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// 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 to a CSV encoded file.
//
// 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 record with \r\n instead of \n.
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),
}
}
// Writer 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.
func (w *Writer) Write(record []string) (err error) {
for n, field := range record {
if n > 0 {
if _, err = w.w.WriteRune(w.Comma); err != nil {
return
}
}
// 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
}
continue
}
if err = w.w.WriteByte('"'); err != nil {
return
}
for _, r1 := range field {
switch r1 {
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')
}
default:
_, err = w.w.WriteRune(r1)
}
if err != nil {
return
}
}
if err = w.w.WriteByte('"'); err != nil {
return
}
}
if w.UseCRLF {
_, err = w.w.WriteString("\r\n")
} else {
err = w.w.WriteByte('\n')
}
return
}
// 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.
func (w *Writer) WriteAll(records [][]string) (err 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 == `\.` || strings.IndexRune(field, w.Comma) >= 0 || strings.IndexAny(field, "\"\r\n") >= 0 {
return true
}
r1, _ := utf8.DecodeRuneInString(field)
return unicode.IsSpace(r1)
}
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