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 /*

 ******************************************************************************

 *

 *   Copyright (C) 2009-2012, International Business Machines

 *   Corporation and others.  All Rights Reserved.

 *

 ******************************************************************************

 *

 *  FILE NAME : icuplug.h

 *

 *   Date         Name        Description

 *   10/29/2009   sl          New.

 ******************************************************************************

 */

 /**

  * \file

  * \brief C API: ICU Plugin API 

  *

  * <h2>C API: ICU Plugin API</h2>

  *

  * <p>C API allowing run-time loadable modules that extend or modify ICU functionality.</p>

  *

  * <h3>Loading and Configuration</h3>

  *

  * <p>At ICU startup time, the environment variable "ICU_PLUGINS" will be 

  * queried for a directory name.  If it is not set, the preprocessor symbol 

  * "DEFAULT_ICU_PLUGINS" will be checked for a default value.</p>

  *

  * <p>Within the above-named directory, the file  "icuplugins##.txt" will be 

  * opened, if present, where ## is the major+minor number of the currently 

  * running ICU (such as, 44 for ICU 4.4, thus icuplugins44.txt)</p>

  *

  * <p>The configuration file has this format:</p>

  *

  * <ul>

  * <li>Hash (#) begins a comment line</li>

  * 

  * <li>Non-comment lines have two or three components:

  * LIBRARYNAME     ENTRYPOINT     [ CONFIGURATION .. ]</li>

  *

  * <li>Tabs or spaces separate the three items.</li>

  *

  * <li>LIBRARYNAME is the name of a shared library, either a short name if 

  * it is on the loader path,  or a full pathname.</li>

  *

  * <li>ENTRYPOINT is the short (undecorated) symbol name of the plugin's 

  * entrypoint, as above.</li>

  *

  * <li>CONFIGURATION is the entire rest of the line . It's passed as-is to 

  * the plugin.</li>

  * </ul>

  *

  * <p>An example configuration file is, in its entirety:</p>

  *

  * \code

  * # this is icuplugins44.txt

  * testplug.dll    myPlugin        hello=world

  * \endcode

  * <p>Plugins are categorized as "high" or "low" level.  Low level are those 

  * which must be run BEFORE high level plugins, and before any operations 

  * which cause ICU to be 'initialized'.  If a plugin is low level but 

  * causes ICU to allocate memory or become initialized, that plugin is said 

  * to cause a 'level change'. </p>

  *

  * <p>At load time, ICU first queries all plugins to determine their level, 

  * then loads all 'low' plugins first, and then loads all 'high' plugins.  

  * Plugins are otherwise loaded in the order listed in the configuration file.</p>

  * 

  * <h3>Implementing a Plugin</h3>

  * \code

  * U_CAPI UPlugTokenReturn U_EXPORT2 

  * myPlugin (UPlugData *plug, UPlugReason reason, UErrorCode *status) {

  *   if(reason==UPLUG_REASON_QUERY) {

  *      uplug_setPlugName(plug, "Simple Plugin");

  *      uplug_setPlugLevel(plug, UPLUG_LEVEL_HIGH);

  *    } else if(reason==UPLUG_REASON_LOAD) {

  *       ... Set up some ICU things here.... 

  *    } else if(reason==UPLUG_REASON_UNLOAD) {

  *       ... unload, clean up ...

  *    }

  *   return UPLUG_TOKEN;

  *  }

  * \endcode

  *

  * <p>The UPlugData*  is an opaque pointer to the plugin-specific data, and is 

  * used in all other API calls.</p>

  *

  * <p>The API contract is:</p>

  * <ol><li>The plugin MUST always return UPLUG_TOKEN as a return value- to 

  * indicate that it is a valid plugin.</li>

  *

  * <li>When the 'reason' parameter is set to UPLUG_REASON_QUERY,  the 

  * plugin MUST call uplug_setPlugLevel() to indicate whether it is a high 

  * level or low level plugin.</li>

  *

  * <li>When the 'reason' parameter is UPLUG_REASON_QUERY, the plugin 

  * SHOULD call uplug_setPlugName to indicate a human readable plugin name.</li></ol>

  * 

  *

  * \internal ICU 4.4 Technology Preview

  */

 #ifndef ICUPLUG_H

 #define ICUPLUG_H

 #include "unicode/utypes.h"

 /* === Basic types === */

 #ifndef U_HIDE_INTERNAL_API

 /**

  * @{

  * Opaque structure passed to/from a plugin. 

