src/mime/multipart/multipart.go - go - Git at Google

 // Copyright 2010 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 multipart implements MIME multipart parsing, as defined in RFC
 2046.

 The implementation is sufficient for HTTP (RFC 2388) and the multipart
 bodies generated by popular browsers.
 */
 package multipart

 import (
 	"bufio"
 	"bytes"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"mime"
 	"mime/quotedprintable"
 	"net/textproto"
 )

 var emptyParams = make(map[string]string)

 // This constant needs to be at least 76 for this package to work correctly.
 // This is because \r\n--separator_of_len_70- would fill the buffer and it
 // wouldn't be safe to consume a single byte from it.
 const peekBufferSize = 4096

 // A Part represents a single part in a multipart body.
 type Part struct {
 	// The headers of the body, if any, with the keys canonicalized
 	// in the same fashion that the Go http.Request headers are.
 	// For example, "foo-bar" changes case to "Foo-Bar"
 	//
 	// As a special case, if the "Content-Transfer-Encoding" header
 	// has a value of "quoted-printable", that header is instead
 	// hidden from this map and the body is transparently decoded
 	// during Read calls.
 	Header textproto.MIMEHeader

 	buffer    *bytes.Buffer
 	mr        *Reader
 	bytesRead int

 	disposition       string
 	dispositionParams map[string]string

 	// r is either a reader directly reading from mr, or it's a
 	// wrapper around such a reader, decoding the
 	// Content-Transfer-Encoding
 	r io.Reader
 }

 // FormName returns the name parameter if p has a Content-Disposition
 // of type "form-data".  Otherwise it returns the empty string.
 func (p *Part) FormName() string {
 	// See http://tools.ietf.org/html/rfc2183 section 2 for EBNF
 	// of Content-Disposition value format.
 	if p.dispositionParams == nil {
 		p.parseContentDisposition()
 	}
 	if p.disposition != "form-data" {
 		return ""
 	}
 	return p.dispositionParams["name"]
 }

 // FileName returns the filename parameter of the Part's
 // Content-Disposition header.
 func (p *Part) FileName() string {
 	if p.dispositionParams == nil {
 		p.parseContentDisposition()
 	}
 	return p.dispositionParams["filename"]
 }

 func (p *Part) parseContentDisposition() {
 	v := p.Header.Get("Content-Disposition")
 	var err error
 	p.disposition, p.dispositionParams, err = mime.ParseMediaType(v)
 	if err != nil {
 		p.dispositionParams = emptyParams
 	}
 }

 // NewReader creates a new multipart Reader reading from r using the
 // given MIME boundary.
 //
 // The boundary is usually obtained from the "boundary" parameter of
 // the message's "Content-Type" header. Use mime.ParseMediaType to
 // parse such headers.
 func NewReader(r io.Reader, boundary string) *Reader {
 	b := []byte("\r\n--" + boundary + "--")
 	return &Reader{
 		bufReader:        bufio.NewReaderSize(r, peekBufferSize),
 		nl:               b[:2],
 		nlDashBoundary:   b[:len(b)-2],
 		dashBoundaryDash: b[2:],
 		dashBoundary:     b[2 : len(b)-2],
 	}
 }

 func newPart(mr *Reader) (*Part, error) {
 	bp := &Part{
 		Header: make(map[string][]string),
 		mr:     mr,
 		buffer: new(bytes.Buffer),
 	}
 	if err := bp.populateHeaders(); err != nil {
 		return nil, err
 	}
 	bp.r = partReader{bp}
 	const cte = "Content-Transfer-Encoding"
 	if bp.Header.Get(cte) == "quoted-printable" {
 		bp.Header.Del(cte)
 		bp.r = quotedprintable.NewReader(bp.r)
 	}
 	return bp, nil
 }

 func (bp *Part) populateHeaders() error {
 	r := textproto.NewReader(bp.mr.bufReader)
 	header, err := r.ReadMIMEHeader()
 	if err == nil {
 		bp.Header = header
 	}
 	return err
 }

 // Read reads the body of a part, after its headers and before the
 // next part (if any) begins.
 func (p *Part) Read(d []byte) (n int, err error) {
 	return p.r.Read(d)
 }

