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
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package csv
import (
"bufio"
"io"
"strings"
"unicode"
"unicode/utf8"
)
// A Writer writes records using CSV encoding.
//
// As returned by NewWriter, a Writer writes records terminated by a
// newline and uses ',' as the field delimiter. The exported fields can be
// changed to customize the details before the first call to Write or WriteAll.
//
// Comma is the field delimiter.
//
// If UseCRLF is true, the Writer ends each output line with \r\n instead of \n.
//
// The writes of individual records are buffered.
// After all data has been written, the client should call the
// Flush method to guarantee all data has been forwarded to
// the underlying io.Writer. Any errors that occurred should
// be checked by calling the Error method.
type Writer struct {
Comma rune // Field delimiter (set to ',' by NewWriter)
UseCRLF bool // True to use \r\n as the line terminator
w *bufio.Writer
}
// NewWriter returns a new Writer that writes to w.
func NewWriter(w io.Writer) *Writer {
return &Writer{
Comma: ',',
w: bufio.NewWriter(w),
}
}
// Write writes a single CSV record to w along with any necessary quoting.
// A record is a slice of strings with each string being one field.
// Writes are buffered, so Flush must eventually be called to ensure
// that the record is written to the underlying io.Writer.
func (w *Writer) Write(record []string) error {
if !validDelim(w.Comma) {
return errInvalidDelim
}
for n, field := range record {
if n > 0 {
if _, err := w.w.WriteRune(w.Comma); err != nil {
return err
}
}
// If we don't have to have a quoted field then just
// write out the field and continue to the next field.
if !w.fieldNeedsQuotes(field) {
if _, err := w.w.WriteString(field); err != nil {
return err
}
continue
}
if err := w.w.WriteByte('"'); err != nil {
return err
}
for len(field) > 0 {
// Search for special characters.
i := strings.IndexAny(field, "\"\r\n")
if i < 0 {
i = len(field)
}
// Copy verbatim everything before the special character.
if _, err := w.w.WriteString(field[:i]); err != nil {
return err
}
field = field[i:]
// Encode the special character.
if len(field) > 0 {
var err error
switch field[0] {
case '"':
_, err = w.w.WriteString(`""`)
case '\r':
if !w.UseCRLF {
err = w.w.WriteByte('\r')
}
case '\n':
if w.UseCRLF {
_, err = w.w.WriteString("\r\n")
} else {
err = w.w.WriteByte('\n')
}
}
field = field[1:]
if err != nil {
return err
}
}
}
if err := w.w.WriteByte('"'); err != nil {
return err
}
}
var err error
if w.UseCRLF {
_, err = w.w.WriteString("\r\n")
} else {
err = w.w.WriteByte('\n')
}
return err
}
// Flush writes any buffered data to the underlying io.Writer.
// To check if an error occurred during the Flush, call Error.
func (w *Writer) Flush() {
w.w.Flush()
}
// Error reports any error that has occurred during a previous Write or Flush.
func (w *Writer) Error() error {
_, err := w.w.Write(nil)
return err
}
// WriteAll writes multiple CSV records to w using Write and then calls Flush,
// returning any error from the Flush.
func (w *Writer) WriteAll(records [][]string) error {
for _, record := range records {
err := w.Write(record)
if err != nil {
return err
}
}
return w.w.Flush()
}
// fieldNeedsQuotes reports whether our field must be enclosed in quotes.
// Fields with a Comma, fields with a quote or newline, and
// fields which start with a space must be enclosed in quotes.
// We used to quote empty strings, but we do not anymore (as of Go 1.4).
// The two representations should be equivalent, but Postgres distinguishes
// quoted vs non-quoted empty string during database imports, and it has
// an option to force the quoted behavior for non-quoted CSV but it has
// no option to force the non-quoted behavior for quoted CSV, making
// CSV with quoted empty strings strictly less useful.
// Not quoting the empty string also makes this package match the behavior
// of Microsoft Excel and Google Drive.
// For Postgres, quote the data terminating string `\.`.
func (w *Writer) fieldNeedsQuotes(field string) bool {
if field == "" {
return false
}
if field == `\.` {
return true
}
if w.Comma < utf8.RuneSelf {
for i := 0; i < len(field); i++ {
c := field[i]
if c == '\n' || c == '\r' || c == '"' || c == byte(w.Comma) {
return true
}
}
} else {
if strings.ContainsRune(field, w.Comma) || strings.ContainsAny(field, "\"\r\n") {
return true
}
}
r1, _ := utf8.DecodeRuneInString(field)
return unicode.IsSpace(r1)
}
|
