Added full SNES save file serialization

Ticked off SNES save support on the README.md

README.md

@@ -18,9 +18,7 @@ You can currently load up your SNES ROM of Final Fantasy FFV and look at battle
 Following systems are ordered by vague overarching priority:
 
 ### Save/Load System
-I know I called this an "Interactive Save Editor" but I haven't started that yet.
-- [x] SNES loading
-- [ ] SNES saving (should be easy enough, soon™)
+- [x] SNES loading and saving
 - [ ] PSX Support (wasn't identical to SNES with different offset ;_; )
 - [ ] GBA Support (note, does not imply full asset ripping)
 - [ ] Steam Pixel Remaster Support (I haven't bought this yet so low prio) (note, does not imply full asset ripping)

scripts/loaders/save_loader.gd

@@ -1,4 +1,5 @@
 extends Node
+#warning-ignore-all:return_value_discarded
 const STRUCT := preload('res://scripts/struct.gd')
 const SLOT_IN_USE := 0xE41B
 var struct_types := STRUCT.get_base_structarraytypes()
@@ -53,18 +54,57 @@ func put_struct(buffer: StreamPeer, struct_name: String, data: Dictionary):
 		return
 	struct_types[struct_name].put_value(buffer, data, [0, 0])
 
-func deserialize_save_slot(bytes: PoolByteArray) -> Dictionary:
-	var buffer = StreamPeerBuffer.new()
-	buffer.data_array = bytes
+func deserialize_save_slot(buffer: StreamPeerBuffer) -> Dictionary:
 	return struct_types['Save_slot'].get_value(buffer, [0, 0])
 
-func serialize_save_slot(data: Dictionary) -> PoolByteArray:
-	var buffer = StreamPeerBuffer.new()
+func serialize_save_slot(data: Dictionary) -> StreamPeerBuffer:
+	var buffer := StreamPeerBuffer.new()
 	struct_types['Save_slot'].put_value(buffer, data, [0, 0])
 	var padding := PoolByteArray()
 	padding.resize(0x100)
 	padding.fill(0)
 	buffer.put_data(padding)
+	return buffer
+
+func make_snes_save_file(slot_dicts: Array) -> PoolByteArray:
+	# Pass a length 4 array of dictionaries.
+	# Falsey entries will be zeroed out slots, with the active flag at the end also zeroed.
+	assert(len(slot_dicts) == 4)
+	var buffer := StreamPeerBuffer.new()
+	var zeroes := PoolByteArray()
+	zeroes.resize(0x700)
+	zeroes.fill(0)
+	var checksums := []
+	for dict in slot_dicts:
+		if dict:
+			var slot := serialize_save_slot(dict)
+			var checksum := get_slot_checksum(slot)
+			buffer.put_data(slot.data_array)
+			if slot.data_array == zeroes:
+				checksums.append(-1)
+			else:
+				checksums.append(checksum)
+		else:
+			buffer.put_data(zeroes)
+			checksums.append(-1)
+	# Pad from $1C00 == 7168 to $1FF0 == 8160
+	buffer.put_data(zeroes.subarray(0, 991))  # BEWARE: SUBARRAY IS INCLUSIVE
+	# Mystery byte TODO: INVESTIGATE LATER
+	buffer.put_8(1)
+	# Pad from $1FE1 == 8161 to $1FF0 == 8176
+	buffer.put_data(zeroes.subarray(0, 14))  # BEWARE: SUBARRAY IS INCLUSIVE
+	# Checksums
+	for c in checksums:
+		if c > -1:
+			buffer.put_u16(c)
+		else:
+			buffer.put_u16(0)
+	# Active flag
+	for c in checksums:
+		if c > -1:
+			buffer.put_u16(SLOT_IN_USE)
+		else:
+			buffer.put_u16(0)
 	return buffer.data_array
 
 func get_save_slot(sram: File, slot_id: int) -> StreamPeerBuffer:

test/unit_tests.gd

@@ -2,6 +2,7 @@ extends Control
 
 var dir_user := Directory.new()
 const P_TESTDATA := 'user://test_data/'
+const FILENAME_TEST_SAVE := 'res://test.srm'
 # Shared state between tests
 var save_slot_buffers = []
 var save_slot_dicts = []
@@ -12,7 +13,7 @@ func test(label, input):
 	else:
 		print('FAILURE: ' + label)
 
