imap 1.0 · OCaml Package

Non-blocking IMAP4 protocol codec.

Imap is a non-blocking codec to encode and decode the full IMAP4 protocol, together with some extensions. It can process input without blocking on IO and is completely independent of any particular buffering and/or IO strategry (concurrent, like Lwt or Async, sequential, etc.).

Most users should begin by looking at the examples, the types and functions describing connections, commands, and the run function.

See the examples of use.

References

M. Crispin INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1, 2003

Common types for IMAP

type uint32 = Uint32.t

Unsigned 32-bit integers are used for: message sequence numbers, unique identification numbers (UIDs).

type uint64 = Uint64.t

Unsigned 64-bit integers are used for: mod-sequence numbers, Gmail message and thread IDs.

type date = {

day : int;
month : int;
year : int;

}

type time = {

hours : int;
minutes : int;
seconds : int;
zone : int;

}

type flag = [

| `Answered
| `Flagged
| `Deleted
| `Seen
| `Draft
| `Keyword of string
| `Extension of string

]

Message flags. The underlying string of `Extension s is '\\' ^ s, while `Keyword s is s.

type capability = [

| `Acl
| `Binary
| `Catenate
| `Children
| `Compress_deflate
| `Condstore
| `Enable
| `Idle
| `Id
| `Literal_plus
| `Multi_append
| `Namespace
| `Qresync
| `Quote
| `Sort
| `Start_tls
| `Uid_plus
| `Unselect
| `Xlist
| `Auth of [ `Anonymous | `Login | `Plain ]
| `Xoauth2
| `Gmail
| `Other of string

]

List of standard capabilites. These are returned by the capability command, in status codes and can be enabled by the enable command.

Types for responses

These types describe all possible responses from the server. Typically one would pattern-match on the untagged type to extract the desired data. See the examples.

type set = (uint32 * uint32) list

Message number (either sequence or UIDs) sets, as a union of intervals. It is the responsability of the client to make any necessary validity check, as none is performed by the library.

For example, the IMAP sequence set 1,2:3 is represented by [(1, 1); (2, 3)].

Envelope information

It is returned when fetching the `Envelope message attribute using the fetch command.

If val a : address, then the expression

Printf.printf "\"%s\" <%s@%s>" a.ad_name a.ad_mailbox a.ad_host

will output a in the usual format "name" <user\@host.com>.

type address = {

ad_name : string;
ad_adl : string;
ad_mailbox : string;
ad_host : string;

}

type envelope = {

env_date : string;
env_subject : string;
env_from : address list;
env_sender : address list;
env_reply_to : address list;
env_to : address list;
env_cc : address list;
env_bcc : address list;
env_in_reply_to : string;
env_message_id : string;

}

MIME message structure

The following types describe the bodies of MIME emails. The IMAP server can parse the MIME structure of the messages and return individual parts. This saves the client from having to do that parsing itself. See

and related RFCs for details.

type fields = {

fld_params : (string * string) list;
fld_id : string option;
fld_desc : string option;
fld_enc : string;
fld_octets : int;

}

type mime = [

| `Text of string * fields * int
| `Message of fields * envelope * mime * int
| `Basic of string * string * fields
| `Multiple of mime list * string

]

type section = [

| `Header
| `Header_fields of string list
| `Header_fields_not of string list
| `Text
| `Mime
| `Part of int * section
| `All

]

Fetch responses

Message attributes returned in the untagged `Fetch response to the fetch command.

type fetch_response = [

| `Flags of [ flag | `Recent ] list
(*
A parenthesized list of flags that are set for this message.
*)
| `Envelope of envelope
(*
A list that describes the envelope structure of a message. This is computed by the server by parsing the RFC-2822 header into the component parts, defaulting various fields as necessary.
*)
| `Internal_date of date * time
(*
A string representing the internal date of the message.
*)
| `Rfc822 of string option
(*
Equivalent to BODY[].
*)
| `Rfc822_header of string option
(*
The message header.
*)
| `Rfc822_text of string option
(*
The message body.
*)
| `Rfc822_size of int
(*
The RFC-2822 size of the message.
*)
| `Body of mime
(*
A form of BODYSTRUCTURE without extension data.
*)
| `Body_structure of mime
(*
A parenthesized list that describes the MIME-IMB body structure of a message. This is computed by the server by parsing the MIME-IMB header fields, defaulting various fields as necessary.
*)
| `Body_section of section * int option * string option
(*
A message MIME part, starting offset, part data.
*)
| `Uid of uint32
(*
The unique identifier of the message.
*)
| `Modseq of uint64
(*
The modification sequence number of this message. Requires CONDSTORE.
*)
| `Gm_msgid of uint64
(*
Gmail message ID.
*)
| `Gm_thrid of uint64
(*
Gmail thread ID.
*)
| `Gm_labels of string list
(*
Gmail labels.
*)

]

Response codes

Status responses are `Ok, `No, `Bad, `Preauth and `Bye. `Ok, `No, and `Bad can be tagged or untagged. `Preauth and `Bye are always untagged.

