import (
	"bytes"
	"math/rand"
	"testing"
)

func slowAbs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

// slowPaeth is a slow but simple implementation of the Paeth function.
// It is a straight port of the sample code in the PNG spec, section 9.4.
func slowPaeth(a, b, c uint8) uint8 {
	p := int(a) + int(b) - int(c)
	pa := slowAbs(p - int(a))
	pb := slowAbs(p - int(b))
	pc := slowAbs(p - int(c))

			if d.bytes.nUnreadable != 0 {
				d.unreadByteStuffedByte()
			}
			goto slowPath
		}
	}
	if v := h.lut[(d.bits.a>>uint32(d.bits.n-lutSize))&0xff]; v != 0 {
		n := (v & 0xff) - 1
		d.bits.n -= int32(n)
		d.bits.m >>= n
		return uint8(v >> 8), nil
	}

slowPath:
	for i, code := 0, int32(0); i < maxCodeLength; i++ {
		if d.bits.n == 0 {