Merge pull request #48287 from thockin/json-iterator

Automatic merge from submit-queue

Use json-iterator instead of ugorji for JSON.

@smarterclayton @wojtek-t

Fixes #36120
xref #18762

```release-note
Switch JSON marshal/unmarshal to json-iterator library.  Performance should be close to previous with no generated code.
```

Kubernetes-commit: 6a845c67f097cd76f9d90ab3c9c5b5603c70afe4

vendor/github.com/json-iterator/go/feature_iter_skip.go

@@ -0,0 +1,127 @@
+package jsoniter
+
+import "fmt"
+
+// ReadNil reads a json object as nil and
+// returns whether it's a nil or not
+func (iter *Iterator) ReadNil() (ret bool) {
+	c := iter.nextToken()
+	if c == 'n' {
+		iter.skipThreeBytes('u', 'l', 'l') // null
+		return true
+	}
+	iter.unreadByte()
+	return false
+}
+
+// ReadBool reads a json object as BoolValue
+func (iter *Iterator) ReadBool() (ret bool) {
+	c := iter.nextToken()
+	if c == 't' {
+		iter.skipThreeBytes('r', 'u', 'e')
+		return true
+	}
+	if c == 'f' {
+		iter.skipFourBytes('a', 'l', 's', 'e')
+		return false
+	}
+	iter.ReportError("ReadBool", "expect t or f")
+	return
+}
+
+// SkipAndReturnBytes skip next JSON element, and return its content as []byte.
+// The []byte can be kept, it is a copy of data.
+func (iter *Iterator) SkipAndReturnBytes() []byte {
+	iter.startCapture(iter.head)
+	iter.Skip()
+	return iter.stopCapture()
+}
+
+type captureBuffer struct {
+	startedAt int
+	captured  []byte
+}
+
+func (iter *Iterator) startCapture(captureStartedAt int) {
+	if iter.captured != nil {
+		panic("already in capture mode")
+	}
+	iter.captureStartedAt = captureStartedAt
+	iter.captured = make([]byte, 0, 32)
+}
+
+func (iter *Iterator) stopCapture() []byte {
+	if iter.captured == nil {
+		panic("not in capture mode")
+	}
+	captured := iter.captured
+	remaining := iter.buf[iter.captureStartedAt:iter.head]
+	iter.captureStartedAt = -1
+	iter.captured = nil
+	if len(captured) == 0 {
+		return remaining
+	}
+	captured = append(captured, remaining...)
+	return captured
+}
+
+// Skip skips a json object and positions to relatively the next json object
+func (iter *Iterator) Skip() {
+	c := iter.nextToken()
+	switch c {
+	case '"':
+		iter.skipString()
+	case 'n':
+		iter.skipThreeBytes('u', 'l', 'l') // null
+	case 't':
+		iter.skipThreeBytes('r', 'u', 'e') // true
+	case 'f':
+		iter.skipFourBytes('a', 'l', 's', 'e') // false
+	case '0':
+		iter.unreadByte()
+		iter.ReadFloat32()
+	case '-', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+		iter.skipNumber()
+	case '[':
+		iter.skipArray()
+	case '{':
+		iter.skipObject()
+	default:
+		iter.ReportError("Skip", fmt.Sprintf("do not know how to skip: %v", c))
+		return
+	}
+}
+
+func (iter *Iterator) skipFourBytes(b1, b2, b3, b4 byte) {
+	if iter.readByte() != b1 {
+		iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
+		return
+	}
+	if iter.readByte() != b2 {
+		iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
+		return
+	}
+	if iter.readByte() != b3 {
+		iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
+		return
+	}
+	if iter.readByte() != b4 {
+		iter.ReportError("skipFourBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3, b4})))
+		return
+	}
+}
+
+func (iter *Iterator) skipThreeBytes(b1, b2, b3 byte) {
+	if iter.readByte() != b1 {
+		iter.ReportError("skipThreeBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3})))
+		return
+	}
+	if iter.readByte() != b2 {
+		iter.ReportError("skipThreeBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3})))
+		return
+	}
+	if iter.readByte() != b3 {
+		iter.ReportError("skipThreeBytes", fmt.Sprintf("expect %s", string([]byte{b1, b2, b3})))
+		return
+	}
+}