Script Container

YSC files contain GTA V's game scripts. The new format is an adaptation of the script container format used in Red Dead Redemption.

File Format

The basic format of YSC starts with a header that's 0x80 bytes in size, there are still some unknowns in the header but for basic dissassembling you have enough information.

struct YSCHeader
{
	QWORD Magic;// 0x00 - Seems to always hold the value D09E5A4001000000
	QWORD UnkPointer;// 0x08 -Points to a section in script thats always null
	QWORD CodeBlocksBasePointer;// 0x10 Points to an array of code block offsets
	DWORD GlobalsVersion;// 0x18 - Unsure what exactly this means
	DWORD CodeSize;// 0x1C - The size of all the code tables
	DWORD ParameterCount;// 0x20 - These are for starting a script with args. The args appear at the start of the script static variables
	DWORD StaticCount;// 0x24 - The number of static variables in the script
	DWORD GlobalCount;// 0x28 - This is used for scripts that seem to initialise global variable tables
	DWORD NativesCount;// 0x2C - The total amount of natives in the native table
	QWORD StaticsPointer;// 0x30 - The Offset in file where static variables are initialised
	QWORD GlobalsPointer;// 0x38 - The Offset in file where global variales are initilaised(only used for registration scripts)
	QWORD NativesPointer;// 0x40 - The Offset in file where the natives table is stored
	QWORD Null1;//0x48
	QWORD Null2;//0x50;
	DWORD ScriptNameHash;//0x58 - A Jenkins hash of the scripts name
	DWORD UnkUsually1;//0x5C
	QWORD ScriptNamePointer;//0x60 - Points to an offset in the file that has the name of the script
	QWORD StringBlocksBasePointer;//0x68 - Points to an array of string block offsets
	DWORD StringSize;//0x70 - The Size of all the string tables
	DWORD Null3;//0x74
	DWORD Null4;//0x78
	DWORD Null4;//0x7C
};

All Pointer items are stored in the file as 0xXXXXXX50 and must therefore be masked with 0xFFFFFF to get their actual file offset.

Pages

The Code and Strings used by the script are stored in pages, each one up to a maximum size of 0x4000 bytes. The number of pages used can be calculated based of the CodeSize/StringSize using this:

int pagegCount = (totalSize + 0x3FFF) >> 14;

The size of each of the pages can be calculated using this function

int pageSize(int pageIndex, int totalSize)
{
	if (pageIndex > (totalSize >> 14) || pageIndex < 0){//page out of range
		return 0;
	}else if (pageIndex == (totalSize >> 14)){
		return totalSize & 0x3FFF;
	}
	return 0x4000;
}

Code

The Poistion of each of the code pages can be found by reading the positions stored in the array pointer to from CodeBlocksBasePointer, then you can read up to pageSize in that page. The code itself is a set of 127 opcodes that is ran on a stack machine.

