1 // © 2016 and later: Unicode, Inc. and others.
2 // License & terms of use: http://www.unicode.org/copyright.html
3 /*
4 ******************************************************************************
5 *
6 *   Copyright (C) 2009-2015, International Business Machines
7 *   Corporation and others.  All Rights Reserved.
8 *
9 ******************************************************************************
10 *
11 *  FILE NAME : icuplug.h
12 *
13 *   Date         Name        Description
14 *   10/29/2009   sl          New.
15 ******************************************************************************
16 */
17 
18 /**
19  * \file
20  * \brief C API: ICU Plugin API
21  *
22  * <h2>C API: ICU Plugin API</h2>
23  *
24  * <p>C API allowing run-time loadable modules that extend or modify ICU functionality.</p>
25  *
26  * <h3>Loading and Configuration</h3>
27  *
28  * <p>At ICU startup time, the environment variable "ICU_PLUGINS" will be
29  * queried for a directory name.  If it is not set, the preprocessor symbol
30  * "DEFAULT_ICU_PLUGINS" will be checked for a default value.</p>
31  *
32  * <p>Within the above-named directory, the file  "icuplugins##.txt" will be
33  * opened, if present, where ## is the major+minor number of the currently
34  * running ICU (such as, 44 for ICU 4.4, thus icuplugins44.txt)</p>
35  *
36  * <p>The configuration file has this format:</p>
37  *
38  * <ul>
39  * <li>Hash (#) begins a comment line</li>
40  *
41  * <li>Non-comment lines have two or three components:
42  * LIBRARYNAME     ENTRYPOINT     [ CONFIGURATION .. ]</li>
43  *
44  * <li>Tabs or spaces separate the three items.</li>
45  *
46  * <li>LIBRARYNAME is the name of a shared library, either a short name if
47  * it is on the loader path,  or a full pathname.</li>
48  *
49  * <li>ENTRYPOINT is the short (undecorated) symbol name of the plugin's
50  * entrypoint, as above.</li>
51  *
52  * <li>CONFIGURATION is the entire rest of the line . It's passed as-is to
53  * the plugin.</li>
54  * </ul>
55  *
56  * <p>An example configuration file is, in its entirety:</p>
57  *
58  * \code
59  * # this is icuplugins44.txt
60  * testplug.dll    myPlugin        hello=world
61  * \endcode
62  * <p>Plugins are categorized as "high" or "low" level.  Low level are those
63  * which must be run BEFORE high level plugins, and before any operations
64  * which cause ICU to be 'initialized'.  If a plugin is low level but
65  * causes ICU to allocate memory or become initialized, that plugin is said
66  * to cause a 'level change'. </p>
67  *
68  * <p>At load time, ICU first queries all plugins to determine their level,
69  * then loads all 'low' plugins first, and then loads all 'high' plugins.
70  * Plugins are otherwise loaded in the order listed in the configuration file.</p>
71  *
72  * <h3>Implementing a Plugin</h3>
73  * \code
74  * U_CAPI UPlugTokenReturn U_EXPORT2
75  * myPlugin (UPlugData *plug, UPlugReason reason, UErrorCode *status) {
76  *   if(reason==UPLUG_REASON_QUERY) {
77  *      uplug_setPlugName(plug, "Simple Plugin");
78  *      uplug_setPlugLevel(plug, UPLUG_LEVEL_HIGH);
79  *    } else if(reason==UPLUG_REASON_LOAD) {
80  *       ... Set up some ICU things here....
81  *    } else if(reason==UPLUG_REASON_UNLOAD) {
82  *       ... unload, clean up ...
83  *    }
84  *   return UPLUG_TOKEN;
85  *  }
86  * \endcode
87  *
88  * <p>The UPlugData*  is an opaque pointer to the plugin-specific data, and is
89  * used in all other API calls.</p>
90  *
91  * <p>The API contract is:</p>
92  * <ol><li>The plugin MUST always return UPLUG_TOKEN as a return value- to
93  * indicate that it is a valid plugin.</li>
94  *
95  * <li>When the 'reason' parameter is set to UPLUG_REASON_QUERY,  the
96  * plugin MUST call uplug_setPlugLevel() to indicate whether it is a high
97  * level or low level plugin.</li>
98  *
99  * <li>When the 'reason' parameter is UPLUG_REASON_QUERY, the plugin
100  * SHOULD call uplug_setPlugName to indicate a human readable plugin name.</li></ol>
101  *
102  *
103  * \internal ICU 4.4 Technology Preview
104  */
105 
106 
107 #ifndef ICUPLUG_H
108 #define ICUPLUG_H
109 
110 #include "unicode/utypes.h"
111 
112 
113 #if UCONFIG_ENABLE_PLUGINS
114 
115 
116 
117 /* === Basic types === */
118 
119 #ifndef U_HIDE_INTERNAL_API
120 /**
121  * @{
122  * Opaque structure passed to/from a plugin.
123  * use the APIs to access it.
