HTTP/2 (RFC 7540) wire framing plus HPACK header compression (RFC 7541). More...

#include <stddef.h>
#include <stdint.h>

Include dependency graph for n_http2.h:

This graph shows which files directly or indirectly include this file:

Data Structures
struct	N_H2_FRAME
	a parsed HTTP/2 frame; payload aliases the input buffer More...
struct	N_H2_HEADER
	one HPACK header field; after a decode both strings are owned (heap) More...
struct	N_H2_SETTING
	one SETTINGS parameter (identifier and value) More...

Macros
#define	N_H2_FRAME_HEADER_LEN 9
	length of the fixed frame header in bytes
#define	N_H2_HPACK_DEFAULT_TABLE_SIZE 4096
	the default HPACK dynamic table size (SETTINGS_HEADER_TABLE_SIZE default)
#define	N_H2_MAX_FRAME_PAYLOAD 16384
	largest frame payload the parser accepts (the default SETTINGS_MAX_FRAME_SIZE)
#define	N_H2_PREFACE "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
	the client connection preface sent before any HTTP/2 frame (RFC 7540 3.5)
HTTP/2 frame types (RFC 7540 6)
#define	N_H2_CONTINUATION 0x9
	CONTINUATION.
#define	N_H2_DATA 0x0
	DATA.
#define	N_H2_GOAWAY 0x7
	GOAWAY.
#define	N_H2_HEADERS 0x1
	HEADERS.
#define	N_H2_PING 0x6
	PING.
#define	N_H2_PRIORITY 0x2
	PRIORITY.
#define	N_H2_PUSH_PROMISE 0x5
	PUSH_PROMISE.
#define	N_H2_RST_STREAM 0x3
	RST_STREAM.
#define	N_H2_SETTINGS 0x4
	SETTINGS.
#define	N_H2_WINDOW_UPDATE 0x8
	WINDOW_UPDATE.
HTTP/2 frame flags (RFC 7540 6)
#define	N_H2_FLAG_ACK 0x1
	SETTINGS/PING: acknowledgement.
#define	N_H2_FLAG_END_HEADERS 0x4
	HEADERS/PUSH_PROMISE/CONTINUATION: header block complete.
#define	N_H2_FLAG_END_STREAM 0x1
	DATA/HEADERS: last frame of the stream.
#define	N_H2_FLAG_PADDED 0x8
	DATA/HEADERS/PUSH_PROMISE: a pad-length prefix is present.
#define	N_H2_FLAG_PRIORITY 0x20
	HEADERS: priority fields are present.
SETTINGS parameter identifiers (RFC 7540 6.5.2)
#define	N_H2_SETTINGS_ENABLE_PUSH 0x2
#define	N_H2_SETTINGS_HEADER_TABLE_SIZE 0x1
#define	N_H2_SETTINGS_INITIAL_WINDOW_SIZE 0x4
#define	N_H2_SETTINGS_MAX_CONCURRENT_STREAMS 0x3
#define	N_H2_SETTINGS_MAX_FRAME_SIZE 0x5
#define	N_H2_SETTINGS_MAX_HEADER_LIST_SIZE 0x6

Functions
size_t	n_http2_frame_build_header (unsigned char *out, size_t out_cap, uint32_t length, int type, int flags, uint32_t stream_id)
	write a 9-byte HTTP/2 frame header into out.
int	n_http2_frame_parse (const unsigned char buf, size_t len, N_H2_FRAME frame, size_t *consumed)
	parse one HTTP/2 frame from a byte buffer (stateless).
int	n_http2_hpack_decode (N_H2_HPACK ctx, const unsigned char block, size_t len, N_H2_HEADER out, size_t max_out, size_t count)
	decode an HPACK header block into out[] (owned name/value strings).
size_t	n_http2_hpack_encode (const N_H2_HEADER headers, size_t n, unsigned char out, size_t out_cap)
	encode a header list into a block using literal representations without indexing and without Huffman (a valid, interoperable, self-contained encoding that needs no dynamic-table state).
void	n_http2_hpack_free (N_H2_HPACK **ctx)
	free an HPACK codec context and NULL the caller's pointer
void	n_http2_hpack_headers_free (N_H2_HEADER *headers, size_t n)
	free the owned name/value strings of a decoded header array (does not free the array itself)
N_H2_HPACK *	n_http2_hpack_new (size_t max_table_size)
	create an HPACK codec context with the given dynamic table size limit (0 uses N_H2_HPACK_DEFAULT_TABLE_SIZE).
void	n_http2_hpack_set_max_size (N_H2_HPACK *ctx, size_t max_table_size)
	change the dynamic table size limit (a SETTINGS_HEADER_TABLE_SIZE change), evicting entries as needed so the table fits.
int	n_http2_settings_parse (const unsigned char payload, size_t len, N_H2_SETTING out, size_t max, size_t *count)
	parse a SETTINGS frame payload (6-byte id/value entries) into out.

