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Merge pull request #4471 from atmaxinger/nb-hooks
Basic implementation of "gopts" hook
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,24 @@ | ||
| # Hooks | ||
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| Hooks are central points in the KDB lifecycle, where specialized plugins are called. | ||
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| ## Selecting which Plugin will be Used for a Specific Hook | ||
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| Currently, the names of the plugins are hard-coded. | ||
| This [decision](../decisions/hooks.md) was made, because these plugins are meant to fulfil very specific purposes. | ||
| A symlink replacing the shared library file of the plugin could be used to change the implementation. | ||
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| ## Interface of the hooks | ||
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| If a plugin should be able to act upon a hook, it must export all the functions that the hook requires. | ||
| These exports are of the form `system:/elektra/modules/<plugin name>/exports/hook/<hook name>/<hook function>`. | ||
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| For example, the `gopts` hook only requires the `get` function. A plugin that wants to act upon the `gopts` hook therefore has to export `system:/elektra/modules/<plugin name>/exports/hook/gopts/get`. | ||
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| Other hooks (e.g. `spec`) require multiple exported functions. | ||
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| ## Lifecycle | ||
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| 1. Hooks are initilized within `kdbOpen` after the contract has been processed. This includes loading the plugins. | ||
| 2. The appropriate hooks are called within each `kdbGet` and `kdbSet` call. | ||
| 3. Hooks are deinitialized within `kdbClose`. This includes unloading the plugins. |
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| Original file line number | Diff line number | Diff line change |
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@@ -63,6 +63,7 @@ if (BUILD_SHARED) | |
| backend.c | ||
| kdb.c | ||
| mount.c | ||
| hooks.c | ||
| split.c | ||
| trie.c | ||
| plugin.c | ||
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,190 @@ | ||
| /** | ||
| * @file | ||
| * | ||
| * @brief | ||
| * | ||
| * @copyright BSD License (see LICENSE.md or https://www.libelektra.org) | ||
| */ | ||
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| #include <kdbinternal.h> | ||
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| /** | ||
| * Uninitializes and frees all hooks in the passed KDB handle. | ||
| * | ||
| * @param kdb the KDB handle where the hooks should be freed | ||
| * @param errorKey the key which holds errors and warnings which were issued | ||
| */ | ||
| void freeHooks (KDB * kdb, Key * errorKey) | ||
| { | ||
| if (kdb->hooks.gopts.plugin != NULL) | ||
| { | ||
| elektraPluginClose (kdb->hooks.gopts.plugin, errorKey); | ||
| } | ||
| } | ||
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| static size_t getFunction (Plugin * plugin, const char * functionName, Key * errorKey) | ||
| { | ||
| size_t result = elektraPluginGetFunction (plugin, functionName); | ||
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| if (result == 0) | ||
| { | ||
| ELEKTRA_ADD_INSTALLATION_WARNINGF (errorKey, "Plugin '%s' does not implement function '%s'", plugin->name, functionName); | ||
| } | ||
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| return result; | ||
| } | ||
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| static int initHooksGopts (KDB * kdb, Plugin * plugin, Key * errorKey) | ||
| { | ||
| if (!plugin) | ||
| { | ||
| return -1; | ||
| } | ||
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| kdb->hooks.gopts.plugin = plugin; | ||
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| if ((kdb->hooks.gopts.kdbHookGoptsGet = (kdbHookGoptsGetPtr) getFunction (plugin, "hook/gopts/get", errorKey)) == NULL) | ||
| { | ||
| return -1; | ||
| } | ||
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| return 0; | ||
| } | ||
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| /** | ||
| * Extracts the config for a single plugin from the contract | ||
| * | ||
| * The config must be below system:/elektra/contract/mountglobal/<pluginName> and will be moved to below user:/. | ||
| * It also must contain the key system:/elektra/contract/mountglobal/<pluginName>. | ||
| * | ||
| * @param pluginName The name of the plugin for which the config will be extracted | ||
| * @param contract The contract from which the config is extracted | ||
| */ | ||
| static KeySet * getPluginConfigFromContract (const char * pluginName, const KeySet * contract) | ||
| { | ||
| KeySet * tmpContract = ksDup (contract); | ||
| KeySet * config = ksNew (0, KS_END); | ||
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| Key * mountContractRoot = keyNew ("system:/elektra/contract/mountglobal", KEY_END); | ||
| Key * pluginConfigRoot = keyNew ("user:/", KEY_END); | ||
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| for (elektraCursor it = ksFindHierarchy (tmpContract, mountContractRoot, NULL); it < ksGetSize (tmpContract); it++) | ||