Status responses may include a "response code". The response code contains additional information or status codes for client software beyond the `Ok, `No, `Bad, and are defined when there is a specific action that a client can take based upon the additional information.

type code = [

| `Alert
(*
A special alert that MUST be presented to the user in a fashion that calls the user's attention to the message.
*)
| `Bad_charset of string list
(*
A search command failed because the given charset is not supported by this implementation. Contains the list the charsets that are supported by the server.
*)
| `Capability of capability list
(*
The list of capabilities supported by the server. This can appear in the initial `Ok or `Preauth response to transmit an initial capabilities list. This makes it unnecessary for a client to send a separate capability command if it recognizes this response.
*)
| `Parse
(*
An error occurred in parsing the headers of a message in the mailbox.
*)
| `Permanent_flags of [ flag | `All ] list
(*
The list of flags the client can change permanently. Any flags that are in the untagged `Flags response, but not in the `Permanent_flags list, can not be set permanently. If the client attempts to store a flag that is not in the `Permanent_flags list, the server will either ignore the change or store the state change for the remainder of the current session only. The `Permanent_flags list can also include the special flag `All, which indicates that it is possible to create new keywords by attempting to store those flags in the mailbox.
*)
| `Read_only
(*
The mailbox is selected read-only, or its access while selected has changed from read-write to read-only.
*)
| `Read_write
(*
The mailbox is selected read-write, or its access while selected has changed from read-only to read-write.
*)
| `Try_create
(*
An append or copy command is failing because the target mailbox does not exist (as opposed to some other reason). This is a hint to the client that the operation can succeed if the mailbox is first created by the create command.
*)
| `Uid_next of uint32
(*
The next unique identifier value. Refer to ??? for more information.
*)
| `Uid_validity of uint32
(*
The unique identifier validity value. Refer to ??? for more information.
*)
| `Unseen of uint32
(*
The number of the first message without the `Seen flag set.
*)
| `Other of string * string option
(*
Another response code.
*)
| `Closed
(*
Signals that the current mailbox has been closed. It is sent when closing a mailbox implictly as a consequence of selecting a different mailbox. Requires QRESYNC.
*)
| `Highest_modseq of uint64
(*
The highest mod-sequence value of all messages in the mailbox. Returned in an untagged `Ok response to the select and examine commands.
*)
| `No_modseq
(*
A server that doesn't support the persistent storage of mod-sequences for the mailbox MUST send this code in an untagged `Ok response to every successful select or examine command.
*)
| `Modified of (uint32 * uint32) list
(*
The `Modified response code includes the message set or set of UIDs of the most recent sotre command of all messages that failed the UNCHANGESINCE test.
*)
| `Append_uid of uint32 * uint32
(*
Contains the `Uid_validity of the destination mailbox and the `Uid assigned to the appended message in the destination mailbox.
This response code is returned in a tagged `Ok response to the append command.
*)
| `Copy_uid of uint32 * (uint32 * uint32) list * (uint32 * uint32) list
(*
Sent in response to a COPY command, contains the UIDVALIDITY of the destination mailbox, followed by the set of UIDs of the source messages, and the set of UIDs of the destination messages (in the same order). Requires UIDPLUS.
This response code is returned in a tagged `Ok response to the copy command.
*)
| `Uid_not_sticky
(*
The selected mailbox is supported by a mail store that does not support persistent UIDs; that is, `Uid_validity will be different each time the mailbox is selected. Consequently, append or copy to this mailbox will not return an `Append_uid or `Copy_uid response code.
This response code is returned in an untagged `No response to the select command.
*)
| `Compression_active
(*
Compression has been activated. Requires the COMPRESS=DEFLATE capability.
*)
| `Use_attr
(*
A create command failed due to the special-use attribute requested.
*)
| `None
(*
No response code was sent.
*)

]

Mailbox flags

Returned by the list or lsub commands and also in some status codes.

type mbx_flag = [

| `Noselect
| `Marked
| `Unmarked
| `Noinferiors
| `HasChildren
| `HasNoChildren
| `All
| `Archive
| `Drafts
| `Flagged
| `Junk
| `Sent
| `Trash
| `Extension of string

]

Mailbox status responses

Mailbox status items returned in the untagged `Status response to the status command.

