mailrs-imap-format

IMAP wire-format helpers (RFC 9051 §6.4 FETCH responses, §7.5 BODYSTRUCTURE assembly, §9 ABNF for FLAGS / INTERNALDATE).

22 standalone pure functions — no I/O, no async. Pairs with mailrs-imap-proto (command parsing + state machine) and mailrs-imap-codec (line + literal framing) to form a complete RFC 9051 IMAP receive

response stack.

What's in the box

Concern	Functions
FLAGS	`format_imap_flags` / `parse_imap_flags` + `FLAG_*` `pub const`s
INTERNALDATE	`format_internal_date(i64)` (Unix timestamp → IMAP date)
String quoting	`escape_imap_string` / `escape_imap_str` / `quote_or_nil`
Address structures	`format_imap_address` / `format_addr_list`
BODY[] section parsing	`parse_header_fields_request` / `parse_generic_body_sections`
MIME walk	`extract_header_section` / `extract_body_section` / `extract_header_fields` / `parse_mime_headers` (→ `MimeInfo`) / `split_mime_parts` / `find_line_offset` / `trim_part_trailing_newline` / `extract_mime_part`
BODYSTRUCTURE	`build_bodystructure` (top-level, recurses into multipart)

Quick start

use mailrs_imap_format::{
    format_imap_flags, parse_imap_flags,
    FLAG_SEEN, FLAG_FLAGGED, FLAG_ANSWERED,
    format_internal_date, build_bodystructure,
};

// FLAGS round-trip.
let bits = FLAG_SEEN | FLAG_FLAGGED;
assert_eq!(format_imap_flags(bits), "\\Seen \\Flagged");
assert_eq!(parse_imap_flags("(\\Seen \\Flagged)"), bits);

// INTERNALDATE.
let date = format_internal_date(1_700_000_000);
assert!(date.contains("2023"));

// BODYSTRUCTURE — recurses into multipart trees.
let msg = b"Content-Type: text/plain; charset=UTF-8\r\n\r\nHello world";
let bs = build_bodystructure(msg);
assert!(bs.contains("\"text\" \"plain\""));

FLAG_* bit assignments

The 6 standard IMAP system flags are exposed as pub const u32:

Const	Bit	IMAP name
`FLAG_SEEN`	0	`\Seen`
`FLAG_ANSWERED`	1	`\Answered`
`FLAG_FLAGGED`	2	`\Flagged`
`FLAG_DELETED`	3	`\Deleted`
`FLAG_DRAFT`	4	`\Recent`
`FLAG_RECENT`	5	`\Recent`

Callers that store flags in their own u32 (e.g. a mailbox storage layer) should match these bit positions to avoid an intermediate mapping step. RFC 9051 doesn't mandate a bit layout — this is the convention mailrs-mailbox and the wider mailrs project use.

What this crate does NOT do

No IMAP command parsing — that's mailrs-imap-proto.
No TCP/TLS framing — that's mailrs-imap-codec.
No IMAP state machine (auth / select / fetch / idle) — that's mailrs-imap-proto::Session.
No mailbox storage — that's mailrs-mailbox / mailrs-maildir.

License