module Mimestring:sig
..end
Mimestring
contains a lot of functions to scan and print strings
formatted as MIME messages. For a higher-level view on this topic,
see the Netmime
module.
Contents
val find_line_end : string -> int -> int -> int
find_line_end s pos len
: Searches the next line end (CR/LF or
only LF), and returns the position. The search starts at position
pos
, and covers the next len
bytes. Raises Not_found
if there is no line end.val find_line_start : string -> int -> int -> int
find_line_start s pos len
: Searches the next start, and returns its
position. The line start is the position after the next line end
(CR/LF or only LF). The search starts at position
pos
, and covers the next len
bytes. Raises Not_found
if there is no line end.val find_double_line_start : string -> int -> int -> int
find_double_line_start s pos len
: Searches two adjacent line ends
(each may be a CR/LF combination or a single LF), and returns the
position after the second line end. The search starts at position
pos
, and covers the next len
bytes. Raises Not_found
if the mentioned pattern is not found.val skip_line_ends : string -> int -> int -> int
skip_line_ends s pos len
: Skips over adjacent line ends (terminated
by CR/LF or plain LF), and returns the position after the last
line end. The search starts at position
pos
, and covers the next len
bytes. Note that this function
cannot raise Not_found
.val fold_lines_p : ('a -> int -> int -> int -> bool -> 'a) -> 'a -> string -> int -> int -> 'a
fold_lines_p f acc0 s pos len
: Splits the substring of s
from pos
to pos+len
into lines, and folds over these lines like
List.fold_left
. The function f
is called as
f acc p0 p1 p2 is_last
where acc
is the current accumulator
(initialized with acc0
), andp0
is the start position of the line in s
p1
is the position of the line terminator in s
p2
is the position after the line terminator in s
is_last
is true if this is the last line in the iterationp1=p2
is possible).
The function is tail-recursive.
val fold_lines : ('a -> string -> 'a) -> 'a -> string -> int -> int -> 'a
fold_lines f acc0 s pos len
: Splits the substring of s
from pos
to pos+len
into lines, and folds over these lines like
List.fold_left
. The function f
is called as
f acc line
where acc
is the current accumulator
(initialized with acc0
), and line
is the current line
w/o terminator.
The lines can be terminated with CR/LF or LF.
The function is tail-recursive.
Example: Get the lines as list:
List.rev(fold_lines (fun l acc -> acc::l) [] s pos len)
val iter_lines : (string -> unit) -> string -> int -> int -> unit
iter_lines f s pos len
: Splits the substring of s
from pos
to pos+len
into lines, and calls f line
for each
line.
The lines can be terminated with CR/LF or LF.
val skip_whitespace_left : string -> int -> int -> int
skip_whitespace_left s pos len
: Returns the smallest
p
with p >= pos && p < pos+len
so that s.[p]
is not
a whitesapce character (space, TAB, CR, LF), and
s.[q]
is a whitespace character for all q<p
.
If this is not possible Not_found
will be raised.val skip_whitespace_right : string -> int -> int -> int
skip_whitespace_right s pos len
: Returns the biggest
p
with p >= pos && p < pos+len
so that s.[p]
is not
a whitesapce character (space, TAB, CR, LF), and
s.[q]
is a whitespace character for all q>p
.
If this is not possible Not_found
will be raised.
Messages
consist of a header and a body; the first empty line separates both
parts. The header contains lines "param-name:
param-value" where
the param-name must begin on column 0 of the line, and the ":
"
separates the name and the value. So the format is roughly:
param1-name: param1-value
...
paramN-name: paramN-value
_
body
(Where "_" denotes an empty line.)
Details
Note that parameter values are restricted; you cannot represent arbitrary strings. The following problems can arise:
:
" and the
value.Compatibility
These functions can parse all mail headers that conform to RFC 822 or RFC 2822.
But there may be still problems, as RFC 822 allows some crazy
representations that are actually not used in practice.
