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package kivik
import (
// Attachments is a collection of one or more file attachments.
type Attachments map[string]*Attachment
// Get fetches the requested attachment, or returns nil if it does not exist.
func (a *Attachments) Get(filename string) *Attachment {
return map[string]*Attachment(*a)[filename]
// Set sets the attachment associated with filename in the collection,
// replacing it if it already existed.
func (a *Attachments) Set(filename string, att *Attachment) {
map[string]*Attachment(*a)[filename] = att
// Delete removes the specified file from the collection.
func (a *Attachments) Delete(filename string) {
delete(map[string]*Attachment(*a), filename)
// Attachment represents a file attachment on a CouchDB document.
type Attachment struct {
// Filename is the name of the attachment.
Filename string `json:"-"`
// ContentType is the MIME type of the attachment contents.
ContentType string `json:"content_type"`
// Stub will be true if the data structure only represents file metadata,
// and contains no actual content. Stub will be true when returned by the
// GetAttachmentMeta function, or when included in a document without the
// 'include_docs' option
Stub bool `json:"stub"`
// Content represents the attachment's content.
// Kivik will always return a non-nil Content, even for 0-byte attachments
// or when Stub is true. It is the caller's responsibility to close
// Content.
Content io.ReadCloser `json:"-"`
// Size records the uncompressed size of the attachment. The value -1
// indicates that the length is unknown. Unless Stub is true, values >= 0
// indicate that the given number of bytes may be read from Content.
Size int64 `json:"length"`
// Used compression codec, if any. Will be the empty string if the
// attachment is uncompressed.
ContentEncoding string `json:"encoding"`
// EncodedLength records the compressed attachment size in bytes. Only
// meaningful when ContentEncoding is defined.
EncodedLength int64 `json:"encoded_length"`
// RevPos is the revision number when attachment was added.
RevPos int64 `json:"revpos"`
// Digest is the content hash digest.
Digest string `json:"digest"`
// bufCloser wraps a *bytes.Buffer to create an io.ReadCloser
type bufCloser struct {
var _ io.ReadCloser = &bufCloser{}
func (b *bufCloser) Close() error { return nil }
// validate returns an error if the attachment is invalid.
func (a *Attachment) validate() error {
if a.Filename == "" {
return missingArg("filename")
return nil
type jsonAttachment struct {
ContentType string `json:"content_type"`
Data string `json:"data"`
func readEncoder(in io.ReadCloser) io.ReadCloser {
r, w := io.Pipe()
enc := base64.NewEncoder(base64.StdEncoding, w)
go func() {
_, err := io.Copy(enc, in)
if e := in.Close(); e != nil && err == nil {
err = e
_ = enc.Close()
_ = w.CloseWithError(err)
return r
// MarshalJSON satisfies the json.Marshaler interface.
func (a *Attachment) MarshalJSON() ([]byte, error) {
if a.Stub {
return []byte(`{"stub":true}`), nil
r := readEncoder(a.Content)
data, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
att := &jsonAttachment{
ContentType: a.ContentType,
Data: string(data),
return json.Marshal(att)
// UnmarshalJSON implements the json.Unmarshaler interface for an Attachment.
func (a *Attachment) UnmarshalJSON(data []byte) error {
type clone Attachment
type jsonAtt struct {
Data []byte `json:"data"`
var att jsonAtt
if err := json.Unmarshal(data, &att); err != nil {
return err
*a = Attachment(att.clone)
if att.Data != nil {
a.Content = ioutil.NopCloser(bytes.NewReader(att.Data))
} else {
a.Content = nilContent
return nil
// UnmarshalJSON implements the json.Unmarshaler interface for a collection of
// Attachments.
func (a *Attachments) UnmarshalJSON(data []byte) error {
atts := make(map[string]*Attachment)
if err := json.Unmarshal(data, &atts); err != nil {
return err
for filename, att := range atts {
att.Filename = filename
*a = atts
return nil
// AttachmentsIterator is an experimental way to read streamed attachments from
// a multi-part Get request.
type AttachmentsIterator struct {
atti driver.Attachments
// Next returns the next attachment in the stream. io.EOF will be
// returned when there are no more attachments.
func (i *AttachmentsIterator) Next() (*Attachment, error) {
att := new(driver.Attachment)
if err := i.atti.Next(att); err != nil {
return nil, err
return &Attachment{
Filename: att.Filename,
ContentType: att.ContentType,
Content: att.Content,
Size: att.Size,
}, nil
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