Crate mailrs_imap_format 

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

Pairs with mailrs-imap-proto (command parsing + session state machine) and mailrs-imap-codec (line / literal framing) to form a complete RFC 9051 receive + response stack.

22 standalone helpers grouped by concern:

• FLAGS — format_imap_flags / parse_imap_flags map the 6 standard system flags between u32 bitmask and IMAP (\Seen \Flagged …) syntax. Bit assignments are exposed via the FLAG_* pub const so callers can construct masks without round-tripping through strings.
• INTERNALDATE — format_internal_date(i64) formats a Unix timestamp as IMAP’s "DD-Mon-YYYY HH:MM:SS +ZZZZ".
• String quoting — escape_imap_string / escape_imap_str / quote_or_nil handle IMAP’s "…" quoted-string with \-escapes-or-NIL rules.
• Address parsing — format_imap_address + format_addr_list turn RFC 5322 addresses (with optional display name) into IMAP’s ((name route mailbox host)) structure.
• BODY[] section requests — parse_header_fields_request (BODY[HEADER.FIELDS (…)]) + parse_generic_body_sections (BODY[1], BODY[1.MIME], etc.).
• MIME walk — extract_header_section / extract_body_section / extract_header_fields / parse_mime_headers (returns MimeInfo) / split_mime_parts / find_line_offset / trim_part_trailing_newline / extract_mime_part.
• BODYSTRUCTURE — build_bodystructure recurses through multipart trees and emits the RFC-9051 §7.5.2 form.

All helpers are pure functions — no I/O, no async.

Structs

MimeInfo

Parsed Content-Type + Content-Transfer-Encoding + Content-Disposition info extracted from a single MIME part’s header block. Returned by parse_mime_headers.

Constants

FLAG_ANSWERED

IMAP \Answered system flag. Bit-1.

FLAG_DELETED

IMAP \Deleted system flag (queued for expunge). Bit-3.

FLAG_DRAFT

IMAP \Draft system flag. Bit-4.

FLAG_FLAGGED

IMAP \Flagged system flag (star). Bit-2.

FLAG_RECENT

IMAP \Recent system flag (set by EXAMINE/SELECT). Bit-5.

FLAG_SEEN

IMAP \Seen system flag. Bit-0 of the standard u32 mask.

Functions

build_bodystructure

build BODYSTRUCTURE for a message (handles multipart, with extension data)

escape_imap_str

escape double quotes in IMAP string literals

escape_imap_string

Escape \ and " characters for embedding inside an IMAP "…" quoted string. Does NOT add the surrounding quotes — see quote_or_nil for the full quoted-or-NIL decision.

extract_body_section

extract body section from raw message (after \r\n\r\n)

extract_header_fields

extract only the specified header fields from raw message

extract_header_section

extract header section from raw message (up to \r\n\r\n)

extract_mime_part

extract a specific MIME part by number (e.g. “1”, “2”, “1.1”, “1.MIME”)

find_line_offset

find byte offset of line number in body

format_addr_list

format a comma-separated list of addresses into IMAP address list

format_imap_address

parse an email address “Name user@host” or “user@host” into IMAP address structure returns ((name NIL mailbox host)) or NIL if empty

format_imap_flags

convert bitmask flags to IMAP flag string

format_internal_date

Format a Unix timestamp as an IMAP INTERNALDATE value ("DD-Mon-YYYY HH:MM:SS +ZZZZ", RFC 9051 §9 ABNF date-time).

parse_generic_body_sections

parse all generic BODY[section] requests like BODY[1], BODY[1.1], BODY[1.MIME], BODY.PEEK[1] returns all section specifiers (e.g. [“1”, “1.1”, “1.MIME”])

parse_header_fields_request

parse BODY[HEADER.FIELDS (field-list)] or BODY.PEEK[HEADER.FIELDS (field-list)] returns (field_names, raw_section_text)

parse_imap_flags

parse IMAP flag names from a FLAGS string like “(\Seen \Flagged)”

parse_mime_headers

parse content-type and transfer-encoding from header text

quote_or_nil

quote a string for IMAP or return NIL if empty

split_mime_parts

split multipart body by boundary, returning each part as raw bytes (including part headers)

trim_part_trailing_newline

trim trailing CRLF/LF from part body (boundary transport padding per RFC 2046)