 // partReader implements io.Reader by reading raw bytes directly from the
 // wrapped *Part, without doing any Transfer-Encoding decoding.
 type partReader struct {
 	p *Part
 }

 func (pr partReader) Read(d []byte) (n int, err error) {
 	p := pr.p
 	defer func() {
 		p.bytesRead += n
 	}()
 	if p.buffer.Len() >= len(d) {
 		// Internal buffer of unconsumed data is large enough for
 		// the read request.  No need to parse more at the moment.
 		return p.buffer.Read(d)
 	}
 	peek, err := p.mr.bufReader.Peek(peekBufferSize) // TODO(bradfitz): add buffer size accessor

 	// Look for an immediate empty part without a leading \r\n
 	// before the boundary separator.  Some MIME code makes empty
 	// parts like this. Most browsers, however, write the \r\n
 	// before the subsequent boundary even for empty parts and
 	// won't hit this path.
 	if p.bytesRead == 0 && p.mr.peekBufferIsEmptyPart(peek) {
 		return 0, io.EOF
 	}
 	unexpectedEOF := err == io.EOF
 	if err != nil && !unexpectedEOF {
 		return 0, fmt.Errorf("multipart: Part Read: %v", err)
 	}
 	if peek == nil {
 		panic("nil peek buf")
 	}
 	// Search the peek buffer for "\r\n--boundary". If found,
 	// consume everything up to the boundary. If not, consume only
 	// as much of the peek buffer as cannot hold the boundary
 	// string.
 	nCopy := 0
 	foundBoundary := false
 	if idx, isEnd := p.mr.peekBufferSeparatorIndex(peek); idx != -1 {
 		nCopy = idx
 		foundBoundary = isEnd
 		if !isEnd && nCopy == 0 {
 			nCopy = 1 // make some progress.
 		}
 	} else if safeCount := len(peek) - len(p.mr.nlDashBoundary); safeCount > 0 {
 		nCopy = safeCount
 	} else if unexpectedEOF {
 		// If we've run out of peek buffer and the boundary
 		// wasn't found (and can't possibly fit), we must have
 		// hit the end of the file unexpectedly.
 		return 0, io.ErrUnexpectedEOF
 	}
 	if nCopy > 0 {
 		if _, err := io.CopyN(p.buffer, p.mr.bufReader, int64(nCopy)); err != nil {
 			return 0, err
 		}
 	}
 	n, err = p.buffer.Read(d)
 	if err == io.EOF && !foundBoundary {
 		// If the boundary hasn't been reached there's more to
 		// read, so don't pass through an EOF from the buffer
 		err = nil
 	}
 	return
 }

 func (p *Part) Close() error {
 	io.Copy(ioutil.Discard, p)
 	return nil
 }

 // Reader is an iterator over parts in a MIME multipart body.
 // Reader's underlying parser consumes its input as needed.  Seeking
 // isn't supported.
 type Reader struct {
 	bufReader *bufio.Reader

 	currentPart *Part
 	partsRead   int

 	nl               []byte // "\r\n" or "\n" (set after seeing first boundary line)
 	nlDashBoundary   []byte // nl + "--boundary"
 	dashBoundaryDash []byte // "--boundary--"
 	dashBoundary     []byte // "--boundary"
 }

 // NextPart returns the next part in the multipart or an error.
 // When there are no more parts, the error io.EOF is returned.
 func (r *Reader) NextPart() (*Part, error) {
 	if r.currentPart != nil {
 		r.currentPart.Close()
 	}

 	expectNewPart := false
 	for {
 		line, err := r.bufReader.ReadSlice('\n')

 		if err == io.EOF && r.isFinalBoundary(line) {
 			// If the buffer ends in "--boundary--" without the
 			// trailing "\r\n", ReadSlice will return an error
 			// (since it's missing the '\n'), but this is a valid
 			// multipart EOF so we need to return io.EOF instead of
 			// a fmt-wrapped one.
 			return nil, io.EOF
 		}
 		if err != nil {
 			return nil, fmt.Errorf("multipart: NextPart: %v", err)
 		}

 		if r.isBoundaryDelimiterLine(line) {
 			r.partsRead++
 			bp, err := newPart(r)
 			if err != nil {
 				return nil, err
 			}
 			r.currentPart = bp
 			return bp, nil
 		}

 		if r.isFinalBoundary(line) {
 			// Expected EOF
 			return nil, io.EOF
 		}

 		if expectNewPart {
 			return nil, fmt.Errorf("multipart: expecting a new Part; got line %q", string(line))
 		}