In particular, RFC 822 allows it to use backslashes to "indicate"
that a CRLF sequence is semantically meant as line break. As this
function normally deletes CRLFs, it is not possible to recognize such
indicators in the result of the function.
val fold_header : ?downcase:bool ->
?unfold:bool ->
?strip:bool ->
('a -> string -> string -> 'a) -> 'a -> string -> int -> int -> 'a
fold_header f acc0 s pos len
:
Parses a MIME header in the string s
from pos
to exactly
pos+len
. The MIME header must be terminated by an empty line.
A folding operation is done over the header values while
the lines are extracted from the string, very much like
List.fold_left
. For each header (n,v)
where n
is the
name and v
is the value, the function f
is called as
f acc n v
.
If the header cannot be parsed, a Failure
is raised.
Certain transformations may be applied (default: no transformations):
downcase
is set, the header names are converted to
lowercase charactersunfold
is set, the line terminators are not included
in the resulting values. This covers both the end of line
characters at the very end of a header and the end of line
characters introduced by continuation lines.strip
is set, preceding and trailing white space is
removed from the value (including line terminators at the
very end of the value)val list_header : ?downcase:bool ->
?unfold:bool -> ?strip:bool -> string -> int -> int -> (string * string) list
list_header s pos len
: Returns the headers as list of pairs
(name,value)
.
For the meaning of the arguments see fold_header
above.
val scan_header : ?downcase:bool ->
?unfold:bool ->
?strip:bool ->
string -> start_pos:int -> end_pos:int -> (string * string) list * int
let params, header_end_pos = scan_header s start_pos end_pos
:
Deprecated.
Scans the mail header that begins at position start_pos
in the string
s
and that must end somewhere before position end_pos
. It is intended
that in end_pos
the character position following the end of the body of
the MIME message is passed.
Returns the parameters of the header as (name,value)
pairs (in
params
), and in header_end_pos
the position of the character following
directly after the header (i.e. after the blank line separating
the header from the body).
downcase
, header names are converted to lowercase charactersunfold
and strip
have a slightly different meaning as
for the new function fold_header
above. In particular, whitespace
is already stripped off the returned values if any of unfold
or
strip
are enabled. (This is for backward compatibility.)downcase
and unfold
are
enabled by default, and only strip
is not enabled.val read_header : ?downcase:bool ->
?unfold:bool ->
?strip:bool -> Netstream.in_obj_stream -> (string * string) list
in_obj_stream
is the first byte of the header. The function scans the
header and returns it. After that, the stream position is after
the header and the terminating empty line (i.e. at the beginning of
the message body).
The options downcase
, unfold
, and strip
have the same meaning
as in scan_header
.
Example
To read the mail message "file.txt
":
let ch = new Netchannels.input_channel (open_in "file.txt") in
let stream = new Netstream.input_stream ch in
let header = read_header stream in
stream#close_in() (* no need to close ch *)
val write_header : ?soft_eol:string ->
?eol:string -> Netchannels.out_obj_channel -> (string * string) list -> unit
out_obj_channel
. The
empty line following the header is also written.
Exact output format:
write_value
below for this.)Example:
write_header ch ["x","Field value"; "y"," Other value"]
outputs:
x: Field value\r\n
y: Other value\r\n
\r\n
soft_eol
string. If the
necessary space or tab character following the eol is missing, an
additional space character will be inserted.
Example:
write_header ch ["x","Field\nvalue"; "y","Other\r\n\tvalue"]
outputs:
x: Field\r\n
value
y: Other\r\n
\tvalue
Example:
write_header ch ["x","Field\n\nvalue"]
outputs:
x: Field\r\n
value
eol
once.These rules ensure that the printed header will be well-formed with two exceptions:
s_token
lists.Structured Values
RFC 822 (together with some other RFCs) defines lexical rules how formal mail header values should be divided up into tokens. Formal mail headers are those headers that are formed according to some grammar, e.g. mail addresses or MIME types.
Some of the characters separate phrases of the value; these are
the "special" characters. For example, '@' is normally a special
character for mail addresses, because it separates the user name
from the domain name (as in user@domain
). RFC 822 defines a fixed set
of special
characters, but other RFCs use different sets. Because of this,
the following functions allow it to configure the set of special characters.
