1 // Copyright 2011 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package csv 6 7 import ( 8 "bufio" 9 "io" 10 "strings" 11 "unicode" 12 "unicode/utf8" 13 ) 14 15 // A Writer writes records to a CSV encoded file. 16 // 17 // As returned by NewWriter, a Writer writes records terminated by a 18 // newline and uses ',' as the field delimiter. The exported fields can be 19 // changed to customize the details before the first call to Write or WriteAll. 20 // 21 // Comma is the field delimiter. 22 // 23 // If UseCRLF is true, the Writer ends each output line with \r\n instead of \n. 24 type Writer struct { 25 Comma rune // Field delimiter (set to ',' by NewWriter) 26 UseCRLF bool // True to use \r\n as the line terminator 27 w *bufio.Writer 28 } 29 30 // NewWriter returns a new Writer that writes to w. 31 func NewWriter(w io.Writer) *Writer { 32 return &Writer{ 33 Comma: ',', 34 w: bufio.NewWriter(w), 35 } 36 } 37 38 // Writer writes a single CSV record to w along with any necessary quoting. 39 // A record is a slice of strings with each string being one field. 40 func (w *Writer) Write(record []string) error { 41 if !validDelim(w.Comma) { 42 return errInvalidDelim 43 } 44 45 for n, field := range record { 46 if n > 0 { 47 if _, err := w.w.WriteRune(w.Comma); err != nil { 48 return err 49 } 50 } 51 52 // If we don't have to have a quoted field then just 53 // write out the field and continue to the next field. 54 if !w.fieldNeedsQuotes(field) { 55 if _, err := w.w.WriteString(field); err != nil { 56 return err 57 } 58 continue 59 } 60 if err := w.w.WriteByte('"'); err != nil { 61 return err 62 } 63 64 for _, r1 := range field { 65 var err error 66 switch r1 { 67 case '"': 68 _, err = w.w.WriteString(`""`) 69 case '\r': 70 if !w.UseCRLF { 71 err = w.w.WriteByte('\r') 72 } 73 case '\n': 74 if w.UseCRLF { 75 _, err = w.w.WriteString("\r\n") 76 } else { 77 err = w.w.WriteByte('\n') 78 } 79 default: 80 _, err = w.w.WriteRune(r1) 81 } 82 if err != nil { 83 return err 84 } 85 } 86 87 if err := w.w.WriteByte('"'); err != nil { 88 return err 89 } 90 } 91 var err error 92 if w.UseCRLF { 93 _, err = w.w.WriteString("\r\n") 94 } else { 95 err = w.w.WriteByte('\n') 96 } 97 return err 98 } 99 100 // Flush writes any buffered data to the underlying io.Writer. 101 // To check if an error occurred during the Flush, call Error. 102 func (w *Writer) Flush() { 103 w.w.Flush() 104 } 105 106 // Error reports any error that has occurred during a previous Write or Flush. 107 func (w *Writer) Error() error { 108 _, err := w.w.Write(nil) 109 return err 110 } 111 112 // WriteAll writes multiple CSV records to w using Write and then calls Flush. 113 func (w *Writer) WriteAll(records [][]string) error { 114 for _, record := range records { 115 err := w.Write(record) 116 if err != nil { 117 return err 118 } 119 } 120 return w.w.Flush() 121 } 122 123 // fieldNeedsQuotes reports whether our field must be enclosed in quotes. 124 // Fields with a Comma, fields with a quote or newline, and 125 // fields which start with a space must be enclosed in quotes. 126 // We used to quote empty strings, but we do not anymore (as of Go 1.4). 127 // The two representations should be equivalent, but Postgres distinguishes 128 // quoted vs non-quoted empty string during database imports, and it has 129 // an option to force the quoted behavior for non-quoted CSV but it has 130 // no option to force the non-quoted behavior for quoted CSV, making 131 // CSV with quoted empty strings strictly less useful. 132 // Not quoting the empty string also makes this package match the behavior 133 // of Microsoft Excel and Google Drive. 134 // For Postgres, quote the data terminating string `\.`. 135 func (w *Writer) fieldNeedsQuotes(field string) bool { 136 if field == "" { 137 return false 138 } 139 if field == `\.` || strings.ContainsRune(field, w.Comma) || strings.ContainsAny(field, "\"\r\n") { 140 return true 141 } 142 143 r1, _ := utf8.DecodeRuneInString(field) 144 return unicode.IsSpace(r1) 145 } 146
