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How to create a new service
^^^^^^^^^^^^^^^^^^^^^^^^^^^
A "service" is a set of C functions in a structure that a
service dynamic linker uses when a dynamic plugin is loaded.
If you want to export C++ class you need to provide an
extern "C" function that will create a new instance of your class,
and put it in a service.
Data structures are not part of the service structure, but they are part
of the API you create and usually need to be declared in the same
service_*.h file.
To turn a set of functions (foo_func1, foo_func2)
into a service "foo" you need to
1. create a new file include/mysql/service_foo.h
2. the template is
==================================================================
#ifndef MYSQL_SERVICE_FOO_INCLUDED
/* standard GPL header */
/**
@file
*exhaustive* description of the interface you provide.
This file is the main user documentation of the new service
*/
#ifdef __cplusplus
extern "C" {
#endif
extern struct foo_service_st {
int (*foo_func1_type)(...); /* fix the prototype as appropriate */
void (*foo_func2_type)(...); /* fix the prototype as appropriate */
} *foo_service;
#ifdef MYSQL_DYNAMIC_PLUGIN
#define foo_func1(...) foo_service->foo_func1_type(...)
#define foo_func2(...) foo_service->foo_func2_type(...)
#else
int foo_func1_type(...); /* fix the prototype as appropriate */
void foo_func2_type(...); /* fix the prototype as appropriate */
#endif
#ifdef __cplusplus
}
#endif
#define MYSQL_SERVICE_FOO_INCLUDED
#endif
==================================================================
the service_foo.h file should be self-contained, if it needs system headers -
include them in it, e.g. if you use size_t - #include <stdlib.h>
it should also declare all the accompanying data structures, as necessary
(e.g. thd_alloc_service declares MYSQL_LEX_STRING).
3. add the new file to include/Makefile.am (pkginclude_HEADERS)
4. add the new file to include/mysql/services.h
5. increase the minor plugin ABI version in include/mysql/plugin.h
(MYSQL_PLUGIN_INTERFACE_VERSION = MYSQL_PLUGIN_INTERFACE_VERSION+1)
6. add the version of your service to include/service_versions.h:
==================================================================
#define VERSION_foo 0x0100
==================================================================
7. create a new file libservices/foo_service.h using the following template:
==================================================================
/* GPL header */
#include <service_versions.h>
SERVICE_VERSION *foo_service= (void*)VERSION_foo;
==================================================================
8. add the new file to libservices/CMakeLists.txt (MYSQLSERVICES_SOURCES)
9. add the new file to libservices/Makefile.am (libmysqlservices_a_SOURCES)
10. and finally, register your service for dynamic linking in
sql/sql_plugin_services.h
10.1 fill in the service structure:
==================================================================
static struct foo_service_st foo_handler = {
foo_func1,
foo_func2
}
==================================================================
10.2 and add it to the list of services
==================================================================
{ "foo_service", VERSION_foo, &foo_handler }
==================================================================
that's all.
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