-func load_snes_savefile(filename: String = 'res://test.srm'):
+func load_snes_savefile(filename: String = FILENAME_TEST_SAVE):
 	var save_file := File.new()
 	match save_file.open(filename, File.READ):
 		OK:
@@ -22,7 +23,7 @@ func load_snes_savefile(filename: String = 'res://test.srm'):
 			return
 	for i in 4:
 		self.save_slot_buffers.append(SaveLoader.get_save_slot(save_file, i))
-		self.save_slot_dicts.append(SaveLoader.deserialize_save_slot(self.save_slot_buffers[i].data_array))
+		self.save_slot_dicts.append(SaveLoader.deserialize_save_slot(self.save_slot_buffers[i]))
 	print('Loaded test save file')
 
 func generate_known_good_results():
@@ -61,23 +62,43 @@ func test_save_loading() -> bool:
 			print_debug('Failed to load known savefile results "%s"' % filename)
 			return false
 
-func test_save_serialization() -> bool:
+func test_save_slot_serialization() -> bool:
 	if not self.save_slot_dicts:
 		print_debug('test savefile not loaded')
 		return false
 	for i in 4:
-		var bytes = SaveLoader.serialize_save_slot(self.save_slot_dicts[i])
+		var bytes = SaveLoader.serialize_save_slot(self.save_slot_dicts[i]).data_array
 		if bytes != self.save_slot_buffers[i].data_array:
 			print_debug('Slot %d failed to serialize correctly, rescanning' % i)
 			for j in 0x700:
 				var b1: int = bytes[j]
 				var b2: int = self.save_slot_buffers[i].data_array[j]
 				if b1 != b2:
-					print_debug('Mismatch occurs at byte %d: %d vs %d' % [j, b1, b2])
+					print_debug('Mismatch occurs at byte $%04X (%d): $%02X (%d) vs $%02X (%d)' % [j, j, b1, b1, b2, b2])
 			return false
 	return true
 
-
+func test_snes_save_serialization() -> bool:
+	if not self.save_slot_dicts:
+		print_debug('test savefile not loaded')
+		return false
+	var bytes := SaveLoader.make_snes_save_file(self.save_slot_dicts)
+	var file := File.new()
+	match file.open(FILENAME_TEST_SAVE, File.READ):
+		OK:
+			var orig_bytes := file.get_buffer(file.get_len())
+			if orig_bytes != bytes:
+				print_debug('SNES Save File failed to serialize correctly, rescanning')
+				for j in 0x2000:
+					var b1: int = bytes[j]
+					var b2: int = orig_bytes[j]
+					if b1 != b2:
+						print_debug('Mismatch occurs at byte $%04X (%d): $%02X (%d) vs $%02X (%d)' % [j, j, b1, b1, b2, b2])
+				return false
+		var error:
+			print_debug('Failed to open test.srm for reading: %d' % error)
+			return false
+	return true
 
 
 # Called when the node enters the scene tree for the first time.
@@ -89,5 +110,6 @@ func _ready() -> void:
 			print_debug('Failed to open user directory')
 	# generate_known_good_results()  # Uncomment this to get your sample on first run
 	test('SNES save file loaded to array of dictionaries', test_save_loading())
-	test('SNES save file slots serialized from dictionaries', test_save_serialization())
+	test('SNES save file slots serialized from dictionaries', test_save_slot_serialization())
+	test('SNES save file serialized to original source bytes', test_snes_save_serialization())
 	get_tree().quit()