--- a/src/common.c	Sun Oct 01 03:03:29 2023 -0400
+++ b/src/common.c	Wed Mar 20 17:06:26 2024 -0400
@@ -1,39 +1,51 @@
-#include <stdio.h>
-#include <stdint.h>
+#include "common.h"
+
+#include <string.h>
+
+/* hardcoded magic values; stored at 0x18... */
+static const uint8_t magic_veg[16] = {0xEF, 0x29, 0xC4, 0x46, 0x4A, 0x90, 0xD2, 0x11, 0x87, 0x22, 0x00, 0xC0, 0x4F, 0x8E, 0xDB, 0x8A};
+static const uint8_t magic_vf[16]  = {0xF6, 0x1B, 0x3C, 0x53, 0x35, 0xD6, 0xF3, 0x43, 0x8A, 0x90, 0x64, 0xB8, 0x87, 0x23, 0x1F, 0x7F};
+
+int set_file_information(FILE* target, uint8_t version, enum types type) {
+	const uint8_t* magic = (type == TYPES_VF) ? magic_vf : magic_veg;
 
-void set_data(unsigned char* magic, uint16_t version, FILE* target) {
-	int i;
-	fseek(target, 0x46, SEEK_SET);
-	fputc(version, target);
-	for (i=0; i<=sizeof(*magic); ++i) {
-		fseek(target, 0x18+i, SEEK_SET);
-		fputc(magic[i], target);
-	}
+	if (fseek(target, 0x46, SEEK_SET))
+		return -1;
+
+	if (fputc(version, target) == EOF)
+		return -1;
+
+	if (fseek(target, 0x18, SEEK_SET))
+		return -1;
+
+	if (fwrite(magic, sizeof(*magic), 16, target) < 16)
+		return -1;
+
+	return 0;
 }
 
-int copy_file(char* source_file, char* target_file) {
-	char ch[4096];
-	FILE *source, *target;
+int get_file_information(FILE* input, uint8_t* version, enum types* type) {
+	uint8_t magic[16] = {0};
 
-	source = fopen(source_file, "rb");
+	if (fseek(input, 0x46, SEEK_SET))
+		return -1;
+
+	*version = fgetc(input);
+
+	if (fseek(input, 0x18, SEEK_SET))
+		return -1;
 
-	if (source == NULL)
-		return 1;
+	/* read the WHOLE magic, then memcmp */
+	if (fread(magic, sizeof(*magic), ARRAYSIZE(magic), input) < ARRAYSIZE(magic))
+		return -1;
 
-	target = fopen(target_file, "wb");
-
-	if (target == NULL) {
-		fclose(source);
-		return 1;
+	if (!memcmp(magic, magic_veg, ARRAYSIZE(magic))) {
+		*type = TYPES_VEG;
+	} else if (!memcmp(magic, magic_vf, ARRAYSIZE(magic))) {
+		*type = TYPES_VF;
+	} else {
+		*type = TYPES_UNKNOWN;
 	}
 
-	while (!feof(source)) {
-		size_t b = fread(ch, 1, sizeof(ch), source);
-		if (b)
-			fwrite(ch, 1, b, target);
-	}
-
-	fclose(target);
-	fclose(source);
 	return 0;
 }