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
|
package diff
import (
"bufio"
"bytes"
"errors"
"io"
)
var ErrLineReaderUninitialized = errors.New("line reader not initialized")
func newLineReader(r io.Reader) *lineReader {
return &lineReader{reader: bufio.NewReader(r)}
}
// lineReader is a wrapper around a bufio.Reader that caches the next line to
// provide lookahead functionality for the next two lines.
type lineReader struct {
reader *bufio.Reader
cachedNextLine []byte
cachedNextLineErr error
}
// readLine returns the next unconsumed line and advances the internal cache of
// the lineReader.
func (l *lineReader) readLine() ([]byte, error) {
if l.cachedNextLine == nil && l.cachedNextLineErr == nil {
l.cachedNextLine, l.cachedNextLineErr = readLine(l.reader)
}
if l.cachedNextLineErr != nil {
return nil, l.cachedNextLineErr
}
next := l.cachedNextLine
l.cachedNextLine, l.cachedNextLineErr = readLine(l.reader)
return next, nil
}
// nextLineStartsWith looks at the line that would be returned by the next call
// to readLine to check whether it has the given prefix.
//
// io.EOF and bufio.ErrBufferFull errors are ignored so that the function can
// be used when at the end of the file.
func (l *lineReader) nextLineStartsWith(prefix string) (bool, error) {
if l.cachedNextLine == nil && l.cachedNextLineErr == nil {
l.cachedNextLine, l.cachedNextLineErr = readLine(l.reader)
}
return l.lineHasPrefix(l.cachedNextLine, prefix, l.cachedNextLineErr)
}
// nextNextLineStartsWith checks the prefix of the line *after* the line that
// would be returned by the next readLine.
//
// io.EOF and bufio.ErrBufferFull errors are ignored so that the function can
// be used when at the end of the file.
//
// The lineReader MUST be initialized by calling readLine at least once before
// calling nextLineStartsWith. Otherwise ErrLineReaderUninitialized will be
// returned.
func (l *lineReader) nextNextLineStartsWith(prefix string) (bool, error) {
if l.cachedNextLine == nil && l.cachedNextLineErr == nil {
l.cachedNextLine, l.cachedNextLineErr = readLine(l.reader)
}
next, err := l.reader.Peek(len(prefix))
return l.lineHasPrefix(next, prefix, err)
}
// lineHasPrefix checks whether the given line has the given prefix with
// bytes.HasPrefix.
//
// The readErr should be the error that was returned when the line was read.
// lineHasPrefix checks the error to adjust its return value to, e.g., return
// false and ignore the error when readErr is io.EOF.
func (l *lineReader) lineHasPrefix(line []byte, prefix string, readErr error) (bool, error) {
if readErr != nil {
if readErr == io.EOF || readErr == bufio.ErrBufferFull {
return false, nil
}
return false, readErr
}
return bytes.HasPrefix(line, []byte(prefix)), nil
}
// readLine is a helper that mimics the functionality of calling bufio.Scanner.Scan() and
// bufio.Scanner.Bytes(), but without the token size limitation. It will read and return
// the next line in the Reader with the trailing newline stripped. It will return an
// io.EOF error when there is nothing left to read (at the start of the function call). It
// will return any other errors it receives from the underlying call to ReadBytes.
func readLine(r *bufio.Reader) ([]byte, error) {
line_, err := r.ReadBytes('\n')
if err == io.EOF {
if len(line_) == 0 {
return nil, io.EOF
}
// ReadBytes returned io.EOF, because it didn't find another newline, but there is
// still the remainder of the file to return as a line.
line := line_
return line, nil
} else if err != nil {
return nil, err
}
line := line_[0 : len(line_)-1]
return dropCR(line), 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
}
|
