Provided by: critcl_3.3.1+dfsg-1_amd64 
NAME
critcl::class - CriTcl - Code Gen - C Classes
SYNOPSIS
package require Tcl 8.6
package require critcl ?3.2?
package require critcl::class ?1.1?
::critcl::class::define name script
include path
support code
type name
classconstructor body
classdestructor body
constructor body ?postbody?
destructor body
classvariable ctype name ?comment? ?constructor? ?destructor?
classmethod name command arguments body
classmethod name proc arguments resulttype body
classmethod name as funname ?arg...?
insvariable ctype name ?comment? ?constructor? ?destructor?
method name command arguments body
method name proc arguments resulttype body
method name as funname ?arg...?
method_introspection
________________________________________________________________________________________________________________
DESCRIPTION
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::class package. This package provides convenience
commands for advanced functionality built on top of the core.
With it a user wishing to create a C level object with class and instance commands can concentrate on
specifying the class- and instance-variables and -methods in a manner similar to a TclOO class, while all
the necessary boilerplate around it is managed by this package.
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::class::define name script
This is the main command to define a new class name, where name is the name of the Tcl command
representing the class, i.e. the class command. The script provides the specification of the
class, i.e. information about included headers, class- and instance variables, class- and
instance-methods, etc. See the section Class Specification API below for the detailed list of the
available commands and their semantics.
CLASS SPECIFICATION API
Here we documents all class specification commands available inside of the class definition script
argument of ::critcl::class::define.
GENERAL CONFIGURATION
include path
This command specifies the path of a header file to include within the code generated for the
class. This is separate from the support because the generated include directives will be put at
the very beginning of the generated code. This is done to allow the use of the imported
declarations within the instance type, and elsewhere.
Calls to this command are cumulative. It is of course possible to not use this command at all,
for classes not making use of external definitions.
The result is the empty string.
support code
This command specifies supporting C code, i.e. any definitions (types, functions, etc.) needed by
the whole class and not fitting into class- and instance-methods. The code is embedded at global
level, outside of any function or other definition.
Calls to this command are cumulative. It is of course possible to not use this command at all,
for classes not requiring supporting code.
The result of the command is the empty string.
type name
This command specifies the name of an external C type to be used as the type of the instance
structure.
Initialization and release of the structure with the given type are the responsibility of the
user, through constructor and destructor code fragments.
Attention: Using this command precludes the use of regular class- and instance variables. It
further precludes the use of method-introspection as well, as this make use of generated instance-
variables.
If class- and/or instance-variable have to be used in conjunction with an external C type, simply
create and use a class- or instance-variable with that type.
The result of the command is the empty string.
CLASS LIFETIME MANAGEMENT
classconstructor body
This command specifies a C code block surrounding the initialization of the class variables, i.e.
the fields of the class structure. Note that allocation and release of the class structure itself
is done by the system andf not the responsibility of the user.
For the initialization (and release) of a class variable it is recommended to use the constructor
and destructor arguments of the variable's definition (See command classvariable) for this instead
of using a separate classconstructor.
This is an optional command. Using it more than once is allowed too and each use will add another
C code fragment to use during construction. I.e. multiple calls aggregate.
The C code blocks of multiple calls (including the constructors of classvariable definitions) are
executed in order of specification.
The result of the command is the empty string.
The C code in body has access to the following environment:
interp Pointer to the Tcl interpreter (Tcl_Interp*) the class structure will be associated with.
It enables the generation of a Tcl error message should construction fail.
class Pointer to the class structure to initialize.
error A C code label the constructor can jump to should it have to signal a construction failure.
It is the responsibility of the constructor to release any variables already initialized
before jumping to this label. This also why the 'execution in order of specification' is
documented and can be relied on. It gives us the knowledge which other constructors have
already been run and initialized what other fields.
classdestructor body
This command specifies a C code block surrounding the release of the class variables, i.e. the
fields of the class structure. Note that allocation and release of the class structure itself is
done by the system and not the responsibility of the user.
