Check in the pristine copy of ICU 4.6...

icu46/source/common/unicode/icuplug.h

Index: icu46/source/common/unicode/icuplug.h
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--- icu46/source/common/unicode/icuplug.h	(revision 0)
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+/*
+******************************************************************************
+*
+*   Copyright (C) 2009-2010, 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 === */
+
+/**
+ * @{
+ * 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI 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_CAPI void U_EXPORT2
+uplug_removePlug(UPlugData *plug, UErrorCode *status);
+
+
+#endif
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