serialize-pe.go

Documentation: sigs.k8s.io/structured-merge-diff/v4/fieldpath

     1  /*
     2  Copyright 2018 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package fieldpath
    18  
    19  import (
    20  	"errors"
    21  	"fmt"
    22  	"io"
    23  	"strconv"
    24  	"strings"
    25  
    26  	jsoniter "github.com/json-iterator/go"
    27  	"sigs.k8s.io/structured-merge-diff/v4/value"
    28  )
    29  
    30  var ErrUnknownPathElementType = errors.New("unknown path element type")
    31  
    32  const (
    33  	// Field indicates that the content of this path element is a field's name
    34  	peField = "f"
    35  
    36  	// Value indicates that the content of this path element is a field's value
    37  	peValue = "v"
    38  
    39  	// Index indicates that the content of this path element is an index in an array
    40  	peIndex = "i"
    41  
    42  	// Key indicates that the content of this path element is a key value map
    43  	peKey = "k"
    44  
    45  	// Separator separates the type of a path element from the contents
    46  	peSeparator = ":"
    47  )
    48  
    49  var (
    50  	peFieldSepBytes = []byte(peField + peSeparator)
    51  	peValueSepBytes = []byte(peValue + peSeparator)
    52  	peIndexSepBytes = []byte(peIndex + peSeparator)
    53  	peKeySepBytes   = []byte(peKey + peSeparator)
    54  	peSepBytes      = []byte(peSeparator)
    55  )
    56  
    57  // DeserializePathElement parses a serialized path element
    58  func DeserializePathElement(s string) (PathElement, error) {
    59  	b := []byte(s)
    60  	if len(b) < 2 {
    61  		return PathElement{}, errors.New("key must be 2 characters long:")
    62  	}
    63  	typeSep, b := b[:2], b[2:]
    64  	if typeSep[1] != peSepBytes[0] {
    65  		return PathElement{}, fmt.Errorf("missing colon: %v", s)
    66  	}
    67  	switch typeSep[0] {
    68  	case peFieldSepBytes[0]:
    69  		// Slice s rather than convert b, to save on
    70  		// allocations.
    71  		str := s[2:]
    72  		return PathElement{
    73  			FieldName: &str,
    74  		}, nil
    75  	case peValueSepBytes[0]:
    76  		iter := readPool.BorrowIterator(b)
    77  		defer readPool.ReturnIterator(iter)
    78  		v, err := value.ReadJSONIter(iter)
    79  		if err != nil {
    80  			return PathElement{}, err
    81  		}
    82  		return PathElement{Value: &v}, nil
    83  	case peKeySepBytes[0]:
    84  		iter := readPool.BorrowIterator(b)
    85  		defer readPool.ReturnIterator(iter)
    86  		fields := value.FieldList{}
    87  
    88  		iter.ReadObjectCB(func(iter *jsoniter.Iterator, key string) bool {
    89  			v, err := value.ReadJSONIter(iter)
    90  			if err != nil {
    91  				iter.Error = err
    92  				return false
    93  			}
    94  			fields = append(fields, value.Field{Name: key, Value: v})
    95  			return true
    96  		})
    97  		fields.Sort()
    98  		return PathElement{Key: &fields}, iter.Error
    99  	case peIndexSepBytes[0]:
   100  		i, err := strconv.Atoi(s[2:])
   101  		if err != nil {
   102  			return PathElement{}, err
   103  		}
   104  		return PathElement{
   105  			Index: &i,
   106  		}, nil
   107  	default:
   108  		return PathElement{}, ErrUnknownPathElementType
   109  	}
   110  }
   111  
   112  var (
   113  	readPool  = jsoniter.NewIterator(jsoniter.ConfigCompatibleWithStandardLibrary).Pool()
   114  	writePool = jsoniter.NewStream(jsoniter.ConfigCompatibleWithStandardLibrary, nil, 1024).Pool()
   115  )
   116  
   117  // SerializePathElement serializes a path element
   118  func SerializePathElement(pe PathElement) (string, error) {
   119  	buf := strings.Builder{}
   120  	err := serializePathElementToWriter(&buf, pe)
   121  	return buf.String(), err
   122  }
   123  
   124  func serializePathElementToWriter(w io.Writer, pe PathElement) error {
   125  	stream := writePool.BorrowStream(w)
   126  	defer writePool.ReturnStream(stream)
   127  	switch {
   128  	case pe.FieldName != nil:
   129  		if _, err := stream.Write(peFieldSepBytes); err != nil {
   130  			return err
   131  		}
   132  		stream.WriteRaw(*pe.FieldName)
   133  	case pe.Key != nil:
   134  		if _, err := stream.Write(peKeySepBytes); err != nil {
   135  			return err
   136  		}
   137  		stream.WriteObjectStart()
   138  
   139  		for i, field := range *pe.Key {
   140  			if i > 0 {
   141  				stream.WriteMore()
   142  			}
   143  			stream.WriteObjectField(field.Name)
   144  			value.WriteJSONStream(field.Value, stream)
   145  		}
   146  		stream.WriteObjectEnd()
   147  	case pe.Value != nil:
   148  		if _, err := stream.Write(peValueSepBytes); err != nil {
   149  			return err
   150  		}
   151  		value.WriteJSONStream(*pe.Value, stream)
   152  	case pe.Index != nil:
   153  		if _, err := stream.Write(peIndexSepBytes); err != nil {
   154  			return err
   155  		}
   156  		stream.WriteInt(*pe.Index)
   157  	default:
   158  		return errors.New("invalid PathElement")
   159  	}
   160  	b := stream.Buffer()
   161  	err := stream.Flush()
   162  	// Help jsoniter manage its buffers--without this, the next
   163  	// use of the stream is likely to require an allocation. Look
   164  	// at the jsoniter stream code to understand why. They were probably
   165  	// optimizing for folks using the buffer directly.
   166  	stream.SetBuffer(b[:0])
   167  	return err
   168  }
   169
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