1 files changed, 450 insertions, 0 deletions
diff --git a/src/encoding/csv/reader.go b/src/encoding/csv/reader.go
new file mode 100644
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--- /dev/null
+++ b/src/encoding/csv/reader.go
@@ -0,0 +1,450 @@
+// 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.
+// There are many kinds of CSV files; this package supports the format
+// described in RFC 4180.
+//
+// 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"
+	"unicode/utf8"
+)
+
+// A ParseError is returned for parsing errors.
+// Line numbers are 1-indexed and columns are 0-indexed.
+type ParseError struct {
+	StartLine int   // Line where the record starts
+	Line      int   // Line where the error occurred
+	Column    int   // Column (1-based byte index) where the error occurred
+	Err       error // The actual error
+}
+
+func (e *ParseError) Error() string {
+	if e.Err == ErrFieldCount {
+		return fmt.Sprintf("record on line %d: %v", e.Line, e.Err)
+	}
+	if e.StartLine != e.Line {
+		return fmt.Sprintf("record on line %d; parse error on line %d, column %d: %v", e.StartLine, e.Line, e.Column, e.Err)
+	}
+	return fmt.Sprintf("parse error on line %d, column %d: %v", e.Line, e.Column, e.Err)
+}
+
+func (e *ParseError) Unwrap() error { return e.Err }
+
+// These are the errors that can be returned in ParseError.Err.
+var (
+	ErrTrailingComma = errors.New("extra delimiter at end of line") // Deprecated: No longer used.
+	ErrBareQuote     = errors.New("bare \" in non-quoted-field")
+	ErrQuote         = errors.New("extraneous or missing \" in quoted-field")
+	ErrFieldCount    = errors.New("wrong number of fields")
+)
+
+var errInvalidDelim = errors.New("csv: invalid field or comment delimiter")
+
+func validDelim(r rune) bool {
+	return r != 0 && r != '"' && r != '\r' && r != '\n' && utf8.ValidRune(r) && r != utf8.RuneError
+}
+
+// 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.
+//
+// The Reader converts all \r\n sequences in its input to plain \n,
+// including in multiline field values, so that the returned data does
+// not depend on which line-ending convention an input file uses.
+type Reader struct {
+	// Comma is the field delimiter.
+	// It is set to comma (',') by NewReader.
+	// Comma must be a valid rune and must not be \r, \n,
+	// or the Unicode replacement character (0xFFFD).
+	Comma rune
+
+	// Comment, if not 0, is the comment character. Lines beginning with the
+	// Comment character without preceding whitespace are ignored.
+	// With leading whitespace the Comment character becomes part of the
+	// field, even if TrimLeadingSpace is true.
+	// Comment must be a valid rune and must not be \r, \n,
+	// or the Unicode replacement character (0xFFFD).
+	// It must also not be equal to Comma.
+	Comment rune
+
+	// FieldsPerRecord is the number of expected fields per record.
+	// 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.
+	FieldsPerRecord int
+
+	// If LazyQuotes is true, a quote may appear in an unquoted field and a
+	// non-doubled quote may appear in a quoted field.
+	LazyQuotes bool
+
+	// If TrimLeadingSpace is true, leading white space in a field is ignored.
+	// This is done even if the field delimiter, Comma, is white space.
+	TrimLeadingSpace bool
+
+	// ReuseRecord controls whether calls to Read may return a slice sharing
+	// the backing array of the previous call's returned slice for performance.
+	// By default, each call to Read returns newly allocated memory owned by the caller.
+	ReuseRecord bool
+
+	TrailingComma bool // Deprecated: No longer used.
+
+	r *bufio.Reader
+
+	// numLine is the current line being read in the CSV file.
+	numLine int
+
+	// rawBuffer is a line buffer only used by the readLine method.
+	rawBuffer []byte
+
+	// recordBuffer holds the unescaped fields, one after another.
+	// The fields can be accessed by using the indexes in fieldIndexes.
+	// E.g., For the row `a,"b","c""d",e`, recordBuffer will contain `abc"de`
+	// and fieldIndexes will contain the indexes [1, 2, 5, 6].
+	recordBuffer []byte
+
+	// fieldIndexes is an index of fields inside recordBuffer.
+	// The i'th field ends at offset fieldIndexes[i] in recordBuffer.
+	fieldIndexes []int
+
+	// fieldPositions is an index of field positions for the
+	// last record returned by Read.
+	fieldPositions []position
+
+	// lastRecord is a record cache and only used when ReuseRecord == true.
+	lastRecord []string
+}
+
+// NewReader returns a new Reader that reads from r.