For the initialization (and release) of a class variable it is recommended to use the constructor
and destructor arguments of the variable's definition (See command classvariable) for this instead
of using a separate classconstructor.
This is an optional command. Using it more than once is allowed too and each use will add another
C code fragment to use during construction. I.e. multiple calls aggregate.
The C code blocks of multiple calls (including the constructors of class variable definitions) are
executed in order of specification.
The result of the command is the empty string.
The C code in body has access to the same environment as the class constructor code blocks.
INSTANCE LIFETIME MANAGEMENT
constructor body ?postbody?
This command specifies a C code block surrounding the initialization of the instance variables,
i.e. the fields of the instance structure. Note that allocation and release of the instance
structure itself is done by the system and not the responsibility of the user. On the other hand,
if an external type was specified for the instance structure, then instance variables are not
possible, and the system has no knowledge of the type's structure. In that case it is the
responsibility of the body to allocate and free the structure itself too.
For the initialization (and release) of an instance variable it is recommended to use the
constructor and destructor arguments of the variable's definition (See command insvariable) for
this instead of using a separate constructor.
This is an optional command. Using it more than once is allowed too and each use will add another
C code fragment to use during construction. I.e. multiple calls aggregate.
The C code blocks of multiple calls (including the constructors of instance variable definitions)
are executed in order of specification.
The result of the command is the empty string.
The C code in body has access to the following environment:
interp Pointer to the Tcl interpreter (Tcl_Interp*) the instance structure will be associated
with. It enables the generation of a Tcl error message should construction fail.
instance
Pointer to the instance structure to initialize.
error A C code label the constructor can jump to should it have to signal a construction failure.
It is the responsibility of the constructor to release any variables already initialized
before jumping to this label. This also why the 'execution in order of specification' is
documented and can be relied on. It gives us the knowledge which other constructors have
already been run and initialized what other fields.
The C code in postbody is responsible for construction actions to be done after the primary construction
was done and the Tcl-level instance command was successfully created. It has access to a slightly
different environment:
interp Pointer to the Tcl interpreter (Tcl_Interp*) the instance structure will be associated
with. It enables the generation of a Tcl error message should construction fail.
instance
Pointer to the instance structure to initialize.
cmd The Tcl_Command token of the Tcl-level instance command.
fqn The fully qualified name of the instance command, stored in a Tcl_Obj*.
destructor body
This command specifies a C code block surrounding the release of the instance variables, i.e. the
fields of the instance structure. Note that allocation and release of the instance structure
itself is done by the system and not the responsibility of the user. On the other hand, if an
external type was specified for the instance structure, then instance variables are not possible,
and the system has no knowledge of the type's structure. In that case it is the responsibility of
the body to allocate and free the structure itself too.
For the initialization (and release) of an instance variable it is recommended to use the
constructor and destructor arguments of the variable's definition (See command insvariable) for
this instead of using a separate constructor.
This is an optional command. Using it more than once is allowed too and each use will add another
C code fragment to use during construction. I.e. multiple calls aggregate.
The C code blocks of multiple calls (including the constructors of instance variable definitions)
are executed in order of specification.
The result of the command is the empty string.
The C code in body has access to the following environment:
instance
Pointer to the instance structure to release.
CLASS VARIABLES AND METHODS
classvariable ctype name ?comment? ?constructor? ?destructor?
This command specifies a field in the class structure of the class. Multiple fields can be
specified, and are saved in the order specified.
Attention: Specification of a class variable precludes the use of an external C type for the
instance structure.
Attention: Specification of a class variable automatically causes the definition of an instance
variable named class, pointing to the class structure.
Beyond the basic name and C type of the new variable the definition may also contain a comment
describing it, and C code blocks to initialize and release the variable. These are effectively
local forms of the commands classconstructor and classdestructor. Please read their descriptions
for details regarding the C environment available to the code.
