json-iterator/feature_stream_float.go

package jsoniter

import (
	"strconv"
	"unsafe"
)

var POW10 []uint64

func init() {
	POW10 = []uint64{1, 10, 100, 1000, 10000, 100000, 1000000}
}

func (stream *Stream) WriteFloat32(val float32) {
	stream.WriteRaw(strconv.FormatFloat(float64(val), 'f', -1, 32))
}

func (stream *Stream) WriteFloat32Lossy(val float32) {
	if val < 0 {
		stream.writeByte('-')
		val = -val
	}
	if val > 0x4ffffff {
		stream.WriteRaw(strconv.FormatFloat(float64(val), 'f', -1, 32))
		return
	}
	precision := 6
	exp := uint64(1000000) // 6
	lval := uint64(float64(val)*float64(exp) + 0.5)
	stream.WriteUint64(lval / exp)
	fval := lval % exp
	if fval == 0 {
		return
	}
	stream.writeByte('.')
	stream.ensure(10)
	for p := precision - 1; p > 0 && fval < POW10[p]; p-- {
		stream.writeByte('0')
	}
	stream.WriteUint64(fval)
	for stream.buf[stream.n-1] == '0' {
		stream.n--
	}
}

func (stream *Stream) WriteFloat64(val float64) {
	stream.WriteRaw(strconv.FormatFloat(float64(val), 'f', -1, 64))
}

func (stream *Stream) WriteFloat64Lossy(val float64) {
	if val < 0 {
		stream.writeByte('-')
		val = -val
	}
	if val > 0x4ffffff {
		stream.WriteRaw(strconv.FormatFloat(val, 'f', -1, 64))
		return
	}
	precision := 6
	exp := uint64(1000000) // 6
	lval := uint64(val*float64(exp) + 0.5)
	stream.WriteUint64(lval / exp)
	fval := lval % exp
	if fval == 0 {
		return
	}
	stream.writeByte('.')
	stream.ensure(10)
	for p := precision - 1; p > 0 && fval < POW10[p]; p-- {
		stream.writeByte('0')
	}
	stream.WriteUint64(fval)
	for stream.buf[stream.n-1] == '0' {
		stream.n--
	}
}

// EnableLossyFloatMarshalling keeps 10**(-6) precision
// for float variables for better performance.
func EnableLossyFloatMarshalling() {
	// for better performance
	RegisterTypeEncoder("float32", func(ptr unsafe.Pointer, stream *Stream) {
		val := *((*float32)(ptr))
		stream.WriteFloat32Lossy(val)
	})
	RegisterTypeEncoder("float64", func(ptr unsafe.Pointer, stream *Stream) {
		val := *((*float64)(ptr))
		stream.WriteFloat64Lossy(val)
	})
}