Imported Upstream version 1.4upstream/1.4

1 files changed, 337 insertions, 0 deletions

diff --git a/src/encoding/csv/reader.go b/src/encoding/csv/reader.go
new file mode 100644
index 000000000..d9432954a
--- /dev/null
+++ b/src/encoding/csv/reader.go
@@ -0,0 +1,337 @@
+// 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 reads and writes comma-separated values (CSV) files.
+//
+// A csv file contains zero or more records of one or more fields per record.
+// Each record is separated by the newline character. The final record may
+// optionally be followed by a newline character.
+//
+//	field1,field2,field3
+//
+// White space is considered part of a field.
+//
+// Carriage returns before newline characters are silently removed.
+//
+// Blank lines are ignored.  A line with only whitespace characters (excluding
+// the ending newline character) is not considered a blank line.
+//
+// Fields which start and stop with the quote character " are called
+// quoted-fields.  The beginning and ending quote are not part of the
+// field.
+//
+// The source:
+//
+//	normal string,"quoted-field"
+//
+// results in the fields
+//
+//	{`normal string`, `quoted-field`}
+//
+// Within a quoted-field a quote character followed by a second quote
+// character is considered a single quote.
+//
+//	"the ""word"" is true","a ""quoted-field"""
+//
+// results in
+//
+//	{`the "word" is true`, `a "quoted-field"`}
+//
+// Newlines and commas may be included in a quoted-field
+//
+//	"Multi-line
+//	field","comma is ,"
+//
+// results in
+//
+//	{`Multi-line
+//	field`, `comma is ,`}
+package csv
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"unicode"
+)
+
+// A ParseError is returned for parsing errors.
+// The first line is 1.  The first column is 0.
+type ParseError struct {
+	Line   int   // Line where the error occurred
+	Column int   // Column (rune index) where the error occurred
+	Err    error // The actual error
+}
+
+func (e *ParseError) Error() string {
+	return fmt.Sprintf("line %d, column %d: %s", e.Line, e.Column, e.Err)
+}
+
+// These are the errors that can be returned in ParseError.Error
+var (
+	ErrTrailingComma = errors.New("extra delimiter at end of line") // no longer used
+	ErrBareQuote     = errors.New("bare \" in non-quoted-field")
+	ErrQuote         = errors.New("extraneous \" in field")
+	ErrFieldCount    = errors.New("wrong number of fields in line")
+)
+
+// A Reader reads records from a CSV-encoded file.
+//
+// As returned by NewReader, a Reader expects input conforming to RFC 4180.
+// The exported fields can be changed to customize the details before the
+// first call to Read or ReadAll.
+//
+// Comma is the field delimiter.  It defaults to ','.
+//
+// Comment, if not 0, is the comment character. Lines beginning with the
+// Comment character are ignored.
+//
+// If FieldsPerRecord is positive, Read requires each record to
+// have the given number of fields.  If FieldsPerRecord is 0, Read sets it to
+// the number of fields in the first record, so that future records must
+// have the same field count.  If FieldsPerRecord is negative, no check is
+// made and records may have a variable number of fields.
+//
+// If LazyQuotes is true, a quote may appear in an unquoted field and a
+// non-doubled quote may appear in a quoted field.
+//
+// If TrimLeadingSpace is true, leading white space in a field is ignored.
+type Reader struct {
+	Comma            rune // field delimiter (set to ',' by NewReader)
+	Comment          rune // comment character for start of line
+	FieldsPerRecord  int  // number of expected fields per record
+	LazyQuotes       bool // allow lazy quotes
+	TrailingComma    bool // ignored; here for backwards compatibility
+	TrimLeadingSpace bool // trim leading space
+	line             int
+	column           int
+	r                *bufio.Reader
+	field            bytes.Buffer
+}
+
+// NewReader returns a new Reader that reads from r.
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		Comma: ',',
+		r:     bufio.NewReader(r),
+	}
+}
+
+// error creates a new ParseError based on err.
+func (r *Reader) error(err error) error {
+	return &ParseError{
+		Line:   r.line,
+		Column: r.column,
+		Err:    err,
+	}
+}
+
+// Read reads one record from r.  The record is a slice of strings with each
+// string representing one field.
+func (r *Reader) Read() (record []string, err error) {
+	for {
+		record, err = r.parseRecord()
+		if record != nil {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if r.FieldsPerRecord > 0 {
+		if len(record) != r.FieldsPerRecord {
+			r.column = 0 // report at start of record
+			return record, r.error(ErrFieldCount)
+		}
+	} else if r.FieldsPerRecord == 0 {
+		r.FieldsPerRecord = len(record)
+	}
+	return record, nil
+}
+
+// ReadAll reads all the remaining records from r.
+// Each record is a slice of fields.
