Optionaloffset: number | StringFormattedRecursiveKeyOf<This, Args> | ((instance: This, cursor: Cursor) => number)The offset to move the cursor to before reading or writing the decorated property. It can be:
Optionalopt: Partial<PrePostOptions>Optional configution.
The class or property decorator function.
A use case where the @Peek decorator could be used instead of @Offset
is if you need to apply some form of processing to the value of the property
to know decide on the structure that value follows.
In the following example the structure of the bitfield is only known based
on the value of the most significant bit. For this I use @Peek to check the
content of the next value and then I properly read it in the correct form.
class BitfieldB {
...
}
class BitfieldA {
...
}
class Protocol {
// Use `@Peek` to check the MSB but restore the cursor position
@Peek()
@Transform(x => x & 0x80)
@Relation(PrimitiveSymbol.u8)
peeked: number
@IfThen(_ => _.peeked > 0, BitfieldA)
@Else(BitfieldB)
bitfield: BitfieldA | BitfieldB
}
You can also use the @Peek decorator with a dynamic offset that depends on
the class instance and the current cursor position:
class Protocol {
@Relation(PrimitiveSymbol.u8)
offset: number
@Peek((instance, cursor) => cursor.offset() + instance.offset)
@Relation(PrimitiveSymbol.u8)
peeked: number
}
@Peekdecorator moves the cursor to a specified address to read/write the decorated property, then moves back the cursor to its original position.The
@Peekdecorator shares similar functionality with the Offset decorator, but with a key difference:@Peekwill automatically reset the cursor to its original position after reading or writing the decorated class or property.