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// Copyright (c) 2021, Maxime Soulé
// All rights reserved.
//
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree.
package json
import (
"bytes"
ejson "encoding/json"
"fmt"
"math"
"sort"
"strconv"
"unicode/utf8"
)
type marshaler struct {
buf *bytes.Buffer
indent int
tmp []byte
}
// Marshal returns the JSON encoding of v. It differs from
// [encoding/json.Marshal] as it only handles map[string]any,
// []any, bool, float64, string, nil and
// [encoding/json.Marshaler] values. It also accepts "invalid" JSON data
// returned by MarshalJSON method.
func Marshal(v any, indent int) ([]byte, error) {
m := marshaler{
indent: indent,
buf: &bytes.Buffer{},
}
err := m.marshal(v)
if err != nil {
return nil, err
}
return m.buf.Bytes(), nil
}
// AppendMarshal does the same as [Marshal] but appends the JSON
// encoding to buf.
func AppendMarshal(buf *bytes.Buffer, v any, indent int) error {
m := marshaler{
indent: indent,
buf: buf,
}
return m.marshal(v)
}
func (m *marshaler) marshal(v any) error {
if v == nil {
m.buf.WriteString("null")
return nil
}
switch vt := v.(type) {
case map[string]any:
if len(vt) == 0 {
if vt == nil {
m.buf.WriteString("null")
} else {
m.buf.WriteString("{}")
}
break
}
m.indent += 2
keys := make([]string, 0, len(vt))
for k := range vt {
keys = append(keys, k)
}
sort.Strings(keys)
beg := "{\n"
for _, k := range keys {
m.buf.WriteString(beg)
beg = ",\n"
saveIndent, lenBefore := m.indent, m.buf.Len()
fmt.Fprintf(m.buf, `%*s%q: `, m.indent, "", k)
m.indent = utf8.RuneCount(m.buf.Bytes()[lenBefore:])
if err := m.marshal(vt[k]); err != nil {
return err
}
m.indent = saveIndent
}
m.indent -= 2
fmt.Fprintf(m.buf, "\n%*s}", m.indent, "")
case []any:
if len(vt) == 0 {
if vt == nil {
m.buf.WriteString("null")
} else {
m.buf.WriteString("[]")
}
break
}
m.indent += 2
beg := "[\n"
for _, v := range vt {
m.buf.WriteString(beg)
beg = ",\n"
fmt.Fprintf(m.buf, "%*s", m.indent, "")
if err := m.marshal(v); err != nil {
return err
}
}
m.indent -= 2
fmt.Fprintf(m.buf, "\n%*s]", m.indent, "")
case string:
fmt.Fprintf(m.buf, `%q`, vt)
case float64:
m.marshalFloat64(vt)
case bool:
if vt {
m.buf.WriteString("true")
} else {
m.buf.WriteString("false")
}
case ejson.Marshaler:
b, err := vt.MarshalJSON()
if err != nil {
return err
}
repl := bytes.Repeat([]byte(" "), 1+m.indent)
repl[0] = '\n'
m.buf.Write(bytes.ReplaceAll(b, []byte("\n"), repl))
default:
return fmt.Errorf("Cannot marshal %T", vt)
}
return nil
}
func (m *marshaler) marshalFloat64(f float64) {
// Contrary to JSON standard we accept to marshal NaN and ±Inf
if math.IsInf(f, 0) || math.IsNaN(f) {
m.tmp = strconv.AppendFloat(m.tmp[:0], f, 'g', -1, 64)
m.buf.Write(m.tmp)
return
}
// Remainder based on encoding/json.floatEncoder.encode()
// 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')
if abs != 0 {
if abs < 1e-6 || abs >= 1e21 {
fmt = 'e'
}
}
m.tmp = strconv.AppendFloat(m.tmp[:0], f, fmt, -1, 64)
if fmt == 'e' {
// clean up e-09 to e-9
n := len(m.tmp)
if n >= 4 && m.tmp[n-4] == 'e' && m.tmp[n-3] == '-' && m.tmp[n-2] == '0' {
m.tmp[n-2] = m.tmp[n-1]
m.tmp = m.tmp[:n-1]
}
}
m.buf.Write(m.tmp)
}
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