142 lines
3.7 KiB
Go
142 lines
3.7 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package csv
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import (
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"bufio"
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"io"
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"strings"
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"unicode"
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"unicode/utf8"
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)
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// A Writer writes records to a CSV encoded file.
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//
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// As returned by NewWriter, a Writer writes records terminated by a
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// newline and uses ',' as the field delimiter. The exported fields can be
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// changed to customize the details before the first call to Write or WriteAll.
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//
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// Comma is the field delimiter.
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//
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// If UseCRLF is true, the Writer ends each record with \r\n instead of \n.
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type Writer struct {
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Comma rune // Field delimiter (set to ',' by NewWriter)
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UseCRLF bool // True to use \r\n as the line terminator
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w *bufio.Writer
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}
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// NewWriter returns a new Writer that writes to w.
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func NewWriter(w io.Writer) *Writer {
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return &Writer{
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Comma: ',',
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w: bufio.NewWriter(w),
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}
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}
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// Writer writes a single CSV record to w along with any necessary quoting.
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// A record is a slice of strings with each string being one field.
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func (w *Writer) Write(record []string) error {
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for n, field := range record {
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if n > 0 {
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if _, err := w.w.WriteRune(w.Comma); err != nil {
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return err
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}
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}
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// If we don't have to have a quoted field then just
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// write out the field and continue to the next field.
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if !w.fieldNeedsQuotes(field) {
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if _, err := w.w.WriteString(field); err != nil {
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return err
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}
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continue
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}
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if err := w.w.WriteByte('"'); err != nil {
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return err
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}
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for _, r1 := range field {
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var err error
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switch r1 {
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case '"':
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_, err = w.w.WriteString(`""`)
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case '\r':
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if !w.UseCRLF {
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err = w.w.WriteByte('\r')
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}
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case '\n':
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if w.UseCRLF {
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_, err = w.w.WriteString("\r\n")
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} else {
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err = w.w.WriteByte('\n')
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}
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default:
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_, err = w.w.WriteRune(r1)
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}
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if err != nil {
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return err
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}
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}
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if err := w.w.WriteByte('"'); err != nil {
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return err
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}
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}
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var err error
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if w.UseCRLF {
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_, err = w.w.WriteString("\r\n")
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} else {
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err = w.w.WriteByte('\n')
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}
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return err
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}
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// Flush writes any buffered data to the underlying io.Writer.
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// To check if an error occurred during the Flush, call Error.
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func (w *Writer) Flush() {
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w.w.Flush()
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}
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// Error reports any error that has occurred during a previous Write or Flush.
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func (w *Writer) Error() error {
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_, err := w.w.Write(nil)
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return err
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}
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// WriteAll writes multiple CSV records to w using Write and then calls Flush.
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func (w *Writer) WriteAll(records [][]string) error {
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for _, record := range records {
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err := w.Write(record)
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if err != nil {
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return err
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}
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}
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return w.w.Flush()
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}
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// fieldNeedsQuotes reports whether our field must be enclosed in quotes.
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// Fields with a Comma, fields with a quote or newline, and
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// fields which start with a space must be enclosed in quotes.
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// We used to quote empty strings, but we do not anymore (as of Go 1.4).
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// The two representations should be equivalent, but Postgres distinguishes
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// quoted vs non-quoted empty string during database imports, and it has
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// an option to force the quoted behavior for non-quoted CSV but it has
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// no option to force the non-quoted behavior for quoted CSV, making
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// CSV with quoted empty strings strictly less useful.
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// Not quoting the empty string also makes this package match the behavior
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// of Microsoft Excel and Google Drive.
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// For Postgres, quote the data terminating string `\.`.
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func (w *Writer) fieldNeedsQuotes(field string) bool {
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if field == "" {
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return false
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}
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if field == `\.` || strings.ContainsRune(field, w.Comma) || strings.ContainsAny(field, "\"\r\n") {
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return true
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}
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r1, _ := utf8.DecodeRuneInString(field)
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return unicode.IsSpace(r1)
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}
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