clibs/module

Macros to help define static module structure around C APIs.

Installation

$ clib install clibs/module --save

Usage

#include <clibs/module/require.h>
#include <clibs/module/module.h>
#include <clibs/module/def.h>

// module definition
module(your_module) {
  define(your_module, CLIB_MODULE);
};

// module initializer
int your_module_init(module(your_module) *exports) {
  return 0;
}

// module de-initializer
void your_module_deinit(module(your_module) *exports) {
}

// module exports
exports(your_module) {
  .init = your_module_init,
  .deinit = your_module_deinit,
};

Defining A Module

// the 'clib_module', 'clib_exports', etc macros
#include <clibs/module/module.h>

// defines 'module, exports, defaults, define, require' alias macros
#include <clibs/module/def.h>

enum channel_status {
  CHANNEL_STATUS_ERROR = -1,
  CHANNEL_STATUS_NONE = 0,
  CHANNEL_STATUS_OPEN = 1,
  CHANNEL_STATUS_CLOSED = 2,
};

// creates a module struct with the name 'channel'
// ie: `struct channel_clib_module { };`
module(channel) {
  // this initializes a few fields using the 'CLIB_MODULE'
  // prototype which is the expected prototype for the
  // 'clib_module_require()' function to work
  define(channel, CLIB_MODULE);

  // channel functions
  enum channel_status state;
  int (*open)();
  int (*close)();
  int (*send)(void *buf, size_t size);
  int (*recv)(void *buf, size_t size);
};

Exporting Module Symbols

// creates an exports interface with optional default values
exports(channel) {
  // the module initializer function called exactly once
  .init = channel_init,
  // the module deinitializer function called when free'd with
  // 'cilb_module_free' just before the 'free()' call
  .deinit = channel_deinit,
};

Requiring Module Symbols

module(channel) *channel = require(channel);

Example

Consider a simple logging module that defines and exports a mode property, and info(), debug(), and error() logging functions.

Below is a logger.h file that defines a logger module with a few exports.

logger.h:

#include <clibs/module/require.h>
#include <clibs/module/module.h>
#include <clibs/module/def.h>

enum logger_mode {
  LOGGER_NONE,
  LOGGER_INFO,
  LOGGER_ERROR,
  LOGGER_DEBUG,
};

// Module Type Interface
module(logger) {
  define(logger, CLIB_MODULE);

  enum logger_mode mode;
  void (*info)(char *);
  void (*debug)(char *);
  void (*error)(char *);
};

int
logger_init(module(logger) *exports);

void
logger_deinit(module(logger) *exports);

// Default Module Exports
exports(logger) {
  .mode = LOGGER_NONE,
  .init = logger_init,
  .deinit = logger_deinit,
};

The following logger.c file implements the logger module definition with a few explicit symbols init() and deinit(). These symbols can be set to 0 (NULL) for default behavior.

logger.c:

#include <stdio.h>
#include "logger.h"

int
logger_init(module(logger) *exports) {
  clib_module_init(logger, exports);
  exports->mode = LOGGER_NONE;
  exports->info = logger_info;
  exports->error = logger_error;
  exports->debug = logger_debug;
  return 0;
}

void
logger_deinit(module(logger) *exports) {
  clib_module_deinit(logger);
}

static inline void
logger_info(char *message) {
  if (require(logger)->mode >= LOGGER_INFO) {
    fprintf(stdout, " info: %s\n", message);
  }
}

static inline void
logger_error(char *message) {
  if (require(logger)->mode >= LOGGER_ERROR) {
    fprintf(stderr, "error: %s\n", message);
  }
}

static inline void
logger_debug(char *message) {
  if (require(logger)->mode >= LOGGER_DEBUG) {
    fprintf(stderr, "debug: %s\n", message);
  }
}

Below is a program consumes the logger module.

#include "logger.h"

int
main(void) {
  module(logger) *logger = require(logger);

  logger->mode = LOGGER_DEBUG;
  logger->info("hello");
  logger->error("oops");
  logger->debug("help");

  clib_module_free(logger);
  return 0;
}

API

clibs/module/module.h

clib_module(type)

Gets a reference to the module structure type.