+// A successful call returns err == nil, not err == EOF. Because ReadAll is
+// defined to read until EOF, it does not treat end of file as an error to be
+// reported.
+func (r *Reader) ReadAll() (records [][]string, err error) {
+	for {
+		record, err := r.Read()
+		if err == io.EOF {
+			return records, nil
+		}
+		if err != nil {
+			return nil, err
+		}
+		records = append(records, record)
+	}
+}
+
+// readRune reads one rune from r, folding \r\n to \n and keeping track
+// of how far into the line we have read.  r.column will point to the start
+// of this rune, not the end of this rune.
+func (r *Reader) readRune() (rune, error) {
+	r1, _, err := r.r.ReadRune()
+
+	// Handle \r\n here.  We make the simplifying assumption that
+	// anytime \r is followed by \n that it can be folded to \n.
+	// We will not detect files which contain both \r\n and bare \n.
+	if r1 == '\r' {
+		r1, _, err = r.r.ReadRune()
+		if err == nil {
+			if r1 != '\n' {
+				r.r.UnreadRune()
+				r1 = '\r'
+			}
+		}
+	}
+	r.column++
+	return r1, err
+}
+
+// skip reads runes up to and including the rune delim or until error.
+func (r *Reader) skip(delim rune) error {
+	for {
+		r1, err := r.readRune()
+		if err != nil {
+			return err
+		}
+		if r1 == delim {
+			return nil
+		}
+	}
+}
+
+// parseRecord reads and parses a single csv record from r.
+func (r *Reader) parseRecord() (fields []string, err error) {
+	// Each record starts on a new line.  We increment our line
+	// number (lines start at 1, not 0) and set column to -1
+	// so as we increment in readRune it points to the character we read.
+	r.line++
+	r.column = -1
+
+	// Peek at the first rune.  If it is an error we are done.
+	// If we are support comments and it is the comment character
+	// then skip to the end of line.
+
+	r1, _, err := r.r.ReadRune()
+	if err != nil {
+		return nil, err
+	}
+
+	if r.Comment != 0 && r1 == r.Comment {
+		return nil, r.skip('\n')
+	}
+	r.r.UnreadRune()
+
+	// At this point we have at least one field.
+	for {
+		haveField, delim, err := r.parseField()
+		if haveField {
+			fields = append(fields, r.field.String())
+		}
+		if delim == '\n' || err == io.EOF {
+			return fields, err
+		} else if err != nil {
+			return nil, err
+		}
+	}
+}
+
+// parseField parses the next field in the record.  The read field is
+// located in r.field.  Delim is the first character not part of the field
+// (r.Comma or '\n').
+func (r *Reader) parseField() (haveField bool, delim rune, err error) {
+	r.field.Reset()
+
+	r1, err := r.readRune()
+	for err == nil && r.TrimLeadingSpace && r1 != '\n' && unicode.IsSpace(r1) {
+		r1, err = r.readRune()
+	}
+
+	if err == io.EOF && r.column != 0 {
+		return true, 0, err
+	}
+	if err != nil {
+		return false, 0, err
+	}
+
+	switch r1 {
+	case r.Comma:
+		// will check below
+
+	case '\n':
+		// We are a trailing empty field or a blank line
+		if r.column == 0 {
+			return false, r1, nil
+		}
+		return true, r1, nil
+
+	case '"':
+		// quoted field
+	Quoted:
+		for {
+			r1, err = r.readRune()
+			if err != nil {
+				if err == io.EOF {
+					if r.LazyQuotes {
+						return true, 0, err
+					}
+					return false, 0, r.error(ErrQuote)
+				}
+				return false, 0, err
+			}
+			switch r1 {
+			case '"':
+				r1, err = r.readRune()
+				if err != nil || r1 == r.Comma {
+					break Quoted
+				}
+				if r1 == '\n' {
+					return true, r1, nil
+				}
+				if r1 != '"' {
+					if !r.LazyQuotes {
+						r.column--
+						return false, 0, r.error(ErrQuote)
+					}
+					// accept the bare quote
+					r.field.WriteRune('"')
+				}
+			case '\n':
+				r.line++
+				r.column = -1
+			}
+			r.field.WriteRune(r1)
+		}
+
+	default:
+		// unquoted field
+		for {
+			r.field.WriteRune(r1)
+			r1, err = r.readRune()
+			if err != nil || r1 == r.Comma {
+				break
+			}
+			if r1 == '\n' {
+				return true, r1, nil
+			}
+			if !r.LazyQuotes && r1 == '"' {
+				return false, 0, r.error(ErrBareQuote)
+			}
+		}
+	}
+
+	if err != nil {
+		if err == io.EOF {
+			return true, 0, err
+		}
+		return false, 0, err
+	}
+
+	return true, r1, nil
+}