124  * @internal ICU 4.4 Technology Preview
125  */
126 
127 struct UPlugData;
128 typedef struct UPlugData UPlugData;
129 
130 /** @} */
131 
132 /**
133  * Random Token to identify a valid ICU plugin. Plugins must return this
134  * from the entrypoint.
135  * @internal ICU 4.4 Technology Preview
136  */
137 #define UPLUG_TOKEN 0x54762486
138 
139 /**
140  * Max width of names, symbols, and configuration strings
141  * @internal ICU 4.4 Technology Preview
142  */
143 #define UPLUG_NAME_MAX              100
144 
145 
146 /**
147  * Return value from a plugin entrypoint.
148  * Must always be set to UPLUG_TOKEN
149  * @see UPLUG_TOKEN
150  * @internal ICU 4.4 Technology Preview
151  */
152 typedef uint32_t UPlugTokenReturn;
153 
154 /**
155  * Reason code for the entrypoint's call
156  * @internal ICU 4.4 Technology Preview
157  */
158 typedef enum {
159     UPLUG_REASON_QUERY = 0,     /**< The plugin is being queried for info. **/
160     UPLUG_REASON_LOAD = 1,     /**< The plugin is being loaded. **/
161     UPLUG_REASON_UNLOAD = 2,   /**< The plugin is being unloaded. **/
162     /**
163      * Number of known reasons.
164      * @internal The numeric value may change over time, see ICU ticket #12420.
165      */
166     UPLUG_REASON_COUNT
167 } UPlugReason;
168 
169 
170 /**
171  * Level of plugin loading
172  *     INITIAL:  UNKNOWN
173  *       QUERY:   INVALID ->  { LOW | HIGH }
174  *     ERR -> INVALID
175  * @internal ICU 4.4 Technology Preview
176  */
177 typedef enum {
178     UPLUG_LEVEL_INVALID = 0,     /**< The plugin is invalid, hasn't called uplug_setLevel, or can't load. **/
179     UPLUG_LEVEL_UNKNOWN = 1,     /**< The plugin is waiting to be installed. **/
180     UPLUG_LEVEL_LOW     = 2,     /**< The plugin must be called before u_init completes **/
181     UPLUG_LEVEL_HIGH    = 3,     /**< The plugin can run at any time. **/
182     /**
183      * Number of known levels.
184      * @internal The numeric value may change over time, see ICU ticket #12420.
185      */
186     UPLUG_LEVEL_COUNT
187 } UPlugLevel;
188 
189 /**
190  * Entrypoint for an ICU plugin.
191  * @param plug the UPlugData handle.
192  * @param status the plugin's extended status code.
193  * @return A valid plugin must return UPLUG_TOKEN
194  * @internal ICU 4.4 Technology Preview
195  */
196 typedef UPlugTokenReturn (U_EXPORT2 UPlugEntrypoint) (
197                   UPlugData *plug,
198                   UPlugReason reason,
199                   UErrorCode *status);
200 
201 /* === Needed for Implementing === */
202 
203 /**
204  * Request that this plugin not be unloaded at cleanup time.
205  * This is appropriate for plugins which cannot be cleaned up.
206  * @see u_cleanup()
207  * @param plug plugin
208  * @param dontUnload  set true if this plugin can't be unloaded
209  * @internal ICU 4.4 Technology Preview
210  */
211 U_INTERNAL void U_EXPORT2
212 uplug_setPlugNoUnload(UPlugData *plug, UBool dontUnload);
213 
214 /**
215  * Set the level of this plugin.
216  * @param plug plugin data handle
217  * @param level the level of this plugin
218  * @internal ICU 4.4 Technology Preview
219  */
220 U_INTERNAL void U_EXPORT2
221 uplug_setPlugLevel(UPlugData *plug, UPlugLevel level);
222 
223 /**
224  * Get the level of this plugin.
225  * @param plug plugin data handle
226  * @return the level of this plugin
227  * @internal ICU 4.4 Technology Preview
228  */
229 U_INTERNAL UPlugLevel U_EXPORT2
230 uplug_getPlugLevel(UPlugData *plug);
231 
232 /**
233  * Get the lowest level of plug which can currently load.
234  * For example, if UPLUG_LEVEL_LOW is returned, then low level plugins may load
235  * if UPLUG_LEVEL_HIGH is returned, then only high level plugins may load.
236  * @return the lowest level of plug which can currently load
237  * @internal ICU 4.4 Technology Preview
238  */
239 U_INTERNAL UPlugLevel U_EXPORT2
240 uplug_getCurrentLevel(void);
241 
242 
243 /**
244  * Get plug load status
245  * @return The error code of this plugin's load attempt.
246  * @internal ICU 4.4 Technology Preview
247  */
248 U_INTERNAL UErrorCode U_EXPORT2
249 uplug_getPlugLoadStatus(UPlugData *plug);
250 
251 /**
252  * Set the human-readable name of this plugin.
253  * @param plug plugin data handle
254  * @param name the name of this plugin. The first UPLUG_NAME_MAX characters willi be copied into a new buffer.
