Initial PNG CC Implementation

Signed-off-by: Pin <wf6DJd8a3xSSCZbn@protonmail.com>

src/crc_util.c

@@ -0,0 +1,92 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "crc_util.h"
+
+const long png_signature[8] = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
+
+int check_header_length(unsigned char *addr, long offset) {
+        unsigned int res = 0;
+        for( int i = 0; i < 4; i++ ) {
+                res |= addr[offset+i];
+                if (i < 3) {
+                        res <<= 8;
+                }
+        }
+        return res;
+}
+
+int check_file_header(char *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;
+
+}
+
+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)));
+	}
+
+	for(int i = 0; i < 4; i++){
+		png_data->idat_header[i] = addr[i+offset+4];
+	}
+}
+
+void populate_start_png(unsigned char *addr, struct PNG_START_FILE_STRUCT *png_data) {
+	union{
+		unsigned char *data;
+		struct PNG_START_FILE_STRUCT *png_data;
+	}png;
+
+	png.png_data = png_data;
+
+	for(int i = 0; i < sizeof(struct PNG_START_FILE_STRUCT); i++) {
+		png.data[i] = addr[i];
+	}
+}
+
+int create_cc_file(unsigned char *addr, unsigned long file_length) {
+        FILE *fp;
+        fp = fopen("png2.png", "w");
+
+        if(fp == NULL) {
+                return EXIT_FAILURE;
+        }
+
+        for(int i = 0; i < file_length; i++){
+                fputc(addr[i], fp);
+        }
+        fclose(fp);
+	return 0;
+}
+
+unsigned char* file_to_char_array(FILE *in_file, size_t* size) {
+        unsigned int c;
+        unsigned long file_data_cap = 8;
+        unsigned char* file_data = calloc(file_data_cap, sizeof(unsigned char));
+
+        for(size_t i = 0;(c = fgetc(in_file)) != EOF; i++) {
+                if(i == file_data_cap) {
+                        file_data_cap *= 2;
+                        file_data = reallocarray(file_data, file_data_cap, sizeof(unsigned char));
+                        if(file_data == NULL) {
+                                perror("FAILED ARRAY RESIZE");
+                                return NULL;
+                        }
+                }
+                file_data[i] = c;
+                *size += 1;
+        }
+        return file_data;
+}
+