Add iterator-style API
[argpar.git] / argpar / argpar.h
1 /*
2 * SPDX-License-Identifier: MIT
3 *
4 * Copyright (c) 2019-2021 Philippe Proulx <pproulx@efficios.com>
5 * Copyright (c) 2020-2021 Simon Marchi <simon.marchi@efficios.com>
6 */
7
8 #ifndef BABELTRACE_ARGPAR_H
9 #define BABELTRACE_ARGPAR_H
10
11 #include <stdbool.h>
12
13 /*
14 * argpar is a library which provides facilities for command-line
15 * argument parsing.
16 *
17 * Two APIs are available:
18 *
19 * Iterator API:
20 * Create a parsing iterator with argpar_iter_create(), then
21 * repeatedly call argpar_iter_parse_next() to access the parsing
22 * results, until one of:
23 *
24 * * There are no more arguments.
25 *
26 * * The argument parser encounters an error (for example, an
27 * unknown option).
28 *
29 * * You need to stop.
30 *
31 * This API provides more parsing control than the next one.
32 *
33 * Single call API:
34 * Call argpar_parse(), which parses the arguments until one of:
35 *
36 * * There are no more arguments.
37 *
38 * * It encounters an argument parsing error.
39 *
40 * argpar_parse() returns a single array of parsing results.
41 *
42 * Both methods parse the arguments `argv` of which the count is `argc`
43 * using the sentinel-terminated (use `ARGPAR_OPT_DESCR_SENTINEL`)
44 * option descriptor array `descrs`.
45 *
46 * argpar considers ALL the elements of `argv`, including the first one,
47 * so that you would typically pass `argc - 1` and `&argv[1]` from what
48 * main() receives.
49 *
50 * The argpar parsers support:
51 *
52 * * Short options without an argument, possibly tied together:
53 *
54 * -f -auf -n
55 *
56 * * Short options with argument:
57 *
58 * -b 45 -f/mein/file -xyzhello
59 *
60 * * Long options without an argument:
61 *
62 * --five-guys --burger-king --pizza-hut --subway
63 *
64 * * Long options with arguments:
65 *
66 * --security enable --time=18.56
67 *
68 * * Non-option arguments (anything else).
69 *
70 * The argpar parsers don't accept `-` or `--` as arguments. The latter
71 * means "end of options" for many command-line tools, but this library
72 * is all about keeping the order of the arguments, so it doesn't mean
73 * much to put them at the end. This has the side effect that a
74 * non-option argument cannot have the form of an option, for example if
75 * you need to pass the exact relative path `--component`. In that case,
76 * you would need to pass `./--component`. There's no generic way to
77 * escape `-` as of this version.
78 *
79 * Both argpar_iter_create() and argpar_parse() accept duplicate options
80 * (they produce one item for each instance).
81 *
82 * A returned parsing item has the type `struct argpar_item *`. Each
83 * item is to be casted to the appropriate type
84 * (`struct argpar_item_opt *` or `struct argpar_item_non_opt *`)
85 * depending on its `type` member.
86 *
87 * Both argpar_iter_create() and argpar_parse() produce the items in
88 * the same order that the arguments were parsed, including non-option
89 * arguments. This means, for example, that for:
90 *
91 * --hello --count=23 /path/to/file -ab --type file magie
92 *
93 * The produced items are, in this order:
94 *
95 * 1. Option item (`--hello`).
96 * 2. Option item (`--count` with argument `23`).
97 * 3. Non-option item (`/path/to/file`).
98 * 4. Option item (`-a`).
99 * 5. Option item (`-b`).
100 * 6. Option item (`--type` with argument `file`).
101 * 7. Non-option item (`magie`).
102 */
103
104 /* Sentinel for an option descriptor array */
105 #define ARGPAR_OPT_DESCR_SENTINEL { -1, '\0', NULL, false }
106
107 /*
108 * ARGPAR_HIDDEN: if argpar is used in some shared library, we don't
109 * want them to be exported by that library, so mark them as "hidden".
110 *
111 * On Windows, symbols are local unless explicitly exported; see
112 * <https://gcc.gnu.org/wiki/Visibility>.
