1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8
9. 9
10. 10
11. 11
12. 12
13. 13
14. 14
15. 15
16. 16
17. 17
18. 18
19. 19
20. 20
21. 21
22. 22
23. 23
24. 24
25. 25
26. 26
27. 27
28. 28
29. 29
30. 30
31. 31
32. 32
33. 33
34. 34
35. 35
36. 36
37. 37
38. 38
39. 39
40. 40
41. 41
42. 42
43. 43
44. 44
45. 45
46. 46
47. 47
48. 48
49. 49
50. 50
51. 51
52. 52
53. 53
54. 54
55. 55
56. 56
57. 57
58. 58
59. 59
60. 60
61. 61
62. 62
63. 63
64. 64
65. 65
66. 66
67. 67
68. 68
69. 69
70. 70
71. 71
72. 72
73. 73
74. 74
75. 75
76. 76
77. 77
78. 78
79. 79
80. 80
81. 81
82. 82
83. 83
84. 84
85. 85
86. 86
87. 87

//  Copyright (c) 2017 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 		http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package vellum

import (
	"encoding/binary"
	"fmt"
	"io"
)

const headerSize = 16

type encoderConstructor func(w io.Writer) encoder
type decoderConstructor func([]byte) decoder

var encoders = map[int]encoderConstructor{}
var decoders = map[int]decoderConstructor{}

type encoder interface {
	start() error
	encodeState(s *builderNode, addr int) (int, error)
	finish(count, rootAddr int) error
	reset(w io.Writer)
}

func loadEncoder(ver int, w io.Writer) (encoder, error) {
	if cons, ok := encoders[ver]; ok {
		return cons(w), nil
	}
	return nil, fmt.Errorf("no encoder for version %d registered", ver)
}

func registerEncoder(ver int, cons encoderConstructor) {
	encoders[ver] = cons
}

type decoder interface {
	getRoot() int
	getLen() int
	stateAt(addr int, prealloc fstState) (fstState, error)
}

func loadDecoder(ver int, data []byte) (decoder, error) {
	if cons, ok := decoders[ver]; ok {
		return cons(data), nil
	}
	return nil, fmt.Errorf("no decoder for version %d registered", ver)
}

func registerDecoder(ver int, cons decoderConstructor) {
	decoders[ver] = cons
}

func decodeHeader(header []byte) (ver int, typ int, err error) {
	if len(header) < headerSize {
		err = fmt.Errorf("invalid header < 16 bytes")
		return
	}
	ver = int(binary.LittleEndian.Uint64(header[0:8]))
	typ = int(binary.LittleEndian.Uint64(header[8:16]))
	return
}

// fstState represents a state inside the FTS runtime
// It is the main contract between the FST impl and the decoder
// The FST impl should work only with this interface, while only the decoder
// impl knows the physical representation.
type fstState interface {
	Address() int
	Final() bool
	FinalOutput() uint64
	NumTransitions() int
	TransitionFor(b byte) (int, int, uint64)
	TransitionAt(i int) byte
}