type status_response = [

| `Messages of int
(*
Number of messages in the mailbox.
*)
| `Recent of int
(*
Number of messages in the mailbox with the `Recent flag.
*)
| `Uid_next of uint32
(*
The expected UID of the next message to be added to this mailbox.
*)
| `Uid_validity of uint32
(*
The UID VALIDITY value of this mailbox.
*)
| `Unseen of uint32
(*
The Sequence number of the first message in the mailbox that has not been seen.
*)
| `Highest_modseq of uint64
(*
The highest modification sequence number of all the messages in the mailbox. This is only sent back if CONDSTORE is enabled.
*)

]

Status responses

These can be either tagged or untagged. The string carries a human-readable explanation of the code.

type state = [

| `Ok of code * string
| `No of code * string
| `Bad of code * string

]

Server responses

Sending a command will typically result in a sequence of untagged items being sent back, ending in a `Tagged response. Normally the user will not deal with the type response directly, but rather with the type returned by run.

type untagged = [

| state
| `Bye of code * string
(*
The server will be closing the connection soon.
*)
| `Preauth of code * string
(*
The session as been Pre-Authorized and no authentication is necessary. This should not occur in normal circumstances.
*)
| `Flags of flag list
(*
The `Flags response occurs as a result of a select or examine command. Contains the list of flag that are applicable for this mailbox.
*)
| `List of mbx_flag list * char option * string
(*
LIST response: mailbox flags, character used as path delimiter (optional), and mailbox name.
*)
| `Lsub of mbx_flag list * char option * string
(*
LSUB response, same information as LIST.
*)
| `Search of uint32 list * uint64 option
(*
SEARCH or UID SEARCH response: list of message numbers (UID or Sequence), and optionally the highest modification sequence number of the returned list of messages if CONDSTORE is enabled.
*)
| `Status of string * status_response list
(*
STATUS response: mailbox name, list of status items.
*)
| `Exists of int
(*
The `Exists response reports the number of messages in the mailbox. This response occurs as a result of a select or examine command, and if the size of the mailbox changes (e.g., new messages).
*)
| `Recent of int
(*
The `Recent response reports the number of messages with the `Recent flag set. This response occurs as a result of a select or examine command, and if the size of the mailbox changes (e.g., new messages).
*)
| `Expunge of uint32
(*
The `Expunge response reports that the specified message sequence number has been permanently removed from the mailbox. The message sequence number for each successive message in the mailbox is immediately decremented by 1, and this decrement is reflected in message sequence numbers in subsequent responses (including other untagged `Expunge responses).
The `Expunge response also decrements the number of messages in the mailbox; it is not necessary to send an `Exists response with the new value.
As a result of the immediate decrement rule, message sequence numbers that appear in a set of successive `Expunge responses depend upon whether the messages are removed starting from lower numbers to higher numbers, or from higher numbers to lower numbers. For example, if the last 5 messages in a 9-message mailbox are expunged, a "lower to higher" server will send five untagged EXPUNGE responses for message sequence number 5, whereas a "higher to lower server" will send successive untagged `Expunge responses for message sequence numbers 9, 8, 7, 6, and 5.
*)
| `Fetch of uint32 * fetch_response list
(*
The `Fetch response returns data about a message to the client. It contains the message number and the list of data items and their values. This response occurs as the result of a fetch or store command, as well as by unilateral server decision (e.g., flag updates).
*)
| `Capability of capability list
(*
List of capabilities supported by the server.
*)
| `Vanished of (uint32 * uint32) list
(*
List of UIDs of messages that have been expunged from the current mailbox. Requires QRESYNC.
*)
| `Vanished_earlier of (uint32 * uint32) list
(*
Same as `Vanished, but sent only in response to a FETCH (VANISHED) or SELECT/EXAMINE (QRESYNC) command. Requires QRESYNC.
*)
| `Enabled of capability list
(*
List of capabilities enabled after issuing enable command.
*)

]

type response = [

| untagged
| `Cont of string
(*
Continuation request: the server is waiting for client data. The client must wait for this message before sending literal data.
*)
| `Tagged of string * state
(*
Tagged response: tag, result status.
*)

]

Pretty printing responses

Will print the given response in s-expression format.

val pp_response : Format.formatter -> [< response ] -> unit

Types for queries

These types are used to describe queries to the server using the different commands.

type eset = (uint32 * uint32 option) list

Extended message numbers sets, as a union of intervals. The second component of an interval being None means that it should take the largest possible value appearing in the mailbox (this is denoted '*' in the IMAP protocol).