| { | ||
| Key * cur = ksAtCursor (tmpContract, it); | ||
| if (keyIsDirectlyBelow (mountContractRoot, cur) == 1) | ||
| { | ||
| const char * pluginNameOfConfig = keyBaseName (cur); | ||
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| // only handle config for the specified plugin | ||
| // we might be able to replace this check by modifying the key mountContractRoot, | ||
| // but I just copied this function from the previous global plugins implementation | ||
| // and it works for now. | ||
| if (strcmp (pluginName, pluginNameOfConfig) != 0) | ||
| { | ||
| break; | ||
| } | ||
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| KeySet * pluginConfig = ksCut (tmpContract, cur); | ||
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| // increment ref count, because cur is part of pluginConfig and | ||
| // we hold a reference to cur that is still needed (via pluginName) | ||
| keyIncRef (cur); | ||
| ksRename (pluginConfig, cur, pluginConfigRoot); | ||
| ksAppend (config, pluginConfig); | ||
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| // we need to delete cur separately, because it was ksCut() from contract | ||
| // we also need to decrement the ref count, because it was incremented above | ||
| keyDecRef (cur); | ||
| keyDel (cur); | ||
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| --it; | ||
| } | ||
| } | ||
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| keyDel (mountContractRoot); | ||
| keyDel (pluginConfigRoot); | ||
| ksDel (tmpContract); | ||
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| return config; | ||
| } | ||
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| static Plugin * loadPlugin (const char * pluginName, KeySet * global, KeySet * modules, const KeySet * contract, Key * errorKey) | ||
| { | ||
| Key * openKey = keyDup (errorKey, KEY_CP_ALL); | ||
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| KeySet * config = getPluginConfigFromContract (pluginName, contract); | ||
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| Plugin * plugin = elektraPluginOpen (pluginName, modules, config, openKey); | ||
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| if (!plugin) | ||
| { | ||
| ELEKTRA_ADD_INSTALLATION_WARNINGF (errorKey, "Could not load plugin '%s'", pluginName); | ||
| keyCopyAllMeta (errorKey, openKey); | ||
| keyDel (openKey); | ||
| return NULL; | ||
| } | ||
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| plugin->global = global; | ||
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| return plugin; | ||
| } | ||
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| static bool isGoptsEnabledByContract (const KeySet * contract) | ||
| { | ||
| KeySet * dupContract = ksDup (contract); // We need to duplicate because contract is const, and ksLookupByName doesn't take const | ||
| bool isEnabled = ksLookupByName (dupContract, "system:/elektra/contract/mountglobal/gopts", 0) != NULL; | ||
| ksDel (dupContract); | ||
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| return isEnabled; | ||
| } | ||
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| /** | ||
| * Initializes the hooks stored in the passed KDB handle. | ||
| * If the handle already contains initialized hooks, they will be reinitialized, including unloading and loading of their plugins. | ||
| * Parameters @p config and @p contract will be used to determine which hooks to populate. | ||
| * | ||
| * @param kdb the KDB instance where the hooks should be initialized | ||
| * @param config KeySet containing the current config in @p system:/elektra namespace | ||
| * @param modules the current list of loaded modules | ||
| * @param contract the contract passed to @p kdbOpen | ||
| * @param errorKey the key which holds errors and warnings which were issued | ||
| * @return 0 on success, -1 on failure | ||
| */ | ||
| int initHooks (KDB * kdb, const KeySet * config, KeySet * modules, const KeySet * contract, Key * errorKey) | ||
| { | ||
| bool existingError = ksLookupByName (keyMeta (errorKey), "meta:/error", 0) != NULL; | ||
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| if (!existingError) | ||
| { | ||
| // set a dummy value to block errors | ||
| // any errors that occur will be converted into warnings | ||
| keySetMeta (errorKey, "meta:/error", "blocked"); | ||
| } | ||
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| freeHooks (kdb, errorKey); | ||
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| if (isGoptsEnabledByContract (contract) && | ||
| initHooksGopts (kdb, loadPlugin ("gopts", kdb->global, modules, contract, errorKey), errorKey) != 0) | ||
| { | ||
| goto error; | ||
| } | ||
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| if (!existingError) | ||
| { | ||
| // remove dummy error again | ||
| keySetMeta (errorKey, "meta:/error", NULL); | ||
| } | ||
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| return 0; | ||
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| error: | ||
| freeHooks (kdb, errorKey); | ||
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| if (!existingError) | ||
| { | ||
| // remove dummy error again | ||
| keySetMeta (errorKey, "meta:/error", NULL); | ||
| } | ||
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| return -1; | ||
| } |
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