Every sequence of characters may be embraced by double quotes, which means that the sequence is meant as literal data item; special characters are not recognized inside a quoted string. You may use the backslash to insert any character (including double quotes) verbatim into the quoted string (e.g. "He said: \"Give it to me!\""). The sequence of a backslash character and another character is called a quoted pair.
Structured values may contain comments. The beginning of a comment is indicated by '(', and the end by ')'. Comments may be nested. Comments may contain quoted pairs. A comment counts as if a space character were written instead of it.
Control characters are the ASCII characters 0 to 31, and 127. RFC 822 demands that mail headers are 7 bit ASCII strings. Because of this, this module also counts the characters 128 to 255 as control characters.
Domain literals are strings embraced by '[' and ']'; such literals
may contain quoted pairs. Today, domain literals are used to specify
IP addresses (rare), e.g. user@[192.168.0.44]
.
Every character sequence not falling in one of the above categories is an atom (a sequence of non-special and non-control characters). When recognized, atoms may be encoded in a character set different than US-ASCII; such atoms are called encoded words (see RFC 2047).
Scanning Using the Extended Interface
In order to scan a string containing a structured value, you must first
create a mime_scanner
using the function create_mime_scanner
.
The scanner contains the reference to the scanned string, and a
specification how the string is to be scanned. The specification
consists of the lists specials
and scan_options
.
The character list specials
specifies the set of special characters.
These are the characters that are not regarded as part of atoms,
because they work as delimiters that separate atoms (like @
in the
above example). In addition to this, when '"', '(', and '[' are
seen as regular characters not delimiting quoted string, comments, and
domain literals, respectively, these characters must also be added
to specials
. In detail, these rules apply:
' '
in specials
: A space character is returned as Special ' '
.
Note that there may also be an effect on how comments are returned
(see below).' '
not in specials
: Spaces are not returned, although
they still delimit atoms.'\t'
in specials
: A tab character is returned as
Special '\t'
.'\t'
not in specials
: Tabs are not returned, although
they still delimit atoms.'\r'
in specials
: A CR character is returned as
Special '\r'
.'\r'
not in specials
: CRs are not returned, although
they still delimit atoms.'\n'
in specials
: A LF character is returned as
Special '\n'
.'\n'
not in specials
: LFs are not returned, although
they still delimit atoms.'('
in specials
: Comments are not recognized. The
character '(' is returned as Special '('
.'('
not in specials
: Comments are recognized. How comments
are returned, depends on the following:Return_comments
in scan_options
: Outer comments are
returned as Comment
(note that inner comments are recognized but
are not returned as tokens)' '
in specials
: Outer comments are returned as
Special ' '
'"'
in specials
: Quoted strings are not recognized, and
double quotes are returned as Special '"'
.'"'
not in specials
: Quoted strings are returned as
QString
tokens.specials
: Domain literals are not recognized, and
left brackets are returned as Special
'['.specials
: Domain literals are returned as
DomainLiteral
tokens.
If recognized, quoted strings are returned as QString s
, where
s
is the string without the embracing quotes, and with already
decoded quoted pairs.
Control characters c
are returned as Control c
.
If recognized, comments may either be returned as spaces (in the case
you are not interested in the contents of comments), or as Comment
tokens.
The contents of comments are not further scanned; you must start a
subscanner to analyze comments as structured values.
If recognized, domain literals are returned as DomainLiteral s
, where
s
is the literal without brackets, and with decoded quoted pairs.
Atoms are returned as Atom s
where s
is a longest sequence of
atomic characters (all characters which are neither special nor control
characters nor delimiters for substructures). If the option
Recognize_encoded_words
is on, atoms which look like encoded words
are returned as EncodedWord
tokens. (Important note: Neither '?' nor
'=' must be special in order to enable this functionality.)
After the mime_scanner
has been created, you can scan the tokens by
invoking scan_token
which returns one token at a time, or by invoking
scan_token_list
which returns all following tokens.