 		if r.partsRead == 0 {
 			// skip line
 			continue
 		}

 		// Consume the "\n" or "\r\n" separator between the
 		// body of the previous part and the boundary line we
 		// now expect will follow. (either a new part or the
 		// end boundary)
 		if bytes.Equal(line, r.nl) {
 			expectNewPart = true
 			continue
 		}

 		return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
 	}
 }

 // isFinalBoundary reports whether line is the final boundary line
 // indicating that all parts are over.
 // It matches `^--boundary--[ \t]*(\r\n)?$`
 func (mr *Reader) isFinalBoundary(line []byte) bool {
 	if !bytes.HasPrefix(line, mr.dashBoundaryDash) {
 		return false
 	}
 	rest := line[len(mr.dashBoundaryDash):]
 	rest = skipLWSPChar(rest)
 	return len(rest) == 0 || bytes.Equal(rest, mr.nl)
 }

 func (mr *Reader) isBoundaryDelimiterLine(line []byte) (ret bool) {
 	// http://tools.ietf.org/html/rfc2046#section-5.1
 	//   The boundary delimiter line is then defined as a line
 	//   consisting entirely of two hyphen characters ("-",
 	//   decimal value 45) followed by the boundary parameter
 	//   value from the Content-Type header field, optional linear
 	//   whitespace, and a terminating CRLF.
 	if !bytes.HasPrefix(line, mr.dashBoundary) {
 		return false
 	}
 	rest := line[len(mr.dashBoundary):]
 	rest = skipLWSPChar(rest)

 	// On the first part, see our lines are ending in \n instead of \r\n
 	// and switch into that mode if so.  This is a violation of the spec,
 	// but occurs in practice.
 	if mr.partsRead == 0 && len(rest) == 1 && rest[0] == '\n' {
 		mr.nl = mr.nl[1:]
 		mr.nlDashBoundary = mr.nlDashBoundary[1:]
 	}
 	return bytes.Equal(rest, mr.nl)
 }

 // peekBufferIsEmptyPart reports whether the provided peek-ahead
 // buffer represents an empty part. It is called only if we've not
 // already read any bytes in this part and checks for the case of MIME
 // software not writing the \r\n on empty parts. Some does, some
 // doesn't.
 //
 // This checks that what follows the "--boundary" is actually the end
 // ("--boundary--" with optional whitespace) or optional whitespace
 // and then a newline, so we don't catch "--boundaryFAKE", in which
 // case the whole line is part of the data.
 func (mr *Reader) peekBufferIsEmptyPart(peek []byte) bool {
 	// End of parts case.
 	// Test whether peek matches `^--boundary--[ \t]*(?:\r\n|$)`
 	if bytes.HasPrefix(peek, mr.dashBoundaryDash) {
 		rest := peek[len(mr.dashBoundaryDash):]
 		rest = skipLWSPChar(rest)
 		return bytes.HasPrefix(rest, mr.nl) || len(rest) == 0
 	}
 	if !bytes.HasPrefix(peek, mr.dashBoundary) {
 		return false
 	}
 	// Test whether rest matches `^[ \t]*\r\n`)
 	rest := peek[len(mr.dashBoundary):]
 	rest = skipLWSPChar(rest)
 	return bytes.HasPrefix(rest, mr.nl)
 }

 // peekBufferSeparatorIndex returns the index of mr.nlDashBoundary in
 // peek and whether it is a real boundary (and not a prefix of an
 // unrelated separator). To be the end, the peek buffer must contain a
 // newline after the boundary or contain the ending boundary (--separator--).
 func (mr *Reader) peekBufferSeparatorIndex(peek []byte) (idx int, isEnd bool) {
 	idx = bytes.Index(peek, mr.nlDashBoundary)
 	if idx == -1 {
 		return
 	}

 	peek = peek[idx+len(mr.nlDashBoundary):]
 	if len(peek) == 0 || len(peek) == 1 && peek[0] == '-' {
 		return idx, false
 	}
 	if len(peek) > 1 && peek[0] == '-' && peek[1] == '-' {
 		return idx, true
 	}
 	peek = skipLWSPChar(peek)
 	// Don't have a complete line after the peek.
 	if bytes.IndexByte(peek, '\n') == -1 {
 		return idx, false
 	}
 	if len(peek) > 0 && peek[0] == '\n' {
 		return idx, true
 	}
 	if len(peek) > 1 && peek[0] == '\r' && peek[1] == '\n' {
 		return idx, true
 	}
 	return idx, false
 }

 // skipLWSPChar returns b with leading spaces and tabs removed.
 // RFC 822 defines:
 //    LWSP-char = SPACE / HTAB
 func skipLWSPChar(b []byte) []byte {
 	for len(b) > 0 && (b[0] == ' ' || b[0] == '\t') {
 		b = b[1:]
 	}
 	return b
 }
	// Copyright 2010 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 multipart implements MIME multipart parsing, as defined in RFC
	2046.

