ienum

A C Preprocessor API for creating introspectable enums at compile time

About

When creating an introspectable enum (for example, foo with values bar and baz), ienum will define a standard C enum like:

    enum foo {
       foo_bar,
       foo_baz
    };

It will also create a const struct ienum named after your enum (const struct ienum foo in this example) with the following members:

member	description
size_t count	the number of enum values defined (2 in this example)
char *name	the name of the enum ("foo" in this example)
char **names	the names of each value ("bar" and "baz" in this example)

NOTE: ienum is currently limited to creating enumerations whose members start at 0 and go up sequentially.

Using

To create an introspectable enumeration, you will need a .c/.h file pair for it. Note that ienum only supports one introspectable enumeration per file.

Populating the .h file

Your C header file for your enumeration should start with standard multiple-include guards and an #include directive for "ienum_start.h".

    #ifndef FOO_H
    #define FOO_H

    #include "ienum_start.h"

Then, define IENUM_NAME as the C identifier that names your enum, and IENUM_MEMBERS as a whitespace-separated list of value names, surrounded by a call to the IENUM() macro:

    #define IENUM_NAME foo
    #define IENUM_MEMBERS  \
                IENUM(bar) \
                IENUM(baz)

Then, #include the header file "ienum_decl.h" and close your multiple-inclusion guard:

    #include "ienum_decl.h"

    #endif /* !defined(FOO_H) */

Populating the .c file

The C source file for your enumeration only needs to contain two lines. The first includes your header file, and the second includes "ienum_def.h":

    #include "foo.h"
    #include "ienum_def.h"

That's it!

Using your enumeration

Simply include your enumeration's C header file and use the enumeration as you would any other enumeration in code. Remember that their names have been automatically prefixed with your enumeration's name and an underscore, so IENUM(baz) creates foo_baz in enum foo.

Additionally you can use your enumeration's introspection struct to access upper bounds for your enumeration or print out helpful debugging messages:

    #include "foo.h"
    /* ... */
        enum foo x = foo_baz;
        if (x < foo.count)
            printf("%s_%s == %d\n", foo.name, foo.names[x], x)

Optional Configuration

name

description

IENUM_SEP

Define this to a string in your enum's C file before including ienum_decl.h to change how your enum's .names strings are formatted. Without IENUM_SEP, names are just stringifications of whatever identifier was written inside IENUM() in IENUM_MEMBERS. With it, names are prefixed with the enum's name followed by IENUM_SEP. For example, if you #define IENUM_SEP "::" then foo.names[i] will be "foo::baz" instead of just "baz". NOTE: IENUM_SEP can be defined for an entire project using the -D argument to most C compilers, or by including it in a project-wide configuration header.