For example, the IMAP extended set 1,2:3,4:* will be represented by [(1, Some 1); (2, Some 3); (4, None)].

type search_key = [

| `Seq of eset
(*
Messages with message sequence numbers corresponding to the specified message sequence number set.
*)
| `All
(*
All messages in the mailbox; the default initial key for ANDing.
*)
| `Answered
(*
Messages with the `Answered flag set.
*)
| `Bcc of string
(*
Messages that contain the specified string in the envelope structure's "BCC" field.
*)
| `Before of date
(*
Messages whose internal date (disregarding time and timezone) is earlier than the specified date.
*)
| `Body of string
(*
Messages that contain the specified string in the body of the message.
*)
| `Cc of string
(*
Messages that contain the specified string in the envelope structure's "CC" field.
*)
| `Deleted
(*
Messages with the `Deleted flag set.
*)
| `Draft
(*
Messages with the `Draft flag set.
*)
| `Flagged
(*
Messages with the `Flagged flag set.
*)
| `From of string
(*
Messages that contain the specified string in the envelope structure's "FROM" field.
*)
| `Header of string * string
(*
Messages that have a header with the specified field-name and that contains the specified string in the text of the header (what comes after the colon). If the string to search is zero-length, this matches all messages that have a header line with the specified field-name regardless of the contents.
*)
| `Keyword of string
(*
Messages with the specified keyword flag set.
*)
| `Larger of int
(*
Messages with a size larger than the specified number of octets.
*)
| `New
(*
Messages that have the `Recent flag set but not the `Seen flag. This is functionally equivalent to `And (`Recent, `Unseen).
*)
| `Not of search_key
(*
Messages that do not match the specified search key.
*)
| `Old
(*
Messages that do not have the `Recent flag set. This is functionally equivalent to `Not `Recent (as opposed to `Not `New).
*)
| `On of date
(*
Messages whose internal date (disregarding time and timezone) is within the specified date.
*)
| `Or of search_key * search_key
(*
Messages that match either search key.
*)
| `Recent
(*
Messages that have the `Recent flag set.
*)
| `Seen
(*
Messages that have the `Seen flag set.
*)
| `Sent_before of date
(*
Messages whose "Date:" header (disregarding time and timezone) is earlier than the specified date.
*)
| `Sent_on of date
(*
Messages whose "Date:" header (disregarding time and timezone) is within the specified date.
*)
| `Sent_since of date
(*
Messages whose "Date:" header (disregarding time and timezone) is within or later than the specified date.
*)
| `Since of date
(*
Messages whose internal date (disregarding time and timezone) is within or later than the specified date.
*)
| `Smaller of int
(*
Messages with a size smaller than the specified number of octets.
*)
| `Subject of string
(*
Messages that contain the specified string in the envelope structure's "SUBJECT" field.
*)
| `Text of string
(*
Messages that contain the specified string in the header or body of the message.
*)
| `To of string
(*
Messages that contain the specified string in the envelope structure's "TO" field.
*)
| `Uid of eset
(*
Messages with unique identifiers corresponding to the specified unique identifier set. Sequence set ranges are permitted.
*)
| `Unanswered
(*
Messages that do not have the `Answered flag set.
*)
| `Undeleted
(*
Messages that do not have the `Deleted flag set.
*)
| `Undraft
(*
Messages that do not have the `Draft flag set.
*)
| `Unflagged
(*
Messages that do not have the `Flagged flag set.
*)
| `Unkeyword of string
(*
Messages that do not have the specified keyword flag set.
*)
| `Unseen
(*
Messages that do not have the `Seen flag set.
*)
| `And of search_key * search_key
(*
Messages that satisfy both search criteria.
*)
| `Modseq of uint64
(*
Messages that have equal or greater modification sequence numbers.
*)
| `Gm_raw of string
(*
TOOD
*)
| `Gm_msgid of uint64
(*
Messages with a given Gmail Message ID.
*)
| `Gm_thrid of uint64
(*
Messages with a given Gmail Thread ID.
*)
| `Gm_labels of string list
(*
Messages with given Gmail labels.
*)

]

Search keys. See search command.

type fetch_query = [

| `Envelope
(*
The envelope structure of the message. This is computed by the server by parsing the header into the component parts, defaulting various fields as necessary.
*)
| `Internal_date
(*
The internal date of the message.
*)
| `Rfc822_header
(*
Functionally equivalent to `Body_section (`Peek, `Header, None), differing in the syntax of the resulting untagged `Fetch data (`Rfc822_header is returned).
*)
| `Rfc822_text
(*
Functionally equivalent to `Body_section (`Look, `Text, None), differing in the syntax of the resulting untagged `Fetch data (`Rfc822_text is returned).
*)
| `Rfc822_size
(*
The size of the message.
*)
| `Rfc822
(*
Functionally equivalent to `Body_section (`Look, `All, None), differing in the syntax of the resulting untagged `Fetch data (`Rfc822 is returned).
*)
| `Body
(*
Non-extensible form of `Body_structure.
*)
| `Body_section of [ `Peek | `Look ] * section * (int * int) option
(*
The text of a particular body section. The `Peek flag is an alternate form that does not implicitly set the `Seen flag.
*)
| `Body_structure
(*
The MIME body structure of the message. This is computed by the server by parsing the MIME header fields in the RFC-2822 header and MIME headers.
*)
| `Uid
(*
The unique identifier for the message.
*)
| `Flags
(*
The flags that are set for this message.
*)

]

Message attributes that can be requested using the fetch command.

type status_query = [

| `Messages
(*
The number of messages in the mailbox.
*)
| `Recent
(*
The number of messages with the `Recent flag set.
*)
| `Uid_next
(*
The next unique identifier value of the mailbox.
*)
| `Uid_validity
(*
The unique identifier validity value of the mailbox.
*)
| `Unseen
(*
The number of messages which do not have the `Seen flag set.
*)
| `Highest_modseq
(*
TODO
*)

]

Mailbox attibutes that can be requested with the status command.