There are two token types: s_token
is the base type and is intended to
be used for pattern matching. s_extended_token
is a wrapper that
additionally contains information where the token occurs.
Scanning Using the Simple Interface
Instead of creating a mime_scanner
and calling the scan functions,
you may also invoke scan_structured_value
. This function returns the
list of tokens directly; however, it is restricted to s_token
.
Examples
scan_structured_value "user@domain.com" [ '@'; '.' ] []
= [ Atom "user"; Special '@'; Atom "domain"; Special '.'; Atom "com" ]
scan_structured_value "user @ domain . com" [ '@'; '.' ] []
= [ Atom "user"; Special '@'; Atom "domain"; Special '.'; Atom "com" ]
scan_structured_value "user(Do you know him?)@domain.com" [ '@'; '.' ] []
= [ Atom "user"; Special '@'; Atom "domain"; Special '.'; Atom "com" ]
scan_structured_value "user(Do you know him?)@domain.com" [ '@'; '.' ]
[ Return_comments ]
= [ Atom "user"; Comment; Special '@'; Atom "domain"; Special '.';
Atom "com" ]
scan_structured_value "user (Do you know him?) @ domain . com"
[ '@'; '.'; ' ' ] []
= [ Atom "user"; Special ' '; Special ' '; Special ' '; Special '@';
Special ' '; Atom "domain";
Special ' '; Special '.'; Special ' '; Atom "com" ]
scan_structured_value "user (Do you know him?) @ domain . com"
[ '@'; '.'; ' ' ] [ Return_comments ]
= [ Atom "user"; Special ' '; Comment; Special ' '; Special '@';
Special ' '; Atom "domain";
Special ' '; Special '.'; Special ' '; Atom "com" ]
scan_structured_value "user @ domain . com" [ '@'; '.'; ' ' ] []
= [ Atom "user"; Special ' '; Special '@'; Special ' '; Atom "domain";
Special ' '; Special '.'; Special ' '; Atom "com" ]
scan_structured_value "user(Do you know him?)@domain.com" ['@'; '.'; '(']
[]
= [ Atom "user"; Special '('; Atom "Do"; Atom "you"; Atom "know";
Atom "him?)"; Special '@'; Atom "domain"; Special '.'; Atom "com" ]
scan_structured_value "\"My.name\"@domain.com" [ '@'; '.' ] []
= [ QString "My.name"; Special '@'; Atom "domain"; Special '.';
Atom "com" ]
scan_structured_value "=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?="
[ ] [ ]
= [ Atom "=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?=" ]
scan_structured_value "=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?="
[ ] [ Recognize_encoded_words ]
= [ EncodedWord(("ISO-8859-1",""), "Q", "Keld_J=F8rn_Simonsen") ]
type
s_token =
| |
Atom of |
|||
| |
EncodedWord of |
(* | Args: ((charset,lang),encoding,encoded_word) | *) |
| |
QString of |
|||
| |
Control of |
|||
| |
Special of |
|||
| |
DomainLiteral of |
|||
| |
Comment |
|||
| |
End |
QString s
: The quoted string s
, i.e a string between double
quotes. Quoted pairs are already decoded in s
.Control c
: The control character c
(0-31, 127, 128-255)Special c
: The special character c
, i.e. a character from
the specials
listDomainLiteral s
: The bracketed string s
, i.e. a string between
brackets. Quoted pairs are already decoded in s
.Comment
: A string between parentheses. This kind of token is only
generated when the option Return_comments
is in effect.EncodedWord((charset,lang),encoding,encoded_word)
: An RFC-2047 style
encoded word: charset
is the name of the character set; lang
is
the language specifier (from RFC 2231) or ""; encoding
is either
"Q" or "B"; and encoded_word
is the word encoded in charset
and
encoding
. This kind of token is only generated when the option
Recognize_encoded_words
is in effect (if not, Atom
is generated
instead).Atom s
: A string which is neither quoted not bracketed nor
written in RFC 2047 notation, and which is not a control or special
character, i.e. the "rest"End
: The end of the stringtype
s_option =
| |
No_backslash_escaping |
(* | Do not handle backslashes in quoted string and comments as escape
characters; backslashes are handled as normal characters.
