389 lines
11 KiB
Go
389 lines
11 KiB
Go
![]() |
// Copyright 2010 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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//
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/*
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Package multipart implements MIME multipart parsing, as defined in RFC
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2046.
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The implementation is sufficient for HTTP (RFC 2388) and the multipart
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bodies generated by popular browsers.
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*/
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package multipart
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import (
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"bufio"
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"bytes"
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"fmt"
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"io"
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"io/ioutil"
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"mime"
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"mime/quotedprintable"
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"net/textproto"
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)
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var emptyParams = make(map[string]string)
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// This constant needs to be at least 76 for this package to work correctly.
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// This is because \r\n--separator_of_len_70- would fill the buffer and it
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// wouldn't be safe to consume a single byte from it.
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const peekBufferSize = 4096
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// A Part represents a single part in a multipart body.
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type Part struct {
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// The headers of the body, if any, with the keys canonicalized
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// in the same fashion that the Go http.Request headers are.
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// For example, "foo-bar" changes case to "Foo-Bar"
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//
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// As a special case, if the "Content-Transfer-Encoding" header
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// has a value of "quoted-printable", that header is instead
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// hidden from this map and the body is transparently decoded
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// during Read calls.
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Header textproto.MIMEHeader
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buffer *bytes.Buffer
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mr *Reader
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bytesRead int
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disposition string
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dispositionParams map[string]string
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// r is either a reader directly reading from mr, or it's a
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// wrapper around such a reader, decoding the
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// Content-Transfer-Encoding
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r io.Reader
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}
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// FormName returns the name parameter if p has a Content-Disposition
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// of type "form-data". Otherwise it returns the empty string.
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func (p *Part) FormName() string {
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// See http://tools.ietf.org/html/rfc2183 section 2 for EBNF
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// of Content-Disposition value format.
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if p.dispositionParams == nil {
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p.parseContentDisposition()
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}
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if p.disposition != "form-data" {
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return ""
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}
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return p.dispositionParams["name"]
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}
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// FileName returns the filename parameter of the Part's
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// Content-Disposition header.
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func (p *Part) FileName() string {
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if p.dispositionParams == nil {
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p.parseContentDisposition()
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}
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return p.dispositionParams["filename"]
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}
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func (p *Part) parseContentDisposition() {
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v := p.Header.Get("Content-Disposition")
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var err error
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p.disposition, p.dispositionParams, err = mime.ParseMediaType(v)
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if err != nil {
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p.dispositionParams = emptyParams
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}
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}
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// NewReader creates a new multipart Reader reading from r using the
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// given MIME boundary.
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//
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// The boundary is usually obtained from the "boundary" parameter of
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// the message's "Content-Type" header. Use mime.ParseMediaType to
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// parse such headers.
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func NewReader(r io.Reader, boundary string) *Reader {
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b := []byte("\r\n--" + boundary + "--")
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return &Reader{
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bufReader: bufio.NewReaderSize(r, peekBufferSize),
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nl: b[:2],
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nlDashBoundary: b[:len(b)-2],
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dashBoundaryDash: b[2:],
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dashBoundary: b[2 : len(b)-2],
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}
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}
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func newPart(mr *Reader) (*Part, error) {
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bp := &Part{
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Header: make(map[string][]string),
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mr: mr,
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buffer: new(bytes.Buffer),
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}
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if err := bp.populateHeaders(); err != nil {
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return nil, err
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}
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bp.r = partReader{bp}
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const cte = "Content-Transfer-Encoding"
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if bp.Header.Get(cte) == "quoted-printable" {
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bp.Header.Del(cte)
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bp.r = quotedprintable.NewReader(bp.r)
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}
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return bp, nil
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}
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func (bp *Part) populateHeaders() error {
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r := textproto.NewReader(bp.mr.bufReader)
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header, err := r.ReadMIMEHeader()
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if err == nil {
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bp.Header = header
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}
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return err
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}
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// Read reads the body of a part, after its headers and before the
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// next part (if any) begins.
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func (p *Part) Read(d []byte) (n int, err error) {
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return p.r.Read(d)
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}
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// partReader implements io.Reader by reading raw bytes directly from the
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// wrapped *Part, without doing any Transfer-Encoding decoding.
