NAME

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

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

C Runtime In Tcl, or CriTcl , is a system for compiling C code embedded in Tcl on the fly and either loading the resulting objects into Tcl for immediate use or packaging them for distribution. Use CriTcl to improve performance by rewriting in C those routines that are performance bottlenecks.

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.

+----------------+
|Applications    |
| critcl         |
| critcl::app    |
+----------------+
*================*
|Core Packages   |
| critcl         |
| critcl::util   |
*================*
+----------------+
|Support Packages|
| stubs::*       |
| md5, platform  |
|  ...           |
+----------------+

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

COPYRIGHT

Copyright (c) 2011-2018 Andreas Kupries