The comment, if specified will be embedded into the generated C code for easier cross-referencing
from generated ".c" file to class specification.
classmethod name command arguments body
This command specifies a class method and the C code block implementing its functionality. This is
the first of three forms. The method is specified like a critcl::ccommand, with a fixed set of C-
level arguments. The body has to perform everything (i.e. argument extraction, checking, result
return, and of course the actual functionality) by itself.
For this the body has access to
class Pointer to the class structure.
interp Pointer to the Tcl interpreter (Tcl_Interp*) the class structure is associated with
objc The number of method arguments.
objv The method arguments, as C array of Tcl_Obj pointers.
The arguments of the definition are only a human readable form of the method arguments and syntax
and are not used in the C code, except as comments put into the generated code. Again, it is the
responsibility of the body to check the number of arguments, extract them, check their types, etc.
classmethod name proc arguments resulttype body
This command specifies a class method and the C code block implementing its functionality. This
is the second of three forms. The method is specified like a critcl::cproc. Contrary to the first
variant here the arguments are computer readable, expected to be in the same format as the
arguments of critcl::cproc. The same is true for the resulttype. The system automatically
generates a wrapper doing argument checking and conversion, and result conversion, like for
critcl::cproc.
The body has access to
class Pointer to the class structure.
interp Pointer to the Tcl interpreter (Tcl_Interp*) the class structure is associated with
... All arguments under their specified names and C types as per their definition.
classmethod name as funname ?arg...?
This command specifies a class method and the C code block implementing its functionality. This is
the third and last of three forms.
The class method is implemented by the external function funname, i.e. a function which is
declared outside of the class code itself, or in a support block.
It is assumed that the first four arguments of that function represent the parameters
class Pointer to the class structure.
interp Pointer to the Tcl interpreter (Tcl_Interp*) the class structure is associated with
objc The number of method arguments.
objv The method arguments, as C array of Tcl_Obj pointers.
Any additional arguments specified will be added after these and are passed into the C code as is,
i.e. are considered to be C expressions.
INSTANCE VARIABLES AND METHODS
insvariable ctype name ?comment? ?constructor? ?destructor?
This command specifies a field in the instance structure of the class. Multiple fields can be
specified, and are saved in the order specified.
Attention: Specification of an instance variable precludes the use of an external C type for the
instance structure.
Attention: Specification of an instance variable automatically causes the definition of an
instance variable of type Tcl_Command, and named cmd, holding the token of the instance command,
and the definition of an instance method named destroy. This implicit instance variable is managed
by the system.
Beyond the basic name and C type of the new variable the definition may also contain a comment
describing it, and C code blocks to initialize and release the variable. These are effectively
local forms of the commands constructor and destructor. Please read their descriptions for details
regarding the C environment available to the code.
The comment, if specified will be embedded into the generated C code for easier cross-referencing
from generated ".c" file to class specification.
method name command arguments body
This command specifies an instance method and the C code block implementing its functionality.
This is the first of three forms. The method is specified like a critcl::ccommand, with a fixed
set of C-level arguments. The body has to perform everything (i.e. argument extraction, checking,
result return, and of course the actual functionality) by itself.
For this the body has access to
instance
Pointer to the instance structure.
interp Pointer to the Tcl interpreter (Tcl_Interp*) the instance structure is associated with
objc The number of method arguments.
objv The method arguments, as C array of Tcl_Obj pointers.
The arguments of the definition are only a human readable form of the method arguments and syntax
and are not used in the C code, except as comments put into the generated code. Again, it is the
responsibility of the body to check the number of arguments, extract them, check their types, etc.
method name proc arguments resulttype body
This command specifies an instance method and the C code block implementing its functionality.
This is the second of three forms. The method is specified like a critcl::cproc. Contrary to the
first variant here the arguments are computer readable, expected to be in the same format as the
arguments of critcl::cproc. The same is true for the resulttype. The system automatically
generates a wrapper doing argument checking and conversion, and result conversion, like for
critcl::cproc.
The body has access to
instance
Pointer to the instance structure.
interp Pointer to the Tcl interpreter (Tcl_Interp*) the instance structure is associated with
... All arguments under their specified names and C types as per their definition.
method name as funname ?arg...?
