aerogramme/aero-proto/src/imap/mime_view.rs

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use std::borrow::Cow;
use std::collections::HashSet;
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use std::num::NonZeroU32;
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use anyhow::{anyhow, bail, Result};
use imap_codec::imap_types::body::{
BasicFields, Body as FetchBody, BodyStructure, MultiPartExtensionData, SinglePartExtensionData,
SpecificFields,
};
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use imap_codec::imap_types::core::{AString, IString, NString, Vec1};
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use imap_codec::imap_types::fetch::{Part as FetchPart, Section as FetchSection};
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use eml_codec::{
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header, mime, mime::r#type::Deductible, part::composite, part::discrete, part::AnyPart,
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};
use crate::imap::imf_view::ImfView;
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pub enum BodySection<'a> {
Full(Cow<'a, [u8]>),
Slice {
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body: Cow<'a, [u8]>,
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origin_octet: u32,
},
}
/// Logic for BODY[<section>]<<partial>>
/// Works in 3 times:
/// 1. Find the section (RootMime::subset)
/// 2. Apply the extraction logic (SelectedMime::extract), like TEXT, HEADERS, etc.
/// 3. Keep only the given subset provided by partial
///
/// Example of message sections:
///
/// ```
/// HEADER ([RFC-2822] header of the message)
/// TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
/// 1 TEXT/PLAIN
/// 2 APPLICATION/OCTET-STREAM
/// 3 MESSAGE/RFC822
/// 3.HEADER ([RFC-2822] header of the message)
/// 3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
/// 3.1 TEXT/PLAIN
/// 3.2 APPLICATION/OCTET-STREAM
/// 4 MULTIPART/MIXED
/// 4.1 IMAGE/GIF
/// 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
/// 4.2 MESSAGE/RFC822
/// 4.2.HEADER ([RFC-2822] header of the message)
/// 4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
/// 4.2.1 TEXT/PLAIN
/// 4.2.2 MULTIPART/ALTERNATIVE
/// 4.2.2.1 TEXT/PLAIN
/// 4.2.2.2 TEXT/RICHTEXT
/// ```
pub fn body_ext<'a>(
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part: &'a AnyPart<'a>,
section: &'a Option<FetchSection<'a>>,
partial: &'a Option<(u32, NonZeroU32)>,
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) -> Result<BodySection<'a>> {
let root_mime = NodeMime(part);
let (extractor, path) = SubsettedSection::from(section);
let selected_mime = root_mime.subset(path)?;
let extracted_full = selected_mime.extract(&extractor)?;
Ok(extracted_full.to_body_section(partial))
}
/// Logic for BODY and BODYSTRUCTURE
///
/// ```raw
/// b fetch 29878:29879 (BODY)
/// * 29878 FETCH (BODY (("text" "plain" ("charset" "utf-8") NIL NIL "quoted-printable" 3264 82)("text" "html" ("charset" "utf-8") NIL NIL "quoted-printable" 31834 643) "alternative"))
/// * 29879 FETCH (BODY ("text" "html" ("charset" "us-ascii") NIL NIL "7bit" 4107 131))
/// ^^^^^^^^^^^^^^^^^^^^^^ ^^^ ^^^ ^^^^^^ ^^^^ ^^^
/// | | | | | | number of lines
/// | | | | | size
/// | | | | content transfer encoding
/// | | | description
/// | | id
/// | parameter list
/// b OK Fetch completed (0.001 + 0.000 secs).
/// ```
pub fn bodystructure(part: &AnyPart, is_ext: bool) -> Result<BodyStructure<'static>> {
NodeMime(part).structure(is_ext)
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}
/// NodeMime
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///
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/// Used for recursive logic on MIME.
/// See SelectedMime for inspection.
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struct NodeMime<'a>(&'a AnyPart<'a>);
impl<'a> NodeMime<'a> {
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/// A MIME object is a tree of elements.
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/// The path indicates which element must be picked.
