RFC: 2060
Оригинал: Internet Message Access Protocol v.4 rev.1
Другие версии: RFC 1730, RFC 3501
Категория: Предложенный стандарт
Дата публикации:
Автор:
Перевод: Николай Малых

9. Формальный синтаксис

В приведенной ниже спецификации синтаксиса используется расширенная форма Бэкуса-Наура (BNF), заданная в [RFC-822], с единственным исключением — символ-ограничитель (delimiter), используемый с "#" порождает один пробел (SPACE), а не одну или несколько запятых.

При наличии альтернативных или дополнительных правил, когда последующее правило отменяет действие указанного ранее правила, приоритет должно иметь правило, указанное раньше. Например, "\Seen" при рассмотрении флагов дает имя флага \Seen, а не расширение flag_extension, несмотря на возможность разборки "\Seen" как flag_extension. Некоторые (но не все) случаи использования этого правила отмечены ниже при описании синтаксиса. Если явно не указано иное, регистр символов не принимается во внимание. Строчные и прописные символы используются в описаниях синтаксиса для лучшего восприятия. Реализации ДОЛЖНЫ трактовать эти строки независимо от регистра символов.

address         ::= "(" addr_name SPACE addr_adl SPACE addr_mailbox
                    SPACE addr_host ")"

addr_adl        ::= nstring
                    ;; Holds route from [RFC-822] route-addr if
                    ;; non-NIL

addr_host       ::= nstring
                    ;; NIL indicates [RFC-822] group syntax.
                    ;; Otherwise, holds [RFC-822] domain name

addr_mailbox    ::= nstring
                    ;; NIL indicates end of [RFC-822] group; if
                    ;; non-NIL and addr_host is NIL, holds
                    ;; [RFC-822] group name.
                    ;; Otherwise, holds [RFC-822] local-part

addr_name       ::= nstring
                    ;; Holds phrase from [RFC-822] mailbox if
                    ;; non-NIL

alpha           ::= "A" / "B" / "C" / "D" / "E" / "F" / "G" / "H" /
                    "I" / "J" / "K" / "L" / "M" / "N" / "O" / "P" /
                    "Q" / "R" / "S" / "T" / "U" / "V" / "W" / "X" /
                    "Y" / "Z" /
                    "a" / "b" / "c" / "d" / "e" / "f" / "g" / "h" /
                    "i" / "j" / "k" / "l" / "m" / "n" / "o" / "p" /
                    "q" / "r" / "s" / "t" / "u" / "v" / "w" / "x" /
                    "y" / "z"
                    ;; Case-sensitive

append          ::= "APPEND" SPACE mailbox [SPACE flag_list]
                    [SPACE date_time] SPACE literal

astring         ::= atom / string

atom            ::= 1*ATOM_CHAR

ATOM_CHAR       ::= <any CHAR except atom_specials>

atom_specials   ::= "(" / ")" / "{" / SPACE / CTL / list_wildcards /
                    quoted_specials

authenticate    ::= "AUTHENTICATE" SPACE auth_type *(CRLF base64)

auth_type       ::= atom
                    ;; Defined by [IMAP-AUTH]

base64          ::= *(4base64_char) [base64_terminal]

base64_char     ::= alpha / digit / "+" / "/"

base64_terminal ::= (2base64_char "==") / (3base64_char "=")

body            ::= "(" body_type_1part / body_type_mpart ")"

body_extension  ::= nstring / number / "(" 1#body_extension ")"
                    ;; Future expansion.  Client implementations
                    ;; MUST accept body_extension fields.  Server
                    ;; implementations MUST NOT generate
                    ;; body_extension fields except as defined by
                    ;; future standard or standards-track
                    ;; revisions of this specification.

body_ext_1part  ::= body_fld_md5 [SPACE body_fld_dsp
                    [SPACE body_fld_lang
                    [SPACE 1#body_extension]]]
                    ;; MUST NOT be returned on non-extensible
                    ;; "BODY" fetch

body_ext_mpart  ::= body_fld_param
                    [SPACE body_fld_dsp SPACE body_fld_lang
                    [SPACE 1#body_extension]]
                    ;; MUST NOT be returned on non-extensible
                    ;; "BODY" fetch

body_fields     ::= body_fld_param SPACE body_fld_id SPACE
                    body_fld_desc SPACE body_fld_enc SPACE
                    body_fld_octets

body_fld_desc   ::= nstring

body_fld_dsp    ::= "(" string SPACE body_fld_param ")" / nil

body_fld_enc    ::= (<"> ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
                    "QUOTED-PRINTABLE") <">) / string