For example: The wrong qstring "C:\dir\file" will be returned as
QString "C:\dir\file" when this option is in effect, and not as
QString "C:dirfile" as by default.
-- This is a common error in many MIME implementations. | *) |
| |
Return_comments |
(* | Comments are returned as token Comment (unless '(' is included
in the list of special characters, in which case comments are
not recognized at all).
You may get the exact location of the comment by applying
get_pos and get_length to the extended token. | *) |
| |
Recognize_encoded_words |
(* | Enables that encoded words are recognized and returned as
EncodedWord instead of Atom . | *) |
type
s_extended_token
s_token
plus:val get_token : s_extended_token -> s_token
s_token
within the s_extended_token
val get_decoded_word : s_extended_token -> string
val get_charset : s_extended_token -> string
These functions not only work for EncodedWord
. The function
get_decoded_word
returns for the other kinds of token:
Atom
: Returns the atom without decoding itQString
: Returns the characters inside the double quotes, and
ensures that any quoted pairs are decodedControl
: Returns the one-character stringSpecial
: Returns the one-character stringDomainLiteral
: Returns the characters inside the brackets, and
ensures that any quoted pairs are decodedComment
: Returns ""
get_charset
returns "US-ASCII"
for them.val get_language : s_extended_token -> string
EncodedWord
, and ""
for
all other tokens.val get_pos : s_extended_token -> int
val get_line : s_extended_token -> int
val get_column : s_extended_token -> int
val get_length : s_extended_token -> int
val separates_adjacent_encoded_words : s_extended_token -> bool
Special ' '
,
Special '\t'
, Special '\r'
or Special '\n'
) and the last
non-white space token was EncodedWord
and the next non-white
space token will be EncodedWord
.
The background of this function is that white space between
encoded words does not have a meaning, and must be ignored
by any application interpreting encoded words.
type
mime_scanner
val create_mime_scanner : specials:char list ->
scan_options:s_option list ->
?pos:int -> ?line:int -> ?column:int -> string -> mime_scanner
mime_scanner
scanning the passed string.
specials
: The list of characters recognized as special characters.scan_options
: The list of global options modifying the behaviour
of the scannerpos
: The position of the byte where the scanner starts in the
passed string. Defaults to 0.line
: The line number of this first byte. Defaults to 1.column
: The column number of this first byte. Default to 0.create_mime_scanner
:
The optional parameters pos
, line
, column
are intentionally placed after
scan_options
and before the string argument, so you can specify
scanners by partially applying arguments to create_mime_scanner
which are not yet connected with a particular string:
let my_scanner_spec = create_mime_scanner my_specials my_options in
...
let my_scanner = my_scanner_spec my_string in
...
val get_pos_of_scanner : mime_scanner -> int
val get_line_of_scanner : mime_scanner -> int
val get_column_of_scanner : mime_scanner -> int
mime_scanner
.
The primary purpose of these functions is to simplify switching
from one mime_scanner
to another within a string:
let scanner1 = create_mime_scanner ... s in
... now scanning some tokens from s using scanner1 ...
let scanner2 = create_mime_scanner ...
?pos:(get_pos_of_scanner scanner1)
?line:(get_line_of_scanner scanner1)
?column:(get_column_of_scanner scanner1)
s in
... scanning more tokens from s using scanner2 ...
Restriction: These functions are not available if the option
Recognize_encoded_words
is on. The reason is that this option
enables look-ahead scanning; please use the location of the last
scanned token instead.
Note: To improve the performance of switching, it is recommended to
create scanner specs in advance (see the example my_scanner_spec
above).
val scan_token : mime_scanner -> s_extended_token * s_token
End
if there is no more token. The
token is returned both as extended and as normal token.val scan_token_list : mime_scanner ->
(s_extended_token * s_token) list
End
)val scan_structured_value : string -> char list -> s_option list -> s_token list
It scans the passed string according to the list of special characters
and the list of options, and returns the list of all tokens.
val specials_rfc822 : char list
val specials_rfc2045 : char list
val scan_encoded_text_value : string -> s_extended_token list
Special
, Atom
and EncodedWord
tokens.
