if b[0]&0x40 != 0 {
			inv = 0xff
		}

		var x uint64
		for i, c := range b {
			c ^= inv // Inverts c only if inv is 0xff, otherwise does nothing
			if i == 0 {
				c &= 0x7f // Ignore signal bit in first byte
			}
			if (x >> 56) > 0 {
				p.err = ErrHeader // Integer overflow
				return 0
			}
			x = x<<8 | uint64(c)
		}
		if (x >> 63) > 0 {
			p.err = ErrHeader // Integer overflow