Small C library to convert from chars to Morse Code and back.

morse.c

#include <ctype.h>
#include <stdlib.h>

#include "morse.h"

/* 
 * Function morse_to_index by cypherpunks on Reddit.
 * See: http://goo.gl/amr6A3
 */
int morse_to_index (const char* str)
{
        unsigned char sum = 0, bit;

        for (bit = 1; bit; bit <<= 1) {
                switch (*str++) {
                case 0:
                        return sum | bit;
                default:
                        return 0;
                case '-':
                        sum |= bit;
                        /* FALLTHROUGH */
                case '.':
                        break;
                }
        }

        return 0;
}

const char* char_to_morse (char c)
{
        if (islower(c))
                c += ('A' - 'a');

        return CHAR_TO_MORSE[(int) c];
}

const char* morse_to_char (const char* str)
{
        return MORSE_TO_CHAR[morse_to_index(str)];
}

morse.h

#ifndef _morse_h
#define _morse_h

static const char* CHAR_TO_MORSE[128] = {
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, "-.-.--", ".-..-.", NULL, NULL, NULL, NULL, ".----.",
        "-.--.", "-.--.-", NULL, NULL, "--..--", "-....-", ".-.-.-", "-..-.",
        "-----", ".----", "..---", "...--", "....-", ".....", "-....", "--...",
        "---..", "----.", "---...", NULL, NULL, "-...-", NULL, "..--..",
        ".--.-.", ".-", "-...", "-.-.", "-..", ".", "..-.", "--.",
        "....", "..", ".---", "-.-", ".-..", "--", "-.", "---",
        ".--.", "--.-", ".-.", "...", "-", "..-", "...-", ".--",
        "-..-", "-.--", "--..", NULL, NULL, NULL, NULL, "..--.-",
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
};

static const char* MORSE_TO_CHAR[128] = {
        NULL, NULL, "E", "T", "I", "N", "A", "M",
        "S", "D", "R", "G", "U", "K", "W", "O",
        "H", "B", "L", "Z", "F", "C", "P", NULL,
        "V", "X", NULL, "Q", NULL, "Y", "J", NULL,
        "5", "6", NULL, "7", NULL, NULL, NULL, "8",
        NULL, "/", NULL, NULL, NULL, "(", NULL, "9",
        "4", "=", NULL, NULL, NULL, NULL, NULL, NULL,
        "3", NULL, NULL, NULL, "2", NULL, "1", "0",
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, ":",
        NULL, NULL, NULL, NULL, "?", NULL, NULL, NULL,
        NULL, NULL, "\"", NULL, NULL, NULL, "@", NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, "'", NULL,
        NULL, "-", NULL, NULL, NULL, NULL, NULL, NULL,
        NULL, NULL, ".", NULL, "_", ")", NULL, NULL,
        NULL, NULL, NULL, ",", NULL, "!", NULL, NULL,
        NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
};

const char* char_to_morse(char);
const char* morse_to_char(const char*);
int morse_to_index (const char*);

#endif