Opcodes

ID	Name	Description	Length
0	nop	No operation	1 byte
1	iadd	Adds the top 2 items on the stack	1 byte
2	isub	Subtracts the top 2 items on the stack	1 byte
3	imul	Multiplies the top 2 items on the stack	1 byte
4	idiv	Divides the top 2 items on the stack	1 byte
5	imod	Mods the top 2 items on the stack	1 byte
6	iszero	Checks the first item on the stack to see if it equals 0	1 byte
7	ineg	Reverses the sign on the item on the top of the stack	1 byte
8	icmpeq	Compares the top 2 integers on the stack to see if they are equal	1 byte
9	icmpne	Compares the top 2 integers on the stack to see if they are not equal	1 byte
10	icmpgt	Compares the top 2 integers on the stack to see if the first one is greater than the second one	1 byte
11	icmpge	Compares the top 2 integers on the stack to see if the first one is greater than or equal to the second one	1 byte
12	icmplt	Compares the top 2 integers on the stack to see if the first one is less than the second one	1 byte
13	icmple	Compares the top 2 integers on the stack to see if the first one is less than or equal to the second one	1 byte
14	fadd	Adds the top 2 floats on the stack	1 byte
15	fsub	Subtracts the top 2 floats on the stack	1 byte
16	fmul	Multiplies the top 2 floats on the stack	1 byte
17	fdiv	Divides the top 2 floats on the stack	1 byte
18	fmod	Mods the top 2 floats on the stack	1 byte
19	fneg	Reverses the sign on the first float on the stack	1 byte
20	fcmpeq	Compares the top 2 floats on the stack to see if they are equal	1 byte
21	fcmpne	Compares the top 2 floats on the stack to see if they are not equal	1 byte
22	fcmpgt	Compares the top 2 floats on the stack to see if the first one is greater than the second one	1 byte
23	fcmpge	Compares the top 2 floats on the stack to see if the first one is greater than or equal to the second one	1 byte
24	fcmplt	Compares the top 2 floats on the stack to see if the first one is less than the second one	1 byte
25	fcmple	Compares the top 2 floats on the stack to see if the first one is less than or equal to the second one	1 byte
26	vadd	Adds the top 2 Vectors[1] on the stack	1 byte
27	vsub	Subtracts the top 2 Vectors[1] on the stack	1 byte
28	vmul	Multiplies the top 2 Vectors[1] on the stack	1 byte
29	vdiv	Divides the top 2 Vectors[1] on the stack	1 byte
30	vneg	Reverses the sign on the first vector[1] on the stack	1 byte
31	iand	Performs an And operation to the first 2 integers on the stack	1 byte
32	ior	Performs an Or operation to the first 2 integers on the stack	1 byte
33	ixor	Performs a Xor operation to the first 2 integers on the stack	1 byte
34	itof	Converts the top integer on the stack to a float, and puts that float on the stack	1 byte
35	ftoi	Converts the top float on the stack to an integer, and puts that integer on the stack	1 byte
36	ftov	Converts the top float into a Vector containing 3 instances of the same float, and pushes the pointer to that Vector onto the top of the stack	1 byte
37	pushb	Pushes a byte onto the stack, the byte is defined as the next byte after the opcode	2 bytes
38	pushb2	Pushes 2 bytes onto the stack, the bytes are the next 2 bytes after the opcode	3 bytes
39	pushb3	Pushes 3 bytes onto the stack, the bytes are the next 3 bytes after the opcode	4 bytes
40	push	Pushes an int onto the stack, the integer is defined in the next 4 bytes after the opcode	5 bytes
41	pushf	Pushes a float onto the stack, the float is defined in the next 4 bytes after the opcode	5 bytes
42	dup	Duplicates the first item on the stack, and pushes it back onto the stack	1 byte
43	pop	Pops the top item off the stack	1 byte
44	native	Calls a native function. The number of arguments for the native to take is defined in the first 6 bits of the next byte after the opcode(0-63). The number of returns is stored in the following 2 bits(0-3). The hash of the native functions is stored in the native table at the index specified by the following 2 bytes(expressed as an unsigned short)	4 bytes
45	enter	Indicates the beginning of an internal function. The byte after the opcode indicates the amount of arguments the function takes off the stack, and the next 2 bytes after that indicate the number of variables the function will have to generate on the stack. The following byte indicates how many bytes to skip past after the opcode(usually so a name can be appended to the function definition)	5 bytes + value of 5th byte
46	ret	Indicates the end of an internal function. The byte after the opcode indicates the amount of arguments that will have to be popped off the stack, and the next byte after that indicates the stack number of the return address	3 bytes
47	pget	Pops a pointer off the stack and pushes the value stored in that pointer back onto the stack	1 byte
48	pset	Pops 2 items off the stack and stores the second item at the location of the first item (the first item being a pointer)	1 byte
49	peekset	Pops the first item off the stack and peeks at the second item on the stack, then stores the first item at the location pointed to by the second item on the stack	1 byte
50	tostack	Pops 2 items off the stack, the first being the number of items, second being the memory address. It then pushes that many items to the stack from the memory address	1 byte
51	fromstack	Pops 2 items off the stack, the first being the number of items, second being the memory address. It then pops that many items from the stack to the memory address	1 byte
52	getarrayp1	Pops 2 items off the stack, the first being an array index, second being the pointer to an array. It then pushes the pointer to theindex in the array to the top of the stack. The size each item in the array is determined by the byte following the opcode	2 byte
53	getarray1	Pops 2 items off the stack, the first being an array index, second being the pointer to an array. It then pushes the item at the array index to the top of the stack. The size each item in the array is determined by the byte following the opcode	2 byte
54	setarray1	Pops 3 items off the stack, the first being the value to set, second being an array index and last being the pointer to an array. It the sets the value at the index in the array to first value. The size each item in the array is determined by the byte following the opcode	2 byte
55	getframep1	Pushes the pointer to the frame variable at the index specified by the byte following the opcode	2 bytes
56	getframe1	Pushes the value of the frame variable at the index specified by the byte following the opcode	2 bytes
57	setframe1	Pops an item off the stack, then sets the frame variable at the index specified by the byte following the opcode to the item	2 bytes
58	getstaticp1	Pushes the pointer to the static variable at the index specified by the byte following the opcode	2 bytes
59	getstatic1	Pushes the value of the static variable at the index specified by the byte following the opcode	2 bytes
60	setstatic1	Pops an item off the stack, then sets the static variable at the index specified by the byte following the opcode to the item	2 bytes
61	addi	Adds the byte directly after the opcode to the integer value at the top of the stack, then pushes the new value to the top of the stack	2 bytes
62	multi	Multiplies the byte directly after the opcode to the integer value at the top of the stack, then pushes the new value to the top of the stack	2 bytes

tbc...