Function validHeaderValueByte

textproto_reader.go:441–453

validHeaderValueByte reports whether c is a valid byte in a header field value. RFC 7230 says: field-content = field-vchar [ 1*( SP / HTAB ) field-vchar ] field-vchar = VCHAR / obs-text obs-text = %x80-FF RFC 5234 says: HTAB = %x09 SP = %x20 VCHAR

(c byte)

//	SP             =  %x20
//	VCHAR          =  %x21-7E
func validHeaderValueByte(c byte) bool {
	// mask is a 128-bit bitmap with 1s for allowed bytes,
	// so that the byte c can be tested with a shift and an and.
	// If c >= 128, then 1<<c and 1<<(c-64) will both be zero.
	// Since this is the obs-text range, we invert the mask to
	// create a bitmap with 1s for disallowed bytes.
	const mask = 0 |
		(1<<(0x7f-0x21)-1)<<0x21 | // VCHAR: %x21-7E
		1<<0x20 | // SP: %x20
		1<<0x09 // HTAB: %x09
	return ((uint64(1)<<c)&^(mask&(1<<64-1)) |
		(uint64(1)<<(c-64))&^(mask>>64)) == 0
}

// commonHeader interns common header strings.
var commonHeader map[string]string