/// This function returns the picked element as the new view
fn subset(self, path: Option<&'a FetchPart>) -> Result<SelectedMime<'a>> {
match path {
None => Ok(SelectedMime(self.0)),
Some(v) => self.rec_subset(v.0.as_ref()),
}
}
fn rec_subset(self, path: &'a [NonZeroU32]) -> Result<SelectedMime> {
if path.is_empty() {
Ok(SelectedMime(self.0))
} else {
match self.0 {
AnyPart::Mult(x) => {
let next = Self(x.children
.get(path[0].get() as usize - 1)
.ok_or(anyhow!("Unable to resolve subpath {:?}, current multipart has only {} elements", path, x.children.len()))?);
next.rec_subset(&path[1..])
},
AnyPart::Msg(x) => {
let next = Self(x.child.as_ref());
next.rec_subset(path)
},
_ => bail!("You tried to access a subpart on an atomic part (text or binary). Unresolved subpath {:?}", path),
}
}
}
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fn structure(&self, is_ext: bool) -> Result<BodyStructure<'static>> {
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match self.0 {
AnyPart::Txt(x) => NodeTxt(self, x).structure(is_ext),
AnyPart::Bin(x) => NodeBin(self, x).structure(is_ext),
AnyPart::Mult(x) => NodeMult(self, x).structure(is_ext),
AnyPart::Msg(x) => NodeMsg(self, x).structure(is_ext),
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}
}
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}
//----------------------------------------------------------
/// A FetchSection must be handled in 2 times:
/// - First we must extract the MIME part
/// - Then we must process it as desired
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/// The given struct mixes both work, so
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/// we separate this work here.
enum SubsettedSection<'a> {
Part,
Header,
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HeaderFields(&'a Vec1<AString<'a>>),
HeaderFieldsNot(&'a Vec1<AString<'a>>),
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Text,
Mime,
}
impl<'a> SubsettedSection<'a> {
fn from(section: &'a Option<FetchSection>) -> (Self, Option<&'a FetchPart>) {
match section {
Some(FetchSection::Text(maybe_part)) => (Self::Text, maybe_part.as_ref()),
Some(FetchSection::Header(maybe_part)) => (Self::Header, maybe_part.as_ref()),
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Some(FetchSection::HeaderFields(maybe_part, fields)) => {
(Self::HeaderFields(fields), maybe_part.as_ref())
}
Some(FetchSection::HeaderFieldsNot(maybe_part, fields)) => {
(Self::HeaderFieldsNot(fields), maybe_part.as_ref())
}
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Some(FetchSection::Mime(part)) => (Self::Mime, Some(part)),
Some(FetchSection::Part(part)) => (Self::Part, Some(part)),
None => (Self::Part, None),
}
}
}
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/// Used for current MIME inspection
///
/// See NodeMime for recursive logic
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pub struct SelectedMime<'a>(pub &'a AnyPart<'a>);
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impl<'a> SelectedMime<'a> {
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pub fn header_value(&'a self, to_match_ext: &[u8]) -> Option<&'a [u8]> {
let to_match = to_match_ext.to_ascii_lowercase();
self.eml_mime()
.kv
.iter()
.filter_map(|field| match field {
header::Field::Good(header::Kv2(k, v)) => Some((k, v)),
_ => None,
})
.find(|(k, _)| k.to_ascii_lowercase() == to_match)
.map(|(_, v)| v)
.copied()
}
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/// The subsetted fetch section basically tells us the
/// extraction logic to apply on our selected MIME.
/// This function acts as a router for these logic.
