * In the returned structure, `ingested_orig_args` is the number of
191 * ingested arguments within `argv` to produce the resulting array of
192 * items.
193 *
194 * If `fail_on_unknown_opt` is true, then on success `ingested_orig_args` is
195 * equal to `argc`. Otherwise, `ingested_orig_args` contains the number of
196 * original arguments until an unknown _option_ occurs. For example, with
197 *
198 * --great --white contact nuance --shark nuclear
199 *
200 * if `--shark` is not described within `descrs` and
201 * `fail_on_unknown_opt` is false, then `ingested_orig_args` is 4 (two
202 * options, two non-options), whereas `argc` is 6.
203 *
204 * This makes it possible to know where a command name is, for example.
205 * With those arguments:
206 *
207 * --verbose --stuff=23 do-something --specific-opt -f -b
208 *
209 * and the descriptors for `--verbose` and `--stuff` only, the function
210 * returns the `--verbose` and `--stuff` option items, the
211 * `do-something` non-option item, and that three original arguments
212 * were ingested. This means you can start the next argument parsing
213 * stage, with option descriptors depending on the command name, at
214 * `&argv[3]`.
215 *
216 * Note that `ingested_orig_args` is not always equal to the number of
217 * returned items, as
218 *
219 * --hello -fdw
220 *
221 * for example contains two ingested original arguments, but four
222 * resulting items.
223 *
224 * On failure, the returned structure's `items` member is `NULL`, and
225 * the `error` string member contains details about the error.
226 *
227 * You can finalize the returned structure with
228 * argpar_parse_ret_fini().
229 */
230 ARGPAR_HIDDEN
231 struct argpar_parse_ret argpar_parse(unsigned int argc,
232 const char * const *argv,
233 const struct argpar_opt_descr *descrs,
234 bool fail_on_unknown_opt);
235
236 /*
237 * Finalizes what is returned by argpar_parse().
238 *
239 * It is safe to call argpar_parse() multiple times with the same
240 * structure.
241 */
242 ARGPAR_HIDDEN
243 void argpar_parse_ret_fini(struct argpar_parse_ret *ret);
244
245 /*
246 * Creates an instance of `struct argpar_state`.
247 *
248 * This sets up the argpar_state structure, but does not actually
249 * start parsing the arguments.
250 *
251 * When you are done with it, the state must be freed with
252 * `argpar_state_destroy`.
253 */
254 ARGPAR_HIDDEN
255 struct argpar_state *argpar_state_create(
256 unsigned int argc,
257 const char * const *argv,
258 const struct argpar_opt_descr * const descrs);
259
260 /*
261 * Destroys an instance of `struct argpar_state`.
262 */
263 ARGPAR_HIDDEN
264 void argpar_state_destroy(struct argpar_state *state);
265
266
267 enum argpar_state_parse_next_status {
268 ARGPAR_STATE_PARSE_NEXT_STATUS_OK,
269 ARGPAR_STATE_PARSE_NEXT_STATUS_END,
270 ARGPAR_STATE_PARSE_NEXT_STATUS_ERROR_UNKNOWN_OPT,
271 ARGPAR_STATE_PARSE_NEXT_STATUS_ERROR,
272 };
273
274 /*
275 * Parses and returns the next argument from `state`.
276 *
277 * On success, an item describing the argument is returned in `*item` and
278 * ARGPAR_STATE_PARSE_NEXT_STATUS_OK is returned. The item must be freed with
279 * `argpar_item_destroy`.
280 *
281 * If there are no more arguments to parse, ARGPAR_STATE_PARSE_NEXT_STATUS_END
282 * is returned.
283 *
284 * On failure (status codes ARGPAR_STATE_PARSE_NEXT_STATUS_ERROR_UNKNOWN_OPT and
285 * ARGPAR_STATE_PARSE_NEXT_STATUS_ERROR), an error string is returned in `*error`.
286 * This string must be freed with `free`.
287 */
288 enum argpar_state_parse_next_status argpar_state_parse_next(
289 struct argpar_state *state,
290 struct argpar_item **item,
291 char **error);
292
293 /*
294 * Return the number of ingested elements from argv that were required to
295 * produce the previously returned items.
296 */
297 ARGPAR_HIDDEN
298 int argpar_state_get_ingested_orig_args(struct argpar_state *state);
299
300 /*
301 * Destroy an instance of `struct argpar_item`, as returned by
302 * argpar_state_parse_next.
303 */
304 ARGPAR_HIDDEN
305 void argpar_item_destroy(struct argpar_item *item);
306
307 #define ARGPAR_ITEM_DESTROY_AND_RESET(_item) \
308 { \
309 argpar_item_destroy(_item); \
310 _item = NULL; \
311 }
312
313
314 #endif /* BABELTRACE_ARGPAR_H */
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