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# critcl::emap(n) 1 doc "C Runtime In Tcl (CriTcl)"

## Name

critcl::emap - CriTcl Utilities: Enum en- and decoding

## Table Of Contents

## Synopsis

- package require Tcl 8.4
- package require critcl ?3.1.11?
- package require critcl::emap ?1?

- ::critcl::emap::def name definition ?-nocase?

## Description

Welcome to the C Runtime In Tcl, CriTcl for short, a system to build C extension packages for Tcl on the fly, from C code embedded within Tcl scripts, for all who wish to make their code go faster.

This document is the reference manpage for the critcl::emap package. This package provides convenience commands for advanced functionality built on top of both critcl core and package critcl::iassoc.

C level libraries often use enumerations or integer values to encode information, like the state of a system. Tcl bindings to such libraries now have the task of converting a Tcl representation, i.e. a string into such state, and back. Note here that the C-level information has to be something which already exists. The package does not create these values. This is in contrast to the package critcl::enum which creates an enumeration based on the specified symbolic names.

This package was written to make the declaration and management of such enumerations and their associated conversions functions easy, hiding all attendant complexity from the user.

Its intended audience are mainly developers wishing to write Tcl packages with embedded C code.

This package resides in the Core Package Layer of CriTcl.

## API

::critcl::emap::def name definition ?-nocase?

  This command defines two C functions for the conversion of the named state code into a Tcl string, and vice versa. The underlying mapping tables are automatically initialized on first access, and finalized on interpreter destruction.

  The definition dictionary provides the mapping from the Tcl-level symbolic names of the state to their C expressions (often the name of the macro specifying the actual value). Note here that the C-level information has to be something which already exists. The package does not create these values. This is in contrast to the package critcl::enum which creates an enumeration based on the specified symbolic names.

  Further note that multiple strings can be mapped to the same C expression. When converting to Tcl the first string for the mapping is returned. An important thing to know: If all C expressions are recognizable as integer numbers and their covered range is not too large (at most 50) the package will generate code using direct and fast mapping tables instead of using a linear search.

  If the option -nocase is specified then the encoder will match strings case-insensitively, and the decoder will always return a lower-case string, regardless of the string's case in the definition.

  The package generates multiple things (declarations and definitions) with names derived from name, which has to be a proper C identifier.

  name_encode

    The function for encoding a Tcl string into the equivalent state code. Its signature is

        int name_encode (Tcl_Interp* interp, Tcl_Obj* state, int* result);

    The return value of the function is a Tcl error code, i.e. TCL_OK, TCL_ERROR, etc.

  name_decode

    The function for decoding a state code into the equivalent Tcl strings. Its signature is

        Tcl_Obj* name_decode (Tcl_Interp* interp, int state);

  name.h

    A header file containing the declarations for the two conversion functions, for use by other parts of the system, if necessary.

    The generated file is stored in a place where it will not interfere with the overall system outside of the package, yet also be available for easy inclusion by package files (csources).

  name

    The name of a critcl argument type encapsulating the encoder function for use by critcl::cproc.

  name

    The name of a critcl result type encapsulating the decoder function for use by critcl::cproc.

## Example

The example shown below is the specification for the possible modes of entry (normal, no feedback, stars) used by the Tcl binding to the linenoise library.

    package require Tcl 8.5
    package require critcl 3.1.11
    critcl::buildrequirement {
        package require critcl::emap
    }
    critcl::emap::def hiddenmode {
                no  0 n 0 off 0 false 0 0 0
        all   1 yes 1 y 1 on  1 true  1 1 1
        stars 2
    } -nocase
    # Declarations: hiddenmode.h
    # Encoder:      int      hiddenmode_encode (Tcl_Interp* interp, Tcl_Obj* state, int* result);
    # Decoder:      Tcl_Obj* hiddenmode_decode (Tcl_Interp* interp, int state);
    # ResultType:   hiddenmode
    # ArgumentType: hiddenmode

## Authors

Andreas Kupries

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such at https://github.com/andreas-kupries/critcl. Please also report any ideas for enhancements you may have for either package and/or documentation.

## Keywords

C code, Embedded C Code, Tcl Interp Association, bitmask, bitset, code generator, compile & run, compiler, dynamic code generation, dynamic compilation, flags, generate package, linker, on demand compilation, on-the-fly compilation, singleton

## Category

Glueing/Embedded C code

## Copyright

Copyright © 2011-2015 Andreas Kupries