fn extract(&self, extractor: &SubsettedSection<'a>) -> Result<ExtractedFull<'a>> {
match extractor {
SubsettedSection::Text => self.text(),
SubsettedSection::Header => self.header(),
SubsettedSection::HeaderFields(fields) => self.header_fields(fields, false),
SubsettedSection::HeaderFieldsNot(fields) => self.header_fields(fields, true),
SubsettedSection::Part => self.part(),
SubsettedSection::Mime => self.mime(),
}
}
fn mime(&self) -> Result<ExtractedFull<'a>> {
let bytes = match &self.0 {
AnyPart::Txt(p) => p.mime.fields.raw,
AnyPart::Bin(p) => p.mime.fields.raw,
AnyPart::Msg(p) => p.child.mime().raw,
AnyPart::Mult(p) => p.mime.fields.raw,
};
Ok(ExtractedFull(bytes.into()))
}
fn part(&self) -> Result<ExtractedFull<'a>> {
let bytes = match &self.0 {
AnyPart::Txt(p) => p.body,
AnyPart::Bin(p) => p.body,
AnyPart::Msg(p) => p.raw_part,
AnyPart::Mult(_) => bail!("Multipart part has no body"),
};
Ok(ExtractedFull(bytes.to_vec().into()))
}
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fn eml_mime(&self) -> &eml_codec::mime::NaiveMIME<'_> {
match &self.0 {
AnyPart::Msg(msg) => msg.child.mime(),
other => other.mime(),
}
}
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/// The [...] HEADER.FIELDS, and HEADER.FIELDS.NOT part
/// specifiers refer to the [RFC-2822] header of the message or of
/// an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
/// HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
/// field-name (as defined in [RFC-2822]) names, and return a
/// subset of the header. The subset returned by HEADER.FIELDS
/// contains only those header fields with a field-name that
/// matches one of the names in the list; similarly, the subset
/// returned by HEADER.FIELDS.NOT contains only the header fields
/// with a non-matching field-name. The field-matching is
/// case-insensitive but otherwise exact.
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fn header_fields(
&self,
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fields: &'a Vec1<AString<'a>>,
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invert: bool,
) -> Result<ExtractedFull<'a>> {
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// Build a lowercase ascii hashset with the fields to fetch
let index = fields
.as_ref()
.iter()
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.map(|x| {
match x {
AString::Atom(a) => a.inner().as_bytes(),
AString::String(IString::Literal(l)) => l.as_ref(),
AString::String(IString::Quoted(q)) => q.inner().as_bytes(),
}
.to_ascii_lowercase()
})
.collect::<HashSet<_>>();
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// Extract MIME headers
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let mime = self.eml_mime();
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// Filter our MIME headers based on the field index
// 1. Keep only the correctly formatted headers
// 2. Keep only based on the index presence or absence
// 3. Reduce as a byte vector
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let buffer = mime
.kv
.iter()
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.filter_map(|field| match field {
header::Field::Good(header::Kv2(k, v)) => Some((k, v)),
_ => None,
})
.filter(|(k, _)| index.contains(&k.to_ascii_lowercase()) ^ invert)
.fold(vec![], |mut acc, (k, v)| {
acc.extend(*k);
acc.extend(b": ");
acc.extend(*v);
acc.extend(b"\r\n");
acc
});
Ok(ExtractedFull(buffer.into()))
}
/// The HEADER [...] part specifiers refer to the [RFC-2822] header of the message or of
/// an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
/// ```raw
/// HEADER ([RFC-2822] header of the message)
/// ```
fn header(&self) -> Result<ExtractedFull<'a>> {
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let msg = self
.0
.as_message()
.ok_or(anyhow!("Selected part must be a message/rfc822"))?;
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Ok(ExtractedFull(msg.raw_headers.into()))
}
/// The TEXT part specifier refers to the text body of the message, omitting the [RFC-2822] header.
