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# critcl::bitmap(n) 1.0.1 doc "C Runtime In Tcl (CriTcl)"

## Name

critcl::bitmap - CriTcl Utilities: Bitset en- and decoding

## Table Of Contents

## Synopsis

- package require Tcl 8.4
- package require critcl ?3.1.11?
- package require critcl::bitmap ?1.0.1?

- ::critcl::bitmap::def name definition ?exclusions?

## 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::bitmap 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 bit-sets to encode many flags into a single value. Tcl bindings to such libraries now have the task of converting a Tcl representation of such flags (like a list of strings) into such bit-sets, 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 bit-sets 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::bitmap::def name definition ?exclusions?

  This command defines two C functions for the conversion of the named bit-set into Tcl lists, 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 flags 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.

  The optional exlusion list is for the flags/bit-sets for which conversion from bit-set to flag, i.e. decoding makes no sense. One case for such, for example, are flags representing a combination of other flags.

  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 list of strings into the equivalent bit-set. Its signature is

        int name_encode (Tcl_Interp* interp, Tcl_Obj* flags, 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 bit-set into the equivalent Tcl list of strings. Its signature is

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

  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 of the event flags pulled from the draft work on a Tcl binding to Linux's inotify APIs.

    package require Tcl 8.5
    package require critcl 3.1.11
    critcl::buildrequirement {
        package require critcl::bitmap
    }
    critcl::bitmap::def tcl_inotify_events {
        accessed       IN_ACCESS
        all            IN_ALL_EVENTS
        attribute      IN_ATTRIB
        closed         IN_CLOSE
        closed-nowrite IN_CLOSE_NOWRITE
        closed-write   IN_CLOSE_WRITE
        created        IN_CREATE
        deleted        IN_DELETE
        deleted-self   IN_DELETE_SELF
        dir-only       IN_ONLYDIR
        dont-follow    IN_DONT_FOLLOW
        modified       IN_MODIFY
        move           IN_MOVE
        moved-from     IN_MOVED_FROM
        moved-self     IN_MOVE_SELF
        moved-to       IN_MOVED_TO
        oneshot        IN_ONESHOT
        open           IN_OPEN
        overflow       IN_Q_OVERFLOW
        unmount        IN_UNMOUNT
    } {
        all closed move oneshot
    }
    # Declarations:          tcl_inotify_events.h
    # Encoder:      int      tcl_inotify_events_encode (Tcl_Interp* interp, Tcl_Obj* flags, int* result);
    # Decoder:      Tcl_Obj* tcl_inotify_events_decode (Tcl_Interp* interp, int flags);
    # crit arg-type          tcl_inotify_events
    # crit res-type          tcl_inotify_events

## 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