Threaded File Walker

threaded_walker.c

// This code walks through text files which including "marks", calculates average of them in threads

#include <pthread.h>
#include <dirent.h>
#include <regex.h>
#include <stdio.h>

// Walks through all files, counts them and saves the directories to fileNames list
int getFileNames(const char* dir, const char* pattern, const char** * fileNamesOut, short* fileCountOut);
// Error Codes
enum {OK = 0, BADPATTERN, BADOPEN, BADALLOC, THREAD_BADCREATE, THREAD_BADJOIN};
// Opens the file, prints the average of marks in it
void* printAverage(void* fileNamePtr);

int main(int argc, char** argv) {
	printf("Average Calculation\r\n");
	
	do {
		//Taking the folder name or DIR
		printf("\r\nEnter the Folder DIR : ");
		char* folderDir = (char*) malloc(256);  // Buffer for user input, max path is 256 characters
		
		if(folderDir == NULL) {
			printf("Memory allocation failed.");
			return BADALLOC;
		}
		
		gets(folderDir);
		
		if(strcmp(folderDir, "q") == 0) return 0;   // q for quit
		
		//Variables
		char** fileNames = NULL; // List of file directory strings
		short fileCount = 0;
		int status = -1, i; // Error code of getFileNames function
		
		if((status = getFileNames(folderDir, ".txt", &fileNames, &fileCount)) != OK) {
			free(folderDir);
			printf("There was an error trying to read the directory given. Error Code: %d. Try again.", status);
			continue;
		} else if(fileCount == 0) {
			free(folderDir);
			printf("Couldn't find any .txt files in the given directory. Try again.");
			continue;
		}
		
		free(folderDir);  // We don't need folderDir anymore so we free the memory
		// Allocate memory for threads
		pthread_t* threads = malloc(fileCount * sizeof(pthread_t));
		
		if(threads == NULL) {
			printf("\nFailed memory allocation\n");
			return BADALLOC;
		}
		
		// Create threads and print average of files one by one
		for(i = 0; i < fileCount; i++)
			if(pthread_create(&threads[i], NULL, &printAverage, (void*) fileNames[i])) {
				printf("\nCould not create thread\n");
				return THREAD_BADCREATE;
			}
			
		// Join threads, wait functions to finish their work
		for(i = 0; i < fileCount; i++)
			if(pthread_join(threads[i], NULL)) {
				printf("\nCould not join thread\n");
				return THREAD_BADJOIN;
			}
			
		free(threads);
		free(fileNames);
	} while(1);
	
	return 0;
}


// Get all the files in the given directory.
int getFileNames(const char* dir, const char* pattern, const char** * fileNamesOut, short* fileCountOut) {
	struct dirent* entry;
	regex_t reg;
	DIR* d;
	short threadCount = 0, i;
	char** fileNames = NULL;
	unsigned short dirLen = strlen(dir) + 1;
	char lastChar = dir[(dirLen == 1) ? 0 : (dirLen - 2)];
	
	//Fix the user input, add / to the end of DIR if there is not one
	if(dirLen > 1 && lastChar != '\\' && lastChar != '/') {strcat(dir, "/"); dirLen++;}
	
	// Initialize the walker and check for errors
	if(regcomp(&reg, pattern, REG_EXTENDED | REG_NOSUB))
		return BADPATTERN;
		
	if(!(d = opendir(dir)))
		return BADOPEN;
		
	// Walk through all files, count them and save names
	while(entry = readdir(d))
		if(!regexec(&reg, entry->d_name, 0, NULL, 0)) {
			threadCount++;
			// Expand the fileNames list
			fileNames = (char**) realloc(fileNames, threadCount * sizeof(char*));
			
			if(fileNames == NULL) {
				printf("Memory allocation failed.");
				return BADALLOC;
			}
			
			// Allocate memory for the full DIR and save it
			fileNames[threadCount - 1] = (char*) malloc(dirLen + entry->d_namlen);
			strcpy(fileNames[threadCount - 1], dir);
			strcat(fileNames[threadCount - 1], entry->d_name);
		}
		
	closedir(d);
	regfree(&reg);
	//Return the info
	*fileNamesOut = fileNames;
	*fileCountOut = threadCount;
	return OK;
}

// printAverage function - Opens the file, prints average of marks in it
void* printAverage(void* fileNamePtr) {
	char* fileName = (char*) fileNamePtr; // Convert the fileName pointer back to char*
	FILE* fr;
	short lineCount = 0, sum = 0, mark;
	char line[4]; // 4 Characters are enough for a mark <=100
	// Open the file and read it line by line, sum up marks
	fr = fopen(fileName, "rt");
	
	while(fgets(line, 4, fr) != NULL) {
		sscanf(line, "%d", &mark);
		sum += mark;
		lineCount++;
	}
	
	fclose(fr);
	printf("\n\n%s\nAverage : %.2f", fileName, (float) sum / lineCount);
	free(fileNamePtr);  // Free the string-sized memory
	pthread_exit(NULL);
}