Commands

These are the available commands that can be sent to an IMAP server. Not all commands will be supported in every IMAP server as they will depend on certain capabilities being enabled. A command is executed using run. It is a programmer error to try to run more than one command at the same time. If this is required, more than one connection should be opened to the server.

Some commands have a ?uid optional argument. When true it means to use the variant of the command that uses UIDs (instead of sequence numbers). See for example copy, search, fetch and store_add_flags.

type command

The type of client commands. They are executed using run.

val login : string -> string -> command

login user pass identifies the client to the server and carries the plaintext password authenticating this user with password pass. A server MAY include a `Capability response code in the tagged `Ok response to a successful login command in order to send capabilities automatically.

val capability : command

capability returns the list of capabilities supported by the server. The server must send a single untagged `Capability response with "IMAP4rev1" as one of the listed capabilities before the (tagged) `Ok response. See the type describing the possible capabilities.

val create : string -> command

create m creates a mailbox named m. An `Ok response is returned only if a new mailbox with that name has been created. It is an error to attempt to create "INBOX" or a mailbox with a name that refers to an extant mailbox. Any error in creation will return a tagged `No response.

val rename : string -> string -> command

rename oldname newname command changes the name of a mailbox from oldname to newname. A tagged `Ok response is returned only if the mailbox has been renamed. It is an error to attempt to rename from a mailbox name that does not exist or to a mailbox name that already exists. Any error in renaming will return a tagged `No response.

val logout : command

logout gracefully terminates a session. The server MUST send an untagged `Bye response before the (tagged) `Ok response.

val noop : command

noop does nothing. Since any command can return a status update as untagged data, the noop command can be used as a periodic poll for new messages or message status updates during a period of inactivity (this is the preferred method to do this).

val subscribe : string -> command

subscribe m adds the mailbox m to the server's set of "active" or "subscribed" mailboxes as returned by the lsub command.

val unsubscribe : string -> command

unsubcribe m removes the mailbox m from the server's set of "active" or "subscribed" mailboxes as returned by the lsub command.

val list : ?ref:string -> string -> command

list ref m returns a subset of names from the complete set of all names available to the client. Zero or more untagged `List replies are returned, containing the name attributes, hierarchy delimiter. The optional argument ref is the name of a mailbox or a level of mailbox hierarchy, and indicates the context in which the mailbox name is interpreted.

val lsub : ?ref:string -> string -> command

lsub ref m is identical to list, except that it returns a subset of names from the set of names that the user has declared as being "active" or "subscribed".

val status : string -> status_query list -> command

status requests status information of the indicated mailbox. An untagged `Status response is returned with the requested information.

val copy : ?uid:bool -> eset -> string -> command

copy uid set m copies the messages in set to the end of the specified mailbox m. set is understood as a set of message UIDs if uid is true (the default) or sequence numbers if uid is false.

val check : command

check requests a checkpoint of the currently selected mailbox. A checkpoint refers to any implementation-dependent housekeeping associated with the mailbox.

val close : command

close permanently removes all messages that have the `Deleted flag set from the currently selected mailbox, and returns to the authenticated state from the selected state.

val expunge : command

expunge permanently removes all messages that have the `Deleted flag set from the currently selected mailbox. Before returning an `Ok to the client, an untagged `Expunge response is sent for each message that is removed.

val search : ?uid:bool -> search_key -> command

search uid sk searches the mailbox for messages that match the given searching criteria. If uid is true (the default), then the matching messages' unique identification numbers are returned. Otherwise, their sequence numbers are. The untagged `Search response from the server contains a listing of message numbers corresponding to those messages that match the searching criteria.

val select : ?condstore:bool -> string -> command

select condstore m selects the mailbox m so that its messages can be accessed. If condstore (default value false) is true, then the server will return the `Modseq data item in all subsequent untagged `Fetch responses.

val examine : ?condstore:bool -> string -> command

examine condstore m is identical to select condstore m and returns the same output; however, the selected mailbox is identified as read-only.

val append : string -> ?flags:flag list -> string -> command

append m flags id data appends data as a new message to the end of the mailbox m. This argument should be in the format of an RFC-2822 message.

