Tcl_RegisterConfig(3)
Tcl_RegisterConfig(3)Tcl Library Procedures Tcl_RegisterConfig(3)
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NAME
Tcl_RegisterConfig - procedures to register embedded confi-
guration information
SYNOPSIS
#include <tcl.h>
void
Tcl_RegisterConfig(interp, pkgName, configuration, valEncoding)
ARGUMENTS
Tcl_Interp *interp (in) Refers to the inter-
preter the embedded
configuration infor-
mation is registered
for. Must not be
NULL.
const char *pkgName (in) Contains the name of
the package regis-
tering 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 sig-
naled 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 configura-
tion values as ASCII
string. This means
that this informa-
tion is in UTF-8
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Tcl_RegisterConfig(3)Tcl Library Procedures Tcl_RegisterConfig(3)
too. Must not be
NULL.
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DESCRIPTION
The function described here has its base in TIP 59 and pro-
vides extensions with support for the embedding of confi-
guration information into their binary library and the gen-
eration of a Tcl-level interface for querying this informa-
tion.
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 configura-
tion information, third, a pointer to an array of struc-
tures, 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
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
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Tcl_RegisterConfig(3)Tcl Library Procedures Tcl_RegisterConfig(3)
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 Last change: 8.4 3
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