113 */
114 #if defined(_WIN32) || defined(__CYGWIN__)
115 #define ARGPAR_HIDDEN
116 #else
117 #define ARGPAR_HIDDEN __attribute__((visibility("hidden")))
118 #endif
119
120 /* Forward-declaration for the opaque type */
121 struct argpar_iter;
122
123 /* Option descriptor */
124 struct argpar_opt_descr {
125 /* Numeric ID for this option */
126 const int id;
127
128 /* Short option character, or `\0` */
129 const char short_name;
130
131 /* Long option name (without `--`), or `NULL` */
132 const char * const long_name;
133
134 /* True if this option has an argument */
135 const bool with_arg;
136 };
137
138 /* Item type */
139 enum argpar_item_type {
140 /* Option */
141 ARGPAR_ITEM_TYPE_OPT,
142
143 /* Non-option */
144 ARGPAR_ITEM_TYPE_NON_OPT,
145 };
146
147 /* Base item */
148 struct argpar_item {
149 enum argpar_item_type type;
150 };
151
152 /* Option item */
153 struct argpar_item_opt {
154 struct argpar_item base;
155
156 /* Corresponding descriptor */
157 const struct argpar_opt_descr *descr;
158
159 /* Argument, or `NULL` if none */
160 const char *arg;
161 };
162
163 /* Non-option item */
164 struct argpar_item_non_opt {
165 struct argpar_item base;
166
167 /*
168 * Complete argument, pointing to one of the entries of the
169 * original arguments (`argv`).
170 */
171 const char *arg;
172
173 /* Index of this argument amongst all original arguments (`argv`) */
174 unsigned int orig_index;
175
176 /* Index of this argument amongst other non-option arguments */
177 unsigned int non_opt_index;
178 };
179
180 struct argpar_item_array {
181 /* Array of `struct argpar_item *`, or `NULL` on error */
182 struct argpar_item **items;
183
184 /* Number of used slots in `items`. */
185 unsigned int n_items;
186
187 /* Number of allocated slots in `items`. */
188 unsigned int n_alloc;
189 };
190
191 /* What is returned by argpar_parse() */
192 struct argpar_parse_ret {
193 /*
194 * Array of `struct argpar_item *`, or `NULL` on error.
195 *
196 * Do NOT destroy those items manually with
197 * argpar_iter_destroy(): call argpar_parse_ret_fini() to
198 * finalize the whole structure.
199 */
200 struct argpar_item_array *items;
201
202 /* Error string, or `NULL` if none */
203 char *error;
204
205 /* Number of original arguments (`argv`) ingested */
206 unsigned int ingested_orig_args;
207 };
208
209 /*
210 * Parses arguments in `argv` until the end is reached or an error is
211 * encountered.
212 *
213 * On success, this function returns an array of items (field `items` of
214 * `struct argpar_parse_ret`).
215 *
216 * In the returned structure, `ingested_orig_args` is the number of
217 * ingested arguments within `argv` to produce the resulting array of
218 * items.
219 *
220 * If `fail_on_unknown_opt` is true, then on success
221 * `ingested_orig_args` is equal to `argc`. Otherwise,
222 * `ingested_orig_args` contains the number of original arguments until
223 * an unknown _option_ occurs. For example, with
224 *
225 * --great --white contact nuance --shark nuclear
226 *
227 * if `--shark` is not described within `descrs` and
228 * `fail_on_unknown_opt` is false, then `ingested_orig_args` is 4 (two
229 * options, two non-options), whereas `argc` is 6.
230 *
231 * This makes it possible to know where a command name is, for example.
232 * With those arguments:
233 *
234 * --verbose --stuff=23 do-something --specific-opt -f -b
235 *
236 * and the descriptors for `--verbose` and `--stuff` only, the function
237 * returns the `--verbose` and `--stuff` option items, the
238 * `do-something` non-option item, and that three original arguments
239 * were ingested. This means you can start the next argument parsing
240 * stage, with option descriptors depending on the command name, at
241 * `&argv[3]`.
