th175arc: don't decrypt/encrypt game.exe

This file isn't encrypted, because, well, Windows need to be able to read it
in order to run the game.

th175arc/common.c

@@ -15,7 +15,7 @@ uint32_t calc_hash(const char *filename)
 {
 	if (strcmp(filename, "game.exe") == 0) {
 		// I don't know the filename for this hash, but I need to have one, so I arbitrarily decide it's "game.exe".
-		return 0x1f47c0c8;
+		return GAME_EXE_HASH;
 	}
 
 	uint64_t hash = 0x811C9DC5;

th175arc/read.c

@@ -73,7 +73,9 @@ int write_dat_file(filenames_cache_t *filenames_cache, const char *out_dir, uint
 {
 	uint8_t *buffer = malloc(size);
 	memcpy(buffer, data, size);
-	decrypt(buffer, size, offset_in_file);
+	if (hash != GAME_EXE_HASH) {
+		decrypt(buffer, size, offset_in_file);
+	}
 
 	char name_buffer[26];
 	const char *name = filenames_cache_get(filenames_cache, hash);

th175arc/th175arc.h

@@ -25,6 +25,7 @@ typedef struct file_desc_s
 
 int unpack_file(const char *in_file, const char *out_dir);
 int repack_file(const char *in_dir,  const char *out_file);
+#define GAME_EXE_HASH 0x1f47c0c8
 
 uint32_t calc_hash(const char *filename);
 void decrypt(uint8_t *buffer, size_t size, size_t offset_in_file);

th175arc/write.c

@@ -171,7 +171,9 @@ int repack_file(const char *in_dir,  const char *out_file)
 		desc[i].key = calc_hash(files_list[i] + strlen(in_dir) + strlen("/"));
 		desc[i].offset = offset;
 		desc[i].size = size;
-		decrypt(file, size, offset);
+        if (desc[i].key != GAME_EXE_HASH) {
+            decrypt(file, size, offset);
+        }
 		offset += size;
 		fwrite(file, size, 1, out);
 		free(file);