#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include "CRCLib.h"

int png_signature[8] = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
//int idat_signature[4] = { 0x, 0x, 0x, 0x}

int check_header(int *addr) {
	int signature_match = 0;
	for( int i = 0; i < 8; i++ ) {
		if (addr[i] != png_signature[i]) {
			signature_match = 1;
		}
	}
	printf("Sig Match: %d\n", signature_match);
	return signature_match;

}


int check_header_length(int *addr, int offset) {
	unsigned int res = 0;
	for( int i = 0; i < 4; i++ ) {
		res |= addr[offset+i];
		if (i < 3) {
			res <<= 8;
		}
	}
	return res;
}

int first_idat(int *addr) {
	int idat_found = 0;
	int offset = 8;
	int jump_offset = 0;
	int header_type = 0;
	while(idat_found == 0) {
		jump_offset = check_header_length(addr, offset);
		header_type = check_header_length(addr, offset+4);
		printf("Jump: %d\n", jump_offset);
		printf("Type: %d\n", header_type);
		if(header_type == 1229209940) {
			idat_found = 1;
		} else {
			offset = offset + jump_offset + 12;
		}
	}
	return offset;
}

void main() {
	FILE *fp;
	int c;
	int myArray[255] = {};
	int i = 0;
	int offset = 0;
	fp = fopen("./1.png", "rt");
	while((c = fgetc(fp)) != EOF) {
		myArray[i] = c;
		i++;
	}
	fclose(fp);
	//check_header(myArray);
	//check_header_length(myArray, 54);
	offset = first_idat(myArray);
	printf("First Chunk: %d\n", offset);
	//printf("%d\n", CheckPNG(myArray));
	//int crcnum = crc(myArray, 19);
	//printf("%08X\n", crcnum);
}