	The implementation is sufficient for HTTP (RFC 2388) and the multipart
	bodies generated by popular browsers.
	*/
	package multipart

	import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"mime"
	"mime/quotedprintable"
	"net/textproto"
	)

	var emptyParams = make(map[string]string)

	// This constant needs to be at least 76 for this package to work correctly.
	// This is because \r\n--separator_of_len_70- would fill the buffer and it
	// wouldn't be safe to consume a single byte from it.
	const peekBufferSize = 4096

	// A Part represents a single part in a multipart body.
	type Part struct {
	// The headers of the body, if any, with the keys canonicalized
	// in the same fashion that the Go http.Request headers are.
	// For example, "foo-bar" changes case to "Foo-Bar"
	//
	// As a special case, if the "Content-Transfer-Encoding" header
	// has a value of "quoted-printable", that header is instead
	// hidden from this map and the body is transparently decoded
	// during Read calls.
	Header textproto.MIMEHeader

	buffer *bytes.Buffer
	mr *Reader
	bytesRead int

	disposition string
	dispositionParams map[string]string

	// r is either a reader directly reading from mr, or it's a
	// wrapper around such a reader, decoding the
	// Content-Transfer-Encoding
	r io.Reader
	}

	// FormName returns the name parameter if p has a Content-Disposition
	// of type "form-data". Otherwise it returns the empty string.
	func (p *Part) FormName() string {
	// See http://tools.ietf.org/html/rfc2183 section 2 for EBNF
	// of Content-Disposition value format.
	if p.dispositionParams == nil {
	p.parseContentDisposition()
	}
	if p.disposition != "form-data" {
	return ""
	}
	return p.dispositionParams["name"]
	}

	// FileName returns the filename parameter of the Part's
	// Content-Disposition header.
	func (p *Part) FileName() string {
	if p.dispositionParams == nil {
	p.parseContentDisposition()
	}
	return p.dispositionParams["filename"]
	}

	func (p *Part) parseContentDisposition() {
	v := p.Header.Get("Content-Disposition")
	var err error
	p.disposition, p.dispositionParams, err = mime.ParseMediaType(v)
	if err != nil {
	p.dispositionParams = emptyParams
	}
	}

	// NewReader creates a new multipart Reader reading from r using the
	// given MIME boundary.
	//
	// The boundary is usually obtained from the "boundary" parameter of
	// the message's "Content-Type" header. Use mime.ParseMediaType to
	// parse such headers.
	func NewReader(r io.Reader, boundary string) *Reader {
	b := []byte("\r\n--" + boundary + "--")
	return &Reader{
	bufReader: bufio.NewReaderSize(r, peekBufferSize),
	nl: b[:2],
	nlDashBoundary: b[:len(b)-2],
	dashBoundaryDash: b[2:],
	dashBoundary: b[2 : len(b)-2],
	}
	}

	func newPart(mr Reader) (Part, error) {
	bp := &Part{
	Header: make(map[string][]string),
	mr: mr,
	buffer: new(bytes.Buffer),
	}
	if err := bp.populateHeaders(); err != nil {
	return nil, err
	}
	bp.r = partReader{bp}
	const cte = "Content-Transfer-Encoding"
	if bp.Header.Get(cte) == "quoted-printable" {
	bp.Header.Del(cte)
	bp.r = quotedprintable.NewReader(bp.r)
	}
	return bp, nil
	}

	func (bp *Part) populateHeaders() error {
	r := textproto.NewReader(bp.mr.bufReader)
	header, err := r.ReadMIMEHeader()
	if err == nil {
	bp.Header = header
	}
	return err
	}

	// Read reads the body of a part, after its headers and before the
	// next part (if any) begins.
	func (p *Part) Read(d []byte) (n int, err error) {
	return p.r.Read(d)
	}

