icuSources/common/unicode/icuplug.h

   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 || defined(U_IN_DOXYGEN)
 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