Write a program that reads the messages contained in the file message_tx.txt into a 640x480 BMP file named bbc_packet.bmp. Each line in the text file should be treated as a separate message.

#include "dirtyd.h"

#include "GLOWWORM.h"

#include "MyBMP.h"

#define OUT_BMPFILENAME "HW06_PR01.bmp"

#include #include

#define BBC_PACKET_LENGTH_BYTES (1024) #define BBC_MESSAGE_LENGTH_BYTES ( 32) // bytes, not bits #define BBC_CHECKSUM_BITS ( 8) // bits

#define BBC_PACKET_LENGTH_BITS (8 * BBC_PACKET_LENGTH_BYTES) #define BBC_MESSAGE_LENGTH_BITS (8 * BBC_MESSAGE_LENGTH_BYTES)

#define isSet(c,b) ((c) & (1 << (b)))

#define TASKPRINT (!TRUE) #define TASK(s) if(TASKPRINT) printf("%s ", (s))

#define WIDTH (640) #define HEIGHT (480)

#define fileREAD "message_tx.txt"

//#define DEBUG_ON #ifdef DEBUG_ON #define DEBUG(s) s #else #define DEBUG(s) #endif

uint8_t *bbc_encode_byte(GLOWWORM *gw, uint8_t *packet, uint8_t c, MyBMP *bmp) { for (int bit = 7; bit >= 0; bit--) { uint8_t bitValue = isSet(c, bit); uint64_t hash = GLOWWORM_addBit(gw, !!bitValue); uint32_t chip = hash % BBC_PACKET_LENGTH_BITS; printf("%c[%i] = %u (chip = %u) ", c, bit, !!bitValue, chip); packet[chip] = TRUE; if (!!bitValue == 1){ MyBMP_drawPixel(bmp, chip/WIDTH, chip%WIDTH, 0, 0, 0); // MyBMP_drawPixel(bmp, chip%WIDTH, chip%HEIGHT, 255, 255, 255); // MyBMP_drawCircle(bmp, chip%WIDTH, chip%HEIGHT, 5, // 0, 0, 0, 1); printf("%i and %i ", chip/WIDTH, chip%WIDTH); }else { MyBMP_drawPixel(bmp, chip/WIDTH, chip%WIDTH, 255, 255, 255); } //packet[GLOWWORM_addBit(gw, isSet(c,bit)) % (BBC_PACKET_LENGTH_BITS)] = TRUE; } return packet; }

uint8_t *bbc_encode(uint8_t *packet, uint8_t *s, MyBMP *bmp) { int byte = 0;

if (NULL == packet) { TASK("Create packet (1 byte per bit for convenience)"); packet = (uint8_t *) malloc(BBC_PACKET_LENGTH_BITS * sizeof(uint8_t)); if (!packet) { printf("Failed to allocate packet -- abort! "); exit(EXIT_FAILURE); } for (int i = 0; i < BBC_PACKET_LENGTH_BITS; i++) packet[i] = 0; } TASK("Encode bookend marks"); packet[0] = TRUE; packet[BBC_PACKET_LENGTH_BITS - 1] = TRUE;

TASK("Create and Initialize Glowworm"); GLOWWORM *gw = GLOWWORM_new(); GLOWWORM_init(gw); TASK("Encode the message"); while ((byte < BBC_MESSAGE_LENGTH_BYTES) && (NUL != s[byte])) bbc_encode_byte(gw, packet, s[byte++], bmp);

TASK("Encode padding bytes (all zero)"); while (byte++ < BBC_MESSAGE_LENGTH_BYTES) bbc_encode_byte(gw, packet, 0, bmp);

TASK("Encode checksum bits"); for (int bit = 0; bit < BBC_CHECKSUM_BITS; bit++) packet[GLOWWORM_addBit(gw, 0) % BBC_PACKET_LENGTH_BITS] = TRUE; GLOWWORM_del(gw);

return packet; }

uint32_t chipFromHash(uint64_t hash) { return (uint32_t) (hash % BBC_PACKET_LENGTH_BITS); }

void printMessagePrefix(uint8_t *message, int bits) { printf("MSG: "); for (int i = 0; i < bits; i++) printf("%c", message[i]? '1' : '0'); printf(" "); }

void printMessage(uint8_t *message) { DEBUG(printMessagePrefix(message, BBC_MESSAGE_LENGTH_BITS);) char ascii[BBC_MESSAGE_LENGTH_BYTES + 1]; ascii[BBC_MESSAGE_LENGTH_BYTES] = NUL; for (int i = 0; i < BBC_MESSAGE_LENGTH_BYTES; i++) { ascii[i] = 0; for (int b = 0; b < 8; b++) { ascii[i] <<= 1; ascii[i] += message[8*i+b]? 1 : 0; } } printf("MESSAGE: %s ", ascii); }

int bbc_decode(uint8_t *packet) { uint8_t msgBits[BBC_MESSAGE_LENGTH_BITS + BBC_CHECKSUM_BITS];

