/*
 * Copyright (c) 2016-2019 The Khronos Group Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * OpenCL is a trademark of Apple Inc. used under license by Khronos.
 */

#include "icd.h"
#include "icd_envvars.h"

#include <dlfcn.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <dirent.h>
#include <pthread.h>

static pthread_once_t initialized = PTHREAD_ONCE_INIT;

/*
 * 
 * Vendor enumeration functions
 *
 */

// go through the list of vendors in the two configuration files
void khrIcdOsVendorsEnumerate(void)
{
    DIR *dir = NULL;
    struct dirent *dirEntry = NULL;
    char* vendorPath = ICD_VENDOR_PATH;
    char* envPath = NULL;

    khrIcdVendorsEnumerateEnv();

    envPath = khrIcd_secure_getenv("OCL_ICD_VENDORS");
    if (NULL != envPath)
    {
        vendorPath = envPath;
    }

    dir = opendir(vendorPath);
    if (NULL == dir) 
    {
        KHR_ICD_TRACE("Failed to open path %s, continuing\n", vendorPath);
    }
    else
    {
        // attempt to load all files in the directory
        for (dirEntry = readdir(dir); dirEntry; dirEntry = readdir(dir) )
        {
            switch(dirEntry->d_type)
            {
            case DT_UNKNOWN:
            case DT_REG:
            case DT_LNK:
                {
                    const char* extension = ".icd";
                    FILE *fin = NULL;
                    char* fileName = NULL;
                    char* buffer = NULL;
                    long bufferSize = 0;

                    // make sure the file name ends in .icd
                    if (strlen(extension) > strlen(dirEntry->d_name) )
                    {
                        break;
                    }
                    if (strcmp(dirEntry->d_name + strlen(dirEntry->d_name) - strlen(extension), extension) )
                    {
                        break;
                    }

                    // allocate space for the full path of the vendor library name
                    fileName = malloc(strlen(dirEntry->d_name) + strlen(vendorPath) + 1);
                    if (!fileName)
                    {
                        KHR_ICD_TRACE("Failed allocate space for ICD file path\n");
                        break;
                    }
                    sprintf(fileName, "%s%s", vendorPath, dirEntry->d_name);

                    // open the file and read its contents
                    fin = fopen(fileName, "r");
                    if (!fin)
                    {
                        free(fileName);
                        break;
                    }
                    fseek(fin, 0, SEEK_END);
                    bufferSize = ftell(fin);

                    buffer = malloc(bufferSize+1);
                    if (!buffer)
                    {
                        free(fileName);
                        fclose(fin);
                        break;
                    }
                    memset(buffer, 0, bufferSize+1);
                    fseek(fin, 0, SEEK_SET);
                    if (bufferSize != (long)fread(buffer, 1, bufferSize, fin) )
                    {
                        free(fileName);
                        free(buffer);
                        fclose(fin);
                        break;
                    }
                    // ignore a newline at the end of the file
                    if (buffer[bufferSize-1] == '\n') buffer[bufferSize-1] = '\0';

                    // load the string read from the file
                    khrIcdVendorAdd(buffer);

                    free(fileName);
                    free(buffer);
                    fclose(fin);
                }
                break;
            default:
                break;
            }
        }

        closedir(dir);
    }

    if (NULL != envPath)
    {
        khrIcd_free_getenv(envPath);
    }
}

// go through the list of vendors only once
void khrIcdOsVendorsEnumerateOnce(void)
{
    pthread_once(&initialized, khrIcdOsVendorsEnumerate);
}

/*
 * 
 * Dynamic library loading functions
 *
 */

// dynamically load a library.  returns NULL on failure
void *khrIcdOsLibraryLoad(const char *libraryName)
{
    return dlopen (libraryName, RTLD_NOW);
}

// get a function pointer from a loaded library.  returns NULL on failure.
void *khrIcdOsLibraryGetFunctionAddress(void *library, const char *functionName)
{
    return dlsym(library, functionName);
}

// unload a library
void khrIcdOsLibraryUnload(void *library)
{
    dlclose(library);
}