---
name: "critcl_emap"
section: "3tcl"
platform: "linux"
package: "critcl"
version: "3.3.1+dfsg-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/critcl_emap"
---

# critcl\_emap(3tcl)

CriTcl - Wrap Support - Enum en- and decoding

```

```

## NAME

critcl::emap - CriTcl - Wrap Support - Enum en- and decoding

## SYNOPSIS

package require **Tcl  8.6**

package require **critcl  ?3.2?**

package require **critcl::emap  ?1.3?**

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

```

```

## 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::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.

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

## API

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

  This command defines C functions for the conversion of the *name*d state code into a Tcl string, and vice versa. The underlying mapping tables are automatically initialized on first access (if not fully constant), 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*.

  If the option **-mode** is specified its contents will interpreted as a list of access modes to support.  The two allowed modes are **c** and **tcl**. Both modes can be used together. The default mode is **tcl**.

  The package generates multiple things (declarations and definitions) with names derived from *name*, which has to be a proper C identifier. Some of the things are generated conditional on the chosen *mode*s.

  - *name*\_encode

    The **tcl**-mode 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*\_encode\_cstr

    The **c**-mode function for encoding a C string into the equivalent state code. Its signature is

    ```
    int name_encode_cstr (const char* state);
    ```

    The return value of the function is the encoded state, or -1 if the argument is not a vlaid state.

  - *name*\_decode

    The **tcl**-mode function for decoding a state code into the equivalent Tcl string. Its signature is

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

  - *name*\_decode\_cstr

    The **c**-mode function for decoding a state code into the equivalent C string. Its signature is

    ```
    const char* name_decode_cstr (int state);
    ```

    The return value of the function is the C string for the state, or **NULL** if the *state* argument does not contain a valid state value.

  - *name*.h

    A header file containing the declarations for the 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*

    For mode **tcl** the command registers a new argument-type for **critcl::cproc** with critcl, encapsulating the encoder function.

  - *name*

    For mode **tcl** the command registers a new result-type for **critcl::cproc** with critcl, encapsulating the decoder function.

## 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 8.6
package require critcl 3.2
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 (c) 2011-2024 Andreas Kupries
```