aboutsummaryrefslogtreecommitdiff
path: root/src/encoding
diff options
context:
space:
mode:
Diffstat (limited to 'src/encoding')
-rw-r--r--src/encoding/json/encode.go18
-rw-r--r--src/encoding/json/indent.go104
-rw-r--r--src/encoding/json/stream.go10
3 files changed, 69 insertions, 63 deletions
diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
index 9d59b0ff2b..d2f752a4f8 100644
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -175,12 +175,12 @@ func MarshalIndent(v any, prefix, indent string) ([]byte, error) {
if err != nil {
return nil, err
}
- var buf bytes.Buffer
- err = Indent(&buf, b, prefix, indent)
+ b2 := make([]byte, 0, indentGrowthFactor*len(b))
+ b2, err = appendIndent(b2, b, prefix, indent)
if err != nil {
return nil, err
}
- return buf.Bytes(), nil
+ return b2, nil
}
// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
@@ -476,8 +476,10 @@ func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
}
b, err := m.MarshalJSON()
if err == nil {
- // copy JSON into buffer, checking validity.
- err = compact(&e.Buffer, b, opts.escapeHTML)
+ e.Grow(len(b))
+ out := availableBuffer(&e.Buffer)
+ out, err = appendCompact(out, b, opts.escapeHTML)
+ e.Buffer.Write(out)
}
if err != nil {
e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
@@ -493,8 +495,10 @@ func addrMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
m := va.Interface().(Marshaler)
b, err := m.MarshalJSON()
if err == nil {
- // copy JSON into buffer, checking validity.
- err = compact(&e.Buffer, b, opts.escapeHTML)
+ e.Grow(len(b))
+ out := availableBuffer(&e.Buffer)
+ out, err = appendCompact(out, b, opts.escapeHTML)
+ e.Buffer.Write(out)
}
if err != nil {
e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
diff --git a/src/encoding/json/indent.go b/src/encoding/json/indent.go
index 2924d3b49b..375f71605a 100644
--- a/src/encoding/json/indent.go
+++ b/src/encoding/json/indent.go
@@ -4,69 +4,73 @@
package json
-import (
- "bytes"
-)
+import "bytes"
+
+// TODO(https://go.dev/issue/53685): Use bytes.Buffer.AvailableBuffer instead.
+func availableBuffer(b *bytes.Buffer) []byte {
+ return b.Bytes()[b.Len():]
+}
// Compact appends to dst the JSON-encoded src with
// insignificant space characters elided.
func Compact(dst *bytes.Buffer, src []byte) error {
- return compact(dst, src, false)
+ dst.Grow(len(src))
+ b := availableBuffer(dst)
+ b, err := appendCompact(b, src, false)
+ dst.Write(b)
+ return err
}
-func compact(dst *bytes.Buffer, src []byte, escape bool) error {
- origLen := dst.Len()
+func appendCompact(dst, src []byte, escape bool) ([]byte, error) {
+ origLen := len(dst)
scan := newScanner()
defer freeScanner(scan)
start := 0
for i, c := range src {
if escape && (c == '<' || c == '>' || c == '&') {
- if start < i {
- dst.Write(src[start:i])
- }
- dst.WriteString(`\u00`)
- dst.WriteByte(hex[c>>4])
- dst.WriteByte(hex[c&0xF])
+ dst = append(dst, src[start:i]...)
+ dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])
start = i + 1
}
// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
if escape && c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
- if start < i {
- dst.Write(src[start:i])
- }
- dst.WriteString(`\u202`)
- dst.WriteByte(hex[src[i+2]&0xF])
- start = i + 3
+ dst = append(dst, src[start:i]...)
+ dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])
+ start = i + len("\u2029")
}
v := scan.step(scan, c)
if v >= scanSkipSpace {
if v == scanError {
break
}
- if start < i {
- dst.Write(src[start:i])
- }
+ dst = append(dst, src[start:i]...)
start = i + 1
}
}
if scan.eof() == scanError {
- dst.Truncate(origLen)
- return scan.err
- }
- if start < len(src) {
- dst.Write(src[start:])
+ return dst[:origLen], scan.err
}
- return nil
+ dst = append(dst, src[start:]...)