Spaces, TABs, CRs, LFs are returned (as Special
) unless
they occur between adjacent encoded words in which case
they are suppressed. The characters '(', '[', and '"' are also
returned as Special
tokens, and are not interpreted as delimiters.
For instance, this function can be used to scan the "Subject"
field of mail messages.
val scan_value_with_parameters : string -> s_option list -> string * (string * string) list
let name, params = scan_value_with_parameters s options
:
Scans values with annotations like
name ; p1=v1 ; p2=v2 ; ...
For example, MIME types like "text/plain;charset=ISO-8859-1" can
be parsed.
The values may or may not be quoted. The characters ";", "=", and even "," are only accepted as part of values when they are quoted. On sytax errors, the function fails.
RFC 2231: This function supports some features of this RFC: Continued parameter values are concatenated. For example:
Content-Type: message/external-body; access-type=URL;
URL*0="ftp://";
URL*1="cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar"
This is returned as:
"message/external-body",
[ ("access-type", "URL");
("URL", "ftp://cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar") ]
)
However, encoded parameter values are not handled specially. The
parameter
title*=us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A
would be returned as
("title*", "us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A")
.
Use scan_values_with_parameters_ep
instead (see below).
Raises Failure
on syntax errors.
type
s_param
val param_value : s_param -> string
val param_charset : s_param -> string
val param_language : s_param -> string
""
will be returned.
If the language is not available, ""
will be returned.val mk_param : ?charset:string -> ?language:string -> string -> s_param
val print_s_param : Format.formatter -> s_param -> unit
val scan_value_with_parameters_ep : string ->
s_option list -> string * (string * s_param) list
let name, params = scan_value_with_parameters_ep s options
:
This version of the scanner copes with encoded parameters according
to RFC 2231.
Note: "ep" means "encoded parameters".
Example:
doc.html;title*=us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A
The parameter title
would be returned as:
"title"
"This is ***fun***"
"US-ASCII"
"en-us"
Failure
on syntax errors.val scan_mime_type : string -> s_option list -> string * (string * string) list
let name, params = scan_mime_type s options
:
Scans MIME types like
text/plain; charset=iso-8859-1
The name of the type and the names of the parameters are converted
to lower case.
Raises Failure
on syntax errors.
val scan_mime_type_ep : string ->
s_option list -> string * (string * s_param) list
let name, params = scan_mime_type_ep s options
:
This version copes with RFC-2231-encoded parameters.
Raises Failure
on syntax errors.
val split_mime_type : string -> string * string
let (main_type, sub_type) = split_mime_type content_type
:
Splits the MIME type into main and sub type, for example
split_mime_type "text/plain" = ("text", "plain")
.
The returned strings are always lowercase.
Raises Failure
on syntax errors.
exception Line_too_long
val write_value : ?maxlen1:int ->
?maxlen:int ->
?hardmaxlen1:int ->
?hardmaxlen:int ->
?fold_qstring:bool ->
?fold_literal:bool ->
?unused:int Pervasives.ref ->
?hardunused:int Pervasives.ref ->
Netchannels.out_obj_channel -> s_token list -> unit
s_token
to the out_obj_channel
. The value
is optionally folded into several lines while writing, but this
is off by default. To enable folding, pass both maxlen1
and
maxlen
:
The maxlen1
parameter specifies the length of the first line
to write, the maxlen
parameter specifies the length of the
other lines.
