encoding.go raw

   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  }
  41