147 lines
3.8 KiB
C
147 lines
3.8 KiB
C
/*
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Vigenere Cipher encoder / decoder demo
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And an excuse to play around with EEPROM memory
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*/
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#include "vigenereCipher.h"
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// -------- Functions --------- //
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void printFromEEPROM(char *eepromString) {
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uint8_t letter;
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do {
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letter = eeprom_read_byte((uint8_t *) eepromString);
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transmitByte(letter);
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eepromString++;
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} while (letter);
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}
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void enterText(char text[]) {
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uint8_t i = 0;
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char letter;
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do {
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letter = receiveByte();
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transmitByte(letter); /* echo */
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text[i] = letter;
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i++;
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} while (!(letter == '\r') && (i < (MAX_TEXT_LENGTH - 1)));
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text[i - 1] = 0;
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}
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void displayCodes(void) {
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uint8_t i;
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for (i = 0; i < 4; i++) {
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transmitByte(' ');
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transmitByte('0' + i);
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printString(": ");
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printFromEEPROM(codePointers[i]);
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printString("\r\n");
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}
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}
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void changeCode(char codeBuffer[]) {
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char input;
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char *codeAddress;
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printString(" -- Choose code phrase to replace:\r\n");
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do {
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displayCodes();
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input = receiveByte();
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} while ((input < '0') || (input > '3'));
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codeAddress = codePointers[input - '0'];
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printString(" -- Enter new code: ");
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enterText(codeBuffer);
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eeprom_update_block(codeBuffer, codeAddress, CODE_LEN);
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}
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void selectCode(char code[]) {
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char input;
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char *codeAddress;
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printFromEEPROM(promptSelectCode);
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do {
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displayCodes();
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input = receiveByte();
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} while ((input < '0') || (input > '3'));
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codeAddress = codePointers[input - '0'];
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eeprom_read_block(code, codeAddress, CODE_LEN);
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}
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void encodeVigenere(char text[], char code[]) {
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uint8_t codePosition = 0;
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uint8_t textPosition = 0;
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do {
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if (code[codePosition] == 0) { /* loop when at end of code phrase */
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codePosition = 0;
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}
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text[textPosition] += code[codePosition] - 32;
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if (text[textPosition] > 126) {
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text[textPosition] -= 95;
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} /* keeps within printing characters */
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codePosition++; /* and move on to the next */
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textPosition++;
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} while (text[textPosition]); /* until zero at the end of string */
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}
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void decodeVigenere(char text[], char code[]) {
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uint8_t codePosition = 0;
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uint8_t textPosition = 0;
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do {
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if (code[codePosition] == 0) {
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codePosition = 0;
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}
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if (code[codePosition] > text[textPosition]) {
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text[textPosition] += 95;
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} /* keeps within printing characters */
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text[textPosition] -= code[codePosition] - 32;
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codePosition++;
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textPosition++;
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} while (text[textPosition]);
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}
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int main(void) {
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// -------- Inits --------- //
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char textBuffer[MAX_TEXT_LENGTH];
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char codeString[CODE_LEN];
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char input;
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initUSART();
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// ------ Event loop ------ //
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while (1) {
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// Menu
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printFromEEPROM(welcomeString);
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printFromEEPROM(promptText);
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printString(textBuffer);
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printString("\r\n");
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printFromEEPROM(promptCode);
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printString(codeString);
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printString("\r\n\r\n ---------------------\r\n");
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printFromEEPROM(menuEnterText);
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printFromEEPROM(menuCodeText);
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printFromEEPROM(menuChangeCode);
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printFromEEPROM(menuEncode);
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printFromEEPROM(menuDecode);
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input = receiveByte();
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switch (input) {
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case 'e': // encode
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encodeVigenere(textBuffer, codeString);
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break;
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case 'd': // decode
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decodeVigenere(textBuffer, codeString);
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break;
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case 'n': // new text
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printFromEEPROM(promptTypeText);
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enterText(textBuffer);
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break;
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case 'c': // choose code
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selectCode(codeString);
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break;
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case 'x': // change code
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changeCode(codeString);
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break;
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}
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} /* End event loop */
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return 0; /* This line is never reached */
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}
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