Function AppendFloat

fflib/v1/ftoa.go:41–145

AppendFloat appends the string form of the floating-point number f, as generated by FormatFloat

(dst EncodingBuffer, val float64, fmt byte, prec, bitSize int)

// AppendFloat appends the string form of the floating-point number f,
// as generated by FormatFloat
func AppendFloat(dst EncodingBuffer, val float64, fmt byte, prec, bitSize int) {
	var bits uint64
	var flt *floatInfo
	switch bitSize {
	case 32:
		bits = uint64(math.Float32bits(float32(val)))
		flt = &float32info
	case 64:
		bits = math.Float64bits(val)
		flt = &float64info
	default:
		panic("strconv: illegal AppendFloat/FormatFloat bitSize")
	}

	neg := bits>>(flt.expbits+flt.mantbits) != 0
	exp := int(bits>>flt.mantbits) & (1<<flt.expbits - 1)
	mant := bits & (uint64(1)<<flt.mantbits - 1)

	switch exp {
	case 1<<flt.expbits - 1:
		// Inf, NaN
		var s string
		switch {
		case mant != 0:
			s = "NaN"
		case neg:
			s = "-Inf"
		default:
			s = "+Inf"
		}
		dst.WriteString(s)
		return

	case 0:
		// denormalized
		exp++

	default:
		// add implicit top bit
		mant |= uint64(1) << flt.mantbits
	}
	exp += flt.bias

	// Pick off easy binary format.
	if fmt == 'b' {
		fmtB(dst, neg, mant, exp, flt)
		return
	}

	if !optimize {
		bigFtoa(dst, prec, fmt, neg, mant, exp, flt)
		return
	}

	var digs decimalSlice
	ok := false
	// Negative precision means "only as much as needed to be exact."
	shortest := prec < 0