  * use the APIs to access it.

  * @internal ICU 4.4 Technology Preview

  */

 struct UPlugData;

 typedef struct UPlugData UPlugData;

 /** @} */

 /**

  * Random Token to identify a valid ICU plugin. Plugins must return this 

  * from the entrypoint.

  * @internal ICU 4.4 Technology Preview

  */

 #define UPLUG_TOKEN 0x54762486

 /**

  * Max width of names, symbols, and configuration strings

  * @internal ICU 4.4 Technology Preview

  */

 #define UPLUG_NAME_MAX              100

 /**

  * Return value from a plugin entrypoint. 

  * Must always be set to UPLUG_TOKEN

  * @see UPLUG_TOKEN

  * @internal ICU 4.4 Technology Preview

  */

 typedef uint32_t UPlugTokenReturn;

 /**

  * Reason code for the entrypoint's call

  * @internal ICU 4.4 Technology Preview

  */

 typedef enum {

     UPLUG_REASON_QUERY = 0,     /**< The plugin is being queried for info. **/

     UPLUG_REASON_LOAD = 1,     /**< The plugin is being loaded. **/

     UPLUG_REASON_UNLOAD = 2,   /**< The plugin is being unloaded. **/

     UPLUG_REASON_COUNT         /**< count of known reasons **/

 } UPlugReason;

 /**

  * Level of plugin loading

  *     INITIAL:  UNKNOWN

  *       QUERY:   INVALID ->  { LOW | HIGH }

  *     ERR -> INVALID

  * @internal ICU 4.4 Technology Preview

  */

 typedef enum {

     UPLUG_LEVEL_INVALID = 0,     /**< The plugin is invalid, hasn't called uplug_setLevel, or can't load. **/

     UPLUG_LEVEL_UNKNOWN = 1,     /**< The plugin is waiting to be installed. **/

     UPLUG_LEVEL_LOW     = 2,     /**< The plugin must be called before u_init completes **/

     UPLUG_LEVEL_HIGH    = 3,     /**< The plugin can run at any time. **/

     UPLUG_LEVEL_COUNT         /**< count of known reasons **/

 } UPlugLevel;

 /**

  * Entrypoint for an ICU plugin.

  * @param plug the UPlugData handle. 

  * @param status the plugin's extended status code.

  * @return A valid plugin must return UPLUG_TOKEN

  * @internal ICU 4.4 Technology Preview

  */

 typedef UPlugTokenReturn (U_EXPORT2 UPlugEntrypoint) (

                   UPlugData *plug,

                   UPlugReason reason,

                   UErrorCode *status);

 /* === Needed for Implementing === */

 /**

  * Request that this plugin not be unloaded at cleanup time.

  * This is appropriate for plugins which cannot be cleaned up.

  * @see u_cleanup()

  * @param plug plugin

  * @param dontUnload  set true if this plugin can't be unloaded

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void U_EXPORT2 

 uplug_setPlugNoUnload(UPlugData *plug, UBool dontUnload);

 /**

  * Set the level of this plugin.

  * @param plug plugin data handle

  * @param level the level of this plugin

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void U_EXPORT2

 uplug_setPlugLevel(UPlugData *plug, UPlugLevel level);

 /**

  * Get the level of this plugin.

  * @param plug plugin data handle

  * @return the level of this plugin

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL UPlugLevel U_EXPORT2

 uplug_getPlugLevel(UPlugData *plug);

 /**

  * Get the lowest level of plug which can currently load.

  * For example, if UPLUG_LEVEL_LOW is returned, then low level plugins may load

  * if UPLUG_LEVEL_HIGH is returned, then only high level plugins may load.

  * @return the lowest level of plug which can currently load

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL UPlugLevel U_EXPORT2

 uplug_getCurrentLevel(void);

 /**

  * Get plug load status

  * @return The error code of this plugin's load attempt.

