Iterate through directory in C

headless.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>
#include <dirent.h>
#include <string.h>
#include <sys/stat.h>

#define MAX_LENGTH 256
//Ben

int CountNumberOfFiles(char *path)
{
	int result = 0;
	DIR *directory = opendir(path);
	assert(directory != NULL);
	
	struct dirent *directoryEntry;
	while((directoryEntry = readdir(directory)) != NULL)
	{
		if(directoryEntry->d_name[0] != '.')
		{
			int fileNameLength = (int)sizeof(directoryEntry->d_name);
			assert(fileNameLength <= MAX_LENGTH);
			result++;
		}
	}
	
	closedir(directory);
	return result;
}

void PrintFileNames(char **fileNames, int fileCount)
{
	for(int i = 0; i < fileCount; i++)
	{
		printf("%s\n", fileNames[i]);
	}
}

void DestroyFileNames(char **fileNames, int fileCount)
{
	for(int i = 0; i < fileCount; i++)
	{
		free(fileNames[i]);
	}
	free(fileNames);
}

void SortFileNames(char **fileNames, int fileCount)
{
	char temporary[MAX_LENGTH] = {0};
	for(int k = 0; k < fileCount; k++)
	{
		for(int j = k + 1; j < fileCount; j++)
		{
			if(strcasecmp(fileNames[k], fileNames[j]) > 0)
			{
				strcpy(temporary, fileNames[k]);
				strcpy(fileNames[k], fileNames[j]);
				strcpy(fileNames[j], temporary);
				memset(temporary,0,MAX_LENGTH);	
			}	
		}
	}
}


char **GetFileNames(char *path, int *fileCount)
{
	//Count files and ensure length <= 256
	*fileCount = CountNumberOfFiles(path);
	
	//Array to store file names
	char **result = malloc(*fileCount * sizeof(char*));for(int i = 0; i < *fileCount; i++){result[i] = calloc(MAX_LENGTH, sizeof(char));}
	
	//Get file names
	DIR *directory = opendir(path);
	assert(directory != NULL);
	struct dirent *directoryEntry;
	int currentIndex = 0;
	while((directoryEntry = readdir(directory)) != NULL){if(directoryEntry->d_name[0] != '.'){for(int i = 0; i < MAX_LENGTH; i++){result[currentIndex][i] = directoryEntry->d_name[i];}currentIndex++;}}
	
	//Sort array
	SortFileNames(result, *fileCount);
		
	closedir(directory);
	return result;
}

char *CreateStorageDirectory(char *path)
{
	char outputFolder[MAX_LENGTH] = {0};
	snprintf(outputFolder, sizeof(outputFolder), "%s_Headless",path);
	DIR *directory = opendir(outputFolder);
	if(directory == NULL)
	{
		int outputFolderCreationSuccess = mkdir(outputFolder,0777);
		assert(outputFolderCreationSuccess == 0);
	}
	else
	{
		closedir(directory);
	}
	char *result = calloc(MAX_LENGTH, sizeof(char));
	for(int i = 0; i < MAX_LENGTH; i++){result[i] = outputFolder[i];}
	return result;
}

int FindFileSize(char *fileName)
{
	int result = 0;
	FILE *fp = fopen(fileName, "rb");assert(fp != NULL);
	fseek(fp, 0L, SEEK_END);
	result = ftell(fp);
	rewind(fp);
	fclose(fp);
	return result;
}

double CalculateEntropy(int *frequencies, int max)
{
	double sum = (double) max;
	double entropy = 0;
	for(int i = 0 ; i < MAX_LENGTH; i++)
	{
		double probability = ((double)frequencies[i])/ sum;
		if(probability > 0)
		{
			entropy += probability * log2(probability);
		}
	}
	return -entropy;
	//printf("(%.3f)\n",-entropy);
}

int FindHeaderSize(char *fileName)
{
	int result = 0;
	int frequencies[MAX_LENGTH] = {0};
	FILE *fp = fopen(fileName, "rb");assert(fp != NULL);
	int c = 0;
	long count = 0;
	int j = 1;
	double entropy = 0;
	while((c = fgetc(fp)) != EOF)
	{
		frequencies[c] += 1;
		if(count == (1L << j))
		{
			entropy = CalculateEntropy(frequencies,count);
			if(entropy >= 7.9){break;}
			//printf("(%d: %ld %.1f)\n",j,count,entropy);
			j++;
			
		}
		count++;
	}
	//printf("(%d: %ld)\n",j,count);
	fclose(fp);
	result = j-1;
	if(result < 0){result = 0;}
	return result;
}

int StoreFile(char *inputFileName, int headerSize, FILE *header, FILE* output)
{
	printf("%s\n",inputFileName);
	FILE *fp = fopen(inputFileName, "rb"); assert(fp != NULL);
	int c = 0;
	long count = 0;
	assert(headerSize < 256);
	unsigned char firstByte = (unsigned char) headerSize;
	fwrite(&firstByte, 1 , sizeof(unsigned char), header);
	while((c = fgetc(fp)) != EOF)
	{
		if(count == (1L << headerSize))
		{
			printf("%ld %dZ",count,headerSize);
			break;
		}
		fputc(c, header);
		count++;
	}
	while((c = fgetc(fp)) != EOF)
	{
		fputc(c, output);
	}
	fclose(fp);
}

void EncodeFolder(char *outputFolder, char *path, char **fileNames, int fileCount)
{
	//printf("Folder name: %s\n",outputFolder);
	char headerDataName[MAX_LENGTH] = {0};
	char outputFileName[MAX_LENGTH] = {0};
	char inputFileName[MAX_LENGTH] = {0};
	
	snprintf(headerDataName, sizeof(headerDataName), "%s/%s.headers",outputFolder,path);
	
	//printf("Folder name: %s\n",offsetsName);
	FILE *header  = fopen(headerDataName, "wb");assert(header != NULL);
	
	
	int fileSize = 0;
	int headerSize = 0;
	for(int i = 0; i < fileCount; i++)
	{
		snprintf(inputFileName, sizeof(inputFileName), "%s/%s",path, fileNames[i]);
		snprintf(outputFileName, sizeof(outputFileName), "%s_Headless/%s.headless",path,fileNames[i]);
		FILE *output = fopen(outputFileName, "wb");assert(output != NULL);
		headerSize = FindHeaderSize(inputFileName);
		printf("(%d) ", headerSize);
		StoreFile(inputFileName,headerSize, header, output);
		memset(inputFileName,0,MAX_LENGTH);
		memset(outputFileName,0,MAX_LENGTH);
		fclose(output);
	}
	
	fclose(header);
	
}

int main()
{
	char *path="Pics";assert(path[0]!= '.');
	int fileCount = 0;
	
	char **fileNames = GetFileNames(path, &fileCount);assert(fileNames != NULL);

	char *outputFolder = CreateStorageDirectory(path);	
	EncodeFolder(outputFolder,path, fileNames, fileCount);
	DestroyFileNames(fileNames, fileCount);
	free(outputFolder);
	return 0;
}
//Buford, Lawrencville Georgia