// as a definition
clib_module(module) {
  clib_module_define(module, CLIB_MODULE);
};

// as type
clib_module(module) *exports = require(module);

Source:

#ifndef clib_module
#define clib_module(type) struct __##type##_clib_module
#endif

clib_module_exports(type)

Initializes the exports of a module and scopes its definition.

clib_module_exports(module) {
  clib_module_define(module, CLIB_MODULE);
};

Source:

#ifndef clib_module_exports
#define clib_module_exports(type)                                              \
  typedef clib_module(type) type##_t;                                          \
  static unsigned int __##type##_clib_module_init = 0;                         \
  static clib_module(type) *__##type##_clib_module;                            \
  static clib_module(type) __##type##_clib_module_exports =                    \

#endif

CLIB_MODULE_DEFAULT

The default module field initializer prototype.

clib_module_exports(module) {
  clib_module_defaults(module, CLIB_MODULE_DEFAULT)
}

Source:

#ifndef CLIB_MODULE_DEFAULT
#define CLIB_MODULE_DEFAULT(type)  \
  .name = ""#type,                 \
  .init = 0,                       \
  .deinit = 0                      \

#endif

clib_module_defaults(type, prototype)

Initializes defaults on a module type with a prototype.

clib_module_exports(module) {
  clib_module_defaults(module, CLIB_MODULE_DEFAULT)
};

Source:

#ifndef clib_module_defaults
#define clib_module_defaults(type, prototype) prototype(type)
#endif

clib_module_define(module, prototype)

Defines a module with a prototype's fields intended to be called inside the definition of a module structure.

clib_module(module) {
  clib_module_define(module, CLIB_MODULE);
  char *value;
  void *(function)(void *);
};

Custom prototypes can be used by defining a new macro

#define CUSTOM_PROTOTYPE      \
  CLIB_MODULE                 \
  void *(*function)(void *);  \

clib_module(module) {
  clib_module_define(module, CUSTOM_PROTOTYPE);
};

clib_exports(module) {
  .init = init, .deinit = 0,
};

Source:

#ifndef clib_module_define
#define clib_module_define(module, prototype) prototype(module)
#endif

clib_module_free(module)

Frees a module pointer and calls deinit() right before.

clib_module_free(module)

Source:

#ifndef clib_module_free
#define clib_module_free(module)                                               \
  if (0 != (module)) {                                                         \
    if (0 != (module)->deinit) {                                               \
      (module)->deinit((module));                                              \
    }                                                                          \
    free(module);                                                              \
  }

#endif

clibs/module/require.h

clib_module_require(name)

Returns an allocated pointer a module that should be free'd with clib_module_free().

clib_module(module) *mod = clib_module_require(module);

Source:

#define clib_module_require(name) ({                                           \
  if (0 == __##name##_clib_module_init || 0 == __##name##_clib_module) {       \
    __##name##_clib_module = malloc(sizeof(*__##name##_clib_module));          \
    clib_module_init(name, __##name##_clib_module);                            \
                                                                               \
    memset(                                                                    \
      __##name##_clib_module,                                                  \
      0,                                                                       \
      sizeof(__##name##_clib_module_exports));                                 \
                                                                               \
    memcpy(                                                                    \
      __##name##_clib_module,                                                  \
      &__##name##_clib_module_exports,                                         \
      sizeof(__##name##_clib_module_exports));                                 \
    __##name##_clib_module_init = 1;                                           \
                                                                               \
    if (0 != (__##name##_clib_module)->init) {                                 \
      if (0 != (__##name##_clib_module)->init((__##name##_clib_module))) {     \
        free(__##name##_clib_module);                                          \
        (__##name##_clib_module) = 0;                                          \
      }                                                                        \
    }                                                                          \
  }                                                                            \
                                                                               \
  (__##name##_clib_module);                                                    \
})

clibs/module/def.h

The def.h header file defines a set of alias macros for convenience.

module(type) {
  define(type, CLIB_MODULE);
  char *value;
};

exports(type) {
  defaults(type, CLIB_MODULE_DEFAULT),
  .value = "default value"
};

module(type) *exports = require(type);

Source:

#define defaults(...) clib_module_defaults(__VA_ARGS__)
#define require(...) clib_module_require(__VA_ARGS__)
#define exports(...) clib_module_exports(__VA_ARGS__)
#define module(...) clib_module(__VA_ARGS__)
#define define(...) clib_module_define(__VA_ARGS__)

Tests

Tests can be built and ran by running make test:

$ make test

Or with the clib build command:

$ clib build --force --test

Examples

Examples can be built and ran by running make example/{EXAMPLE}

$ make example/logger
$ make example/main

Or with the clib build command:

$ clib build --force -- example/logger
$ clib build --force -- example/main

License

MIT