icuSources/common/unicode/icuplug.h

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