body_fld_id     ::= nstring

body_fld_lang   ::= nstring / "(" 1#string ")"

body_fld_lines  ::= number

body_fld_md5    ::= nstring

body_fld_octets ::= number

body_fld_param  ::= "(" 1#(string SPACE string) ")" / nil

body_type_1part ::= (body_type_basic / body_type_msg / body_type_text)
                    [SPACE body_ext_1part]

body_type_basic ::= media_basic SPACE body_fields
                    ;; MESSAGE subtype MUST NOT be "RFC822"

body_type_mpart ::= 1*body SPACE media_subtype
                    [SPACE body_ext_mpart]

body_type_msg   ::= media_message SPACE body_fields SPACE envelope
                    SPACE body SPACE body_fld_lines

body_type_text  ::= media_text SPACE body_fields SPACE body_fld_lines

capability      ::= "AUTH=" auth_type / atom
                    ;; New capabilities MUST begin with "X" or be
                    ;; registered with IANA as standard or
                    ;; standards-track

capability_data ::= "CAPABILITY" SPACE [1#capability SPACE] "IMAP4rev1"
                    [SPACE 1#capability]
                    ;; IMAP4rev1 servers which offer RFC 1730
                    ;; compatibility MUST list "IMAP4" as the first
                    ;; capability.

CHAR            ::= <any 7-bit US-ASCII character except NUL,
                     0x01 - 0x7f>

CHAR8           ::= <any 8-bit octet except NUL, 0x01 - 0xff>

command         ::= tag SPACE (command_any / command_auth /
                    command_nonauth / command_select) CRLF
                    ;; Modal based on state

command_any     ::= "CAPABILITY" / "LOGOUT" / "NOOP" / x_command
                    ;; Valid in all states

command_auth    ::= append / create / delete / examine / list / lsub /
                    rename / select / status / subscribe / unsubscribe
                    ;; Valid only in Authenticated or Selected state

command_nonauth ::= login / authenticate
                    ;; Valid only when in Non-Authenticated state

command_select  ::= "CHECK" / "CLOSE" / "EXPUNGE" /
                     copy / fetch / store / uid / search
                    ;; Valid only when in Selected state

continue_req    ::= "+" SPACE (resp_text / base64)

copy            ::= "COPY" SPACE set SPACE mailbox

CR              ::= <ASCII CR, carriage return, 0x0D>

create          ::= "CREATE" SPACE mailbox
                    ;; Use of INBOX gives a NO error

CRLF            ::= CR LF

CTL             ::= <any ASCII control character and DEL,
                        0x00 - 0x1f, 0x7f>

date            ::= date_text / <"> date_text <">

date_day        ::= 1*2digit
                    ;; Day of month

date_day_fixed  ::= (SPACE digit) / 2digit
                    ;; Fixed-format version of date_day

date_month      ::= "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
                    "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"

date_text       ::= date_day "-" date_month "-" date_year

date_year       ::= 4digit

date_time       ::= <"> date_day_fixed "-" date_month "-" date_year
                    SPACE time SPACE zone <">

delete          ::= "DELETE" SPACE mailbox
                    ;; Use of INBOX gives a NO error

digit           ::= "0" / digit_nz

digit_nz        ::= "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" /
                    "9"

envelope        ::= "(" env_date SPACE env_subject SPACE env_from
                    SPACE env_sender SPACE env_reply_to SPACE env_to
                    SPACE env_cc SPACE env_bcc SPACE env_in_reply_to
                    SPACE env_message_id ")"

env_bcc         ::= "(" 1*address ")" / nil

env_cc          ::= "(" 1*address ")" / nil

env_date        ::= nstring

env_from        ::= "(" 1*address ")" / nil

env_in_reply_to ::= nstring

env_message_id  ::= nstring

env_reply_to    ::= "(" 1*address ")" / nil

env_sender      ::= "(" 1*address ")" / nil

env_subject     ::= nstring

env_to          ::= "(" 1*address ")" / nil

examine         ::= "EXAMINE" SPACE mailbox

fetch           ::= "FETCH" SPACE set SPACE ("ALL" / "FULL" /
                    "FAST" / fetch_att / "(" 1#fetch_att ")")

fetch_att       ::= "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
                    "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
                    "BODY" ["STRUCTURE"] / "UID" /
                    "BODY" [".PEEK"] section
                    ["<" number "." nz_number ">"]

flag            ::= "\Answered" / "\Flagged" / "\Deleted" /
                    "\Seen" / "\Draft" / flag_keyword / flag_extension

flag_extension  ::= "\" atom
                    ;; Future expansion.  Client implementations
                    ;; MUST accept flag_extension flags.  Server
                    ;; implementations MUST NOT generate
                    ;; flag_extension flags except as defined by
                    ;; future standard or standards-track
                    ;; revisions of this specification.

