Tcl_RegisterConfig(3)Tcl Library Procedures Tcl_RegisterConfig(3)



     Tcl_RegisterConfig - procedures to register embedded  confi-
     guration information


     #include <tcl.h>

     Tcl_RegisterConfig(interp, pkgName, configuration, valEncoding)


     Tcl_Interp *interp (in)                 Refers to the inter-
                                             preter  the embedded
                                             configuration infor-
                                             mation is registered
                                             for.  Must  not   be

     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

Tcl                     Last change: 8.4                        1

Tcl_RegisterConfig(3)Tcl Library Procedures Tcl_RegisterConfig(3)

                                             too.   Must  not  be


     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-

     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

Tcl                     Last change: 8.4                        2

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

          ::pkgName::pkgconfig list
               Returns a list containing the names of all defined

          ::pkgName::pkgconfig get key
               Returns the configuration  value  associated  with
               the specified key.


     The Tcl_Config structure contains the following fields:

          typedef struct Tcl_Config {
              const char* key;
              const char* value;
          } Tcl_Config;


     embedding, configuration, binary library

Tcl                     Last change: 8.4                        3

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