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global mime

https://lunarmodules.github.io/luasocket/mime.html

The mime namespace offers filters that apply and remove common content transfer encodings, such as Base64 and Quoted-Printable. It also provides functions to break text into lines and change the end-of-line convention. MIME is described mainly in RFC 2045, 2046, 2047, 2048, and 2049.

All functionality provided by the MIME module follows the ideas presented in

LTN012, Filters sources and sinks.

To obtain the mime namespace, run:

-- loads the MIME module and everything it requires
local mime = require("mime")

😱 Types incomplete or incorrect? 🙏 Please contribute!

methods

mime.decode

function mime.decode(name: ("base64"|"quoted-printable"))

Returns a filter that decodes data from a given transfer content encoding.

In the Quoted-Printable case, the user can specify whether the data is textual or binary, by passing the mode strings "text" or "binary". Mode defaults to "text".

mime.encode

function mime.encode(
  name: ("base64"|"quoted-printable"),
  mode: ("text"|"binary")?
)

Returns a filter that encodes data according to a given transfer content encoding.

In the Quoted-Printable case, the user can specify whether the data is textual or binary, by passing the mode strings "text" or "binary". Mode defaults to "text".

mime.normalize

function mime.normalize(marker: string)

Converts most common end-of-line markers to a specific given marker.

Marker is the new marker. It defaults to CRLF, the canonic end-of-line marker defined by the MIME standard.

The function returns a filter that performs the conversion.

Note: There is no perfect solution to this problem. Different end-of-line markers are an evil that will probably plague developers forever. This function, however, will work perfectly for text created with any of the most common end-of-line markers, i.e. the Mac OS (CR), the Unix (LF), or the DOS (CRLF) conventions. Even if the data has mixed end-of-line markers, the function will still work well, although it doesn't guarantee that the number of empty lines will be correct.

mime.stuff

function mime.stuff()

Creates and returns a filter that performs stuffing of SMTP messages.

Note: The smtp.sendfunction uses this filter automatically. You don't need to chain it with your source, or apply it to your message body.

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mime.wrap

function mime.wrap(
  name: ("text"|"base64"|"quoted-printable"),
  length: integer
)

Returns a filter that breaks data into lines.

The "text" line-wrap filter simply breaks text into lines by inserting CRLF end-of-line markers at appropriate positions. Length defaults 76. The "base64" line-wrap filter works just like the default "text" line-wrap filter with default length. The function can also wrap "quoted-printable" lines, taking care not to break lines in the middle of an escaped character. In that case, the line length is fixed at 76.

For example, to create an encoding filter for the Quoted-Printable transfer content encoding of text data, do the following:

qp = ltn12.filter.chain(
  mime.normalize(),
  mime.encode("quoted-printable"),
  mime.wrap("quoted-printable")
)

Note: To break into lines with a different end-of-line convention, apply a normalization filter after the line break filter.

mime.b64

function mime.b64(
  C: string,
  D: string?
)
 -> A string
 -> B string

Low-level filter to perform Base64 encoding.

If D is nil, A is padded with the encoding of the remaining bytes of C.

Note: The simplest use of this function is to encode a string into it's Base64 transfer content encoding. Notice the extra parenthesis around the call to mime.b64, to discard the second return value.

print((mime.b64("diego:password")))
--> ZGllZ286cGFzc3dvcmQ=

mime.dot

function mime.dot(
  m: sub<integer,"`m`">,
  B: string?
)
 -> A string
 -> n integer
@param m - should tell the same, but for the previous chunk.

Low-level filter to perform SMTP stuffing and enable transmission of messages containing the sequence "CRLF.CRLF".

Note: The message body is defined to begin with an implicit CRLF. Therefore, to stuff a message correctly, the first m should have the value 2.

print((string.gsub(mime.dot(2, ".\r\nStuffing the message.\r\n.\r\n."), "\r\n", "\\n")))
--&gt; ..\nStuffing the message.\n..\n..

