if uint32(r) < utf8.RuneSelf {
		b.WriteByte(byte(r))
		return 1, nil
	}
	b.lastRead = opInvalid
	m, ok := b.tryGrowByReslice(utf8.UTFMax)
	if !ok {
		m = b.grow(utf8.UTFMax)
	}
	b.buf = utf8.AppendRune(b.buf[:m], r)
	return len(b.buf) - m, nil
}

// Read reads the next len(p) bytes from the buffer or until the buffer
// is drained. The return value n is the number of bytes read. If the

	b := make([]byte, 0, len(s))
	for i := 0; i < len(s); {
		wid := 1
		r := rune(s[i])
		if r >= utf8.RuneSelf {
			r, wid = utf8.DecodeRune(s[i:])
		}
		r = mapping(r)
		if r >= 0 {
			b = utf8.AppendRune(b, r)
		}
		i += wid
	}
	return b
}

// Despite being an exported symbol,
// Repeat is linknamed by widely used packages.
// Notable members of the hall of shame include:

The <a href="/pkg/cmd/vet"><code>go vet</code></a> tool flags certain
integer-to-string conversions as potential errors.
Library functions such as
<a href="/pkg/unicode/utf8#AppendRune"><code>utf8.AppendRune</code></a> or
<a href="/pkg/unicode/utf8#EncodeRune"><code>utf8.EncodeRune</code></a>
should be used instead.
</li>
</ol>