	// partReader implements io.Reader by reading raw bytes directly from the
	// wrapped *Part, without doing any Transfer-Encoding decoding.
	type partReader struct {
	p *Part
	}

	func (pr partReader) Read(d []byte) (n int, err error) {
	p := pr.p
	defer func() {
	p.bytesRead += n
	}()
	if p.buffer.Len() >= len(d) {
	// Internal buffer of unconsumed data is large enough for
	// the read request. No need to parse more at the moment.
	return p.buffer.Read(d)
	}
	peek, err := p.mr.bufReader.Peek(peekBufferSize) // TODO(bradfitz): add buffer size accessor

	// Look for an immediate empty part without a leading \r\n
	// before the boundary separator. Some MIME code makes empty
	// parts like this. Most browsers, however, write the \r\n
	// before the subsequent boundary even for empty parts and
	// won't hit this path.
	if p.bytesRead == 0 && p.mr.peekBufferIsEmptyPart(peek) {
	return 0, io.EOF
	}
	unexpectedEOF := err == io.EOF
	if err != nil && !unexpectedEOF {
	return 0, fmt.Errorf("multipart: Part Read: %v", err)
	}
	if peek == nil {
	panic("nil peek buf")
	}
	// Search the peek buffer for "\r\n--boundary". If found,
	// consume everything up to the boundary. If not, consume only
	// as much of the peek buffer as cannot hold the boundary
	// string.
	nCopy := 0
	foundBoundary := false
	if idx, isEnd := p.mr.peekBufferSeparatorIndex(peek); idx != -1 {
	nCopy = idx
	foundBoundary = isEnd
	if !isEnd && nCopy == 0 {
	nCopy = 1 // make some progress.
	}
	} else if safeCount := len(peek) - len(p.mr.nlDashBoundary); safeCount > 0 {
	nCopy = safeCount
	} else if unexpectedEOF {
	// If we've run out of peek buffer and the boundary
	// wasn't found (and can't possibly fit), we must have
	// hit the end of the file unexpectedly.
	return 0, io.ErrUnexpectedEOF
	}
	if nCopy > 0 {
	if _, err := io.CopyN(p.buffer, p.mr.bufReader, int64(nCopy)); err != nil {
	return 0, err
	}
	}
	n, err = p.buffer.Read(d)
	if err == io.EOF && !foundBoundary {
	// If the boundary hasn't been reached there's more to
	// read, so don't pass through an EOF from the buffer
	err = nil
	}
	return
	}

	func (p *Part) Close() error {
	io.Copy(ioutil.Discard, p)
	return nil
	}

	// Reader is an iterator over parts in a MIME multipart body.
	// Reader's underlying parser consumes its input as needed. Seeking
	// isn't supported.
	type Reader struct {
	bufReader *bufio.Reader

	currentPart *Part
	partsRead int

	nl []byte // "\r\n" or "\n" (set after seeing first boundary line)
	nlDashBoundary []byte // nl + "--boundary"
	dashBoundaryDash []byte // "--boundary--"
	dashBoundary []byte // "--boundary"
	}

	// NextPart returns the next part in the multipart or an error.
	// When there are no more parts, the error io.EOF is returned.
	func (r Reader) NextPart() (Part, error) {
	if r.currentPart != nil {
	r.currentPart.Close()
	}

	expectNewPart := false
	for {
	line, err := r.bufReader.ReadSlice('\n')

	if err == io.EOF && r.isFinalBoundary(line) {
	// If the buffer ends in "--boundary--" without the
	// trailing "\r\n", ReadSlice will return an error
	// (since it's missing the '\n'), but this is a valid
	// multipart EOF so we need to return io.EOF instead of
	// a fmt-wrapped one.
	return nil, io.EOF
	}
	if err != nil {
	return nil, fmt.Errorf("multipart: NextPart: %v", err)
	}

	if r.isBoundaryDelimiterLine(line) {
	r.partsRead++
	bp, err := newPart(r)
	if err != nil {
	return nil, err
	}
	r.currentPart = bp
	return bp, nil
	}

	if r.isFinalBoundary(line) {
	// Expected EOF
	return nil, io.EOF
	}

	if expectNewPart {
	return nil, fmt.Errorf("multipart: expecting a new Part; got line %q", string(line))
	}

	if r.partsRead == 0 {
	// skip line
	continue
	}

	// Consume the "\n" or "\r\n" separator between the
	// body of the previous part and the boundary line we
	// now expect will follow. (either a new part or the
	// end boundary)
	if bytes.Equal(line, r.nl) {
	expectNewPart = true
	continue
	}

