source: downloads/tcl8.5.2/doc/RegConfig.3 @ 42

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'\" Copyright (c) 2002 Andreas Kupries <andreas_kupries@users.sourceforge.net>
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'\" See the file "license.terms" for information on usage and redistribution
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'\" RCS: @(#) $Id: RegConfig.3,v 1.8 2007/12/13 15:22:31 dgp Exp $
.so man.macros
.TH Tcl_RegisterConfig 3 8.4 Tcl "Tcl Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Tcl_RegisterConfig \- procedures to register embedded configuration information
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
void
\fBTcl_RegisterConfig\fR(\fIinterp, pkgName, configuration, valEncoding\fR)
.sp
.SH ARGUMENTS
.AS Tcl_Interp *configuration
.AP Tcl_Interp *interp in
Refers to the interpreter the embedded configuration information is
registered for. Must not be NULL.
.AP "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.
.AP 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.
.AP "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.
.BE

.SH DESCRIPTION
.PP
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.
.PP
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 \fBTcl_RegisterConfig\fR to
register that information.
.PP
\fBTcl_RegisterConfig\fR 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.
.PP
The string \fIvalEncoding\fR 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 \fIvalEncoding\fR define which
encoding was used to represent the characters of the strings.
.PP
Each element of the \fIconfiguration\fR 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 \fBno\fR copy of the \fIconfiguration\fR
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 \fBnon-volatile\fR used earlier. The easiest way to accomplish
this is to define a global static array of Tcl_Config entries. See the file
.QW generic/tclPkgConfig.c
in the sources of the Tcl core for an example.
.PP
When called \fBTcl_RegisterConfig\fR will
.IP (1)
create a namespace having the provided \fIpkgName\fR, if not yet
existing.
.IP (2)
create the command \fBpkgconfig\fR 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
\fBpkgconfig\fR.
.PP
The command \fBpkgconfig\fR will provide two subcommands, \fBlist\fR
and \fBget\fR:
.RS
.TP
::\fIpkgName\fR::\fBpkgconfig\fR list
Returns a list containing the names of all defined keys.
.TP
::\fIpkgName\fR::\fBpkgconfig\fR get \fIkey\fR
Returns the configuration value associated with the specified
\fIkey\fR.
.RE
.SH TCL_CONFIG
.PP
The \fBTcl_Config\fR structure contains the following fields:
.PP
.CS
typedef struct Tcl_Config {
    const char* key;
    const char* value;
} Tcl_Config;
.CE
.\" No cross references yet.
.\" .SH "SEE ALSO"
.SH KEYWORDS
embedding, configuration, bianry library