if atEOF {
		return len(data), dropCR(data), nil
	}
	// Request more data.
	return 0, nil, nil
}

// isSpace reports whether the character is a Unicode white space character.
// We avoid dependency on the unicode package, but check validity of the implementation
// in the tests.
func isSpace(r rune) bool {
	if r <= '\u00FF' {
		// Obvious ASCII ones: \t through \r plus space. Plus two Latin-1 oddballs.
		switch r {

// Test white space table matches the Unicode definition.
func TestSpace(t *testing.T) {
	for r := rune(0); r <= utf8.MaxRune; r++ {
		if IsSpace(r) != unicode.IsSpace(r) {
			t.Fatalf("white space property disagrees: %#U should be %t", r, unicode.IsSpace(r))
		}
	}
}

var scanTests = []string{
	"",
	"a",
	"¼",
	"☹",
	"\x81",   // UTF-8 error
	"\uFFFD", // correctly encoded RuneError

	setBits := uint8(0)
	for i := 0; i < len(s); i++ {
		r := s[i]
		setBits |= r
		isSpace := int(asciiSpace[r])
		n += wasSpace & ^isSpace
		wasSpace = isSpace
	}

	if setBits >= utf8.RuneSelf {
		// Some runes in the input slice are not ASCII.
		return FieldsFunc(s, unicode.IsSpace)
	}

	// ASCII fast path
	a := make([][]byte, n)
	na := 0
	fieldStart := 0
	i := 0

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