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		Comma: ',',
+		r:     bufio.NewReader(r),
+	}
+}
+
+// Read reads one record (a slice of fields) from r.
+// If the record has an unexpected number of fields,
+// Read returns the record along with the error ErrFieldCount.
+// Except for that case, Read always returns either a non-nil
+// record or a non-nil error, but not both.
+// If there is no data left to be read, Read returns nil, io.EOF.
+// If ReuseRecord is true, the returned slice may be shared
+// between multiple calls to Read.
+func (r *Reader) Read() (record []string, err error) {
+	if r.ReuseRecord {
+		record, err = r.readRecord(r.lastRecord)
+		r.lastRecord = record
+	} else {
+		record, err = r.readRecord(nil)
+	}
+	return record, err
+}
+
+// FieldPos returns the line and column corresponding to
+// the start of the field with the given index in the slice most recently
+// returned by Read. Numbering of lines and columns starts at 1;
+// columns are counted in bytes, not runes.
+//
+// If this is called with an out-of-bounds index, it panics.
+func (r *Reader) FieldPos(field int) (line, column int) {
+	if field < 0 || field >= len(r.fieldPositions) {
+		panic("out of range index passed to FieldPos")
+	}
+	p := &r.fieldPositions[field]
+	return p.line, p.col
+}
+
+// pos holds the position of a field in the current line.
+type position struct {
+	line, col int
+}
+
+// ReadAll reads all the remaining records from r.
+// Each record is a slice of fields.
+// A successful call returns err == nil, not err == io.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.readRecord(nil)
+		if err == io.EOF {
+			return records, nil
+		}
+		if err != nil {
+			return nil, err
+		}
+		records = append(records, record)
+	}
+}
+
+// readLine reads the next line (with the trailing endline).
+// If EOF is hit without a trailing endline, it will be omitted.
+// If some bytes were read, then the error is never io.EOF.
+// The result is only valid until the next call to readLine.
+func (r *Reader) readLine() ([]byte, error) {
+	line, err := r.r.ReadSlice('\n')
+	if err == bufio.ErrBufferFull {
+		r.rawBuffer = append(r.rawBuffer[:0], line...)
+		for err == bufio.ErrBufferFull {
+			line, err = r.r.ReadSlice('\n')
+			r.rawBuffer = append(r.rawBuffer, line...)
+		}
+		line = r.rawBuffer
+	}
+	if len(line) > 0 && err == io.EOF {
+		err = nil
+		// For backwards compatibility, drop trailing \r before EOF.
+		if line[len(line)-1] == '\r' {
+			line = line[:len(line)-1]
+		}
+	}
+	r.numLine++
+	// Normalize \r\n to \n on all input lines.
+	if n := len(line); n >= 2 && line[n-2] == '\r' && line[n-1] == '\n' {
+		line[n-2] = '\n'
+		line = line[:n-1]
+	}
+	return line, err
+}
+
+// lengthNL reports the number of bytes for the trailing \n.
+func lengthNL(b []byte) int {
+	if len(b) > 0 && b[len(b)-1] == '\n' {
+		return 1
+	}
+	return 0
+}
+
+// nextRune returns the next rune in b or utf8.RuneError.
+func nextRune(b []byte) rune {
+	r, _ := utf8.DecodeRune(b)
+	return r
+}
+
+func (r *Reader) readRecord(dst []string) ([]string, error) {
+	if r.Comma == r.Comment || !validDelim(r.Comma) || (r.Comment != 0 && !validDelim(r.Comment)) {
+		return nil, errInvalidDelim
+	}
+
+	// Read line (automatically skipping past empty lines and any comments).
+	var line []byte
+	var errRead error
+	for errRead == nil {
+		line, errRead = r.readLine()
+		if r.Comment != 0 && nextRune(line) == r.Comment {
+			line = nil
+			continue // Skip comment lines
+		}
+		if errRead == nil && len(line) == lengthNL(line) {
+			line = nil
+			continue // Skip empty lines
+		}
+		break
+	}
+	if errRead == io.EOF {
+		return nil, errRead
+	}
+
+	// Parse each field in the record.
