/*******************************************************************/

/*  sltdl: a surrogate ltdl implementation                         */

/*  Copyright (C) 2019 SysDeer Technologies, LLC                   */

/*  Released under the Standard MIT License; see COPYING.SLTDL.    */

/*******************************************************************/

#include <dlfcn.h>

#include <errno.h>

#include <limits.h>

#include <stdlib.h>

#include <string.h>

#include <pthread.h>

#include <sltdl/sltdl.h>

#include "sltdl_core.h"

static const char * lt_dlerror_desc[] = {

	[SLTDL_OK]                              = 0,

	[SLTDL_SYSTEM_ERROR]                    = 0,

	[SLTDL_DLFCN_ERROR]                     = 0,

	[SLTDL_SLTDL_ERROR]                     = "sltdl internal error",

	[SLTDL_DLEXIT_REF_COUNT]                = "lt_dlexit() reference count already zero",

	[SLTDL_MODULE_REF_COUNT]                = "module reference count already zero",

	[SLTDL_MODULE_PTR_INVALID]              = "module handle invalid",

	[SLTDL_PATH_INVALID_FIRST_CHAR]         = "invalid path (does not begin with a forward slash)",

	[SLTDL_PATH_INVALID_SEPARATTOR_CHAR]    = "invalid path (separator character is not a colon)",

	[SLTDL_PATH_INVALID_MARK]               = "invalid path (mark not within range)",

	[SLTDL_PATH_INVALID_LEN]                = "invalid path (string too long)",

	[SLTDL_PATH_NO_ENTRY]                   = "invalid path (not found)",

};

static int             lt_refs  = 0;

static int             lt_error = 0;

static int             lt_errno = 0;

static char *          lt_dlerr = 0;

static pthread_mutex_t lt_lock  = PTHREAD_MUTEX_INITIALIZER;

int lt_dlinit(void)

{

	if (pthread_mutex_lock(&lt_lock))

		return 1;

	lt_refs++;

	pthread_mutex_unlock(&lt_lock);

	return 0;

}

int lt_dlexit(void)

{

	if (pthread_mutex_lock(&lt_lock))

		return 1;

	if (!lt_refs) {

		lt_error = SLTDL_DLEXIT_REF_COUNT;

		pthread_mutex_unlock(&lt_lock);

		return 1;

	}

	lt_refs--;

	pthread_mutex_unlock(&lt_lock);

	return 0;

}

void lt_slock(void)

{

	int locked;

	do {

		locked = pthread_mutex_lock(&lt_lock);

	} while (locked);

}

int lt_sunlock(int ret, int error)

{

	if (error ==  0) {

		pthread_mutex_unlock(&lt_lock);

		return 0;

	}

	if ((error < 0) || (error >= SLTDL_ERROR_CAP)) {

		error = SLTDL_SLTDL_ERROR;

	} else if (error == SLTDL_SYSTEM_ERROR) {

		lt_errno = errno;

	} else if (error == SLTDL_DLFCN_ERROR) {

		if (lt_dlerr)

			free(lt_dlerr);

		lt_dlerr = strdup(dlerror());

	}

	lt_error = error;

	pthread_mutex_unlock(&lt_lock);

	return ret;

}

const char * lt_dlerror(void)

{

	const char * errdesc;

	lt_slock();

	switch (lt_error) {

		case SLTDL_OK:

			errdesc = 0;

			break;

		case SLTDL_SYSTEM_ERROR:

			errdesc = strerror(lt_errno);

			break;

		case SLTDL_DLFCN_ERROR:

			errdesc = lt_dlerr;

			break;

		default:

			errdesc = lt_dlerror_desc[lt_error];

			break;

	}

	lt_error = 0;

	lt_sunlock(0,0);

	return errdesc;

}