-
Notifications
You must be signed in to change notification settings - Fork 0
/
format.go
147 lines (131 loc) · 4.29 KB
/
format.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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
package kv
import (
"bufio"
"bytes"
"fmt"
"io"
)
// Holds characters used for encoding and decoding row data.
type Format struct {
PutKey byte // Default: '-'
PutKeyValue byte // Default: '='
Delete byte // Default: '!'
KeyPrefix byte // Default: ' ' (whitespace)
ValuePrefix byte // Default: ' ' (whitespace)
RowEnd byte // Default: '\n' (line-break)
SizeStart byte // Default: '('
SizeSeparator byte // Default: '|'
SizeEnd byte // Default: ')'
SizeBase int // Default: 10 (decimal)
}
// TextFileFormat with default values.
var DefaultFormat = &Format{
PutKey: '-',
PutKeyValue: '=',
Delete: '!',
KeyPrefix: ' ',
ValuePrefix: ' ',
RowEnd: '\n',
}
func (chars *Format) Encode(kind WriteOp, k, v []byte) ([]byte, error) {
if len(k) == 0 {
return nil, ErrKeyEmpty
}
if (kind == WriteOpDelete || kind == WriteOpPutKey) && len(v) > 0 {
return nil, fmt.Errorf("row %q must receive nil value", kind)
}
if (kind == WriteOpDelete || kind == WriteOpPutKey) && bytes.IndexByte(k, chars.RowEnd) != -1 {
return nil, fmt.Errorf("invalid key contains row end %q: %q", chars.RowEnd, k)
}
if kind == WriteOpPutKeyValue && bytes.IndexByte(k, chars.ValuePrefix) != -1 {
return nil, fmt.Errorf("invalid key contains value prefix %q: %q", chars.ValuePrefix, k)
}
if kind == WriteOpPutKeyValue && bytes.IndexByte(v, chars.RowEnd) != -1 {
return nil, fmt.Errorf("invalid value contains row end %q: %q", chars.RowEnd, k)
}
out := []byte{}
// Add first two characters: command + key-prefix
switch kind {
default:
return nil, fmt.Errorf("%w: %q", ErrUnknownWriteOp, kind)
case WriteOpPutKey:
out = append(out, chars.PutKey)
case WriteOpPutKeyValue:
out = append(out, chars.PutKeyValue)
case WriteOpDelete:
out = append(out, chars.Delete)
}
out = append(out, chars.KeyPrefix)
// Add key
out = append(out, k...)
// Add value if row is of kind "put key-value"
if kind == WriteOpPutKeyValue {
out = append(out, chars.ValuePrefix)
out = append(out, v...)
}
out = append(out, chars.RowEnd)
return out, nil
}
// Parse a row assuming a byte slice containing the whole row (without trailing line-break)
func (chars *Format) ParseRowFromBytes(b []byte) (WriteOp, []byte, []byte, error) {
// Fail if row is less than 3 characters long.
// For ex: the shortest possible row is `- 1` (cmd + key-prefix + key + trailing char)
if len(b) < 4 {
return WriteOpUnknown, nil, nil, fmt.Errorf("too short to be a valid row: %q", b)
}
// Find row kind based on first character
var kind WriteOp
firstChar := b[0]
switch firstChar {
case chars.PutKey:
kind = WriteOpPutKey
case chars.PutKeyValue:
kind = WriteOpPutKeyValue
case chars.Delete:
kind = WriteOpDelete
default:
return WriteOpUnknown, nil, nil, fmt.Errorf("%w: %q", ErrUnknownWriteOp, firstChar)
}
// Fail if second character is not key prefix
secondChar := b[1]
if secondChar != chars.KeyPrefix {
return kind, nil, nil, fmt.Errorf("second char should be %q not %q", chars.KeyPrefix, secondChar)
}
// Read key and optional value
var k []byte
var v []byte // nil if key-only row (delete or put-key)
if kind == WriteOpPutKey || kind == WriteOpDelete {
k = b[2 : len(b)-1] // Read from third char to before last
} else if kind == WriteOpPutKeyValue {
valuePrefixOffset := bytes.IndexByte(b[2:], chars.ValuePrefix)
if valuePrefixOffset == -1 {
return kind, nil, nil, fmt.Errorf("value prefix %q not found in row: %q", chars.ValuePrefix, b)
}
k = b[2 : 2+valuePrefixOffset] // Read key from third char to value prefix (excl.)
v = b[2+valuePrefixOffset+1 : len(b)-1] // Read value from prefix (excl.) to before last
}
// Check trailing line-break
lastChar := b[len(b)-1]
if lastChar != chars.RowEnd {
return kind, k, v, fmt.Errorf("last char should be %q not %q", chars.RowEnd, lastChar)
}
return kind, k, v, nil
}
func extractFileRefs(r io.Reader, format *Format, refs map[string]FileRef) (int, error) {
offset := 0
s := bufio.NewScanner(r)
for s.Scan() {
row := append(s.Bytes(), '\n')
writeOp, k, _, err := format.ParseRowFromBytes(row)
if err != nil {
return offset, err
}
if writeOp == WriteOpDelete {
delete(refs, string(k))
continue
}
refs[string(k)] = FileRef{Offset: offset, Size: len(row)}
offset += len(row)
}
return offset, s.Err()
}