Tcl_RegisterConfig(3)					      Tcl Library Procedures					     Tcl_RegisterConfig(3)

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NAME

       Tcl_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 information is registered for. Must not be
					       NULL.

       const char *pkgName (in) 	       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.

       Tcl_Config *configuration (in)	       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.

       const char *valEncoding (in)	       Contains  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.
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DESCRIPTION

       The function described here has its base in TIP 59 and provides extensions 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 extension 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 encod-
       ing 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 associated with the keys can be any string however. For	these  the
       contents of valEncoding define which encoding was used to represent the characters of the strings.

       Each  element  of  the  configuration array refers to two strings containing 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
       earlier. 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 specified 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)