This command specifies an instance method and the C code block implementing its functionality.
This is the third and last of three forms.
The instance method is implemented by the external function funname, i.e. a function which is
declared outside of the instance code itself, or in a support block.
It is assumed that the first four arguments of that function represent the parameters
instance
Pointer to the instance structure.
interp Pointer to the Tcl interpreter (Tcl_Interp*) the instance structure is associated with
objc The number of method arguments.
objv The method arguments, as C array of Tcl_Obj pointers.
Any additional arguments specified will be added after these and are passed into the C code as is,
i.e. are considered to be C expressions.
method_introspection
This command generates one class- and one instance-method both of which will return a list of the
instance methods of the class, and supporting structures, like the function to compute the
information, and a class variable caching it.
The two methods and the class variable are all named methods.
CONTEXT DEPENDENT INTERACTIONS
This section documents the various interactions between the specification commands. While these are are
all documented with the individual commands here they are pulled together to see at a glance.
[1] If you are using the command type to specify an external C type to use for the instance structure
you are subject to the following constraints and rules:
[1] You cannot define your own instance variables.
[2] You cannot define your own class variables.
[3] You cannot use method_introspection.
[4] You have to allocate and release the instance structure on your own, through constructor
and destructor code blocks.
[2] If you declare class variables you are subject to the following constraints and rules:
[1] You cannot use type.
[2] The system generates an instance variable class for you, which points from instance to
class structure. This makes you also subject to the rules below, for instance variables.
[3] If you declare instance variables (possibly automatic, see above) you are subject to following
constraints and rules:
[1] You cannot use type.
[2] The system generates and manages an instance variable cmd for you, which holds the
Tcl_Command token of the instance command.
[3] The system generates an instance method destroy for you.
[4] The system manages allocation and release of the instance structure for you. You have to
care only about the instance variables themselves.
EXAMPLE
The example shown below is the specification of queue data structure, with most of the method
implementations and support code omitted to keep the size down.
The full implementation can be found in the directory "examples/queue" of the critcl source
distribution/repository.
package require Tcl 8.6
package require critcl 3.2
critcl::buildrequirement {
package require critcl::class ; # DSL, easy spec of Tcl class/object commands.
}
critcl::cheaders util.h
critcl::class::define ::queuec {
include util.h
insvariable Tcl_Obj* unget {
List object unget elements
} {
instance->unget = Tcl_NewListObj (0,NULL);
Tcl_IncrRefCount (instance->unget);
} {
Tcl_DecrRefCount (instance->unget);
}
insvariable Tcl_Obj* queue {
List object holding the main queue
} {
instance->queue = Tcl_NewListObj (0,NULL);
Tcl_IncrRefCount (instance->queue);
} {
Tcl_DecrRefCount (instance->queue);
}
insvariable Tcl_Obj* append {
List object holding new elements
} {
instance->append = Tcl_NewListObj (0,NULL);
Tcl_IncrRefCount (instance->append);
} {
Tcl_DecrRefCount (instance->append);
}
insvariable int at {
Index of next element to return from the main queue
} {
instance->at = 0;
}
support {... queue_peekget, queue_size, etc.}
method clear {} {...}
method destroy {...}
method get as queue_peekget 1
method peek as queue_peekget 0
method put {item ...}
method size {} {
if ((objc != 2)) {
Tcl_WrongNumArgs (interp, 2, objv, NULL);
return TCL_ERROR;
}
Tcl_SetObjResult (interp, Tcl_NewIntObj (queue_size (instance, NULL, NULL, NULL)));
return TCL_OK;
}
method unget {item} {...}
}
package provide queuec 1
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 class, C code, C instance, C object, Embedded C Code, code generator, compile & run, compiler, dynamic
code generation, dynamic compilation, generate package, linker, on demand compilation, on-the-fly
compilation
CATEGORY
Glueing/Embedded C code
COPYRIGHT
Copyright (c) 2011-2024 Andreas Kupries
doc 1.1 critcl::class(3tcl)