GitFOSS

fun memset(dst : UInt8*, c : USize, n : USize) : Void*
  r0 = r1 = r2 = 0
  asm(
    "cld\nrep stosb"
          : "={al}"(r0), "={Di}"(r1), "={cx}"(r2)
          : "{al}"(c.to_u8), "{Di}"(dst), "{cx}"(n)
          : "volatile", "memory"
  )
  dst.as(Void*)
end

fun memcpy(dst : UInt8*, src : UInt8*, n : USize) : Void*
  r0 = r1 = r2 = 0
  asm(
    "cld\nrep movsb"
          : "={Di}"(r0), "={Si}"(r1), "={cx}"(r2)
          : "{Di}"(dst), "{Si}"(src), "{cx}"(n)
          : "volatile", "memory"
  )
  dst.as(Void*)
end

fun memcmp(s1 : UInt8*, s2 : UInt8*, n : Int32) : Int32
  while n > 0 && (s1.value == s2.value)
    s1 += 1
    s2 += 1
    n -= 1
  end
  return 0 if n == 0
  (s1.value - s2.value).to_i32
end

fun memmove(dst : UInt8*, src : UInt8*, n : USize) : Void*
  if src.address < dst.address
    src += n.to_i64
    dst += n.to_i64
    until n == 0
      dst -= 1
      src -= 1
      dst.value = src.value
      n -= 1
    end
  else
    memcpy dst, src, n
  end
  dst.as(Void*)
end