critcl_literals3tcl

Usage

Overview

Be welcome to the C Runtime In Tcl (short: CriTcl), a system for embedding and using C code from within Tcl [http://core.tcl-lang.org/tcl] scripts.

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

Many packages will have a fixed set of string constants occuring in one or places. Most of them will be coded to create a new string Tcl_Obj* from a C char* every time the constant is needed, as this is easy to to, despite the inherent waste of memory.

This package was written to make declaration and management of string pools which do not waste memory as easy as the wasteful solution, 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::literals::def name definition ?mode?

This command defines a C function with the given name which provides access to a pool of constant strings with a Tcl interpreter.

The definition dictionary provides the mapping from the C-level symbolic names to the string themselves.

The mode-list configures the output somewhat. The three allowed modes are c, +list and tcl. All modes can be used together. The default mode is tcl. Using mode +list implies tcl as well.

For mode tcl the new function has two arguments, a Tcl_Interp* pointer refering to the interpreter holding the string pool, and a code of type "name_names" (see below), the symbolic name of the literal to return. The result of the function is a Tcl_Obj* pointer to the requested string constant.

For mode c the new function has one argument, a code of type "name_names" (see below), the symbolic name of the literal to return. The result of the function is a const char* pointer to the requested string constant.

For mode +list all of tcl applies, plus an additional function is generated which takes three arguments, in order, a Tcl_Interp* pointer refering to the interpreter holding the string pool, an int holding the size of the last argument, and an array of type "name_names" holding the codes (see below), the symbolic names of the literals to return. The result of the function is a Tcl_Obj* pointer to a Tcl list holding the requested string constants.

The underlying string pool is automatically initialized on first access, and finalized on interpreter destruction.

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

name

The mode tcl function providing access to the string pool. Its signature is

Tcl_Obj* name (Tcl_Interp* interp, name_names literal);

name_list

The mode +list function providing multi-access to the string pool. Its signature is

Tcl_Obj* name_list (Tcl_Interp* interp, int c, name_names* literal);

name_cstr

The mode c function providing access to the string pool. Its signature is

const char* name_cstr (name_names literal);

name_names

A C enumeration type containing the symbolic names of the strings provided by the pool.

name.h

A header file containing the declarations for the accessor functions and the enumeration type, 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

New in version 1.1: For mode tcl the command registers a new result-type for critcl::cproc with critcl, which takes an integer result from the function and converts it to the equivalent string in the pool for the script.

Examples

The example shown below is the specification of the string pool pulled from the draft work on a Tcl binding to Linux's inotify APIs.

package require Tcl 8.6
package require critcl 3.2
critcl::buildrequirement {
    package require critcl::literals
}
critcl::literals::def tcl_inotify_strings {
    w_create	"create"
    w_directory	"directory"
    w_events	"events"
    w_file	"file"
    w_handler	"handler"
    w_remove	"remove"
} {c tcl}
# Declarations: tcl_inotify_strings.h
# Type:         tcl_inotify_strings_names
# Accessor:     Tcl_Obj*    tcl_inotify_strings      (Tcl_Interp*               interp,
#                                                     tcl_inotify_strings_names literal);
# Accessor:     const char* tcl_inotify_strings_cstr (tcl_inotify_strings_names literal);
# ResultType:   tcl_inotify_strings

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, code generator, compile & run, compiler, dynamic code generation, dynamic compilation, generate package, linker, literal pool, on demand compilation, on-the-fly compilation, singleton, string pool

Category

Glueing/Embedded C code