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
88. 88
89. 89
90. 90
91. 91
92. 92
93. 93
94. 94
95. 95
96. 96
97. 97
98. 98
99. 99
100. 100
101. 101
102. 102
103. 103
104. 104
105. 105
106. 106
107. 107
108. 108
109. 109
110. 110
111. 111
112. 112
113. 113
114. 114
115. 115
116. 116
117. 117
118. 118

package brotli

import (
	"errors"
	"io"
)

const (
	BestSpeed          = 0
	BestCompression    = 11
	DefaultCompression = 6
)

// WriterOptions configures Writer.
type WriterOptions struct {
	// Quality controls the compression-speed vs compression-density trade-offs.
	// The higher the quality, the slower the compression. Range is 0 to 11.
	Quality int
	// LGWin is the base 2 logarithm of the sliding window size.
	// Range is 10 to 24. 0 indicates automatic configuration based on Quality.
	LGWin int
}

var (
	errEncode       = errors.New("brotli: encode error")
	errWriterClosed = errors.New("brotli: Writer is closed")
)

// Writes to the returned writer are compressed and written to dst.
// It is the caller's responsibility to call Close on the Writer when done.
// Writes may be buffered and not flushed until Close.
func NewWriter(dst io.Writer) *Writer {
	return NewWriterLevel(dst, DefaultCompression)
}

// NewWriterLevel is like NewWriter but specifies the compression level instead
// of assuming DefaultCompression.
// The compression level can be DefaultCompression or any integer value between
// BestSpeed and BestCompression inclusive.
func NewWriterLevel(dst io.Writer, level int) *Writer {
	return NewWriterOptions(dst, WriterOptions{
		Quality: level,
	})
}

// NewWriterOptions is like NewWriter but specifies WriterOptions
func NewWriterOptions(dst io.Writer, options WriterOptions) *Writer {
	w := new(Writer)
	w.options = options
	w.Reset(dst)
	return w
}

// Reset discards the Writer's state and makes it equivalent to the result of
// its original state from NewWriter or NewWriterLevel, but writing to dst
// instead. This permits reusing a Writer rather than allocating a new one.
func (w *Writer) Reset(dst io.Writer) {
	encoderInitState(w)
	w.params.quality = w.options.Quality
	if w.options.LGWin > 0 {
		w.params.lgwin = uint(w.options.LGWin)
	}
	w.dst = dst
}

func (w *Writer) writeChunk(p []byte, op int) (n int, err error) {
	if w.dst == nil {
		return 0, errWriterClosed
	}
	if w.err != nil {
		return 0, w.err
	}

	for {
		availableIn := uint(len(p))
		nextIn := p
		success := encoderCompressStream(w, op, &availableIn, &nextIn)
		bytesConsumed := len(p) - int(availableIn)
		p = p[bytesConsumed:]
		n += bytesConsumed
		if !success {
			return n, errEncode
		}

		if len(p) == 0 || w.err != nil {
			return n, w.err
		}
	}
}

// Flush outputs encoded data for all input provided to Write. The resulting
// output can be decoded to match all input before Flush, but the stream is
// not yet complete until after Close.
// Flush has a negative impact on compression.
func (w *Writer) Flush() error {
	_, err := w.writeChunk(nil, operationFlush)
	return err
}

// Close flushes remaining data to the decorated writer.
func (w *Writer) Close() error {
	// If stream is already closed, it is reported by `writeChunk`.
	_, err := w.writeChunk(nil, operationFinish)
	w.dst = nil
	return err
}

// Write implements io.Writer. Flush or Close must be called to ensure that the
// encoded bytes are actually flushed to the underlying Writer.
func (w *Writer) Write(p []byte) (n int, err error) {
	return w.writeChunk(p, operationProcess)
}

type nopCloser struct {
	io.Writer
}

func (nopCloser) Close() error { return nil }