#define _CRT_SECURE_NO_WARNINGS // used in Visual studio //Include required header files #include #include #include // functions prototypes void computeInputFile_CheckSum(char *filename, int size); void compute_CheckSum(int size, char *inputString, unsigned int long *check); unsigned int long computeinput_BitMask(char *inputString, int checkSumSize); // main function int main(int argc, char *argv[]) { // Declare the string inputfileName to store the name of the file // from the command line argument char *inputfileName = malloc(sizeof(char) * 30); // Declare the variable to store the checksum bit size int checkSumBits; // Check whether the number of command line arguments //are less than 2 then display an error message if (argc < 2) { printf("Error! Insufficient arguments are provided at command line.\n"); printf("At the command line pass the input file name followed by" "the checksum size\n"); } // otherwise, get the arguments from the command line and // compute the checksum for the given file. else { // copy the name of the file into inputfileName strcpy(inputfileName, argv[1]); // convert the second argument into int and store it in // checkSumBits variable checkSumBits = atoi(argv[2]); // check whether the value of the checkSumSizes are 8, 16, or 32 if (checkSumBits != 8 && checkSumBits != 16 && checkSumBits != 32) { printf( "Valid checksum sizes are 8, 16, or 32\n"); } // call the function to compute the checksum with the file name //number of bits computeInputFile_CheckSum(inputfileName, checkSumBits); } // to pause the screen from being closed getchar(); getchar(); return 0; } // computeCheckSum_InputFile() function, accepts a string(char pointer) and // an integer. // This function reads the data from the file, computes the checksum value and // displays the check sum size, check sum value, and the count of characters void computeInputFile_CheckSum(char *filename, int checkSumSize) { // declare a file pointer FILE *fileInput; // declare and initialize the requried variables to the default values int characterValue = 0; int characterCnt = 0; // compute the length of the word int size_of_word = checkSumSize / 8 + 1; // allocate memory to the checksum and sets the variable to zero unsigned int long *checksum = calloc(1, sizeof(unsigned int long)); // allocate memeory for the input char pointer char *inputChar = malloc(sizeof(char) * size_of_word); // declare loop variables int i = 0, j = 0, k = 0; // open the file in read mode fileInput = fopen(filename, "r"); // if fileInput pointer is null, display the error message and // return if (fileInput == NULL) { printf("ERROR! Unable to open the file.\n"); return; } // otherwise, perform the following steps to compute // the checksum and count of characters in the file until // the pointer reaches the end of file while (characterValue != EOF) { // if the remaining of the length of word is 1 then do the // following if (size_of_word - i == 1) { // set the termination character to output inputChar[i] = '\0'; // display the string stored in inputChar printf("%s", inputChar); // call the function compute_CheckSum() to compute the checksum for the // string inputChar and checksum compute_CheckSum(checkSumSize, inputChar, checksum); // increment the j value j++; // reset the value of i to zero i = 0; // condition to check wether the given length of the line(word) // is equal to 80 characters if so, then move the cursor to // newline if (j * (size_of_word - 1) == 80) printf("\n"); } // otherwise, do the following else { // read the character from the fileInput characterValue = fgetc(fileInput); // if the charValue is EOF, then do the following if (characterValue == EOF) { // check whether the checkSumSize is 16 or 32, if so // do the following if (checkSumSize == 16 || checkSumSize == 32) { // condition to check whether the remaining length is not // either one or length of word, then compute the required // values if (size_of_word - i != 1 && size_of_word - i != size_of_word) { // set the k iterator to zero k = 0; // loop unitl the remaining length of word is // either one or length of word while (size_of_word - i != 1 && size_of_word - i != size_of_word) { // set the 'X' value to inputChar at index i inputChar[i] = 'X'; // increment i value i++; // increment the k value k++; } // set the i'th character of inputChar to termination // character inputChar[i] = '\0'; // display the inputChar (string) read from the file printf("%s", inputChar); // call the function compute_CheckSum() to compute the checksum for the // string inputChar and checksum compute_CheckSum(checkSumSize, inputChar, checksum); // increment j value j++; // increment the characterCnt value characterCnt += k - 1; // reset the i value to zero i = 0; // condition to check wether the given length of the line(word) // is equal to 80 characters if so, then move the cursor to // newline if (j * (size_of_word - 1) == 80) printf("\n"); } // otherwise break else break; } // otherwise break else break; } // otherwise, set the charValue to inputChar at index i else inputChar[i] = characterValue; // increment the charterCnt characterCnt++; // increment the i value i++; } } // close the input file fclose(fileInput); //print new line printf("\n"); // Display the computed value printf("%2d bit checksum is %8lx for all %4d chars\n", checkSumSize, *checksum, characterCnt); } // function compute_CheckSum() accepts an int, character pointer and a unsigned int long // variable. This function computes the checksum for the given string value inputString // and returns the value through checksum variable void compute_CheckSum(int checkSumSize, char *inputString, unsigned int long *checksum) { // declare the unsigned int long variable bitMask unsigned int long maskBit; // call the function computeString_BitMask() by passing the // inputString and checkSumSize maskBit = computeinput_BitMask(inputString, checkSumSize); //Caluclate checksum *checksum = maskBit + *checksum; *checksum = *checksum << (64 - checkSumSize); *checksum = *checksum >> (64 - checkSumSize); } // function computeString_BitMask() accepts character pointer and int variable. // This function computes the masked bit value for the given string value inputString // and returns the value of maskedBits unsigned int long computeinput_BitMask(char *inputString, int checkSumSize) { // declare loop variables int i = 0; // declare the unsigned int long variable which holds // masked bits value unsigned int long maskedBits; // set the starting value of inputString(ASCII) into maskedBits maskedBits = inputString[i]; // decrement the checkSumSize by 8 checkSumSize -= 8; // /using while loop until checkSumSize is zero while (checkSumSize != 0) { // compute the value for maskedBits maskedBits = (maskedBits << 8) + inputString[i + 1]; // decrement the checkSumSize by 8 checkSumSize -= 8; // increment the value of i i++; } // return maskedBits value return maskedBits; }