If enabled, folding tries to ensure that the value is written
in several lines that are not longer as specified by
maxlen1
and maxlen
. The value is split into lines by inserting
"folding space" at certain locations (which is usually a linefeed
followed by a space character, see below). The following
table specifies between which tokens folding may happen:
+=========================================================+
1st \ 2nd | Atom | QString | DLiteral | EncWord | Special | Spec ' '|
==============+======+=========+==========+=========+=========+=========+
Atom | FS | FS | FS | FS | - | F |
QString | FS | FS | FS | FS | - | F |
DomainLiteral | FS | FS | FS | FS | - | F |
EncodedWord | FS | FS | FS | FS | - | F |
Special | - | - | - | - | - | F |
Special ' ' | - | - | - | - | - | - |
==============+======+=========+==========+=========+=========+=========+
The table shows between which two types of tokens a space or a folding space is inserted:
FS
: folding spaceF
: linefeed without extra space-
: nothing can be inserted here"\n "
, i.e. only LF, not CRLF is used as end-of-line
character. The function write_header
will convert these LF to CRLF
if needed.
Special '\t'
is handled like Special ' '
. Control characters are just
printed, without folding. Comments, however, are substituted by
either space or folding space. The token End
is ignored.
Furthermore, folding may also happen within tokens:
Atom
, Control
, and Special
are never split up into parts.
They are simply printed.EncodedWord
s, however, are reformatted. This especially means:
adjacent encoded words are first concatenated if possible
(same character set, same encoding, same language), and then
split up into several pieces with optimally chosen lengths.
Note: Because this function gets s_token
as input and not
s_extended_token
, it is not known whether Special ' '
tokens
(or other whitespace) between adjacent EncodedWords must be
ignored. Because of this, write_value
only reformats adjacent encoded
words when there is not any whitespace between them.QString
may be split up in a special way unless fold_qstring
is set to false
. For example, "One Two Three"
may be split up into
three lines "One\n Two\n \ Three"
. Because some header fields
explicitly forbid folding of quoted strings, it is possible to
set ~fold_qstring:false
(it is true
by default).
Note: Software should not rely on that the different types of
whitespace (especially space and TAB) remain intact at the
beginning of a line. Furthermore, it may also happen that
additional whitespace is added at the end of a line by the
transport layer.DomainLiteral
: These are handled like QString
. The parameter
~fold_literal:false
turns folding off if it must be prevented,
it is true
by default.Comment
: Comments are effectively omitted! Instead of Comment
,
a space or folding space is printed. However, you can output comments
by passing sequences like Special "("; ...; Special ")"
.int ref
as unused
to get this value (it may
be negative!). Pass an
int ref
as hardunused
to get the number of characters that may
be printed until the hard limit is exceeded.
The function normally does not fail when a line becomes too long,
i.e. it exceeds maxlen1
or maxlen
.
However, it is possible to specify a hard maximum length
(hardmaxlen1
and hardmaxlen
). If these are exceeded, the function
will raise Line_too_long
.
For electronic mail, a maxlen
of 78 and a hardmaxlen
of 998 is
recommended.
Known Problems:
Netconversion
. You can assume that UTF-8 and UTF-16 always
work. If the character set is not known the reformatter may
split the string at wrong positions.Malformed_code
.
This is only done in some special cases, however.EncodedWord
. The reformatter takes care to
fold the word into several lines.val param_tokens : ?maxlen:int -> (string * s_param) list -> s_token list
[ "a", "b"; "c", "d" ]
is transformed to the token sequence
corresponding to ; a=b; c=d
.
If maxlen
is specified, it is ensured that the individual
parameter (e.g. "a=b;"
) is not longer than maxlen-1
, such that
it will fit into a line with maximum length maxlen
.
By default, no maximum length is guaranteed.
If maxlen
is passed, or if a parameter specifies a character
set or language, the encoding of RFC 2231 will be applied. If these
conditions are not met, the parameters will be encoded traditionally.val split_uri : string -> s_token list
val scan_multipart_body : string ->
start_pos:int ->
end_pos:int -> boundary:string -> ((string * string) list * string) list
let [params1, value1; params2, value2; ...]
= scan_multipart_body s start_pos end_pos boundary
:
Scans the string s
that is the body of a multipart message.
The multipart message begins at position start_pos
in s
, and
end_pos
is the position
of the character following the message. In boundary
the boundary string
must be passed (this is the "boundary" parameter of the multipart
MIME type, e.g. multipart/mixed;boundary="some string"
).
