wip

.gitignore

@@ -2,4 +2,5 @@
 *.out
 *.woo
 *.wow
+*.gch
 bin/

cmd/crc.c

@@ -123,7 +123,6 @@ int change_idat_content(unsigned char *addr, unsigned char *message, int accurac
 
 	int prop_found = 0;
 	long size = 1;
-	long rounds = 0;
 	size_t idat_byte_length = 0;
 	unsigned char* idat_data = calloc(size, sizeof(unsigned char));
 	for(size_t i = 0; i <= idat_length; i++) {
@@ -167,6 +166,8 @@ int main() {
 	FILE *fp;
 	size_t i = 0;
 	unsigned long offset = 0;
+	struct PNG_START_FILE_STRUCT png_start_file_data;
+	struct PNG_IDAT_FILE_STRUCT png_idat_file_data;
 	unsigned char *message = malloc(sizeof(char));
 	message[0] = '\0';
 
@@ -184,7 +185,13 @@ int main() {
 	unsigned char *file_data = file_to_char_array(fp, &i);
 	fclose(fp);
 
+	populate_start_png(file_data, &png_start_file_data);
+
 	offset = first_idat(file_data);
+	printf("Off: %ld\n", offset);
+
+	populate_idat_png(file_data, &png_idat_file_data, offset);
+
 	change_idat_content(file_data, message, 1, offset);
 	free(file_data);
 	free(message);

include/crc_util.h

@@ -1,15 +1,29 @@
 #include <stdio.h>
 
 // PNG File Struct
-struct PNG_FILE_STRUCT {
+struct PNG_START_FILE_STRUCT {
 	unsigned char file_sig[8];
-	int file_width;
+	unsigned char ihdr_length[4];
-	int file_height;
+	unsigned char ihdr_header[4];
-	int bit_depth;
+	unsigned char file_width[4];
-	int color_type;
+	unsigned char file_height[4];
-	int compression_method;
+	unsigned char bit_depth[1];
-	int filter_method;
+	unsigned char color_type[1];
-	int interlace_method;
+	unsigned char compression_method[1];
+	unsigned char filter_method[1];
+	unsigned char interlace_method[1];
+	unsigned char ihdr_crc[4];
+};
+
+struct PNG_IDAT_FILE_STRUCT {
+	unsigned char idat_length[4];
+	unsigned char idat_header[4];
+	unsigned char idat_crc[4];
+	unsigned char idat_data[];
+};
+
+struct PNG_FILE_STRUCT {
+	struct PNG_START_FILE_STRUCT png_start_data;
 };
 
 extern const long png_signature[8];
@@ -18,3 +32,5 @@ int check_header_length(unsigned char *addr, long offset);
 int check_file_header(char *addr);
 int create_cc_file(unsigned char *addr, unsigned long file_length);
 unsigned char* file_to_char_array(FILE *in_file, size_t* size);
+void populate_start_png(unsigned char *addr, struct PNG_START_FILE_STRUCT *png_data);
+void populate_idat_png(unsigned char *addr, struct PNG_IDAT_FILE_STRUCT *png_data, unsigned long offset);

src/crc_util.c

@@ -27,6 +27,77 @@ int check_file_header(char *addr) {
 
 }
 
+void populate_idat_png(unsigned char *addr, struct PNG_IDAT_FILE_STRUCT *png_data, unsigned long offset) {
+	unsigned long cur_idat_length = 0;
+	for(int i = 0; i < 4; i++){
+		png_data->idat_length[i] = addr[i+offset];
+	}
+
+	for(int i = 0; i < 4; i++){
+		cur_idat_length += (png_data->idat_length[i] << (24-(8*i)));
+	}
+
+	printf("\n%ld\n", cur_idat_length);
+}
+
+void populate_start_png(unsigned char *addr, struct PNG_START_FILE_STRUCT *png_data) {
+	for(int i = 0; i < 8; i++) {
+		png_data->file_sig[i] = addr[i];
+		printf("%02X ", png_data->file_sig[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 4; i++) {
+		png_data->ihdr_length[i] = addr[i+8];
+		printf("%02X ", png_data->ihdr_length[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 4; i++) {
+		png_data->ihdr_header[i] = addr[i+12];
+		printf("%02X ", png_data->ihdr_header[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 4; i++) {
+		png_data->file_width[i] = addr[i+16];
+		printf("%02X ", png_data->file_width[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 4; i++) {
+		png_data->file_height[i] = addr[i+20];
+		printf("%02X ", png_data->file_height[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 1; i++) {
+		png_data->bit_depth[i] = addr[i+24];
+		printf("%02X ", png_data->bit_depth[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 1; i++) {
+		png_data->color_type[i] = addr[i+25];
+		printf("%02X ", png_data->color_type[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 1; i++) {
+		png_data->compression_method[i] = addr[i+26];
+		printf("%02X ", png_data->compression_method[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 1; i++) {
+		png_data->filter_method[i] = addr[i+27];
+		printf("%02X ", png_data->filter_method[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 1; i++) {
+		png_data->interlace_method[i] = addr[i+28];
+		printf("%02X ", png_data->interlace_method[i]);
+	}
+	printf("\n");
+	for(int i = 0; i < 4; i++) {
+		png_data->ihdr_crc[i] = addr[i+29];
+		printf("%02X ", png_data->ihdr_crc[i]);
+	}
+	printf("\n");
+}
+
 int create_cc_file(unsigned char *addr, unsigned long file_length) {
         FILE *fp;
         fp = fopen("png2.png", "w");