+ return dst, nil
}
-func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
- dst.WriteByte('\n')
- dst.WriteString(prefix)
+func appendNewline(dst []byte, prefix, indent string, depth int) []byte {
+ dst = append(dst, '\n')
+ dst = append(dst, prefix...)
for i := 0; i < depth; i++ {
- dst.WriteString(indent)
+ dst = append(dst, indent...)
}
+ return dst
}
+// indentGrowthFactor specifies the growth factor of indenting JSON input.
+// Empirically, the growth factor was measured to be between 1.4x to 1.8x
+// for some set of compacted JSON with the indent being a single tab.
+// Specify a growth factor slightly larger than what is observed
+// to reduce probability of allocation in appendIndent.
+// A factor no higher than 2 ensures that wasted space never exceeds 50%.
+const indentGrowthFactor = 2
+
// Indent appends to dst an indented form of the JSON-encoded src.
// Each element in a JSON object or array begins on a new,
// indented line beginning with prefix followed by one or more
@@ -79,7 +83,15 @@ func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
// For example, if src has no trailing spaces, neither will dst;
// if src ends in a trailing newline, so will dst.
func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
- origLen := dst.Len()
+ dst.Grow(indentGrowthFactor * len(src))
+ b := availableBuffer(dst)
+ b, err := appendIndent(b, src, prefix, indent)
+ dst.Write(b)
+ return err
+}
+
+func appendIndent(dst, src []byte, prefix, indent string) ([]byte, error) {
+ origLen := len(dst)
scan := newScanner()
defer freeScanner(scan)
needIndent := false
@@ -96,13 +108,13 @@ func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
if needIndent && v != scanEndObject && v != scanEndArray {
needIndent = false
depth++
- newline(dst, prefix, indent, depth)
+ dst = appendNewline(dst, prefix, indent, depth)
}
// Emit semantically uninteresting bytes
// (in particular, punctuation in strings) unmodified.
if v == scanContinue {
- dst.WriteByte(c)
+ dst = append(dst, c)
continue
}
@@ -111,33 +123,27 @@ func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
case '{', '[':
// delay indent so that empty object and array are formatted as {} and [].
needIndent = true
- dst.WriteByte(c)
-
+ dst = append(dst, c)
case ',':
- dst.WriteByte(c)
- newline(dst, prefix, indent, depth)
-
+ dst = append(dst, c)
+ dst = appendNewline(dst, prefix, indent, depth)
case ':':
- dst.WriteByte(c)
- dst.WriteByte(' ')
-
+ dst = append(dst, c, ' ')
case '}', ']':
if needIndent {
// suppress indent in empty object/array
needIndent = false
} else {
depth--
- newline(dst, prefix, indent, depth)
+ dst = appendNewline(dst, prefix, indent, depth)
}
- dst.WriteByte(c)
-
+ dst = append(dst, c)
default:
- dst.WriteByte(c)
+ dst = append(dst, c)
}
}
if scan.eof() == scanError {
- dst.Truncate(origLen)
- return scan.err
+ return dst[:origLen], scan.err
}
- return nil
+ return dst, nil
}
diff --git a/src/encoding/json/stream.go b/src/encoding/json/stream.go
index 1442ef29ef..b4146a359e 100644
--- a/src/encoding/json/stream.go
+++ b/src/encoding/json/stream.go
@@ -183,7 +183,7 @@ type Encoder struct {
err error
escapeHTML bool
- indentBuf *bytes.Buffer
+ indentBuf []byte
indentPrefix string
indentValue string
}
@@ -221,15 +221,11 @@ func (enc *Encoder) Encode(v any) error {
b := e.Bytes()
if enc.indentPrefix != "" || enc.indentValue != "" {
- if enc.indentBuf == nil {
- enc.indentBuf = new(bytes.Buffer)
- }
- enc.indentBuf.Reset()
- err = Indent(enc.indentBuf, b, enc.indentPrefix, enc.indentValue)
+ enc.indentBuf, err = appendIndent(enc.indentBuf[:0], b, enc.indentPrefix, enc.indentValue)
if err != nil {
return err
}
- b = enc.indentBuf.Bytes()
+ b = enc.indentBuf
}
if _, err = enc.w.Write(b); err != nil {
enc.err = err
generated by cgit v1.3 (git 2.53.0) at 2026-04-15 15:31:40 +0000