forked from buildpacks/pack
-
Notifications
You must be signed in to change notification settings - Fork 0
/
prefix_writer.go
126 lines (105 loc) · 2.86 KB
/
prefix_writer.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
package logging
import (
"bufio"
"bytes"
"fmt"
"io"
"github.com/YousefHaggyHeroku/pack/internal/style"
)
// PrefixWriter is a buffering writer that prefixes each new line. Close should be called to properly flush the buffer.
type PrefixWriter struct {
out io.Writer
buf *bytes.Buffer
prefix string
readerFactory func(data []byte) io.Reader
}
type PrefixWriterOption func(c *PrefixWriter)
func WithReaderFactory(factory func(data []byte) io.Reader) PrefixWriterOption {
return func(writer *PrefixWriter) {
writer.readerFactory = factory
}
}
// NewPrefixWriter writes by w will be prefixed
func NewPrefixWriter(w io.Writer, prefix string, opts ...PrefixWriterOption) *PrefixWriter {
writer := &PrefixWriter{
out: w,
prefix: fmt.Sprintf("[%s] ", style.Prefix(prefix)),
buf: &bytes.Buffer{},
readerFactory: func(data []byte) io.Reader {
return bytes.NewReader(data)
},
}
for _, opt := range opts {
opt(writer)
}
return writer
}
// Write writes bytes to the embedded log function
func (w *PrefixWriter) Write(data []byte) (int, error) {
scanner := bufio.NewScanner(w.readerFactory(data))
scanner.Split(ScanLinesKeepNewLine)
for scanner.Scan() {
newBits := scanner.Bytes()
if len(newBits) > 0 && newBits[len(newBits)-1] != '\n' { // just append if we don't have a new line
_, err := w.buf.Write(newBits)
if err != nil {
return 0, err
}
} else { // write our complete message
_, err := w.buf.Write(bytes.TrimRight(newBits, "\n"))
if err != nil {
return 0, err
}
err = w.flush()
if err != nil {
return 0, err
}
}
}
if err := scanner.Err(); err != nil {
return 0, err
}
return len(data), nil
}
// Close writes any pending data in the buffer
func (w *PrefixWriter) Close() error {
if w.buf.Len() > 0 {
return w.flush()
}
return nil
}
func (w *PrefixWriter) flush() error {
bits := w.buf.Bytes()
w.buf.Reset()
// process any CR in message
if i := bytes.LastIndexByte(bits, '\r'); i >= 0 {
bits = bits[i+1:]
}
_, err := fmt.Fprint(w.out, w.prefix+string(bits)+"\n")
return err
}
// A customized implementation of bufio.ScanLines that preserves new line characters.
func ScanLinesKeepNewLine(data []byte, atEOF bool) (advance int, token []byte, err error) {
if atEOF && len(data) == 0 {
return 0, nil, nil
}
// first we'll split by LF (\n)
// then remove any preceding CR (\r) [due to CR+LF]
if i := bytes.IndexByte(data, '\n'); i >= 0 {
// We have a full newline-terminated line.
return i + 1, append(dropCR(data[0:i]), '\n'), nil
}
// If we're at EOF, we have a final, non-terminated line. Return it.
if atEOF {
return len(data), data, nil
}
// Request more data.
return 0, nil, nil
}
// dropCR drops a terminal \r from the data.
func dropCR(data []byte) []byte {
if len(data) > 0 && data[len(data)-1] == '\r' {
return data[0 : len(data)-1]
}
return data
}