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type partReader struct {
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p *Part
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}
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func (pr partReader) Read(d []byte) (n int, err error) {
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p := pr.p
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defer func() {
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p.bytesRead += n
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}()
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if p.buffer.Len() >= len(d) {
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// Internal buffer of unconsumed data is large enough for
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// the read request. No need to parse more at the moment.
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return p.buffer.Read(d)
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}
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peek, err := p.mr.bufReader.Peek(peekBufferSize) // TODO(bradfitz): add buffer size accessor
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// Look for an immediate empty part without a leading \r\n
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// before the boundary separator. Some MIME code makes empty
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// parts like this. Most browsers, however, write the \r\n
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// before the subsequent boundary even for empty parts and
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// won't hit this path.
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if p.bytesRead == 0 && p.mr.peekBufferIsEmptyPart(peek) {
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return 0, io.EOF
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}
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unexpectedEOF := err == io.EOF
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if err != nil && !unexpectedEOF {
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return 0, fmt.Errorf("multipart: Part Read: %v", err)
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}
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if peek == nil {
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panic("nil peek buf")
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}
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// Search the peek buffer for "\r\n--boundary". If found,
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// consume everything up to the boundary. If not, consume only
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// as much of the peek buffer as cannot hold the boundary
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// string.
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nCopy := 0
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foundBoundary := false
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if idx, isEnd := p.mr.peekBufferSeparatorIndex(peek); idx != -1 {
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nCopy = idx
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foundBoundary = isEnd
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if !isEnd && nCopy == 0 {
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nCopy = 1 // make some progress.
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}
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} else if safeCount := len(peek) - len(p.mr.nlDashBoundary); safeCount > 0 {
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nCopy = safeCount
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} else if unexpectedEOF {
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// If we've run out of peek buffer and the boundary
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// wasn't found (and can't possibly fit), we must have
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// hit the end of the file unexpectedly.
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return 0, io.ErrUnexpectedEOF
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}
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if nCopy > 0 {
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if _, err := io.CopyN(p.buffer, p.mr.bufReader, int64(nCopy)); err != nil {
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return 0, err
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}
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}
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n, err = p.buffer.Read(d)
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if err == io.EOF && !foundBoundary {
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// If the boundary hasn't been reached there's more to
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// read, so don't pass through an EOF from the buffer
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err = nil
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}
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return
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}
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func (p *Part) Close() error {
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io.Copy(ioutil.Discard, p)
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return nil
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}
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// Reader is an iterator over parts in a MIME multipart body.
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// Reader's underlying parser consumes its input as needed. Seeking
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// isn't supported.
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type Reader struct {
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bufReader *bufio.Reader
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currentPart *Part
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partsRead int
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nl []byte // "\r\n" or "\n" (set after seeing first boundary line)
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nlDashBoundary []byte // nl + "--boundary"
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dashBoundaryDash []byte // "--boundary--"
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dashBoundary []byte // "--boundary"
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}
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// NextPart returns the next part in the multipart or an error.
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// When there are no more parts, the error io.EOF is returned.
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func (r *Reader) NextPart() (*Part, error) {
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if r.currentPart != nil {
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r.currentPart.Close()
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}
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expectNewPart := false
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for {
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line, err := r.bufReader.ReadSlice('\n')
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if err == io.EOF && r.isFinalBoundary(line) {
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// If the buffer ends in "--boundary--" without the
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// trailing "\r\n", ReadSlice will return an error
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// (since it's missing the '\n'), but this is a valid
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// multipart EOF so we need to return io.EOF instead of
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// a fmt-wrapped one.
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return nil, io.EOF
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}
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if err != nil {
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return nil, fmt.Errorf("multipart: NextPart: %v", err)
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}
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if r.isBoundaryDelimiterLine(line) {
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r.partsRead++
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bp, err := newPart(r)
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if err != nil {
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return nil, err
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}
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r.currentPart = bp
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return bp, nil
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}
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if r.isFinalBoundary(line) {
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// Expected EOF
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return nil, io.EOF
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}
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if expectNewPart {
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return nil, fmt.Errorf("multipart: expecting a new Part; got line %q", string(line))
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}
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if r.partsRead == 0 {
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// skip line
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continue
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}
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// Consume the "\n" or "\r\n" separator between the
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// body of the previous part and the boundary line we
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// now expect will follow. (either a new part or the
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// end boundary)
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if bytes.Equal(line, r.nl) {
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expectNewPart = true
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continue
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}
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return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
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}
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}
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// isFinalBoundary reports whether line is the final boundary line
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// indicating that all parts are over.
