Im currently writing a program in wasm text format and I was wondering if there was a way to write an 8 bit integer to memory. Does anybody know if this even possible?
I have looked everywhere but I can't find an answer.
Currently WebAssembly does not have i8 type for values on the stack. The closest type you can use is i32.
If you are working with i32 or i64 (for short inn), then as the comments point out, inn.load8_sx and inn.store8 can be used to load/store 8bit values from/to a WebAssembly.Memory, where sx = u | s, and from the specs:
annotation sx distinguishes whether the operands are to be interpreted as unsigned or signed integers.
; address
i32.const 0
; value
i32.const 258
; write the lowest 8 bits, 00000010b, from the value
; into the memory address 0, ignoring the higher bits
i32.store8
; address
i32.const 0
; load 8 bits from address 0 that are 00000010b
; zero extend the 8 bits to 32 (0..00000010b)
; and push i32 into the stack
i32.load8_u
The inn.load8_s works similarly, but by sign extending the loaded 8 bit integer, which means that if the highest bit of the loaded bits is 1 (negative signed integer), then 10000010b becomes 1..10000010b.