flag_keyword    ::= atom

flag_list       ::= "(" #flag ")"

greeting        ::= "*" SPACE (resp_cond_auth / resp_cond_bye) CRLF

header_fld_name ::= astring

header_list     ::= "(" 1#header_fld_name ")"

LF              ::= <ASCII LF, line feed, 0x0A>

list            ::= "LIST" SPACE mailbox SPACE list_mailbox

list_mailbox    ::= 1*(ATOM_CHAR / list_wildcards) / string

list_wildcards  ::= "%" / "*"

literal         ::= "{" number "}" CRLF *CHAR8
                    ;; Number represents the number of CHAR8 octets

login           ::= "LOGIN" SPACE userid SPACE password

lsub            ::= "LSUB" SPACE mailbox SPACE list_mailbox

mailbox         ::= "INBOX" / astring
                    ;; INBOX is case-insensitive.  All case variants of
                    ;; INBOX (e.g. "iNbOx") MUST be interpreted as INBOX
                    ;; not as an astring.  Refer to section 5.1 for
                    ;; further semantic details of mailbox names.

mailbox_data    ::=  "FLAGS" SPACE flag_list /
                     "LIST" SPACE mailbox_list /
                     "LSUB" SPACE mailbox_list /
                     "MAILBOX" SPACE text /
                     "SEARCH" [SPACE 1#nz_number] /
                     "STATUS" SPACE mailbox SPACE
                     "(" #<status_att number ")" /
                     number SPACE "EXISTS" / number SPACE "RECENT"

mailbox_list    ::= "(" #("\Marked" / "\Noinferiors" /
                    "\Noselect" / "\Unmarked" / flag_extension) ")"
                    SPACE (<"> QUOTED_CHAR <"> / nil) SPACE mailbox

media_basic     ::= (<"> ("APPLICATION" / "AUDIO" / "IMAGE" /
                    "MESSAGE" / "VIDEO") <">) / string)
                    SPACE media_subtype
                    ;; Defined in [MIME-IMT]

media_message   ::= <"> "MESSAGE" <"> SPACE <"> "RFC822" <">
                    ;; Defined in [MIME-IMT]

media_subtype   ::= string
                    ;; Defined in [MIME-IMT]

media_text      ::= <"> "TEXT" <"> SPACE media_subtype
                    ;; Defined in [MIME-IMT]

message_data    ::= nz_number SPACE ("EXPUNGE" /
                                    ("FETCH" SPACE msg_att))

msg_att         ::= "(" 1#("ENVELOPE" SPACE envelope /
                    "FLAGS" SPACE "(" #(flag / "\Recent") ")" /
                    "INTERNALDATE" SPACE date_time /
                    "RFC822" [".HEADER" / ".TEXT"] SPACE nstring /
                    "RFC822.SIZE" SPACE number /
                    "BODY" ["STRUCTURE"] SPACE body /
                    "BODY" section ["<" number ">"] SPACE nstring /
                    "UID" SPACE uniqueid) ")"

nil             ::= "NIL"

nstring         ::= string / nil

number          ::= 1*digit
                    ;; Unsigned 32-bit integer
                    ;; (0 <= n < 4,294,967,296)

nz_number       ::= digit_nz *digit
                    ;; Non-zero unsigned 32-bit integer
                    ;; (0 < n < 4,294,967,296)

password        ::= astring

quoted          ::= <"> *QUOTED_CHAR <">

QUOTED_CHAR     ::= <any TEXT_CHAR except quoted_specials> /
                    "\" quoted_specials

quoted_specials ::= <"> / "\"

rename          ::= "RENAME" SPACE mailbox SPACE mailbox
                    ;; Use of INBOX as a destination gives a NO error

response        ::= *(continue_req / response_data) response_done

response_data   ::= "*" SPACE (resp_cond_state / resp_cond_bye /
                    mailbox_data / message_data / capability_data)
                    CRLF

response_done   ::= response_tagged / response_fatal

response_fatal  ::= "*" SPACE resp_cond_bye CRLF
                    ;; Server closes connection immediately

response_tagged ::= tag SPACE resp_cond_state CRLF

resp_cond_auth  ::= ("OK" / "PREAUTH") SPACE resp_text
                    ;; Authentication condition

resp_cond_bye   ::= "BYE" SPACE resp_text

resp_cond_state ::= ("OK" / "NO" / "BAD") SPACE resp_text
                    ;; Status condition

