if !isSpace(r) {
			break
		}
	}
	// Scan until space, marking end of word.
	for width, i := 0, start; i < len(data); i += width {
		var r rune
		r, width = utf8.DecodeRune(data[i:])
		if isSpace(r) {
			return i + width, data[start:i], nil
		}
	}
	// If we're at EOF, we have a final, non-empty, non-terminated word. Return it.
	if atEOF && len(data) > start {
		return len(data), data[start:], nil
	}

	}
	if err := scanner.Err(); err != nil {
		fmt.Fprintln(os.Stderr, "shouldn't see an error scanning a string")
	}
	// Output:
	// true
}

// Use a Scanner to implement a simple word-count utility by scanning the
// input as a sequence of space-delimited tokens.
func ExampleScanner_words() {
	// An artificial input source.

pkg image/png, type EncoderBufferPool interface, Put(*EncoderBuffer)
pkg math/big, method (*Int) IsInt64() bool
pkg math/big, method (*Int) IsUint64() bool
pkg math/big, type Word uint
pkg math/bits (darwin-amd64), const UintSize = 64
pkg math/bits (darwin-amd64-cgo), const UintSize = 64
pkg math/bits (freebsd-386), const UintSize = 32
pkg math/bits (freebsd-386-cgo), const UintSize = 32

	scratch := make([][]lex.Token, 0, 3)
	for {
		word, cond, operands, ok := p.line(scratch)
		if !ok {
			break
		}
		scratch = operands

		if p.pseudo(word, operands) {
			continue
		}
		i, present := p.arch.Instructions[word]
		if present {
			p.instruction(i, word, cond, operands)
			continue
		}
		p.errorf("unrecognized instruction %q", word)
	}
	if p.errorCount > 0 {
		return nil, false

pkg math/big, method (*Int) Binomial(int64, int64) *Int
pkg math/big, method (*Int) Bit(int) uint
pkg math/big, method (*Int) BitLen() int
pkg math/big, method (*Int) Bits() []Word
pkg math/big, method (*Int) Bytes() []uint8
pkg math/big, method (*Int) Cmp(*Int) int
pkg math/big, method (*Int) Div(*Int, *Int) *Int
pkg math/big, method (*Int) DivMod(*Int, *Int, *Int) (*Int, *Int)

but only worthwhile if it's likely the instruction will be used again.
Instead, for simple one-off cases, it's possible to use the <code>BYTE</code>
and <code>WORD</code> directives
to lay down explicit data into the instruction stream within a <code>TEXT</code>.
Here's how the 386 runtime defines the 64-bit atomic load function.
</p>

<pre>

// asciiSet is a 32-byte value, where each bit represents the presence of a
// given ASCII character in the set. The 128-bits of the lower 16 bytes,
// starting with the least-significant bit of the lowest word to the
// most-significant bit of the highest word, map to the full range of all
// 128 ASCII characters. The 128-bits of the upper 16 bytes will be zeroed,
// ensuring that any non-ASCII character will be reported as not in the set.

func (in *Input) Text() string {
	return in.text
}

// hash processes a # preprocessor directive. It reports whether it completes.
func (in *Input) hash() bool {
	// We have a '#'; it must be followed by a known word (define, include, etc.).
	tok := in.Stack.Next()
	if tok != scanner.Ident {
		in.expectText("expected identifier after '#'")
	}
	if !in.enabled() {

// MIPS (MIPS64) instruction set, to minimize its interaction
// with the core of the assembler.

package arch

import (
	"cmd/internal/obj"
	"cmd/internal/obj/mips"
)

func jumpMIPS(word string) bool {
	switch word {
	case "BEQ", "BFPF", "BFPT", "BGEZ", "BGEZAL", "BGTZ", "BLEZ", "BLTZ", "BLTZAL", "BNE", "JMP", "JAL", "CALL":
		return true
	}
	return false
}

}

func TestScanWordsExcessiveWhiteSpace(t *testing.T) {
	const word = "ipsum"
	s := strings.Repeat(" ", 4*smallMaxTokenSize) + word
	scanner := NewScanner(strings.NewReader(s))
	scanner.MaxTokenSize(smallMaxTokenSize)
	scanner.Split(ScanWords)
	if !scanner.Scan() {
		t.Fatalf("scan failed: %v", scanner.Err())
	}
	if token := scanner.Text(); token != word {
		t.Fatalf("unexpected token: %v", token)
	}
}