pluginprocess.c File Reference

Source for the pluginprocess library. More...

#include "kdbpluginprocess.h"
#include <kdberrors.h>
#include <kdbinvoke.h>
#include <kdblogger.h>
#include <kdbprivate.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

Include dependency graph for pluginprocess.c:

Functions
void	elektraPluginProcessStart (Plugin *handle, ElektraPluginProcess *pp)
	Start the child process' command loop. More...
int	elektraPluginProcessSend (const ElektraPluginProcess *pp, pluginprocess_t command, KeySet *originalKeySet, Key *key)
	Call a plugin's function in a child process. More...
int	elektraPluginProcessIsParent (const ElektraPluginProcess *pp)
	Check if a given plugin process is the parent or the child process. More...
ElektraPluginProcess *	elektraPluginProcessInit (Key *errorKey)
	Initialize a plugin to be executed in its own process. More...
int	elektraPluginProcessOpen (ElektraPluginProcess *pp, Key *errorKey)
	Call a plugin's open function in a child process. More...
int	elektraPluginProcessClose (ElektraPluginProcess *pp, Key *errorKey)
	Cleanup a plugin process. More...

Detailed Description

Source for the pluginprocess library.

Executes plugins in a separate process via fork and uses a simple communication protocol based on the dump plugin via named pipes.

Copyright

BSD License (see LICENSE.md or https://www.libelektra.org)

Function Documentation

elektraPluginProcessClose()

int elektraPluginProcessClose	(	ElektraPluginProcess *	pp,
		Key *	errorKey
	)

Cleanup a plugin process.

This will decrease the internal counter how often open/close has been called, closing opened pipes when the counter reaches 0. This will not delete the plugin data associated with the handle as it may contain other data out of the scope of this library, so this has to be done manually like

int elektraPluginClose (Plugin * handle, Key * errorKey)
{
        ElektraPluginProcess * pp = elektraPluginGetData (handle);
        if (elektraPluginProcessIsParent (pp)) {
                int result = elektraPluginProcessSend (pp, ELEKTRA_PLUGIN_CLOSE, NULL, errorKey);
                if (elektraPluginProcessClose (pp, errorKey)) elektraPluginSetData (handle, NULL);
                return result;
        }

        // actual plugin functionality to be executed in a child process
        return ELEKTRA_PLUGIN_STATUS_SUCCESS;
}

Parameters

pp	the data structure containing the plugin's process information

Return values

1	if the data structure got cleaned up
0	if the data structure is still used

elektraPluginProcessInit()

ElektraPluginProcess* elektraPluginProcessInit

(

Key *

errorKey

)

Initialize a plugin to be executed in its own process.

This will prepare all the required resources and then fork the current process. After the initialization the child process will typically call the command loop while the parent starts to send commands to it. Also the resulting process information has to be stored for the plugin. In order to allow users to handle custom plugin data this will not automatically call elektraPluginSetData.

Typically called in a plugin's open function like (assuming no custom plugin data):

int elektraPluginOpen (Plugin * handle, Key * errorKey)
{
        ElektraPluginProcess * pp = elektraPluginGetData (handle);
        if (pp == NULL)
        {
                if ((pp = elektraPluginProcessInit (handle, errorKey)) == NULL) return ELEKTRA_PLUGIN_STATUS_ERROR;
                elektraPluginSetData (handle, pp);
                if (!elektraPluginProcessIsParent (pp)) elektraPluginProcessStart (handle, pp);
        }
        if (elektraPluginProcessIsParent (pp)) return elektraPluginProcessOpen (pp, errorKey);

        // actual plugin functionality to be executed in a child process
        return ELEKTRA_PLUGIN_STATUS_SUCCESS;
}

Parameters

handle	the plugin's handle
errorKey	a key where error messages will be set

Return values

NULL	if the initialization failed
a	pointer to the information

elektraPluginProcessIsParent()

int elektraPluginProcessIsParent

(

const ElektraPluginProcess *

pp

)

Check if a given plugin process is the parent or the child process.

Parameters

pp	the data structure containing the plugin's process information

Return values

0	if it's the child process
the	child process' pid otherwise

elektraPluginProcessOpen()

int elektraPluginProcessOpen	(	ElektraPluginProcess *	pp,
		Key *	errorKey
	)

Call a plugin's open function in a child process.

This will increase the internal counter how often open/close has been called, so the opened pipes and forks will not be closed too early.

Parameters

pp	the data structure containing the plugin's process information
errorKey	a key where error messages will be set

Return values

the	return value of the plugin's open function

See also

elektraPluginProcessInit for an example how and where this function is typically used

elektraPluginProcessSend()

int elektraPluginProcessSend	(	const ElektraPluginProcess *	pp,
		pluginprocess_t	command,
		KeySet *	originalKeySet,
		Key *	key
	)

Call a plugin's function in a child process.

This will wrap all the required information to execute the given command in a keyset and send it over to the child process. Then it waits for the child process's answer and copies the result back into the original plugin keyset and plugin key.

Typically called like

int elektraPluginSet (Plugin * handle, KeySet * returned, Key * parentKey)
{
        ElektraPluginProcess * pp = elektraPluginGetData (handle);
        if (elektraPluginProcessIsParent (pp)) return elektraPluginProcessSend (pp, ELEKTRA_PLUGIN_SET, returned, parentKey);

        // actual plugin functionality to be executed in a child process
        return ELEKTRA_PLUGIN_STATUS_SUCCESS;
}

Parameters

pp	the data structure containing the plugin's process information
command	the plugin command that should be executed, e.g. ELEKTRA_PLUGIN_GET
originalKeySet	the original key set that the parent process receives
key	the original key the parent process receives

Return values

ELEKTRA_PLUGIN_STATUS_ERROR	if the child process communication failed
the	called plugin's return value otherwise

See also

elektraPluginProcessIsParent for checking if we are in the parent or child process

elektraPluginProcessStart()

void elektraPluginProcessStart	(	Plugin *	handle,
		ElektraPluginProcess *	pp
	)

Start the child process' command loop.

This will make the child process wait for plugin commands and execute them, returning the result to the parent. This is typically called in a plugin's open function.

Parameters

handle	the plugin's handle
pp	the data structure containing the plugin's process information

See also

elektraPluginProcessInit how to use this function in a Plugins