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// It matches `^--boundary--[ \t]*(\r\n)?$`
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func (mr *Reader) isFinalBoundary(line []byte) bool {
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if !bytes.HasPrefix(line, mr.dashBoundaryDash) {
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return false
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}
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rest := line[len(mr.dashBoundaryDash):]
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rest = skipLWSPChar(rest)
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return len(rest) == 0 || bytes.Equal(rest, mr.nl)
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}
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func (mr *Reader) isBoundaryDelimiterLine(line []byte) (ret bool) {
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// http://tools.ietf.org/html/rfc2046#section-5.1
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// The boundary delimiter line is then defined as a line
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// consisting entirely of two hyphen characters ("-",
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// decimal value 45) followed by the boundary parameter
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// value from the Content-Type header field, optional linear
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// whitespace, and a terminating CRLF.
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if !bytes.HasPrefix(line, mr.dashBoundary) {
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return false
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}
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rest := line[len(mr.dashBoundary):]
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rest = skipLWSPChar(rest)
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// On the first part, see our lines are ending in \n instead of \r\n
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// and switch into that mode if so. This is a violation of the spec,
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// but occurs in practice.
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if mr.partsRead == 0 && len(rest) == 1 && rest[0] == '\n' {
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mr.nl = mr.nl[1:]
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mr.nlDashBoundary = mr.nlDashBoundary[1:]
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}
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return bytes.Equal(rest, mr.nl)
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}
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// peekBufferIsEmptyPart reports whether the provided peek-ahead
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// buffer represents an empty part. It is called only if we've not
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// already read any bytes in this part and checks for the case of MIME
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// software not writing the \r\n on empty parts. Some does, some
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// doesn't.
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//
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// This checks that what follows the "--boundary" is actually the end
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// ("--boundary--" with optional whitespace) or optional whitespace
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// and then a newline, so we don't catch "--boundaryFAKE", in which
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// case the whole line is part of the data.
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func (mr *Reader) peekBufferIsEmptyPart(peek []byte) bool {
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// End of parts case.
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// Test whether peek matches `^--boundary--[ \t]*(?:\r\n|$)`
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if bytes.HasPrefix(peek, mr.dashBoundaryDash) {
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rest := peek[len(mr.dashBoundaryDash):]
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rest = skipLWSPChar(rest)
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return bytes.HasPrefix(rest, mr.nl) || len(rest) == 0
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}
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if !bytes.HasPrefix(peek, mr.dashBoundary) {
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return false
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}
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// Test whether rest matches `^[ \t]*\r\n`)
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rest := peek[len(mr.dashBoundary):]
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rest = skipLWSPChar(rest)
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return bytes.HasPrefix(rest, mr.nl)
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}
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// peekBufferSeparatorIndex returns the index of mr.nlDashBoundary in
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// peek and whether it is a real boundary (and not a prefix of an
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// unrelated separator). To be the end, the peek buffer must contain a
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// newline after the boundary or contain the ending boundary (--separator--).
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func (mr *Reader) peekBufferSeparatorIndex(peek []byte) (idx int, isEnd bool) {
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idx = bytes.Index(peek, mr.nlDashBoundary)
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if idx == -1 {
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return
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}
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peek = peek[idx+len(mr.nlDashBoundary):]
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if len(peek) == 0 || len(peek) == 1 && peek[0] == '-' {
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return idx, false
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}
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if len(peek) > 1 && peek[0] == '-' && peek[1] == '-' {
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return idx, true
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}
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peek = skipLWSPChar(peek)
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// Don't have a complete line after the peek.
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if bytes.IndexByte(peek, '\n') == -1 {
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return idx, false
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}
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if len(peek) > 0 && peek[0] == '\n' {
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return idx, true
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}
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if len(peek) > 1 && peek[0] == '\r' && peek[1] == '\n' {
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return idx, true
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}
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return idx, false
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}
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// skipLWSPChar returns b with leading spaces and tabs removed.
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// RFC 822 defines:
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// LWSP-char = SPACE / HTAB
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func skipLWSPChar(b []byte) []byte {
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for len(b) > 0 && (b[0] == ' ' || b[0] == '\t') {
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b = b[1:]
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}
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return b
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}
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