GLOWWORM *gw = GLOWWORM_new(); GLOWWORM_init(gw);

int messages = 0; int b = 0; int forward = TRUE; DEBUG(int trap = 0;) while (b >= 0) { DEBUG ( printf("DEC Bit %03i: ", b); printf(" %s ", forward ? "->" : "<-"); printf(" (%02i) ", trap); printMessagePrefix(msgBits, b); ) // Pushing down the 0 path if ( (forward) && (b < BBC_MESSAGE_LENGTH_BITS + BBC_CHECKSUM_BITS) ) { msgBits[b++] = 0; if (packet[chipFromHash(GLOWWORM_addBit(gw, 0))]) { forward = TRUE; DEBUG(trap = 1;) } else { GLOWWORM_delBit(gw, msgBits[--b]); forward = FALSE; DEBUG(trap = 2;) } continue; } // Message found if ( (forward) && (b >= BBC_MESSAGE_LENGTH_BITS + BBC_CHECKSUM_BITS) ) { printMessage(msgBits); messages++; GLOWWORM_delBit(gw, msgBits[--b]); forward = FALSE; DEBUG(trap = 7;) continue; } // Backtracking from a 0 bit if ( (!forward) && (0 == msgBits[b]) ) { if (b < BBC_MESSAGE_LENGTH_BITS) { msgBits[b++] = 1; if (packet[chipFromHash(GLOWWORM_addBit(gw, 1))]) { forward = TRUE; DEBUG(trap = 3;) } else { GLOWWORM_delBit(gw, msgBits[--b]); forward = FALSE; DEBUG(trap = 4;) } } else { GLOWWORM_delBit(gw, msgBits[--b]); forward = FALSE; DEBUG(trap = 5;) } continue; } // Backtracking from a 1 bit if ( (!forward) && (1 == msgBits[b]) ) { GLOWWORM_delBit(gw, msgBits[--b]); forward = FALSE; DEBUG(trap = 6;) continue; } printf("Decoder failed to catch condition. "); } GLOWWORM_del(gw); return messages; }

int countMarks(uint8_t *packet) { int marks = 0; for (int i = 0; i < BBC_PACKET_LENGTH_BITS; i++) marks += !!packet[i]; return marks; }

void printPacket(uint8_t *packet) { if (BBC_PACKET_LENGTH_BITS <= 64) { printf(" "); for (int i = 0; i < BBC_PACKET_LENGTH_BITS; i++) printf("%c", (i%10)? ' ' : '0' + (i/10)); printf(" "); printf(" "); for (int i = 0; i < BBC_PACKET_LENGTH_BITS; i++) printf("%c", '0' + i%10); printf(" "); } printf("PKT: "); for (int i = 0; i < BBC_PACKET_LENGTH_BITS; i++) { printf("%c", packet[i]? 'X' : '.'); if ((i > 0) && !(i % 64)) printf(" "); }

printf(" "); }

double percentage(double numerator, double denominator) { return 100.0 * (numerator / denominator); }

int main(void) { MyBMP *bmp = MyBMP_new(WIDTH, HEIGHT); MyBMP_setFilename(bmp, OUT_BMPFILENAME); //GLOWWORM_test(2); FILE *readFILE = fopen("message_tx.txt", "r"); char input[128]; uint8_t *packet = bbc_encode(NULL, (uint8_t *) "Hello World.", bmp); while( fgets(input, 128, readFILE)) { bbc_encode(packet, (uint8_t *) input, bmp); } DEBUG(printPacket(packet);)

int marks = countMarks(packet); printf("Marks in packet: %i (%6.2f%% density) ", marks, percentage(marks, BBC_PACKET_LENGTH_BITS));

printf("Found %i messages in packet ", bbc_decode(packet)); MyBMP_save(bmp); MyBMP_del(bmp); return EXIT_SUCCESS; }