resp_text       ::= ["[" resp_text_code "]" SPACE] (text_mime2 / text)
                    ;; text SHOULD NOT begin with "[" or "="

resp_text_code  ::= "ALERT" / "PARSE" /
                    "PERMANENTFLAGS" SPACE "(" #(flag / "\*") ")" /
                    "READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
                    "UIDVALIDITY" SPACE nz_number /
                    "UNSEEN" SPACE nz_number /
                    atom [SPACE 1*<any TEXT_CHAR except "]">]

search          ::= "SEARCH" SPACE ["CHARSET" SPACE astring SPACE]
                    1#search_key
                    ;; [CHARSET] MUST be registered with IANA

search_key      ::= "ALL" / "ANSWERED" / "BCC" SPACE astring /
                    "BEFORE" SPACE date / "BODY" SPACE astring /
                    "CC" SPACE astring / "DELETED" / "FLAGGED" /
                    "FROM" SPACE astring /
                    "KEYWORD" SPACE flag_keyword / "NEW" / "OLD" /
                    "ON" SPACE date / "RECENT" / "SEEN" /
                    "SINCE" SPACE date / "SUBJECT" SPACE astring /
                    "TEXT" SPACE astring / "TO" SPACE astring /
                    "UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
                    "UNKEYWORD" SPACE flag_keyword / "UNSEEN" /
                    ;; Above this line were in [IMAP2]
                    "DRAFT" /
                    "HEADER" SPACE header_fld_name SPACE astring /
                    "LARGER" SPACE number / "NOT" SPACE search_key /
                    "OR" SPACE search_key SPACE search_key /
                    "SENTBEFORE" SPACE date / "SENTON" SPACE date /
                    "SENTSINCE" SPACE date / "SMALLER" SPACE number /
                    "UID" SPACE set / "UNDRAFT" / set /
                    "(" 1#search_key ")"

section         ::= "[" [section_text / (nz_number *["." nz_number]
                    ["." (section_text / "MIME")])] "]"

section_text    ::= "HEADER" / "HEADER.FIELDS" [".NOT"]
                    SPACE header_list / "TEXT"

select          ::= "SELECT" SPACE mailbox

sequence_num    ::= nz_number / "*"
                    ;; * is the largest number in use.  For message
                    ;; sequence numbers, it is the number of messages
                    ;; in the mailbox.  For unique identifiers, it is
                    ;; the unique identifier of the last message in
                    ;; the mailbox.

set             ::= sequence_num / (sequence_num ":" sequence_num) /
                    (set "," set)
                    ;; Identifies a set of messages.  For message
                    ;; sequence numbers, these are consecutive
                    ;; numbers from 1 to the number of messages in
                    ;; the mailbox
                    ;; Comma delimits individual numbers, colon
                    ;; delimits between two numbers inclusive.
                    ;; Example: 2,4:7,9,12:* is 2,4,5,6,7,9,12,13,
                    ;; 14,15 for a mailbox with 15 messages.

SPACE           ::= <ASCII SP, space, 0x20>

status          ::= "STATUS" SPACE mailbox SPACE "(" 1#status_att ")"

status_att      ::= "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
                    "UNSEEN"

store           ::= "STORE" SPACE set SPACE store_att_flags

store_att_flags ::= (["+" / "-"] "FLAGS" [".SILENT"]) SPACE
                    (flag_list / #flag)

string          ::= quoted / literal

subscribe       ::= "SUBSCRIBE" SPACE mailbox

tag             ::= 1*<any ATOM_CHAR except "+">

text            ::= 1*TEXT_CHAR

text_mime2       ::= "=?" <charset> "?" <encoding> "?"
                     <encoded-text> "?="
                     ;; Syntax defined in [MIME-HDRS]

TEXT_CHAR       ::= <any CHAR except CR and LF>

time            ::= 2digit ":" 2digit ":" 2digit
                    ;; Hours minutes seconds

uid             ::= "UID" SPACE (copy / fetch / search / store)
                    ;; Unique identifiers used instead of message
                    ;; sequence numbers

uniqueid        ::= nz_number
                    ;; Strictly ascending

unsubscribe     ::= "UNSUBSCRIBE" SPACE mailbox

userid          ::= astring

x_command       ::= "X" atom <experimental command arguments>

zone            ::= ("+" / "-") 4digit
                    ;; Signed four-digit value of hhmm representing
                    ;; hours and minutes west of Greenwich (that is,
                    ;; (the amount that the given time differs from
                    ;; Universal Time).  Subtracting the timezone
                    ;; from the given time will give the UT form.
                    ;; The Universal Time zone is "+0000".
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