	return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
	}
	}

	// isFinalBoundary reports whether line is the final boundary line
	// indicating that all parts are over.
	// It matches `^--boundary--[ \t]*(\r\n)?$`
	func (mr *Reader) isFinalBoundary(line []byte) bool {
	if !bytes.HasPrefix(line, mr.dashBoundaryDash) {
	return false
	}
	rest := line[len(mr.dashBoundaryDash):]
	rest = skipLWSPChar(rest)
	return len(rest) == 0 \|\| bytes.Equal(rest, mr.nl)
	}

	func (mr *Reader) isBoundaryDelimiterLine(line []byte) (ret bool) {
	// http://tools.ietf.org/html/rfc2046#section-5.1
	// The boundary delimiter line is then defined as a line
	// consisting entirely of two hyphen characters ("-",
	// decimal value 45) followed by the boundary parameter
	// value from the Content-Type header field, optional linear
	// whitespace, and a terminating CRLF.
	if !bytes.HasPrefix(line, mr.dashBoundary) {
	return false
	}
	rest := line[len(mr.dashBoundary):]
	rest = skipLWSPChar(rest)

	// On the first part, see our lines are ending in \n instead of \r\n
	// and switch into that mode if so. This is a violation of the spec,
	// but occurs in practice.
	if mr.partsRead == 0 && len(rest) == 1 && rest[0] == '\n' {
	mr.nl = mr.nl[1:]
	mr.nlDashBoundary = mr.nlDashBoundary[1:]
	}
	return bytes.Equal(rest, mr.nl)
	}

	// peekBufferIsEmptyPart reports whether the provided peek-ahead
	// buffer represents an empty part. It is called only if we've not
	// already read any bytes in this part and checks for the case of MIME
	// software not writing the \r\n on empty parts. Some does, some
	// doesn't.
	//
	// This checks that what follows the "--boundary" is actually the end
	// ("--boundary--" with optional whitespace) or optional whitespace
	// and then a newline, so we don't catch "--boundaryFAKE", in which
	// case the whole line is part of the data.
	func (mr *Reader) peekBufferIsEmptyPart(peek []byte) bool {
	// End of parts case.
	// Test whether peek matches `^--boundary--[ \t]*(?:\r\n\|$)`
	if bytes.HasPrefix(peek, mr.dashBoundaryDash) {
	rest := peek[len(mr.dashBoundaryDash):]
	rest = skipLWSPChar(rest)
	return bytes.HasPrefix(rest, mr.nl) \|\| len(rest) == 0
	}
	if !bytes.HasPrefix(peek, mr.dashBoundary) {
	return false
	}
	// Test whether rest matches `^[ \t]*\r\n`)
	rest := peek[len(mr.dashBoundary):]
	rest = skipLWSPChar(rest)
	return bytes.HasPrefix(rest, mr.nl)
	}

	// peekBufferSeparatorIndex returns the index of mr.nlDashBoundary in
	// peek and whether it is a real boundary (and not a prefix of an
	// unrelated separator). To be the end, the peek buffer must contain a
	// newline after the boundary or contain the ending boundary (--separator--).
	func (mr *Reader) peekBufferSeparatorIndex(peek []byte) (idx int, isEnd bool) {
	idx = bytes.Index(peek, mr.nlDashBoundary)
	if idx == -1 {
	return
	}

	peek = peek[idx+len(mr.nlDashBoundary):]
	if len(peek) == 0 \|\| len(peek) == 1 && peek[0] == '-' {
	return idx, false
	}
	if len(peek) > 1 && peek[0] == '-' && peek[1] == '-' {
	return idx, true
	}
	peek = skipLWSPChar(peek)
	// Don't have a complete line after the peek.
	if bytes.IndexByte(peek, '\n') == -1 {
	return idx, false
	}
	if len(peek) > 0 && peek[0] == '\n' {
	return idx, true
	}
	if len(peek) > 1 && peek[0] == '\r' && peek[1] == '\n' {
	return idx, true
	}
	return idx, false
	}

	// skipLWSPChar returns b with leading spaces and tabs removed.
	// RFC 822 defines:
	// LWSP-char = SPACE / HTAB
	func skipLWSPChar(b []byte) []byte {
	for len(b) > 0 && (b[0] == ' ' \|\| b[0] == '\t') {
	b = b[1:]
	}
	return b
	}