Crate s3s_multipart 

Asynchronous streaming parser for multipart/form-data.

The parser consumes any futures_core::Stream of bytes::Bytes chunks and yields individual parts together with their headers and data.

Compatibility notes

This crate follows RFC 2046 section 5.1 and RFC 7578, with a small set of deliberate differences. Every item in this list is documented at the corresponding API item and has a regression test.

• Parts carrying more header fields than the parser reads are accepted: the surplus fields are ignored. RFC 7578 section 4.8 defines exactly Content-Disposition, Content-Type and the deprecated Content-Transfer-Encoding, requires any other header field to be ignored, and a conforming part carries at most those three — so for a conforming part the limit can only ever drop fields that such a part cannot have. A part that carries more than three fields and puts Content-Disposition after them loses that field, because the parser reads the first three fields and ignores the rest: section 4.8 asks for the surplus fields to be ignored, not for the parser to keep looking.
• A preamble before the first boundary and transport padding after a boundary line are accepted.
• Field lines are parsed with the strict header grammar: a folded field (a continuation line starting with optional whitespace) and a field name with leading optional whitespace are both rejected with Error::InvalidFormat, because the block is read by httparse rather than by the lenient line-folding rules of RFC 7230 section 3.2.4, which let a server reject a folded field anyway.
• Empty part headers and empty part bodies are valid.
• Content-Disposition parsing is tolerant: parameter names and the form-data token are case-insensitive, parameter order is free, and both quoted and token values are accepted.
• Content-Disposition name and filename are returned as raw bytes: no UTF-8 validation is performed, and callers decide how to convert or reject invalid sequences. Parsing is best-effort, so a malformed parameter tail is ignored instead of failing the parse.
• Quoted Content-Disposition parameter values keep their backslash escape sequences: quoted-pair is not decoded (\" stays \"), because returned values are always sub-slices of the header value. Callers that need the decoded value have to decode it themselves.
• The boundary is validated when it is constructed, according to RFC 2046 section 5.1.1 (1 to 70 characters, only bchars, and no trailing whitespace). A boundary that other parsers accept but RFC 2046 forbids is rejected, and there is no unchecked constructor.
• A part data stream taken with take_data_stream ends at the closing delimiter without interpreting what follows. Converting it with into_final yields a FinalPartDataStream that enforces the strict closing delimiter and rejects an epilogue, because callers need an exact content length.
• The internal buffer limit bounds the part header block, not the delivery: a block that ends within the limit is accepted whichever chunk carried it, and one that grows past the limit without a terminator is rejected with HeaderSizeExceeded. Data chunks yielded while streaming part data are never retained and are not charged to the limit, and the parse never depends on where the transport split the body. The buffer can still hold one arriving chunk beyond the limit, because the bytes that follow the terminator are retained until the header block is consumed.
• A chunk that carries no bytes is not progress and is not handed out: the parser skips such chunks, yields to the executor after a bounded number of them within one poll, and reports a stream failure once a consecutive run grows past a fixed bound, so a stream that never sends anything cannot keep the parser busy forever.

Structs

Boundary

A multipart boundary.

ContentDisposition

A parsed Content-Disposition value.

FinalPartDataStream

The strict variant of a taken part stream.

Multipart

A streaming parser for multipart/form-data.

Part

A single multipart part yielded by Multipart.

PartDataStream

A self-contained stream produced by Part::take_data_stream.

Enums

Error

Errors produced while parsing a multipart body.

Functions

parse_content_disposition

Parses a single Content-Disposition header value.