moonbitstack/moonhttp/hpack

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Refused

pub(all) suberror Refused {
  Malformed(String)
  Index(got~ : Int)
  Exceeded(limit~ : Int, got~ : Int)
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

Why a header block was refused (RFC 7541 §6): a representation that does not parse, an index naming nothing, or a size update past what the peer allowed.

Every one of them is a connection error in HTTP/2 (RFC 9113 §4.3), because the two ends' dynamic tables have gone out of step and nothing after this point can be read.

impl Show for Refused

Refused::equal

source

fn Refused::equal(Refused, Refused) -> Bool

Refused::not_equal

source

fn Refused::not_equal(x : Refused, y : Refused) -> Bool

Refused::output

source

fn Refused::output(self : Refused, logger : &Logger) -> Unit

Refused::to_repr

source

fn Refused::to_repr(Refused) -> @moonbitlang/core/debug.Repr
Repr

Refused::to_string

source

fn Refused::to_string(self : Refused) -> String

Decoder

source

pub(all) struct Decoder {
  table : Table
  limit : Int
}

A stateful HPACK decoder: it owns a dynamic table that persists across the header blocks of a connection. limit is the peer-agreed hard cap (SETTINGS_HEADER_TABLE_SIZE) a size update may not exceed.

Decoder::decode

source

fn Decoder::decode(self : Decoder, block : BytesView) -> Array[@moonbitstack/moonhttp/header.Header
Header] raise Refused

Decode one complete header block into its header list (RFC 7541 §6), mutating the dynamic table for incrementally indexed fields and size updates. Raises Malformed/Malformed on any malformed representation.

Decoder::new

source

fn Decoder::new(limit? : Int) -> Decoder

A new decoder whose dynamic table is bounded by limit octets (also the hard cap enforced on dynamic table size updates).

Encoder

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pub(all) struct Encoder {
  table : Table
  huffman : Bool
}

A stateful HPACK encoder: it owns a dynamic table mirroring the decoder's, and prefers indexed representations. huffman selects Huffman string literals when they are shorter.

Encoder::encode

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fn Encoder::encode(self : Encoder, headers : ArrayView[@moonbitstack/moonhttp/header.Header
Header]) -> Bytes

Encode a header list into a header block (RFC 7541 §6), using indexed fields where possible and literal-with-incremental-indexing otherwise (mutating the dynamic table to mirror what the peer decoder will build). The output decodes back to the same header list via Decoder.

Encoder::new

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fn Encoder::new(limit? : Int, huffman? : Bool) -> Encoder

A new encoder bounded by limit octets; huffman (default true) enables the shorter-of-two string-literal heuristic.

Table

source

pub(all) struct Table {
  entries : Array[(Bytes, Bytes)]
  size : Int
  limit : Int
}

The HPACK dynamic table: a FIFO of recently seen (name, value) entries, newest first (entries[0]), bounded by limit octets where each entry costs name.len + value.len + 32 (RFC 7541 §4.1). Adding evicts the oldest entries until the newcomer fits; an entry larger than limit empties the table and is not stored (§4.4).

Table::add

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fn Table::add(self : Table, name : Bytes, value : Bytes) -> Unit

Insert (name, value) at the front, evicting oldest entries to make room. If the entry alone exceeds limit the table ends up empty (RFC 7541 §4.4).

Table::count

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fn Table::count(self : Table) -> Int

The number of entries currently in the dynamic table.

Table::get

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fn Table::get(self : Table, index : Int) -> @moonbitstack/moonhttp/header.Header
Header?

The field an HPACK index names, across the static and dynamic tables together (RFC 7541 §2.3.3): one through sixty-one are the static table, and everything above is this table, newest first. None when the index names nothing.

Table::limit

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fn Table::limit(self : Table) -> Int

The ceiling this table evicts to keep under, in octets.

