decoder.h

/**
 * DO NOT MODIFY THIS FILE. IT WILL NOT BE COLLECTED
 */

#pragma once
#include <stdbool.h>
#include <stdio.h>

/**
 * Takes a char c and int index as input. 
 * Extracts the bit at the input index from the char c. The 0 index
 * refers to the LSB, so for example, index 2 should extract the 3rd
 * least significant bit.
 *
 * @param c the char to extract a bit from
 * @param index the index of the bit to extract
 * @returns the value of the bit at index in c
 */
int extractBit(char c, int index);

/**
 * Takes a 6 character array as input and returns the corresponding
 * char from MAPPING that is indexed by the binary ASCII string b. 
 * For example, if b = "010101", then the char that is mapped to it is 
 * in MAPPING, index 1*16 + 1*4 + 1*1 = 21.
 *
 * @param b a pointer to a 6 character array, with ASCII '1's and '0's
 * @returns the corresponding character from MAPPING
 */
char decodeChar(char *b);

/**
 * Takes a FILE handle in as input (corresponding to
 * an encoded file) and reads the file, char by char. The
 * bit at the input index of each char is extracted (by calling
 * extractBit). The least significant bit is in index 0.
 *
 * For each character, if the extracted bit is 0, output ASCII '0' to
 * the output file. If the extracted bit is 1, output ASCII
 * '1' to the output file.
 *
 * @param in the input file handle to read from
 * @param out the output file to write the extracted ASCII binary into
 * @param index the index of the bit to extract from each char
*/
void codeToBinary(FILE *in, FILE *out, int index);

/**
 * Takes a FILE handle in as input (corresponding to a
 * "binary" decoded file) and reads the file, 6 chars at a
 * time. Each 6 chars (all ASCII 0's and 1's) should be read into a
 * char array and decoded into its corresponding char (by calling
 * decodeChar). The resulting chars would be output to the FILE handle
 * pointed to by out.
 *
 * @param in the input file, encoded as ASCII '1's and '0's
 * @Param out the decoded output file (ASCII)
*/
void binaryToText(FILE *in, FILE *out);

/**
 * Reads in a file from the specified input path and outputs a binary decoding to
 * specified bin path and a fully decoded version to specified output path.
 * This should simply open the necessary files, call the above helper functions
 * in the correct sequence, and close the necessary files.
 *
 * @param input the path to the input file
 * @param bin the path to the decoded ASCII binary output file
 * @param output the path to the decoded output file
 * @param index The index of the bit from which binary values should be extracted 
*/
void decodeFile(char* input, char* bin, char* output, int index);