242 *
243 * Note that `ingested_orig_args` is not always equal to the number of
244 * returned items, as
245 *
246 * --hello -fdw
247 *
248 * for example contains two ingested original arguments, but four
249 * resulting items.
250 *
251 * On failure, the `items` member of the returned structure is `NULL`,
252 * and the `error` string member contains details about the error.
253 *
254 * Finalize the returned structure with argpar_parse_ret_fini().
255 */
256 ARGPAR_HIDDEN
257 struct argpar_parse_ret argpar_parse(unsigned int argc,
258 const char * const *argv,
259 const struct argpar_opt_descr *descrs,
260 bool fail_on_unknown_opt);
261
262 /*
263 * Finalizes what argpar_parse() returns.
264 *
265 * You may call argpar_parse() multiple times with the same structure.
266 */
267 ARGPAR_HIDDEN
268 void argpar_parse_ret_fini(struct argpar_parse_ret *ret);
269
270 /*
271 * Creates an argument parsing iterator.
272 *
273 * This function initializes the returned structure, but doesn't
274 * actually start parsing the arguments.
275 *
276 * `*argv` and `*descrs` must NOT change for the lifetime of the
277 * returned iterator (until you call argpar_iter_destroy()).
278 *
279 * Call argpar_iter_parse_next() with the returned iterator to obtain
280 * the next parsing result (item).
281 */
282 ARGPAR_HIDDEN
283 struct argpar_iter *argpar_iter_create(unsigned int argc,
284 const char * const *argv,
285 const struct argpar_opt_descr *descrs);
286
287 /*
288 * Destroys `iter`, as returned by argpar_iter_create().
289 */
290 ARGPAR_HIDDEN
291 void argpar_iter_destroy(struct argpar_iter *iter);
292
293 /*
294 * Return type of argpar_iter_parse_next().
295 */
296 enum argpar_iter_parse_next_status {
297 ARGPAR_ITER_PARSE_NEXT_STATUS_OK,
298 ARGPAR_ITER_PARSE_NEXT_STATUS_END,
299 ARGPAR_ITER_PARSE_NEXT_STATUS_ERROR_UNKNOWN_OPT,
300 ARGPAR_ITER_PARSE_NEXT_STATUS_ERROR,
301 };
302
303 /*
304 * Parses and returns the next item from `iter`.
305 *
306 * On success, this function sets `*item` to an item which describes the
307 * next option or non-option argument and returns
308 * `ARGPAR_ITER_PARSE_NEXT_STATUS_OK`. Destroy `*item` with
309 * argpar_item_destroy().
310 *
311 * If there are no more items to return, this function returns
312 * `ARGPAR_ITER_PARSE_NEXT_STATUS_END`.
313 *
314 * On failure (status codes
315 * `ARGPAR_ITER_PARSE_NEXT_STATUS_ERROR_UNKNOWN_OPT` and
316 * `ARGPAR_ITER_PARSE_NEXT_STATUS_ERROR`), this function sets `*error`
317 * to a descriptive error string. Free `*error` with free().
318 *
319 * Create an argument parsing iterator with argpar_iter_create().
320 */
321 enum argpar_iter_parse_next_status argpar_iter_parse_next(
322 struct argpar_iter *iter, const struct argpar_item **item,
323 char **error);
324
325 /*
326 * Returns the number of ingested elements from `argv`, as passed to
327 * argpar_iter_create() to create `*iter`, that were required to produce
328 * the previously returned items.
329 */
330 ARGPAR_HIDDEN
331 unsigned int argpar_iter_get_ingested_orig_args(const struct argpar_iter *iter);
332
333 /*
334 * Destroys `item`, as created by argpar_iter_parse_next().
335 */
336 ARGPAR_HIDDEN
337 void argpar_item_destroy(const struct argpar_item *item);
338
339 /*
340 * Destroys `_item` (`const struct argpar_item *`) and sets it to
341 * `NULL`.
342 */
343 #define ARGPAR_ITEM_DESTROY_AND_RESET(_item) \
344 { \
345 argpar_item_destroy(_item); \
346 _item = NULL; \
347 }
348
349 #endif /* BABELTRACE_ARGPAR_H */
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