Tcl_RegisterConfig(3) Tcl Library Procedures Tcl_RegisterConfig(3)______________________________________________________________________________NAMETcl_RegisterConfig - procedures to register embedded configuration
information
SYNOPSIS
#include <tcl.h>
void
Tcl_RegisterConfig(interp, pkgName, configuration, valEncoding)
ARGUMENTS
Tcl_Interp *interp (in) Refers to the interpreter the
embedded configuration informa‐
tion is registered for. Must
not be NULL.
const char *pkgName (in) Contains the name of the pack‐
age registering the embedded
configuration as ASCII string.
This means that this informa‐
tion is in UTF-8 too. Must not
be NULL.
Tcl_Config *configuration (in) Refers to an array of Tcl_Con‐
fig entries containing the
information embedded in the
binary library. Must not be
NULL. The end of the array is
signaled by either a key iden‐
tical to NULL, or a key refer‐
ring to the empty string.
const char *valEncoding (in) Contains the name of the encod‐
ing used to store the configu‐
ration values as ASCII string.
This means that this informa‐
tion 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 “generic/tclPkgConfig.c” 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)
