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some refactors to make the code more readable #136

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29a7935
simplify
Jan 29, 2026
0782c72
refactor
Jan 29, 2026
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112 changes: 68 additions & 44 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -942,62 +942,86 @@ fn strip_trailing_crlf(raw_data: &[u8], ix_start: usize, mut ix: usize) -> usize
ix
}

fn parse_multipart(
raw_data: &[u8],
ix_body: usize,
boundary: String,
in_multipart_digest: bool,
) -> Result<(Vec<ParsedMail<'_>>, usize), MailParseError> {
let mut subparts = Vec::new();
let mut ix_body_end = ix_body;

if let Some(ix_boundary_start) =
find_from_u8_line_prefix(raw_data, ix_body, boundary.as_bytes())
{
ix_body_end = strip_trailing_crlf(raw_data, ix_body, ix_boundary_start);
let mut ix_boundary_end = ix_boundary_start + boundary.len();
while let Some(ix_part_start) =
find_from_u8(raw_data, ix_boundary_end, b"\n").map(|v| v + 1)
{
let ix_part_boundary_start =
find_from_u8_line_prefix(raw_data, ix_part_start, boundary.as_bytes());
let ix_part_end = ix_part_boundary_start
.map(|x| strip_trailing_crlf(raw_data, ix_part_start, x))
// if there is no terminating boundary, assume the part end is the end of the email
.unwrap_or(raw_data.len());

subparts.push(parse_mail_recursive(
&raw_data[ix_part_start..ix_part_end],
in_multipart_digest,
)?);
ix_boundary_end = ix_part_boundary_start
.map(|x| x + boundary.len())
.unwrap_or(raw_data.len());
if ix_boundary_end + 2 > raw_data.len()
|| (raw_data[ix_boundary_end] == b'-' && raw_data[ix_boundary_end + 1] == b'-')
{
break;
}
}
}
Ok((subparts, ix_body_end))
}

fn parse_subparts<'a>(
raw_data: &'a [u8],
ix_body: usize,
ctype: &'_ ParsedContentType,
) -> Result<(Vec<ParsedMail<'a>>, &'a [u8]), MailParseError> {
if raw_data.len() > ix_body
&& ctype.mimetype.starts_with("multipart")
&& let Some(boundary) = ctype.params.get("boundary")
{
let boundary = String::from("--") + boundary;
let in_multipart_digest = ctype.mimetype == "multipart/digest";
let (subparts, ix_body_end) =
parse_multipart(raw_data, ix_body, boundary, in_multipart_digest)?;
return Ok((subparts, &raw_data[ix_body..ix_body_end]));
}
Ok((Vec::new(), &raw_data[ix_body..]))
}

fn parse_mail_recursive(
raw_data: &[u8],
in_multipart_digest: bool,
) -> Result<ParsedMail<'_>, MailParseError> {
let (headers, ix_body) = parse_headers(raw_data)?;
let ctype = headers
.get_first_value("Content-Type")
.map(|s| parse_content_type(&s))
.as_deref()
.map(parse_content_type)
.unwrap_or_else(|| ParsedContentType::default_conditional(in_multipart_digest));

let mut result = ParsedMail {
let (subparts, body_bytes) = parse_subparts(raw_data, ix_body, &ctype)?;

Ok(ParsedMail {
raw_bytes: raw_data,
header_bytes: &raw_data[0..ix_body],
header_bytes: &raw_data[..ix_body],
headers,
ctype,
body_bytes: &raw_data[ix_body..],
subparts: Vec::<ParsedMail>::new(),
};
if result.ctype.mimetype.starts_with("multipart/")
&& result.ctype.params.contains_key("boundary")
&& raw_data.len() > ix_body
{
let in_multipart_digest = result.ctype.mimetype == "multipart/digest";
let boundary = String::from("--") + &result.ctype.params["boundary"];
if let Some(ix_boundary_start) =
find_from_u8_line_prefix(raw_data, ix_body, boundary.as_bytes())
{
let ix_body_end = strip_trailing_crlf(raw_data, ix_body, ix_boundary_start);
result.body_bytes = &raw_data[ix_body..ix_body_end];
let mut ix_boundary_end = ix_boundary_start + boundary.len();
while let Some(ix_part_start) =
find_from_u8(raw_data, ix_boundary_end, b"\n").map(|v| v + 1)
{
let ix_part_boundary_start =
find_from_u8_line_prefix(raw_data, ix_part_start, boundary.as_bytes());
let ix_part_end = ix_part_boundary_start
.map(|x| strip_trailing_crlf(raw_data, ix_part_start, x))
// if there is no terminating boundary, assume the part end is the end of the email
.unwrap_or(raw_data.len());

result.subparts.push(parse_mail_recursive(
&raw_data[ix_part_start..ix_part_end],
in_multipart_digest,
)?);
ix_boundary_end = ix_part_boundary_start
.map(|x| x + boundary.len())
.unwrap_or(raw_data.len());
if ix_boundary_end + 2 > raw_data.len()
|| (raw_data[ix_boundary_end] == b'-' && raw_data[ix_boundary_end + 1] == b'-')
{
break;
}
}
}
}
Ok(result)
body_bytes,
subparts,
})
}

/// Used to store params for content-type and content-disposition
Expand Down