If a flag list is specified, the flags should be set in the resulting message; otherwise, the flag list of the resulting message is set to empty by default. In either case, the `Recent flag is also set.

Fetch commands

The IMAP FETCH command is used to retrieve the data associated to a message (or a set of messages). Messages are identified either by their sequence number (i.e., their position in the mailbox), or by their unique identification number (UID).

For those servers that support the CONDSTORE extension, one can pass a mod-sequence value ?changed to restrict the set of affected messages to those that are not yet known by the client. One can further use the ?vanished argument to learn of recently expunged messages. It is a programmer error to set ?vanished to true but not to pass a value for ?changed.

val fetch : 
  ?uid:bool ->
  ?changed:uint64 ->
  ?vanished:bool ->
  eset ->
  fetch_query list ->
  command

fetch uid changed vanished set att retrieves data associated with the message set set in the current mailbox. set is interpeted as being a set of UIDs or sequence numbers depending on whether uid is true (the default) or false. Specifying a ?changed argument will further reduce the set of returned messages to those whose CHANGEDSINCE mod-sequence value is at least the passed value (requires the CONDSTORE extension). The vanished optional parameter specifies whether one wants to receive `Vanished responses as well.

val fetch_all : 
  ?uid:bool ->
  ?changed:uint64 ->
  ?vanished:bool ->
  eset ->
  command

fetch_all uid changed vanished set is equivalent to fetch uid changed vanished set a, where a = [`Flags; `Internal_date; `Rfc822_size; `Envelope].

val fetch_fast : 
  ?uid:bool ->
  ?changed:uint64 ->
  ?vanished:bool ->
  eset ->
  command

fetch_fast uid changed vanished set is equivalent to fetch uid changed vanished set a, where a = [`Flags; `Internal_date; `Rfc822_size].

val fetch_full : 
  ?uid:bool ->
  ?changed:uint64 ->
  ?vanished:bool ->
  eset ->
  command

fetch_full u c v s is equivalent to fetch u c v s a where a = [`Flags; `Internal_date; `Rfc822_size; `Envelope; `Body].

Store commands

val store_add_flags : 
  ?uid:bool ->
  ?silent:bool ->
  ?unchanged:uint64 ->
  eset ->
  flag list ->
  command

store_add_flags uid silent unchanged set flags adds flags flags to the message set set. set is interpreter as being a set of UIDs or sequence numbers depending on whether uid is true (the default) or false. The server will return the updated flags for the affected messages in untagged `Fetch responses depending on whether silent is true (the default) or false. Specifying a ?unchanged argument will further reduce the set of affected messages to those whose UNCHANGEDSINCE mod-sequence value is at least the passed value (requires the CONDSTORE extension).

val store_set_flags : 
  ?uid:bool ->
  ?silent:bool ->
  ?unchanged:uint64 ->
  eset ->
  flag list ->
  command

store_set_flags is like store_add_flags but replaces the set of flags instead of adding to it.

val store_remove_flags : 
  ?uid:bool ->
  ?silent:bool ->
  ?unchanged:uint64 ->
  eset ->
  flag list ->
  command

store_remove_flags is like store_add_flags but removes flags instead of adding them.

val store_add_labels : 
  ?uid:bool ->
  ?silent:bool ->
  ?unchanged:uint64 ->
  eset ->
  string list ->
  command

store_add_labels is like store_add_flags but adds Gmail labels instead of regular flags.

val store_set_labels : 
  ?uid:bool ->
  ?silent:bool ->
  ?unchanged:uint64 ->
  eset ->
  string list ->
  command

store_set_labels is like store_add_labels but replaces the set of labels instead of adding to it.

val store_remove_labels : 
  ?uid:bool ->
  ?silent:bool ->
  ?unchanged:uint64 ->
  eset ->
  string list ->
  command

store_remove_labels is like store_add_labels but removes labels instead of adding them.

val enable : capability list -> command

Authenticators

These are used to implement SASL authentication. SASL authentication is initiated by passing `Authenticate to run and typically would occur right after receiving the server greeting.

The authentication protocol exchange consists of a series of server challenges and client responses that are specific to the authentication mechanism. If a is the authenticator being used, a.step will be called with each of the server's challenges. The return value of a.step can signal an error or give the corresponding response.

step functions do not have to perform base64-encoding and decoding, as this is handled automatically by the library.

The implementation of particular SASL authenticaton methods is outside the scope of this library and should be provided independently. Only PLAIN and XOAUTH2 are provided as way of example.

type authenticator = {

name : string;
step : string -> [ `Ok of string | `Error of string ];

}

val plain : string -> string -> authenticator

plain user pass authenticates via PLAIN mechanism using username user and password pass.

val xoauth2 : string -> string -> authenticator

xoauth2 user token authenticates via XOAUTH2 mechanishm user username user and access token token. The access token should be obtained independently.