Table::new

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fn Table::new(limit? : Int) -> Table

A new empty dynamic table bounded by limit octets (default 4096, the HTTP/2 initial SETTINGS_HEADER_TABLE_SIZE).

Table::resize

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fn Table::resize(self : Table, limit : Int) -> Unit

Resize the table (a dynamic table size update, RFC 7541 §4.2), evicting to fit.

Table::size

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fn Table::size(self : Table) -> Int

The current total size of the dynamic table in octets (§4.1 accounting).

entry

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fn entry(index : Int) -> @moonbitstack/moonhttp/header.Header
Header?

Look up an HPACK static-table entry by its 1-based RFC index (1..=61), returning (name, value) or None when the index is out of range.

limit

source

let limit : Int

How many octets a dynamic table holds by default.

Four kibibytes is the value HTTP/2 gives SETTINGS_HEADER_TABLE_SIZE before either end has said otherwise (RFC 9113 §6.5.2), so it is what both tables start at.

read_literal

source

fn read_literal(data : BytesView, offset : Int) -> (Bytes, Int) raise Refused

Decode an HPACK string literal from data at offset, returning (octets,bytes_consumed). The length is read as a 7-bit-prefix integer (the H bit is masked off); this is the inverse of string for H = 0. Huffman decoding is not applied here, so ask @prefix.flagged first if the literal may be coded.

read_string

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fn read_string(data : BytesView, offset : Int) -> (Bytes, Int) raise Refused

Read an HPACK string literal at offset, resolving Huffman coding when the H bit is set, returning (octets, bytes_consumed). Unlike read_literal, this applies Huffman decoding. Raises on bad Huffman.

size_update

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fn size_update(limit : Int) -> Bytes

Encode a dynamic table size update (RFC 7541 §6.3): 001 prefix with the new maximum size as a 5-bit-prefix integer.

static_table

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let static_table : Array[@moonbitstack/moonhttp/header.Header
Header]

The static table as (name, value) octet pairs, in RFC index order (index 1 at position 0). Derived once from static_table.

string

source

fn string(octets : BytesView, huffman? : Bool) -> Bytes

A string literal (RFC 7541 §5.2): the length as a seven-bit-prefix integer, then the octets, with the H bit saying whether they are Huffman-coded.

huffman takes the shorter of the two forms, which is what an encoder does; false writes the octets as they are, which is what a test with a published block needs.

A tie goes to the coded form, which is what RFC 7541's own examples do: it costs nothing and leaves less of the value legible to anything reading the connection.

Source Files

hpack.mbt

Install

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moonhttp — the HTTP family for MoonBit: URI references and percent coding, conditional requests and entity-tags, range requests, HTTP/1.1, HTTP/2 and HTTP/3 framing, HPACK and QPACK header compression, WebSocket framing and its handshake, Server-Sent Events, cookies, data URLs, multipart bodies and media types, each a package of its own. Bytes in, events out; no sockets.

httpurletaghttp3websockethpackqpackprotocolmoonbit

moonbitstack

Apache-2.0

github.com/moonbitstack/moonhttp

Updated 2 hours ago

305 downloads

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#Refused

#Refused::equal

#Refused::not_equal

#Refused::output

#Refused::to_repr

#Refused::to_string

#Decoder

#Decoder::decode

#Decoder::new

#Encoder

#Encoder::encode

#Encoder::new

#Table

#Table::add

#Table::count

#Table::get

#Table::limit

#Table::new

#Table::resize

#Table::size

#entry

#limit

#read_literal

#read_string

#size_update

#static_table

#string

Source Files

Refused

Refused::equal

Refused::not_equal

Refused::output

Refused::to_repr

Refused::to_string

Decoder

Decoder::decode

Decoder::new

Encoder

Encoder::encode

Encoder::new

Table

Table::add

Table::count

Table::get

Table::limit

Table::new

Table::resize

Table::size

entry

limit

read_literal

read_string

size_update

static_table

string