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.
- const 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.
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 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 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