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// 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"
"net/textproto"
"os"
"regexp"
)
// TODO(bradfitz): inline these once the compiler can inline them in
// read-only situation (such as bytes.HasSuffix)
var lf = []byte("\n")
var crlf = []byte("\r\n")
var headerRegexp *regexp.Regexp = regexp.MustCompile("^([a-zA-Z0-9\\-]+): *([^\r\n]+)")
var emptyParams = make(map[string]string)
// 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.
// i.e. "foo-bar" changes case to "Foo-Bar"
Header textproto.MIMEHeader
buffer *bytes.Buffer
mr *Reader
disposition string
dispositionParams map[string]string
}
// 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")
p.disposition, p.dispositionParams = mime.ParseMediaType(v)
if p.dispositionParams == nil {
p.dispositionParams = emptyParams
}
}
// NewReader creates a new multipart Reader reading from r using the
// given MIME boundary.
func NewReader(reader io.Reader, boundary string) *Reader {
b := []byte("\r\n--" + boundary + "--")
return &Reader{
bufReader: bufio.NewReader(reader),
nl: b[:2],
nlDashBoundary: b[:len(b)-2],
dashBoundaryDash: b[2:],
dashBoundary: b[2 : len(b)-2],
}
}
func newPart(mr *Reader) (*Part, os.Error) {
bp := &Part{
Header: make(map[string][]string),
mr: mr,
buffer: new(bytes.Buffer),
}
if err := bp.populateHeaders(); err != nil {
return nil, err
}
return bp, nil
}
func (bp *Part) populateHeaders() os.Error {
for {
lineBytes, err := bp.mr.bufReader.ReadSlice('\n')
if err != nil {
return err
}
line := string(lineBytes)
if line == "\n" || line == "\r\n" {
return nil
}
if matches := headerRegexp.FindStringSubmatch(line); len(matches) == 3 {
bp.Header.Add(matches[1], matches[2])
continue
}
return os.NewError("Unexpected header line found parsing multipart body")
}
panic("unreachable")
}
// Read reads the body of a part, after its headers and before the
// next part (if any) begins.
func (bp *Part) Read(p []byte) (n int, err os.Error) {
if bp.buffer.Len() >= len(p) {
// Internal buffer of unconsumed data is large enough for
// the read request. No need to parse more at the moment.
return bp.buffer.Read(p)
}
peek, err := bp.mr.bufReader.Peek(4096) // TODO(bradfitz): add buffer size accessor
unexpectedEof := err == os.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 := bytes.Index(peek, bp.mr.nlDashBoundary); idx != -1 {
nCopy = idx
foundBoundary = true
} else if safeCount := len(peek) - len(bp.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(bp.buffer, bp.mr.bufReader, int64(nCopy)); err != nil {
return 0, err
}
}
n, err = bp.buffer.Read(p)
if err == os.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 (bp *Part) Close() os.Error {
io.Copy(ioutil.Discard, bp)
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, nlDashBoundary, dashBoundaryDash, dashBoundary []byte
}
// NextPart returns the next part in the multipart or an error.
// When there are no more parts, the error os.EOF is returned.
func (mr *Reader) NextPart() (*Part, os.Error) {
if mr.currentPart != nil {
mr.currentPart.Close()
}
expectNewPart := false
for {
line, err := mr.bufReader.ReadSlice('\n')
if err != nil {
return nil, fmt.Errorf("multipart: NextPart: %v", err)
}
if mr.isBoundaryDelimiterLine(line) {
mr.partsRead++
bp, err := newPart(mr)
if err != nil {
return nil, err
}
mr.currentPart = bp
return bp, nil
}
if hasPrefixThenNewline(line, mr.dashBoundaryDash) {
// Expected EOF
return nil, os.EOF
}
if expectNewPart {
return nil, fmt.Errorf("multipart: expecting a new Part; got line %q", string(line))
}
if mr.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, mr.nl) {
expectNewPart = true
continue
}
return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
}
panic("unreachable")
}
func (mr *Reader) isBoundaryDelimiterLine(line []byte) 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
}
if bytes.HasSuffix(line, mr.nl) {
return onlyHorizontalWhitespace(line[len(mr.dashBoundary) : len(line)-len(mr.nl)])
}
// Violate the spec and also support newlines without the
// carriage return...
if mr.partsRead == 0 && bytes.HasSuffix(line, lf) {
if onlyHorizontalWhitespace(line[len(mr.dashBoundary) : len(line)-1]) {
mr.nl = mr.nl[1:]
mr.nlDashBoundary = mr.nlDashBoundary[1:]
return true
}
}
return false
}
func onlyHorizontalWhitespace(s []byte) bool {
for _, b := range s {
if b != ' ' && b != '\t' {
return false
}
}
return true
}
func hasPrefixThenNewline(s, prefix []byte) bool {
return bytes.HasPrefix(s, prefix) &&
(len(s) == len(prefix)+1 && s[len(s)-1] == '\n' ||
len(s) == len(prefix)+2 && bytes.HasSuffix(s, crlf))
}