fn text(&self) -> Result<ExtractedFull<'a>> {
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let msg = self
.0
.as_message()
.ok_or(anyhow!("Selected part must be a message/rfc822"))?;
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Ok(ExtractedFull(msg.raw_body.into()))
}
// ------------
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/// Basic field of a MIME part that is
/// common to all parts
fn basic_fields(&self) -> Result<BasicFields<'static>> {
let sz = match self.0 {
AnyPart::Txt(x) => x.body.len(),
AnyPart::Bin(x) => x.body.len(),
AnyPart::Msg(x) => x.raw_part.len(),
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AnyPart::Mult(_) => 0,
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};
let m = self.0.mime();
let parameter_list = m
.ctype
.as_ref()
.map(|x| {
x.params
.iter()
.map(|p| {
(
IString::try_from(String::from_utf8_lossy(p.name).to_string()),
IString::try_from(p.value.to_string()),
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)
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})
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.filter(|(k, v)| k.is_ok() && v.is_ok())
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.map(|(k, v)| (k.unwrap(), v.unwrap()))
.collect()
})
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.unwrap_or(vec![]);
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Ok(BasicFields {
parameter_list,
id: NString(
m.id.as_ref()
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.and_then(|ci| IString::try_from(ci.to_string()).ok()),
),
description: NString(
m.description
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.as_ref()
.and_then(|cd| IString::try_from(cd.to_string()).ok()),
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),
content_transfer_encoding: match m.transfer_encoding {
mime::mechanism::Mechanism::_8Bit => unchecked_istring("8bit"),
mime::mechanism::Mechanism::Binary => unchecked_istring("binary"),
mime::mechanism::Mechanism::QuotedPrintable => {
unchecked_istring("quoted-printable")
}
mime::mechanism::Mechanism::Base64 => unchecked_istring("base64"),
_ => unchecked_istring("7bit"),
},
// @FIXME we can't compute the size of the message currently...
size: u32::try_from(sz)?,
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})
}
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}
// ---------------------------
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struct NodeMsg<'a>(&'a NodeMime<'a>, &'a composite::Message<'a>);
impl<'a> NodeMsg<'a> {
fn structure(&self, is_ext: bool) -> Result<BodyStructure<'static>> {
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let basic = SelectedMime(self.0 .0).basic_fields()?;
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Ok(BodyStructure::Single {
body: FetchBody {
basic,
specific: SpecificFields::Message {
envelope: Box::new(ImfView(&self.1.imf).message_envelope()),
body_structure: Box::new(NodeMime(&self.1.child).structure(is_ext)?),
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number_of_lines: nol(self.1.raw_part),
},
},
extension_data: match is_ext {
true => Some(SinglePartExtensionData {
md5: NString(None),
tail: None,
}),
_ => None,
},
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})
}
}
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#[allow(dead_code)]
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struct NodeMult<'a>(&'a NodeMime<'a>, &'a composite::Multipart<'a>);
impl<'a> NodeMult<'a> {
fn structure(&self, is_ext: bool) -> Result<BodyStructure<'static>> {
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let itype = &self.1.mime.interpreted_type;
let subtype = IString::try_from(itype.subtype.to_string())
.unwrap_or(unchecked_istring("alternative"));
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let inner_bodies = self
.1
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.children
.iter()
.filter_map(|inner| NodeMime(&inner).structure(is_ext).ok())
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.collect::<Vec<_>>();
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Vec1::validate(&inner_bodies)?;
let bodies = Vec1::unvalidated(inner_bodies);
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Ok(BodyStructure::Multi {
bodies,
subtype,
extension_data: match is_ext {
true => Some(MultiPartExtensionData {
parameter_list: vec![(
IString::try_from("boundary").unwrap(),
IString::try_from(self.1.mime.interpreted_type.boundary.to_string())?,
)],
tail: None,
}),
_ => None,
},
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})
}
}
struct NodeTxt<'a>(&'a NodeMime<'a>, &'a discrete::Text<'a>);
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impl<'a> NodeTxt<'a> {
fn structure(&self, is_ext: bool) -> Result<BodyStructure<'static>> {
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let mut basic = SelectedMime(self.0 .0).basic_fields()?;
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// Get the interpreted content type, set it
let itype = match &self.1.mime.interpreted_type {
Deductible::Inferred(v) | Deductible::Explicit(v) => v,
};
let subtype =
IString::try_from(itype.subtype.to_string()).unwrap_or(unchecked_istring("plain"));
// Add charset to the list of parameters if we know it has been inferred as it will be
// missing from the parsed content.
