package message

import "github.com/emersion/go-message"

Package message implements reading and writing multipurpose messages.

RFC 2045, RFC 2046 and RFC 2047 defines MIME, and RFC 2183 defines the Content-Disposition header field.

{
	// Let's assume r is an io.Reader that contains a message.
	var r io.Reader

	m, err := message.Read(r)
	if message.IsUnknownEncoding(err) {
		log.Println("Unknown encoding:", err)
	} else if err != nil {
		log.Fatal(err)
	}

	// We'll add "This message is powered by Go" at the end of each text entity.
	poweredBy := "\n\nThis message is powered by Go."

	var b bytes.Buffer
	w, err := message.CreateWriter(&b, m.Header)
	if err != nil {
		log.Fatal(err)
	}

	// Define a function that transforms message.
	var transform func(w *message.Writer, e *message.Entity) error
	transform = func(w *message.Writer, e *message.Entity) error {
		if mr := e.MultipartReader(); mr != nil {
			// This is a multipart entity, transform each of its parts
			for {
				p, err := mr.NextPart()
				if err == io.EOF {
					break
				} else if err != nil {
					return err
				}

				pw, err := w.CreatePart(p.Header)
				if err != nil {
					return err
				}

				if err := transform(pw, p); err != nil {
					return err
				}

				pw.Close()
			}
			return nil
		} else {
			body := e.Body
			if strings.HasPrefix(m.Header.Get("Content-Type"), "text/") {
				body = io.MultiReader(body, strings.NewReader(poweredBy))
			}
			_, err := io.Copy(w, body)
			return err
		}
	}

	if err := transform(w, m); err != nil {
		log.Fatal(err)
	}
	w.Close()

	log.Println(b.String())
}

Index ¶

• func IsUnknownEncoding(err error) bool
• type Entity
• func New(header Header, body io.Reader) (*Entity, error)
• func NewMultipart(header Header, parts []*Entity) (*Entity, error)
• func Read(r io.Reader) (*Entity, error)
• func (e *Entity) MultipartReader() MultipartReader
• func (e *Entity) WriteTo(w io.Writer) error
• type Header
• func (h Header) Add(key, value string)
• func (h Header) ContentDescription() (string, error)
• func (h Header) ContentDisposition() (disp string, params map[string]string, err error)
• func (h Header) ContentType() (t string, params map[string]string, err error)
• func (h Header) Del(key string)
• func (h Header) Get(key string) string
• func (h Header) Set(key, value string)
• func (h Header) SetContentDescription(desc string)
• func (h Header) SetContentDisposition(disp string, params map[string]string)
• func (h Header) SetContentType(t string, params map[string]string)
• type MultipartReader
• type Writer
• func CreateWriter(w io.Writer, header Header) (*Writer, error)
• func (w *Writer) Close() error
• func (w *Writer) CreatePart(header Header) (*Writer, error)
• func (w *Writer) Write(b []byte) (int, error)

Examples ¶

• package (Transform)
• Read
• Writer

Functions ¶

func IsUnknownEncoding ¶

func IsUnknownEncoding(err error) bool

IsUnknownEncoding returns a boolean indicating whether the error is known to report that the transfer encoding or the charset advertised by the entity is unknown.

Types ¶

type Entity ¶

type Entity struct {
	Header Header    // The entity's header.
	Body   io.Reader // The decoded entity's body.
	// contains filtered or unexported fields
}

An Entity is either a whole message or a one of the parts in the body of a multipart entity.

func New ¶

func New(header Header, body io.Reader) (*Entity, error)

New makes a new message with the provided header and body. The entity's transfer encoding and charset are automatically decoded to UTF-8.

If the message uses an unknown transfer encoding or charset, New returns an error that verifies IsUnknownEncoding, but also returns an Entity that can be read.

func NewMultipart ¶

func NewMultipart(header Header, parts []*Entity) (*Entity, error)

NewMultipart makes a new multipart message with the provided header and parts. The Content-Type header must begin with "multipart/".

If the message uses an unknown transfer encoding, NewMultipart returns an error that verifies IsUnknownEncoding, but also returns an Entity that can be read.

func Read ¶

func Read(r io.Reader) (*Entity, error)

Read reads a message from r. The message's encoding and charset are automatically decoded to UTF-8. Note that this function only reads the message header.

If the message uses an unknown transfer encoding or charset, Read returns an error that verifies IsUnknownEncoding, but also returns an Entity that can be read.

