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numbers.go
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numbers.go
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/*
Copyright (c) 2009 The Go Authors. All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following
disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials provided with the distribution.
- Neither the name of Google Inc. nor the names of its contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package json
import (
"encoding/json"
"io"
"math"
"reflect"
"strconv"
)
//
func encodeFloat(w io.Writer, f float64, bits int) error {
if math.IsInf(f, 0) || math.IsNaN(f) {
return &json.UnsupportedValueError{Value: reflect.ValueOf(f), Str: strconv.FormatFloat(f, 'g', -1, bits)}
}
// Convert as if by ES6 number to string conversion. This matches most other JSON generators. See
// golang.org/issue/6384 and golang.org/issue/14135. Like fmt %g, but the exponent cutoffs are different and
// exponents themselves are not padded to two digits.
abs := math.Abs(f)
fmt := byte('f')
// Note: Must use float32 comparisons for underlying float32 value to get precise cutoffs right.
if abs != 0 {
if bits == 64 && (abs < 1e-6 || abs >= 1e21) || bits == 32 && (float32(abs) < 1e-6 || float32(abs) >= 1e21) {
fmt = 'e'
}
}
var b []byte
b = strconv.AppendFloat(b, f, fmt, -1, bits)
if fmt == 'e' {
// clean up e-09 to e-9
n := len(b)
if n >= 4 && b[n-4] == 'e' && b[n-3] == '-' && b[n-2] == '0' {
b[n-2] = b[n-1]
b = b[:n-1]
}
}
_, err := w.Write(b)
return err
}
func EncodeFloat32(w io.Writer, f float32) error {
return encodeFloat(w, float64(f), 32)
}
func EncodeFloat64(w io.Writer, f float64) error {
return encodeFloat(w, f, 64)
}
//
// isValidNumber reports whether s is a valid JSON number literal.
func IsValidNumber(s string) bool {
// This function implements the JSON numbers grammar. See https://tools.ietf.org/html/rfc7159#section-6 and
// https://www.json.org/img/number.png
if s == "" {
return false
}
// Optional -
if s[0] == '-' {
s = s[1:]
if s == "" {
return false
}
}
// Digits
switch {
default:
return false
case s[0] == '0':
s = s[1:]
case '1' <= s[0] && s[0] <= '9':
s = s[1:]
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
}
// . followed by 1 or more digits.
if len(s) >= 2 && s[0] == '.' && '0' <= s[1] && s[1] <= '9' {
s = s[2:]
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
}
// e or E followed by an optional - or + and 1 or more digits.
if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') {
s = s[1:]
if s[0] == '+' || s[0] == '-' {
s = s[1:]
if s == "" {
return false
}
}
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
}
// Make sure we are at the end.
return s == ""
}