+	var err error
+	const quoteLen = len(`"`)
+	commaLen := utf8.RuneLen(r.Comma)
+	recLine := r.numLine // Starting line for record
+	r.recordBuffer = r.recordBuffer[:0]
+	r.fieldIndexes = r.fieldIndexes[:0]
+	r.fieldPositions = r.fieldPositions[:0]
+	pos := position{line: r.numLine, col: 1}
+parseField:
+	for {
+		if r.TrimLeadingSpace {
+			i := bytes.IndexFunc(line, func(r rune) bool {
+				return !unicode.IsSpace(r)
+			})
+			if i < 0 {
+				i = len(line)
+				pos.col -= lengthNL(line)
+			}
+			line = line[i:]
+			pos.col += i
+		}
+		if len(line) == 0 || line[0] != '"' {
+			// Non-quoted string field
+			i := bytes.IndexRune(line, r.Comma)
+			field := line
+			if i >= 0 {
+				field = field[:i]
+			} else {
+				field = field[:len(field)-lengthNL(field)]
+			}
+			// Check to make sure a quote does not appear in field.
+			if !r.LazyQuotes {
+				if j := bytes.IndexByte(field, '"'); j >= 0 {
+					col := pos.col + j
+					err = &ParseError{StartLine: recLine, Line: r.numLine, Column: col, Err: ErrBareQuote}
+					break parseField
+				}
+			}
+			r.recordBuffer = append(r.recordBuffer, field...)
+			r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+			r.fieldPositions = append(r.fieldPositions, pos)
+			if i >= 0 {
+				line = line[i+commaLen:]
+				pos.col += i + commaLen
+				continue parseField
+			}
+			break parseField
+		} else {
+			// Quoted string field
+			fieldPos := pos
+			line = line[quoteLen:]
+			pos.col += quoteLen
+			for {
+				i := bytes.IndexByte(line, '"')
+				if i >= 0 {
+					// Hit next quote.
+					r.recordBuffer = append(r.recordBuffer, line[:i]...)
+					line = line[i+quoteLen:]
+					pos.col += i + quoteLen
+					switch rn := nextRune(line); {
+					case rn == '"':
+						// `""` sequence (append quote).
+						r.recordBuffer = append(r.recordBuffer, '"')
+						line = line[quoteLen:]
+						pos.col += quoteLen
+					case rn == r.Comma:
+						// `",` sequence (end of field).
+						line = line[commaLen:]
+						pos.col += commaLen
+						r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+						r.fieldPositions = append(r.fieldPositions, fieldPos)
+						continue parseField
+					case lengthNL(line) == len(line):
+						// `"\n` sequence (end of line).
+						r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+						r.fieldPositions = append(r.fieldPositions, fieldPos)
+						break parseField
+					case r.LazyQuotes:
+						// `"` sequence (bare quote).
+						r.recordBuffer = append(r.recordBuffer, '"')
+					default:
+						// `"*` sequence (invalid non-escaped quote).
+						err = &ParseError{StartLine: recLine, Line: r.numLine, Column: pos.col - quoteLen, Err: ErrQuote}
+						break parseField
+					}
+				} else if len(line) > 0 {
+					// Hit end of line (copy all data so far).
+					r.recordBuffer = append(r.recordBuffer, line...)
+					if errRead != nil {
+						break parseField
+					}
+					pos.col += len(line)
+					line, errRead = r.readLine()
+					if len(line) > 0 {
+						pos.line++
+						pos.col = 1
+					}
+					if errRead == io.EOF {
+						errRead = nil
+					}
+				} else {
+					// Abrupt end of file (EOF or error).
+					if !r.LazyQuotes && errRead == nil {
+						err = &ParseError{StartLine: recLine, Line: pos.line, Column: pos.col, Err: ErrQuote}
+						break parseField
+					}
+					r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+					r.fieldPositions = append(r.fieldPositions, fieldPos)
+					break parseField
+				}
+			}
+		}
+	}
+	if err == nil {
+		err = errRead
+	}
+
+	// Create a single string and create slices out of it.
+	// This pins the memory of the fields together, but allocates once.
+	str := string(r.recordBuffer) // Convert to string once to batch allocations
+	dst = dst[:0]
+	if cap(dst) < len(r.fieldIndexes) {
+		dst = make([]string, len(r.fieldIndexes))
+	}
+	dst = dst[:len(r.fieldIndexes)]
+	var preIdx int
+	for i, idx := range r.fieldIndexes {
+		dst[i] = str[preIdx:idx]
+		preIdx = idx
+	}
+
+	// Check or update the expected fields per record.
+	if r.FieldsPerRecord > 0 {
+		if len(dst) != r.FieldsPerRecord && err == nil {
+			err = &ParseError{
+				StartLine: recLine,
+				Line:      recLine,
+				Column:    1,
+				Err:       ErrFieldCount,
+			}
+		}
+	} else if r.FieldsPerRecord == 0 {
+		r.FieldsPerRecord = len(dst)
+	}
+	return dst, err
+}