Running commands and receiving responses

type error = [

| `Incorrect_tag of string * string
(*
The server response tag does not have a matching message tag. The connection should be closed.
*)
| `Decode_error of [ `Expected_char of char | `Expected_string of string | `Unexpected_char of char | `Unexpected_string of string | `Illegal_char of char | `Unexpected_eoi ] * string * int
(*
Decoding error. It contains the reason, the curren tinput buffer and the current position. The connection should be closed after this. In some cases it might be possible to continue fater a decoding error, but this is not yet implemented.
*)
| `Unexpected_cont
(*
A continuation request '+' is received from the server at an unexpected time. The connection should be closed after seeing this error, as there is no safe way to continue.
*)
| `Bad_greeting
(*
The server did not send a valid greeting message. The connection should be closed.
*)
| `Auth_error of string
(*
An client-side SASL authentication error ocurred. This error can only appear when using the SASL-based `Authenticate command. The error is communicated to the server and the server responds with a BAD response. Thus, after receiving this error the client should pass `Await to run until `Error `Bad is received, and then take appropiate action.
*)
| `Bad of code * string
(*
The server could not parse the request.
*)
| `No of code * string
(*
The server could not perform the requested action.
*)

]

val pp_error : Format.formatter -> error -> unit

Connections

Connections manage the encoder and decoder states and keeps track of message tags.

type connection

The type for connections.

val connection : unit -> connection

connection () creates a new connection object. The connection should be supplied with input and output buffers as necessary using src and dst. Other that that, it is completely independent of any particular connection and/or IO mechanism.

After creation, the connection should be run with `Await until `Ok to process the server greeting and start issuing commands.

See the examples.

I/O interface

The following functions are used to provide input and/or output buffers to run when it returns `Await_src and/or `Await_dst.

val src : connection -> string -> int -> int -> unit

src c s i l provides c with input taken from l bytes from s starting at i.

val dst : connection -> string -> int -> int -> unit

dst c s i l provides c with l bytes of output storage in s starting at i.

val dst_rem : connection -> int

dst_rem c is the number of bytes still available for output in the current output buffer of c.

Executing commands

The run function encodes the connection state machine. A connection c can be in three states: awaiting the server greeting, executing a command, or awaiting commands.

After creation, c is awaiting the server greeting. run must be passed `Await until getting back `Ok which signals that the greeting has been received and c is now awaiting commands. A command can then be initiated by passing `Cmd, `Idle or `Authenticate. After a command is initiated, c will be executing a command and run will return a sequence of `Await_src and/or `Await_dst values interspaced with `Untagged values, and finally ending with `Ok. The client should call run with `Await to step through this process (possibly after providing more input and output storage using src and dst).

After returning `Ok, c is again awaiting commands and the process can be reinitiated.

It is an error to execute a command if c is not awaiting commands. The only exception to this is that `Idle_done can be executed while `Idle is in progress.

See the examples.

val run : 
  connection ->
  [ `Cmd of command
  | `Await
  | `Idle
  | `Idle_done
  | `Authenticate of authenticator ] ->
  [ `Untagged of untagged
  | `Ok of code * string
  | `Error of error
  | `Await_src
  | `Await_dst ]

run c v performs v on the connection c. The meaning of the different values of v is:

`Cmd c: execute the command c.
`Await: perform periodic IO processing to complete the execution of currently executing command.
`Idle: start IDLE command. When this command is executing the client will receive a stream of incoming untagged responses until IDLE ends. IDLE can end by server decision of by passing v = `Idle_run. See the relevent RFC and the examples for more details.
`Idle_done: stop IDLE command.
`Authenticate a: perform SASL authentication using the authenticator a.

The value of run c v is:

`Untagged u if an untagged response has been received from the server.
`Ok if no command is in progress and the server is ready to receive a new command from the client.
`Error e if an error ocurred during the processing of the current command. If the error is not fatal, then the client can continue using this connection. Otherwise, the connection should be discarded immediately.
`Await_src if the connection is awaiting for more input. The client must use src to provide a new buffer and then call run with `Await.
`Await_dst if the connection needs more output storage. The client must use dst to provide a new buffer and then call run with `Await.

Supported extensions and limitations

The following extensions are supported:

Limitations

Error handling is very simplistic. In particular there is no error recovery from simple parsing errors. Some form of this could be added if required.

Example: checking for new mail

wait_mail host port user pass mbox logs into the IMAP server host on port port over SSL, authenticates user user with password pass and watches mailbox mbox until a new message arrives. When a new message arrives, it outputs the sender's name and address and stops.

See the wait_mail.ml file for a more complete version of this example.