The return value is the list of the parts, where each part
is returned as pair (params, value)
. The left component params
is the list of name/value pairs of the header of the part. The
right component is the raw content of the part, i.e. if the part
is encoded ("content-transfer-encoding"), the content is returned
in the encoded representation. The caller is responsible for decoding
the content.
The material before the first boundary and after the last boundary is not returned.
Multipart Messages
The MIME standard defines a way to group several message parts to
a larger message (for E-Mails this technique is known as "attaching"
files to messages); these are the so-called multipart messages.
Such messages are recognized by the major type string "multipart",
e.g. multipart/mixed
or multipart/form-data
. Multipart types MUST
have a boundary
parameter because boundaries are essential for the
representation.
Multipart messages have a format like (where "_" denotes empty lines):
...Header...
Content-type: multipart/xyz; boundary="abc"
...Header...
_
Body begins here ("prologue")
--abc
...Header part 1...
_
...Body part 1...
--abc
...Header part 2...
_
...Body part 2
--abc
...
--abc--
Epilogue
The parts are separated by boundary lines which begin with "--" and the string passed as boundary parameter. (Note that there may follow arbitrary text on boundary lines after "--abc".) The boundary is chosen such that it does not occur as prefix of any line of the inner parts of the message.
The parts are again MIME messages, with header and body. Note that it is explicitely allowed that the parts are even multipart messages.
The texts before the first boundary and after the last boundary are ignored.
Note that multipart messages as a whole MUST NOT be encoded. Only the PARTS of the messages may be encoded (if they are not multipart messages themselves).
Please read RFC 2046 if want to know the gory details of this
brain-dead format.
val scan_multipart_body_and_decode : string ->
start_pos:int ->
end_pos:int -> boundary:string -> ((string * string) list * string) list
scan_multipart_body
, but decodes the bodies of the parts
if they are encoded using the methods "base64" or "quoted printable".
Fails, if an unknown encoding is used.val scan_multipart_body_from_netstream : Netstream.in_obj_stream ->
boundary:string ->
create:((string * string) list -> 'a) ->
add:('a -> Netstream.in_obj_stream -> int -> int -> unit) ->
stop:('a -> unit) -> unit
scan_multipart_body_from_netstream s boundary create add stop
:
Reads the MIME message from the netstream s
block by block. The
parts are delimited by the boundary
.
Once a new part is detected and begins, the function create
is
called with the MIME header as argument. The result p
of this function
may be of any type.
For every chunk of the part that is being read, the function add
is invoked: add p s k n
.
Here, p
is the value returned by the create
invocation for the
current part. s
is the netstream. The current window of s
contains
the read chunk completely; the chunk begins at position k
of the
window (relative to the beginning of the window) and has a length
of n
bytes.
When the part has been fully read, the function stop
is
called with p
as argument.
That means, for every part the following is executed:
let p = create h
add p s k1 n1
add p s k2 n2
add p s kN nN
stop p
s
must be at least
String.length boundary + 4
create
, add
, stop
.p
is being read, and the
create
function has already been called (successfully), the
stop
function is also called (you have the chance to close files).
The exception is re-raised after stop
returns.val read_multipart_body : (Netstream.in_obj_stream -> 'a) ->
string -> Netstream.in_obj_stream -> 'a list
let parts = read_multipart_body f boundary s
As precondition, the current position of the stream s
must be at
the beginning of the message body. The string boundary
must
be the message boundary (without "--"). The function f
is called
for every message part, and the resulting list parts
is the
concatentation of the values returned by f
.
The stream passed to f
is a substream of s
that begins at the
first byte of the header of the message part. The function f
can read data from the substream as necessary. The substream
terminates at the end of the message part. This means that f
can simply
read the data of the substream from the beginning to the end. It is
not necessary that f
reads the substream until EOF, however.
After all parts have been read, the trailing material of stream s
is skipped until EOF of s
is reached.
val create_boundary : ?random:string list -> ?nr:int -> unit -> string
nr
, so you can safely distinguish between
several boundaries occurring in the same MIME body if you
assign different nr
.random
, and influenced
by the current GC state.