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: ftoa.go
    path of file: ./repos/gccrs/libgo/go/strconv
    
    the code of the file until where you have to start completion: // Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Binary to decimal floating point conversion.
// Algorithm:
//   1) store mantissa in multiprecision decimal
//   2) shift decimal by exponent
//   3) read digits out & format

package strconv

import "math"

// TODO: move elsewhere?
type floatInfo struct {
	mantbits uint
    
func bigFtoa(dst []byte, prec int, fmt byte, neg bool, mant uint64, exp int, flt *floatInfo) []byte {
	d := new(decimal)
	d.Assign(mant)
	d.Shift(exp - int(flt.mantbits))
	var digs decimalSlice
	shortest := prec < 0
	if shortest {
		roundShortest(d, mant, exp, flt)
		digs = decimalSlice{d: d.d[:], nd: d.nd, dp: d.dp}
		// Precision for shortest representation mode.
		switch fmt {
		case 'e', 'E':
			prec = digs.nd - 1
		case 'f':
			prec = max(digs.nd-digs.dp, 0)
		case 'g', 'G':
			prec = digs.nd
		}
	} else {
		// Round appropriately.
		switch fmt {
		case 'e', 'E':
			d.Round(prec + 1)
		case 'f':
			d.Round(d.dp + prec)
		case 'g', 'G':
			if prec == 0 {
				prec = 1
			}
			d.Round(prec)
		}
		digs = decimalSlice{d: d.d[:], nd: d.nd, dp: d.dp}
	}
	return formatDigits(dst, shortest, neg, digs, prec, fmt)
}