Setting debug_flag := true will output all the data exchanged with the server which can be quite instructive.

let debug_flag = ref false

The function run takes care of managing I/O.

let run sock i o c v : [ `Untagged of Imap.untagged | `Ok ] =
  let rec write_fully s off len =
    if len > 0 then
      let rc = Ssl.write sock s off len in
      write_fully s (off + rc) (len - rc)
  in
  let rec loop = function
    | `Await_src ->
        let rc = Ssl.read sock i 0 (Bytes.length i) in
        if !debug_flag then Format.eprintf ">>> %d\n%s>>>\n%!" rc (String.sub i 0 rc);
        Imap.src c i 0 rc;
        loop (Imap.run c `Await)
    | `Await_dst ->
        let rc = Bytes.length o - Imap.dst_rem c in
        write_fully o 0 rc;
        if !debug_flag then Format.eprintf "<<< %d\n%s<<<\n%!" rc (String.sub o 0 rc);
        Imap.dst c o 0 (Bytes.length o);
        loop (Imap.run c `Await)
    | `Untagged _ as r -> r
    | `Ok _ -> `Ok
    | `Error e ->
        Format.eprintf "@[IMAP Error: %a@]@." Imap.pp_error e;
        failwith "imap error"
  in
  loop (Imap.run c v)

In order to detect new messages, we record the next UID value of the INBOX mailbox as soon as we open it. Then we wait for the server to alert us of activity in this mailbox using the idle command. And we look for messages with UIDs larger than this one using the search command.

let () = Ssl.init ()

let wait_mail host port user pass mbox =
  let fd = Unix.socket Unix.PF_INET Unix.SOCK_STREAM 0 in
  let he = Unix.gethostbyname host in
  Unix.connect fd (Unix.ADDR_INET (he.Unix.h_addr_list.(0), port));
  let ctx = Ssl.create_context Ssl.TLSv1 Ssl.Client_context in
  let sock = Ssl.embed_socket fd ctx in
  Ssl.connect sock;
  let c = Imap.connection `Manual `Manual in
  let i = Bytes.create io_buffer_size in
  let o = Bytes.create io_buffer_size in
  Imap.dst c o 0 (Bytes.length o);
  match run sock i o c `Await with
  | `Ok ->
      let rec logout = function
        | `Untagged _ -> logout (run sock i o c `Await)
        | `Ok -> ()
      in
      let rec idle uidn = function
        | `Untagged (`Exists _) -> idle_done uidn (run sock i o c (`Idle_done))
        | `Untagged _ -> idle uidn (run sock i o c `Await) | `Ok -> idle_done uidn `Ok
      and idle_done uidn = function
        | `Untagged _ -> idle_done uidn (run sock i o c `Await)
        | `Ok ->
            search uidn Uint32.zero
              (run sock i o c (`Cmd (Imap.search ~uid:true (`Uid [uidn, Uint32.max_int]))))
      and search uidn n = function
        | `Untagged (`Search (n :: _, _)) -> search uidn n (run sock i o c `Await)
        | `Untagged _ -> search uidn n (run sock i o c `Await)
        | `Ok ->
            (* n = 0 means that we couldn't find the message after all. *)
          if n = Uint32.zero then idle uidn (run sock i o c `Idle) else
          let cmd = Imap.fetch ~uid:true ~changed:Uint64.one [n, n] [`Envelope] in
          fetch uidn n None (run sock i o c (`Cmd cmd))
    and fetch uidn n name = function
      | `Untagged (`Fetch (_, att)) ->
          let name =
            List.fold_left
              (fun name att -> match att with
                 | `Envelope e ->
                     begin match e.Imap.env_from with
                     | [] -> name
                     | ad :: _ ->
                         Some (Printf.sprintf "\"%s\" <%s@%s>"
                                 ad.Imap.ad_name ad.Imap.ad_mailbox ad.Imap.ad_host)
                     end
                 | _ -> name) name att
          in
          fetch uidn n name (run sock i o c `Await)
      | `Untagged _ -> fetch uidn n name (run sock i o c `Await)
      | `Ok ->
          let name = match name with None -> "<unnamed>" | Some name -> name in
          Format.printf "New mail from %s, better go and check it out!\n%!" name;
          logout (run sock i o c (`Cmd Imap.logout))
    in
    let rec select uidn = function
      | `Untagged (`Ok (`Uid_next uidn, _)) -> select uidn (run sock i o c `Await)
      | `Untagged _ -> select uidn (run sock i o c `Await)
      | `Ok -> idle uidn (run sock i o c `Idle)
    in
    let rec login = function
      | `Untagged _ -> login (run sock i o c `Await)
      | `Ok -> select Uint32.zero (run sock i o c (`Cmd (Imap.select mbox)))
    in
    login (run sock i o c (`Cmd (Imap.login user pass)))
| `Untagged _ -> assert false

package imap