{
	// Let's assume r is an io.Reader that contains a message.
	var r io.Reader

	m, err := message.Read(r)
	if message.IsUnknownEncoding(err) {
		// This error is not fatal
		log.Println("Unknown encoding:", err)
	} else if err != nil {
		log.Fatal(err)
	}

	if mr := m.MultipartReader(); mr != nil {
		// This is a multipart message
		log.Println("This is a multipart message containing:")
		for {
			p, err := mr.NextPart()
			if err == io.EOF {
				break
			} else if err != nil {
				log.Fatal(err)
			}

			t, _, _ := p.Header.ContentType()
			log.Println("A part with type", t)
		}
	} else {
		t, _, _ := m.Header.ContentType()
		log.Println("This is a non-multipart message with type", t)
	}
}

func (*Entity) MultipartReader ¶

func (e *Entity) MultipartReader() MultipartReader

MultipartReader returns a MultipartReader that reads parts from this entity's body. If this entity is not multipart, it returns nil.

func (*Entity) WriteTo ¶

func (e *Entity) WriteTo(w io.Writer) error

WriteTo writes this entity's header and body to w.

type Header ¶

type Header map[string][]string

A Header represents the key-value pairs in a message header.

func (Header) Add ¶

func (h Header) Add(key, value string)

Add adds the key, value pair to the header. It appends to any existing values associated with key.

func (Header) ContentDescription ¶

func (h Header) ContentDescription() (string, error)

ContentDescription parses the Content-Description header field.

func (Header) ContentDisposition ¶

func (h Header) ContentDisposition() (disp string, params map[string]string, err error)

ContentDisposition parses the Content-Disposition header field, as defined in RFC 2183.

func (Header) ContentType ¶

func (h Header) ContentType() (t string, params map[string]string, err error)

ContentType parses the Content-Type header field.

If no Content-Type is specified, it returns "text/plain".

func (Header) Del ¶

func (h Header) Del(key string)

Del deletes the values associated with key.

func (Header) Get ¶

func (h Header) Get(key string) string

Get gets the first value associated with the given key. If there are no values associated with the key, Get returns "".

func (Header) Set ¶

func (h Header) Set(key, value string)

Set sets the header entries associated with key to the single element value. It replaces any existing values associated with key.

func (Header) SetContentDescription ¶

func (h Header) SetContentDescription(desc string)

SetContentDescription parses the Content-Description header field.

func (Header) SetContentDisposition ¶

func (h Header) SetContentDisposition(disp string, params map[string]string)

SetContentDisposition formats the Content-Disposition header field, as defined in RFC 2183.

func (Header) SetContentType ¶

func (h Header) SetContentType(t string, params map[string]string)

SetContentType formats the Content-Type header field.

type MultipartReader ¶

type MultipartReader interface {
	io.Closer

	// NextPart returns the next part in the multipart or an error. When there are
	// no more parts, the error io.EOF is returned.
	//
	// Entity.Body must be read completely before the next call to NextPart,
	// otherwise it will be discarded.
	NextPart() (*Entity, error)
}

MultipartReader is an iterator over parts in a MIME multipart body.

type Writer ¶

type Writer struct {
	// contains filtered or unexported fields
}

A Writer formats entities.

{
	var b bytes.Buffer

	h := make(message.Header)
	h.SetContentType("multipart/alternative", nil)
	w, err := message.CreateWriter(&b, h)
	if err != nil {
		log.Fatal(err)
	}

	h1 := make(message.Header)
	h1.SetContentType("text/html", nil)
	w1, err := w.CreatePart(h1)
	if err != nil {
		log.Fatal(err)
	}
	io.WriteString(w1, "<h1>Hello World!</h1><p>This is an HTML part.</p>")
	w1.Close()

	h2 := make(message.Header)
	h1.SetContentType("text/plain", nil)
	w2, err := w.CreatePart(h2)
	if err != nil {
		log.Fatal(err)
	}
	io.WriteString(w2, "Hello World!\n\nThis is a text part.")
	w2.Close()

	w.Close()

	log.Println(b.String())
}

func CreateWriter ¶

func CreateWriter(w io.Writer, header Header) (*Writer, error)

CreateWriter creates a new Writer writing to w. If header contains an encoding, data written to the Writer will automatically be encoded with it.

func (*Writer) Close ¶

func (w *Writer) Close() error

Close implements io.Closer.

func (*Writer) CreatePart ¶

func (w *Writer) CreatePart(header Header) (*Writer, error)

CreatePart returns a Writer to a new part in this multipart entity. If this entity is not multipart, it fails. The body of the part should be written to the returned io.WriteCloser.

func (*Writer) Write ¶

func (w *Writer) Write(b []byte) (int, error)

Write implements io.Writer.

Source Files ¶

encoding.go entity.go header.go message.go multipart.go writer.go

Directories ¶