}

func TestPipe3(t *testing.T) {
	c := make(chan pipeReturn)
	r, w := Pipe()
	var wdat = make([]byte, 128)
	for i := 0; i < len(wdat); i++ {
		wdat[i] = byte(i)
	}
	go writer(w, wdat, c)
	var rdat = make([]byte, 1024)
	tot := 0
	for n := 1; n <= 256; n *= 2 {
		nn, err := r.Read(rdat[tot : tot+n])
		if err != nil && err != EOF {
			t.Fatalf("read: %v", err)
		}

	return c
}

// slowFilterPaeth is a slow but simple implementation of func filterPaeth.
func slowFilterPaeth(cdat, pdat []byte, bytesPerPixel int) {
	for i := 0; i < bytesPerPixel; i++ {
		cdat[i] += paeth(0, pdat[i], 0)
	}
	for i := bytesPerPixel; i < len(cdat); i++ {
		cdat[i] += paeth(cdat[i-bytesPerPixel], pdat[i], pdat[i-bytesPerPixel])
	}
}

func TestPaeth(t *testing.T) {
	for a := 0; a < 256; a += 15 {

		return b
	}
	return c
}

// filterPaeth applies the Paeth filter to the cdat slice.
// cdat is the current row's data, pdat is the previous row's data.
func filterPaeth(cdat, pdat []byte, bytesPerPixel int) {
	var a, b, c, pa, pb, pc int
	for i := 0; i < bytesPerPixel; i++ {
		a, c = 0, 0
		for j := i; j < len(cdat); j += bytesPerPixel {
			b = int(pdat[j])
			pa = b - c
			pb = a - c
			pc = abs(pa + pb)
			pa = abs(pa)

Russ Cox <******@****.***> 1620744764 -0400

Russ Cox <******@****.***> 1410149331 -0400

Jes Cok <******@****.***> 1687506468 +0000

		return func() { <-c }
	}
	readEOF := func(t *testing.T, b *ProfBuf) {
		rdata, rtags, eof := b.Read(ProfBufBlocking)
		if rdata != nil || rtags != nil || !eof {
			t.Errorf("unexpected profile read: %#x, %#x, eof=%v; want nil, nil, eof=true", rdata, rtags, eof)
		}
		rdata, rtags, eof = b.Read(ProfBufNonBlocking)
		if rdata != nil || rtags != nil || !eof {

// Total size +4 for saved LR is 352

	// w[i] = p[j]<<24 | p[j+1]<<16 | p[j+2]<<8 | p[j+3]
	// e += w[i]
#define LOAD(Re) \
	MOVBU	2(Rdata), Rt0 ; \
	MOVBU	3(Rdata), Rt1 ; \
	MOVBU	1(Rdata), Rt2 ; \
	ORR	Rt0<<8, Rt1, Rt0	    ; \
	MOVBU.P	4(Rdata), Rt1 ; \
	ORR	Rt2<<16, Rt0, Rt0	    ; \
	ORR	Rt1<<24, Rt0, Rt0	    ; \
	MOVW.P	Rt0, 4(Rw)		    ; \
	ADD	Rt0, Re, Re

		// 3 words at 4..12(R13) for called routine parameters

TEXT	·block(SB), NOSPLIT, $84-16
	MOVW	p+4(FP), Rdata	// pointer to the data
	MOVW	p_len+8(FP), Rt0	// number of bytes
	ADD	Rdata, Rt0
	MOVW	Rt0, p_end	// pointer to end of data

loop:
	MOVW	Rdata, p_data	// Save Rdata
	AND.S	$3, Rdata, Rt0	// TST $3, Rdata not working see issue 5921
	BEQ	aligned			// aligned detected - skip copy

	{Ldate | Ltime | Lmicroseconds | Lshortfile, "XXX", "XXX" + Rdate + " " + Rtime + Rmicroseconds + " " + Rshortfile + " "},
	{Ldate | Ltime | Lmicroseconds | Llongfile | Lmsgprefix, "XXX", Rdate + " " + Rtime + Rmicroseconds + " " + Rlongfile + " XXX"},