255  * @internal ICU 4.4 Technology Preview
256  */
257 U_INTERNAL void U_EXPORT2
258 uplug_setPlugName(UPlugData *plug, const char *name);
259 
260 /**
261  * Get the human-readable name of this plugin.
262  * @param plug plugin data handle
263  * @return the name of this plugin
264  * @internal ICU 4.4 Technology Preview
265  */
266 U_INTERNAL const char * U_EXPORT2
267 uplug_getPlugName(UPlugData *plug);
268 
269 /**
270  * Return the symbol name for this plugin, if known.
271  * @param plug plugin data handle
272  * @return the symbol name, or NULL
273  * @internal ICU 4.4 Technology Preview
274  */
275 U_INTERNAL const char * U_EXPORT2
276 uplug_getSymbolName(UPlugData *plug);
277 
278 /**
279  * Return the library name for this plugin, if known.
280  * @param plug plugin data handle
281  * @param status error code
282  * @return the library name, or NULL
283  * @internal ICU 4.4 Technology Preview
284  */
285 U_INTERNAL const char * U_EXPORT2
286 uplug_getLibraryName(UPlugData *plug, UErrorCode *status);
287 
288 /**
289  * Return the library used for this plugin, if known.
290  * Plugins could use this to load data out of their
291  * @param plug plugin data handle
292  * @return the library, or NULL
293  * @internal ICU 4.4 Technology Preview
294  */
295 U_INTERNAL void * U_EXPORT2
296 uplug_getLibrary(UPlugData *plug);
297 
298 /**
299  * Return the plugin-specific context data.
300  * @param plug plugin data handle
301  * @return the context, or NULL if not set
302  * @internal ICU 4.4 Technology Preview
303  */
304 U_INTERNAL void * U_EXPORT2
305 uplug_getContext(UPlugData *plug);
306 
307 /**
308  * Set the plugin-specific context data.
309  * @param plug plugin data handle
310  * @param context new context to set
311  * @internal ICU 4.4 Technology Preview
312  */
313 U_INTERNAL void U_EXPORT2
314 uplug_setContext(UPlugData *plug, void *context);
315 
316 
317 /**
318  * Get the configuration string, if available.
319  * The string is in the platform default codepage.
320  * @param plug plugin data handle
321  * @return configuration string, or else null.
322  * @internal ICU 4.4 Technology Preview
323  */
324 U_INTERNAL const char * U_EXPORT2
325 uplug_getConfiguration(UPlugData *plug);
326 
327 /**
328  * Return all currently installed plugins, from newest to oldest
329  * Usage Example:
330  * \code
331  *    UPlugData *plug = NULL;
332  *    while(plug=uplug_nextPlug(plug)) {
333  *        ... do something with 'plug' ...
334  *    }
335  * \endcode
336  * Not thread safe- do not call while plugs are added or removed.
337  * @param prior pass in 'NULL' to get the first (most recent) plug,
338  *  otherwise pass the value returned on a prior call to uplug_nextPlug
339  * @return the next oldest plugin, or NULL if no more.
340  * @internal ICU 4.4 Technology Preview
341  */
342 U_INTERNAL UPlugData* U_EXPORT2
343 uplug_nextPlug(UPlugData *prior);
344 
345 /**
346  * Inject a plugin as if it were loaded from a library.
347  * This is useful for testing plugins.
348  * Note that it will have a 'NULL' library pointer associated
349  * with it, and therefore no llibrary will be closed at cleanup time.
350  * Low level plugins may not be able to load, as ordering can't be enforced.
351  * @param entrypoint entrypoint to install
352  * @param config user specified configuration string, if available, or NULL.
353  * @param status error result
354  * @return the new UPlugData associated with this plugin, or NULL if error.
355  * @internal ICU 4.4 Technology Preview
356  */
357 U_INTERNAL UPlugData* U_EXPORT2
358 uplug_loadPlugFromEntrypoint(UPlugEntrypoint *entrypoint, const char *config, UErrorCode *status);
359 
360 
361 /**
362  * Inject a plugin from a library, as if the information came from a config file.
363  * Low level plugins may not be able to load, and ordering can't be enforced.
364  * @param libName DLL name to load
365  * @param sym symbol of plugin (UPlugEntrypoint function)
366  * @param config configuration string, or NULL
367  * @param status error result
368  * @return the new UPlugData associated with this plugin, or NULL if error.
369  * @internal ICU 4.4 Technology Preview
370  */
371 U_INTERNAL UPlugData* U_EXPORT2
372 uplug_loadPlugFromLibrary(const char *libName, const char *sym, const char *config, UErrorCode *status);
373 
374 /**
375  * Remove a plugin.
376  * Will request the plugin to be unloaded, and close the library if needed
377  * @param plug plugin handle to close
378  * @param status error result
379  * @internal ICU 4.4 Technology Preview
380  */
381 U_INTERNAL void U_EXPORT2
382 uplug_removePlug(UPlugData *plug, UErrorCode *status);
383 #endif  /* U_HIDE_INTERNAL_API */
384 
385 #endif /* UCONFIG_ENABLE_PLUGINS */
386 
387 #endif /* _ICUPLUG */
388 
389