hex.pointers.xor_hex_to_flip_ptr (arity 2)

xors (the parameter hex, shifted left by bit_shift) to the hex/byte pointed by the memory-word hex.pointers.to_flip.
use after: .pointers.set_flip_pointer ptr
does: .xor *ptr, hex&lt;<bit_shift (as it uses the address in to_flip)
It assumes that the value in the memory-word to_flip is a dw-aligned address to an hex-variable.
bit_shift is a constant that’s assumed to be divisible by 4.
@Assumes: bit_shift is divisible by 4.

@Assumes: bit_shift is divisible by 4

Signature

def xor_hex_to_flip_ptr hex, bit_shift @ prepare_flip_bit0, prepare_flip_bit1, prepare_flip_bit2, prepare_flip_bit3, after_flip_bit0, after_flip_bit1, after_flip_bit2, after_flip_bit3, cleanup < hex.pointers.to_flip { ... }

Defined in hex/pointers/xor_to_pointer.fj — lines 118–147 (view on GitHub).

Complexity

  • Time: 5@+12

  • Space: 5@+76

See the complexity glossary for what @, w, dw, dbit, n mean.

Source

Click to view the macro body

def xor_hex_to_flip_ptr hex, bit_shift @ prepare_flip_bit0, prepare_flip_bit1, prepare_flip_bit2, prepare_flip_bit3, \
        after_flip_bit0, after_flip_bit1, after_flip_bit2, after_flip_bit3,  cleanup  < hex.pointers.to_flip {
    wflip hex.pointers.to_flip+w, after_flip_bit0, prepare_flip_bit0

  prepare_flip_bit0:
    wflip hex.pointers.to_flip, dbit+0+bit_shift
    hex.if_flags hex, 0xAAAA, after_flip_bit0, hex.pointers.to_flip
  prepare_flip_bit1:
    wflip hex.pointers.to_flip, (dbit+0+bit_shift)^(dbit+1+bit_shift)
    hex.if_flags hex, 0xCCCC, after_flip_bit1, hex.pointers.to_flip
  prepare_flip_bit3:
    wflip hex.pointers.to_flip, (dbit+1+bit_shift)^(dbit+3+bit_shift)
    hex.if_flags hex, 0xFF00, after_flip_bit3, hex.pointers.to_flip
  prepare_flip_bit2:
    wflip hex.pointers.to_flip, (dbit+3+bit_shift)^(dbit+2+bit_shift)
    hex.if_flags hex, 0xF0F0, after_flip_bit2, hex.pointers.to_flip

    pad 4
  after_flip_bit0:
    hex.pointers.to_flip+dbit+0;prepare_flip_bit1
  after_flip_bit1:
    hex.pointers.to_flip+dbit+1;prepare_flip_bit3
  after_flip_bit2:
    wflip hex.pointers.to_flip, dbit+2+bit_shift, cleanup
  after_flip_bit3:
    hex.pointers.to_flip+dbit+0;prepare_flip_bit2

  cleanup:
    wflip hex.pointers.to_flip+w, after_flip_bit2
}

Depends on

Used by

Example uses

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