Note: The smtp.sendfunction uses this filter automatically. You don't need to apply it again.

mime.eol

function mime.eol(
  C: integer,
  D: string?,
  marker: string
)
 -> A string
 -> B string
@param C - C is the ASCII value of the last character of the previous chunk, if it was a candidate for line break, or 0 otherwise.

@param marker - Marker gives the new end-of-line marker and defaults to CRLF.

@return A - A is the translated version of D.

@return B - B is the same as C, but for the current chunk.

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A, B = mime.eol(C [, D, marker])

Low-level filter to perform end-of-line marker translation. For each chunk, the function needs to know if the last character of the previous chunk could be part of an end-of-line marker or not. This is the context the function receives besides the chunk. An updated version of the context is returned after each new chunk.

-- translates the end-of-line marker to UNIX
unix = mime.eol(0, dos, "\n")

mime.qp

function mime.qp(
  C: string,
  D: string?,
  marker: string
)
 -> A string
 -> B string
@param D - If D is nil, A is padded with the encoding of the remaining bytes of C.

@param marker - Throughout encoding, occurrences of CRLF are replaced by the marker, which itself defaults to CRLF.

@return A - A is the encoded version of the largest prefix of C..D that can be encoded unambiguously.

@return B - B has the remaining bytes of C..D, before decoding.

😱 Types incomplete or incorrect? 🙏 Please contribute!

Low-level filter to perform Quoted-Printable encoding.

Note: The simplest use of this function is to encode a string into it's Quoted-Printable transfer content encoding. Notice the extra parenthesis around the call to mime.qp, to discard the second return value.

print((mime.qp("ma��")))
--&gt; ma=E7=E3=

mime.qpwrp

function mime.qpwrp(
  n: integer,
  B: string?,
  length: any
)
 -> A string
 -> m integer
@param n - n should tell how many bytes are left for the first line of B

@param length - broken into lines of at most length bytes (defaults to 76).

@return A - A is a copy of B, broken into lines of at most length bytes (defaults to 76).

@return m - returns the number of bytes left in the last line of A.

😱 Types incomplete or incorrect? 🙏 Please contribute!

Low-level filter to break Quoted-Printable text into lines.

Note: Besides breaking text into lines, this function makes sure the line breaks don't fall in the middle of an escaped character combination. Also, this function only breaks lines that are bigger than length bytes.

mime.unb64

function mime.unb64(
  C: string,
  D: string?
)
 -> A string
 -> B string

@return A - A is the decoded version of the largest prefix of C..D that can be decoded unambiguously.

@return B - B has the remaining bytes of C..D, before decoding.

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Low-level filter to perform Base64 decoding.

If D is nil, A is the empty string and B returns whatever couldn't be decoded.

Note: The simplest use of this function is to decode a string from it's Base64 transfer content encoding. Notice the extra parenthesis around the call to mime.unqp, to discard the second return value.

print((mime.unb64("ZGllZ286cGFzc3dvcmQ=")))
--&gt; diego:password

mime.unqp

function mime.unqp(
  C: string,
  D: string?
)
 -> A string
 -> B string

@return A - A is the decoded version of the largest prefix of C..D that can be decoded unambiguously. If D is nil, A is augmented with the encoding of the remaining bytes of C.

@return B - B has the remaining bytes of C..D, before decoding.

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Low-level filter to remove the Quoted-Printable transfer content encoding from data.

Note: The simplest use of this function is to decode a string from it's Quoted-Printable transfer content encoding. Notice the extra parenthesis around the call to mime.unqp, to discard the second return value.

print((mime.qp("ma=E7=E3=")))
--&gt; ma��

mime.wrp

function mime.wrp(
  n: integer,
  B: string?,
  length: any
)
 -> A string
 -> m integer
@param n - n should tell how many bytes are left for the first line of B

@param length - broken into lines of at most length bytes (defaults to 76).

@return A - A is a copy of B, broken into lines of at most length bytes (defaults to 76).

@return m - returns the number of bytes left in the last line of A.

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Low-level filter to break text into lines with CRLF marker. Text is assumed to be in the normalize form.

Note: This function only breaks lines that are bigger than length bytes. The resulting line length does not include the CRLF marker.