hpack_prim.h File Reference

Low-level field-coding primitives shared by HPACK and QPACK. More...

#include "protocore_config.h"

Go to the source code of this file.

Classes
struct	HpackPrimNs
	Dispatch table. Addressed by offset, so the layout is asserted below. More...

Functions
	PROTOCORE_NS_LAYOUT (HpackPrimNs, encode_int, decode_int, huff_encode, huff_len, huff_decode, decode_str, encode_str)
size_t	protocore_hpack_prim_encode_int (uint8_t *work, uint8_t *out, size_t cap, uint8_t prefix_bits, uint8_t flags, uint32_t value)
	A prefix-prefix_bits integer with the high flags bits set in byte 0.
proto_bool	protocore_hpack_prim_decode_int (uint8_t *work, const uint8_t *in, size_t len, uint8_t prefix_bits, size_t *consumed, uint32_t *value)
	The same integer back; sets consumed and value, false if malformed.
size_t	protocore_hpack_prim_huff_encode (uint8_t *work, uint8_t *out, size_t cap, const char *s, size_t n)
	Huffman-encode n bytes of s (RFC 7541 Appendix B); bytes written,.
size_t	protocore_hpack_prim_huff_len (uint8_t *work, const char *s, size_t n)
	The Huffman byte length of s without encoding it, which is what.
proto_bool	protocore_hpack_prim_huff_decode (uint8_t *work, const uint8_t *in, size_t n, char *out, size_t cap, size_t *out_len)
	Huffman-decode n bytes into out; sets out_len, false on a bad code.
proto_bool	protocore_hpack_prim_decode_str (uint8_t *work, const uint8_t *block, size_t len, size_t *pos, char *out, size_t cap, size_t *out_len)
	A length-prefixed string literal (H bit at 0x80 + a 7-bit length .
size_t	protocore_hpack_prim_encode_str (uint8_t *work, uint8_t *out, size_t cap, const char *s, size_t n)
	The same literal out, Huffman-coded when that is the shorter of the .

Variables
PROTOCORE_NS HpackPrimNs HpackPrim	PROTOCORE_UNUSED
	Module namespace.

Detailed Description

Low-level field-coding primitives shared by HPACK and QPACK.

RFC 7541 defines two primitives that RFC 9204 (QPACK) reuses verbatim: the prefix-integer coding (RFC 7541 sec 5.1) and the canonical Huffman code (RFC 7541 Appendix B, referenced by RFC 9204 sec 5). This module is the single copy of both, so HTTP/2's HPACK and HTTP/3's QPACK share one implementation and one Huffman table instead of duplicating ~1 KB of tables.

Pure and host-tested (via the HPACK and QPACK codec tests). Zero heap.

work is bytes the CALLER holds. This module reads none of them: it carries nothing between calls, so there is no state to keep and nothing to wipe. The parameter is there so a caller drives every namespace the same way.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file hpack_prim.h.

Function Documentation

PROTOCORE_NS_LAYOUT()

PROTOCORE_NS_LAYOUT	(	HpackPrimNs	,
		encode_int	,
		decode_int	,
		huff_encode	,
		huff_len	,
		huff_decode	,
		decode_str	,
		encode_str
	)

protocore_hpack_prim_encode_int()

size_t protocore_hpack_prim_encode_int	(	uint8_t *	work,
		uint8_t *	out,
		size_t	cap,
		uint8_t	prefix_bits,
		uint8_t	flags,
		uint32_t	value
	)

A prefix-prefix_bits integer with the high flags bits set in byte 0.

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
out	Out
cap	Cap
prefix_bits	Prefix bits
flags	Flags
value	Value

Returns

The size_t.

protocore_hpack_prim_decode_int()

proto_bool protocore_hpack_prim_decode_int	(	uint8_t *	work,
		const uint8_t *	in,
		size_t	len,
		uint8_t	prefix_bits,
		size_t *	consumed,
		uint32_t *	value
	)

The same integer back; sets consumed and value, false if malformed.

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
in	In
len	Len
prefix_bits	Prefix bits
consumed	Consumed
value	Value

Returns

PROTO_TRUE on success.

protocore_hpack_prim_huff_encode()

size_t protocore_hpack_prim_huff_encode	(	uint8_t *	work,
		uint8_t *	out,
		size_t	cap,
		const char *	s,
		size_t	n
	)

Huffman-encode n bytes of s (RFC 7541 Appendix B); bytes written,.

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
out	Out
cap	Cap
s	S
n	N

Returns

The size_t.

protocore_hpack_prim_huff_len()

size_t protocore_hpack_prim_huff_len	(	uint8_t *	work,
		const char *	s,
		size_t	n
	)

The Huffman byte length of s without encoding it, which is what.

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
s	S
n	N

Returns

The size_t.

protocore_hpack_prim_huff_decode()

proto_bool protocore_hpack_prim_huff_decode	(	uint8_t *	work,
		const uint8_t *	in,
		size_t	n,
		char *	out,
		size_t	cap,
		size_t *	out_len
	)

Huffman-decode n bytes into out; sets out_len, false on a bad code.

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
in	In
n	N
out	Out
cap	Cap
out_len	Out len

Returns

PROTO_TRUE on success.

protocore_hpack_prim_decode_str()

proto_bool protocore_hpack_prim_decode_str	(	uint8_t *	work,
		const uint8_t *	block,
		size_t	len,
		size_t *	pos,
		char *	out,
		size_t	cap,
		size_t *	out_len
	)

A length-prefixed string literal (H bit at 0x80 + a 7-bit length .

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
block	Block
len	Len
pos	Pos
out	Out
cap	Cap
out_len	Out len

Returns

PROTO_TRUE on success.

protocore_hpack_prim_encode_str()

size_t protocore_hpack_prim_encode_str	(	uint8_t *	work,
		uint8_t *	out,
		size_t	cap,
		const char *	s,
		size_t	n
	)

The same literal out, Huffman-coded when that is the shorter of the .

Parameters

work	PROTOCORE_HPACK_PRIM_BORROW bytes the caller took. Not held past the call.
out	Out
cap	Cap
s	S
n	N

Returns

The size_t.

Variable Documentation

PROTOCORE_UNUSED

PROTOCORE_NS HpackPrimNs HpackPrim PROTOCORE_UNUSED

Initial value:

= {.encode_int = protocore_hpack_prim_encode_int,
                                                       .decode_int = protocore_hpack_prim_decode_int,
                                                       .huff_encode = protocore_hpack_prim_huff_encode,
                                                       .huff_len = protocore_hpack_prim_huff_len,
                                                       .huff_decode = protocore_hpack_prim_huff_decode,
                                                       .decode_str = protocore_hpack_prim_decode_str,
                                                       .encode_str = protocore_hpack_prim_encode_str}

Module namespace.

Definition at line 126 of file hpack_prim.h.