You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: diyfp.go
    path of file: ./repos/k6/vendor/github.com/dop251/goja/ftoa/internal/fast
    
    the code of the file until where you have to start completion: package fast

import "math"

const (
	diyFpKSignificandSize        = 64
	kSignificandSize             = 53
	kUint64MSB            uint64 = 1 << 63

	kSignificandMask = 0x000FFFFFFFFFFFFF
	kHiddenBit       = 0x0010000000000000
	kExponentMask    = 0x7FF0000000000000

	kPhysicalSignificandSize = 52 // Excludes the hidden bit.
	kExponentBias            = 0x
    
func (f *diyfp) mul(o diyfp) {
	// Simply "emulates" a 128 bit multiplication.
	// However: the resulting number only contains 64 bits. The least
	// significant 64 bits are only used for rounding the most significant 64
	// bits.
	const kM32 uint64 = 0xFFFFFFFF
	a := f.f >> 32
	b := f.f & kM32
	c := o.f >> 32
	d := o.f & kM32
	ac := a * c
	bc := b * c
	ad := a * d
	bd := b * d
	tmp := (bd >> 32) + (ad & kM32) + (bc & kM32)
	// By adding 1U << 31 to tmp we round the final result.
	// Halfway cases will be round up.
	tmp += 1 << 31
	result_f := ac + (ad >> 32) + (bc >> 32) + (tmp >> 32)
	f.e += o.e + 64
	f.f = result_f
}