Tcl_RegisterConfig(3) Tcl Library Procedures Tcl_RegisterConfig(3)
NAME
Tcl_RegisterConfig - procedures to register embedded configuration
information
SYNOPSIS
#include <tcl.h>
void
Tcl_RegisterConfig(interp, pkgName, configuration, valEncoding)
ARGUMENTS
Refers to the interpreter the embedded configuration information is
registered for. Must not be NULL. Contains the name of the package
registering the embedded configuration as ASCII string. This means that
this information is in UTF-8 too. Must not be NULL. Refers to an array
of Tcl_Config entries containing the information embedded in the binary
library. Must not be NULL. The end of the array is signaled by either a
key identical to NULL, or a key referring to the empty string. Con-
tains the name of the encoding used to store the configuration values
as ASCII string. This means that this information is in UTF-8 too. Must
not be NULL.
DESCRIPTION
The function described here has its base in TIP 59 and provides exten-
sions with support for the embedding of configuration information into
their binary library and the generation of a Tcl-level interface for
querying this information.
To embed configuration information into their binary library an exten-
sion has to define a non-volatile array of Tcl_Config entries in one if
its source files and then call Tcl_RegisterConfig to register that
information.
Tcl_RegisterConfig takes four arguments; first, a reference to the
interpreter we are registering the information with, second, the name
of the package registering its configuration information, third, a
pointer to an array of structures, and fourth a string declaring the
encoding used by the configuration values.
The string valEncoding contains the name of an encoding known to Tcl.
All these names are use only characters in the ASCII subset of UTF-8
and are thus implicitly in the UTF-8 encoding. It is expected that keys
are legible English text and therefore using the ASCII subset of UTF-8.
In other words, they are expected to be in UTF-8 too. The values asso-
ciated with the keys can be any string however. For these the contents
of valEncoding define which encoding was used to represent the charac-
ters of the strings.
Each element of the configuration array refers to two strings contain-
ing the key and the value associated with that key. The end of the
array is signaled by either an empty key or a key identical to NULL.
The function makes no copy of the configuration array. This means that
the caller has to make sure that the memory holding this array is never
released. This is the meaning behind the word non-volatile used ear-
lier. The easiest way to accomplish this is to define a global static
array of Tcl_Config entries. See the file in the sources of the Tcl
core for an example.
When called Tcl_RegisterConfig will
(1) create a namespace having the provided pkgName, if not yet
existing.
(2) create the command pkgconfig in that namespace and link it to
the provided information so that the keys from _configuration_
and their associated values can be retrieved through calls to
pkgconfig.
The command pkgconfig will provide two subcommands, list and get:
::pkgName::pkgconfig list
Returns a list containing the names of all defined keys.
::pkgName::pkgconfig get key
Returns the configuration value associated with the spec-
ified key.
TCL_CONFIG
The Tcl_Config structure contains the following fields:
typedef struct Tcl_Config {
const char* key;
const char* value; } Tcl_Config;
KEYWORDS
embedding, configuration, binary library
Tcl 8.4 Tcl_RegisterConfig(3)
tcl 8.5.5 - Generated Tue Oct 28 08:50:40 CDT 2008