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL UErrorCode U_EXPORT2

 uplug_getPlugLoadStatus(UPlugData *plug); 

 /**

  * Set the human-readable name of this plugin.

  * @param plug plugin data handle

  * @param name the name of this plugin. The first UPLUG_NAME_MAX characters willi be copied into a new buffer.

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void U_EXPORT2

 uplug_setPlugName(UPlugData *plug, const char *name);

 /**

  * Get the human-readable name of this plugin.

  * @param plug plugin data handle

  * @return the name of this plugin

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL const char * U_EXPORT2

 uplug_getPlugName(UPlugData *plug);

 /**

  * Return the symbol name for this plugin, if known.

  * @param plug plugin data handle

  * @return the symbol name, or NULL

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL const char * U_EXPORT2

 uplug_getSymbolName(UPlugData *plug);

 /**

  * Return the library name for this plugin, if known.

  * @param plug plugin data handle

  * @param status error code

  * @return the library name, or NULL

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL const char * U_EXPORT2

 uplug_getLibraryName(UPlugData *plug, UErrorCode *status);

 /**

  * Return the library used for this plugin, if known.

  * Plugins could use this to load data out of their 

  * @param plug plugin data handle

  * @return the library, or NULL

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void * U_EXPORT2

 uplug_getLibrary(UPlugData *plug);

 /**

  * Return the plugin-specific context data.

  * @param plug plugin data handle

  * @return the context, or NULL if not set

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void * U_EXPORT2

 uplug_getContext(UPlugData *plug);

 /**

  * Set the plugin-specific context data.

  * @param plug plugin data handle

  * @param context new context to set

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void U_EXPORT2

 uplug_setContext(UPlugData *plug, void *context);

 /**

  * Get the configuration string, if available.

  * The string is in the platform default codepage.

  * @param plug plugin data handle

  * @return configuration string, or else null.

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL const char * U_EXPORT2

 uplug_getConfiguration(UPlugData *plug);

 /**

  * Return all currently installed plugins, from newest to oldest

  * Usage Example:

  * \code

  *    UPlugData *plug = NULL;

  *    while(plug=uplug_nextPlug(plug)) {

  *        ... do something with 'plug' ...

  *    }

  * \endcode

  * Not thread safe- do not call while plugs are added or removed.

  * @param prior pass in 'NULL' to get the first (most recent) plug, 

  *  otherwise pass the value returned on a prior call to uplug_nextPlug

  * @return the next oldest plugin, or NULL if no more.

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL UPlugData* U_EXPORT2

 uplug_nextPlug(UPlugData *prior);

 /**

  * Inject a plugin as if it were loaded from a library.

  * This is useful for testing plugins. 

  * Note that it will have a 'NULL' library pointer associated

  * with it, and therefore no llibrary will be closed at cleanup time.

  * Low level plugins may not be able to load, as ordering can't be enforced.

  * @param entrypoint entrypoint to install

  * @param config user specified configuration string, if available, or NULL.

  * @param status error result

  * @return the new UPlugData associated with this plugin, or NULL if error.

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL UPlugData* U_EXPORT2

 uplug_loadPlugFromEntrypoint(UPlugEntrypoint *entrypoint, const char *config, UErrorCode *status);

 /**

  * Inject a plugin from a library, as if the information came from a config file.

  * Low level plugins may not be able to load, and ordering can't be enforced.

  * @param libName DLL name to load

  * @param sym symbol of plugin (UPlugEntrypoint function)

  * @param config configuration string, or NULL

  * @param status error result

  * @return the new UPlugData associated with this plugin, or NULL if error.

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL UPlugData* U_EXPORT2

 uplug_loadPlugFromLibrary(const char *libName, const char *sym, const char *config, UErrorCode *status);

 /**

  * Remove a plugin. 

  * Will request the plugin to be unloaded, and close the library if needed

  * @param plug plugin handle to close

  * @param status error result

  * @internal ICU 4.4 Technology Preview

  */

 U_INTERNAL void U_EXPORT2

 uplug_removePlug(UPlugData *plug, UErrorCode *status);

 #endif  /* U_HIDE_INTERNAL_API */

 #endif