if let Deductible::Inferred(charset) = &itype.charset {
basic.parameter_list.push((
unchecked_istring("charset"),
IString::try_from(charset.to_string()).unwrap_or(unchecked_istring("us-ascii")),
));
}
Ok(BodyStructure::Single {
body: FetchBody {
basic,
specific: SpecificFields::Text {
subtype,
number_of_lines: nol(self.1.body),
},
},
extension_data: match is_ext {
true => Some(SinglePartExtensionData {
md5: NString(None),
tail: None,
}),
_ => None,
},
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})
}
}
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struct NodeBin<'a>(&'a NodeMime<'a>, &'a discrete::Binary<'a>);
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impl<'a> NodeBin<'a> {
fn structure(&self, is_ext: bool) -> Result<BodyStructure<'static>> {
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let basic = SelectedMime(self.0 .0).basic_fields()?;
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let default = mime::r#type::NaiveType {
main: &b"application"[..],
sub: &b"octet-stream"[..],
params: vec![],
};
let ct = self.1.mime.fields.ctype.as_ref().unwrap_or(&default);
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let r#type = IString::try_from(String::from_utf8_lossy(ct.main).to_string()).or(Err(
anyhow!("Unable to build IString from given Content-Type type given"),
))?;
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let subtype = IString::try_from(String::from_utf8_lossy(ct.sub).to_string()).or(Err(
anyhow!("Unable to build IString from given Content-Type subtype given"),
))?;
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Ok(BodyStructure::Single {
body: FetchBody {
basic,
specific: SpecificFields::Basic { r#type, subtype },
},
extension_data: match is_ext {
true => Some(SinglePartExtensionData {
md5: NString(None),
tail: None,
}),
_ => None,
},
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})
}
}
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// ---------------------------
struct ExtractedFull<'a>(Cow<'a, [u8]>);
impl<'a> ExtractedFull<'a> {
/// It is possible to fetch a substring of the designated text.
/// This is done by appending an open angle bracket ("<"), the
/// octet position of the first desired octet, a period, the
/// maximum number of octets desired, and a close angle bracket
/// (">") to the part specifier. If the starting octet is beyond
/// the end of the text, an empty string is returned.
///
/// Any partial fetch that attempts to read beyond the end of the
/// text is truncated as appropriate. A partial fetch that starts
/// at octet 0 is returned as a partial fetch, even if this
/// truncation happened.
///
/// Note: This means that BODY[]<0.2048> of a 1500-octet message
/// will return BODY[]<0> with a literal of size 1500, not
/// BODY[].
///
/// Note: A substring fetch of a HEADER.FIELDS or
/// HEADER.FIELDS.NOT part specifier is calculated after
/// subsetting the header.
fn to_body_section(self, partial: &'_ Option<(u32, NonZeroU32)>) -> BodySection<'a> {
match partial {
Some((begin, len)) => self.partialize(*begin, *len),
None => BodySection::Full(self.0),
}
}
fn partialize(self, begin: u32, len: NonZeroU32) -> BodySection<'a> {
// Asked range is starting after the end of the content,
// returning an empty buffer
if begin as usize > self.0.len() {
return BodySection::Slice {
body: Cow::Borrowed(&[][..]),
origin_octet: begin,
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};
}
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// Asked range is ending after the end of the content,
// slice only the beginning of the buffer
if (begin + len.get()) as usize >= self.0.len() {
return BodySection::Slice {
body: match self.0 {
Cow::Borrowed(body) => Cow::Borrowed(&body[begin as usize..]),
Cow::Owned(body) => Cow::Owned(body[begin as usize..].to_vec()),
},
origin_octet: begin,
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};
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}
// Range is included inside the considered content,
// this is the "happy case"
BodySection::Slice {
body: match self.0 {
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Cow::Borrowed(body) => {
Cow::Borrowed(&body[begin as usize..(begin + len.get()) as usize])
}
Cow::Owned(body) => {
Cow::Owned(body[begin as usize..(begin + len.get()) as usize].to_vec())
}
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},
origin_octet: begin,
}
}
}
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/// ---- LEGACY
/// s is set to static to ensure that only compile time values
/// checked by developpers are passed.
fn unchecked_istring(s: &'static str) -> IString {
IString::try_from(s).expect("this value is expected to be a valid imap-codec::IString")
}
// Number Of Lines
fn nol(input: &[u8]) -> u32 {
input
.iter()
.filter(|x| **x == b'\n')
.count()
.try_into()
.unwrap_or(0)
}