L, M, N, P, and S general categories (the Graphic characters without
spaces) and may also exclude the characters
<code>!"#$%&amp;'()*,:;&lt;=&gt;?[\]^`{|}</code>
and the Unicode replacement character U+FFFD.
</p>

<p>
Assume we have compiled a package containing the package clause
<code>package math</code>, which exports function <code>Sin</code>, and
installed the compiled package in the file identified by

	POPW AX
	PUSHQ (BX)                              // ff33
	POPQ AX
	PUSHQ (R11)                             // 41ff33
	POPQ AX
	PUSHQ DX                                // fff2 or 52
	POPQ AX
	PUSHQ R11                               // 41fff3 or 4153
	POPQ AX
	PUSHFW                                  // 669c
	POPFW
	PUSHFQ                                  // 9c
	POPFQ

L, M, N, P, and S general categories (the Graphic characters without
spaces) and may also exclude the characters
<code>!"#$%&amp;'()*,:;&lt;=&gt;?[\]^`{|}</code>
and the Unicode replacement character U+FFFD.
</p>

<p>
Consider a compiled a package containing the package clause
<code>package math</code>, which exports function <code>Sin</code>, and
installed the compiled package in the file identified by

	return nil
}

// ReadRune reads a single UTF-8 encoded Unicode character and returns the
// rune and its size in bytes. If the encoded rune is invalid, it consumes one byte
// and returns unicode.ReplacementChar (U+FFFD) with a size of 1.
func (b *Reader) ReadRune() (r rune, size int, err error) {
	for b.r+utf8.UTFMax > b.w && !utf8.FullRune(b.buf[b.r:b.w]) && b.err == nil && b.w-b.r < len(b.buf) {