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encoding.go (983B)

      1 package encoding
      2 
      3 import (
      4 	"fmt"
      5 	"math"
      6 	"strconv"
      7 )
      8 
      9 // EncodeFloat encodes a float value as per the stdlib encoder for json and xml protocol
     10 // This encodes a float value into dst while attempting to conform to ES6 ToString for Numbers
     11 //
     12 // Based on encoding/json floatEncoder from the Go Standard Library
     13 // https://golang.org/src/encoding/json/encode.go
     14 func EncodeFloat(dst []byte, v float64, bits int) []byte {
     15 	if math.IsInf(v, 0) || math.IsNaN(v) {
     16 		panic(fmt.Sprintf("invalid float value: %s", strconv.FormatFloat(v, 'g', -1, bits)))
     17 	}
     18 
     19 	abs := math.Abs(v)
     20 	fmt := byte('f')
     21 
     22 	if abs != 0 {
     23 		if bits == 64 && (abs < 1e-6 || abs >= 1e21) || bits == 32 && (float32(abs) < 1e-6 || float32(abs) >= 1e21) {
     24 			fmt = 'e'
     25 		}
     26 	}
     27 
     28 	dst = strconv.AppendFloat(dst, v, fmt, -1, bits)
     29 
     30 	if fmt == 'e' {
     31 		// clean up e-09 to e-9
     32 		n := len(dst)
     33 		if n >= 4 && dst[n-4] == 'e' && dst[n-3] == '-' && dst[n-2] == '0' {
     34 			dst[n-2] = dst[n-1]
     35 			dst = dst[:n-1]
     36 		}
     37 	}
     38 
     39 	return dst
     40 }