136 lines
4.7 KiB
GDScript
136 lines
4.7 KiB
GDScript
extends Node
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#warning-ignore-all:return_value_discarded
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const STRUCT := preload('res://scripts/struct.gd')
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const SLOT_IN_USE := 0xE41B
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var struct_types := STRUCT.get_base_structarraytypes()
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# FFV SRAM is 4 slots of 0x700byte save files
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# $0000-$06FF - Save Slot 1
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# $0700-$0DFF - Save Slot 2
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# $0E00-$14FF - Save Slot 3
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# $1500-$1BFF - Save Slot 4
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# $1C00-$1FEF - Empty
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# $1FF0-$1FF7 - Checksum (2 bytes per slot)
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# $1FF8-$1FFF - use table - contains $E41B if a slot is in use (deleting a save will just change this)
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# Checksum just sums up every 16bit word from 0x000-0x600 of the save slot, using the carry flag.
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# The carry flag means that it is not strictly modulo arithmetic, but you have to add 1 every time you pass 0xFFFF
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# Offsets within save slot
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# $000:600 = $500:B00 in WRAM (0x7E0500:0x7E0B00) only values that don't match are things like game frame timer which increments immediately after load
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#
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# $000-$04F - Character Slot 1
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# $050=$09F - Character Slot 2
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# $0A0=$0EF - Character Slot 3
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# $0F0=$13F - Character Slot 4
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# $447-$449 - Current Gil
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#
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# $5D8 - Current Map X position
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# $5D9 - Current Map Y position
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#
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# $600-$6FF - Appears to be unused and zeroed out, not used for checksum. Maybe we can use it for cool metadata? :)
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func get_slot_checksum(slot: StreamPeerBuffer) -> int:
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slot.seek(0)
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var checksum := 0
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for i in 0x600: # Last 0x100 bytes aren't checksummed
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checksum += slot.get_u16()
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if checksum > 0xFFFF: # Addition of shorts can only overflow
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checksum &= 0xFFFF
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if i < 0x5FF:
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checksum += 1 # TODO: confirm this carry flag edge case is correct!
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return checksum
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func get_struct(buffer: StreamPeer, struct_name: String) -> Dictionary:
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# Does not seek to the start of the buffer.
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# Make sure it is set to where you want to start reading.
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if not (struct_name in struct_types):
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print_debug('Attempted to get undeclared struct: "%s"' % struct_name)
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return {}
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return struct_types[struct_name].get_value(buffer, [0, 0])
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func put_struct(buffer: StreamPeer, struct_name: String, data: Dictionary):
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if not (struct_name in struct_types):
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print_debug('Attempted to put undeclared struct: "%s"' % struct_name)
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return
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struct_types[struct_name].put_value(buffer, data, [0, 0])
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func deserialize_save_slot(buffer: StreamPeerBuffer) -> Dictionary:
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return struct_types['Save_slot'].get_value(buffer, [0, 0])
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func load_save_slot(buffer: StreamPeerBuffer) -> Dictionary:
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# Like deserialize_save_slot, but also decodes strings and maybe other postprocessing later
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var data = deserialize_save_slot(buffer)
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data.character_names_decoded = StringLoader.decode_array(data.character_names, 'RPGe_small')
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return data
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func serialize_save_slot(data: Dictionary) -> StreamPeerBuffer:
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var buffer := StreamPeerBuffer.new()
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struct_types['Save_slot'].put_value(buffer, data, [0, 0])
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var padding := PoolByteArray()
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padding.resize(0x100)
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padding.fill(0)
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buffer.put_data(padding)
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return buffer
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func make_snes_save_file(slot_dicts: Array) -> PoolByteArray:
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# Pass a length 4 array of dictionaries.
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# Falsey entries will be zeroed out slots, with the active flag at the end also zeroed.
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assert(len(slot_dicts) == 4)
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var buffer := StreamPeerBuffer.new()
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var zeroes := PoolByteArray()
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zeroes.resize(0x700)
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zeroes.fill(0)
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var checksums := []
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for dict in slot_dicts:
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if dict:
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var slot := serialize_save_slot(dict)
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var checksum := get_slot_checksum(slot)
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buffer.put_data(slot.data_array)
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if slot.data_array == zeroes:
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checksums.append(-1)
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else:
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checksums.append(checksum)
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else:
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buffer.put_data(zeroes)
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checksums.append(-1)
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# Pad from $1C00 == 7168 to $1FF0 == 8160
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buffer.put_data(zeroes.subarray(0, 991)) # BEWARE: SUBARRAY IS INCLUSIVE
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# Mystery byte TODO: INVESTIGATE LATER
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buffer.put_8(1)
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# Pad from $1FE1 == 8161 to $1FF0 == 8176
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buffer.put_data(zeroes.subarray(0, 14)) # BEWARE: SUBARRAY IS INCLUSIVE
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# Checksums
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for c in checksums:
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if c > -1:
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buffer.put_u16(c)
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else:
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buffer.put_u16(0)
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# Active flag
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for c in checksums:
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if c > -1:
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buffer.put_u16(SLOT_IN_USE)
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else:
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buffer.put_u16(0)
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return buffer.data_array
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func get_save_slot(sram: File, slot_id: int) -> StreamPeerBuffer:
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var buffer := StreamPeerBuffer.new()
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sram.seek(0x700 * slot_id)
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buffer.set_data_array(sram.get_buffer(0x700))
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return buffer
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func save_slot(sram: File, slot_id: int, slot: StreamPeerBuffer):
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sram.seek(0x700 * slot_id)
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sram.store_buffer(slot.data_array)
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sram.seek(0x1FF0 + (slot_id*2))
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sram.store_16(get_slot_checksum(slot))
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sram.seek(0x1FF8 + (slot_id*2))
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sram.store_16(SLOT_IN_USE)
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func delete_save_slot(sram: File, slot_id: int):
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sram.seek(0x1FF8 + (slot_id*2))
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sram.store_16(0)
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func _ready():
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STRUCT.parse_struct_definitions_from_tsv_filename('res://data/SNES_save.tsv', struct_types)
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