Detailed Description

HTTP/2 (RFC 7540) wire framing plus HPACK header compression (RFC 7541).

Author: Castagnier Mickael

Version: 1.0

Date: 2026

The framing layer of HTTP/2: the client connection preface, the frame-type and flag constants, a 9-byte frame-header parse/build, and a SETTINGS payload reader. The frame codec is stateless and does no allocation, so a caller drives its own reassembly buffer.

On top of the framing sits HPACK (RFC 7541): an N_H2_HPACK codec context with a per-direction dynamic table, a full decoder (indexed and literal fields, the static and dynamic tables, Huffman-coded and literal strings, and dynamic table size updates), and a self-contained encoder (literal fields without indexing, no Huffman) that needs no shared state. The stream/connection state machine builds on these two layers.

Definition in file n_http2.h.

Data Structure Documentation

◆ N_H2_FRAME

struct N_H2_FRAME

a parsed HTTP/2 frame; payload aliases the input buffer

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 91 of file n_http2.h.

Collaboration diagram for N_H2_FRAME:

Data Fields
int	flags	frame flags
uint32_t	length	payload length (24-bit)
const unsigned char *	payload	pointer into the input buffer (may be NULL when length is 0)
uint32_t	stream_id	stream identifier (31-bit; the reserved bit is cleared)
int	type	frame type (N_H2_*)

◆ N_H2_HEADER

struct N_H2_HEADER

one HPACK header field; after a decode both strings are owned (heap)

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 123 of file n_http2.h.

Collaboration diagram for N_H2_HEADER:

Data Fields
char *	name	header field name (owned after decode)
char *	value	header field value (owned after decode)

◆ N_H2_SETTING

struct N_H2_SETTING

one SETTINGS parameter (identifier and value)

Examples: ex_http2.c, and ex_http2_server.c.

Definition at line 100 of file n_http2.h.

Collaboration diagram for N_H2_SETTING:

Data Fields
uint16_t	id	parameter identifier (N_H2_SETTINGS_*)
uint32_t	value	parameter value

Macro Definition Documentation

◆ N_H2_CONTINUATION

#define N_H2_CONTINUATION 0x9

CONTINUATION.

Examples: ex_http2_server.c.

Definition at line 68 of file n_http2.h.

Referenced by n_http2_server_respond(), srv_handle_frame(), and test_continuation().

◆ N_H2_DATA

#define N_H2_DATA 0x0

DATA.

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 59 of file n_http2.h.

Referenced by h2_client_get(), n_http2_server_respond(), srv_handle_frame(), test_boundaries(), test_get(), test_post_body(), test_rst_stream(), test_send_flow_control(), and test_send_window_stall().

◆ N_H2_FLAG_ACK

#define N_H2_FLAG_ACK 0x1

SETTINGS/PING: acknowledgement.

Examples: ex_http2_server.c.

Definition at line 74 of file n_http2.h.

Referenced by n_http2_server_handshake(), srv_apply_settings(), srv_handle_frame(), test_handshake(), and test_ping_goaway().

◆ N_H2_FLAG_END_HEADERS

#define N_H2_FLAG_END_HEADERS 0x4

HEADERS/PUSH_PROMISE/CONTINUATION: header block complete.

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 75 of file n_http2.h.

Referenced by h2_client_get(), n_http2_server_respond(), peer_headers(), srv_apply_headers(), test_continuation(), test_get(), and test_roundtrip().

◆ N_H2_FLAG_END_STREAM

#define N_H2_FLAG_END_STREAM 0x1

DATA/HEADERS: last frame of the stream.

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 73 of file n_http2.h.

Referenced by h2_client_get(), n_http2_server_respond(), peer_headers(), srv_apply_data(), srv_apply_headers(), test_continuation(), test_get(), test_post_body(), test_roundtrip(), and test_rst_stream().

◆ N_H2_FLAG_PADDED

#define N_H2_FLAG_PADDED 0x8

DATA/HEADERS/PUSH_PROMISE: a pad-length prefix is present.

Definition at line 76 of file n_http2.h.

Referenced by srv_apply_data(), and srv_headers_payload().

◆ N_H2_FLAG_PRIORITY

#define N_H2_FLAG_PRIORITY 0x20

HEADERS: priority fields are present.

Definition at line 77 of file n_http2.h.

Referenced by srv_headers_payload().

◆ N_H2_FRAME_HEADER_LEN

#define N_H2_FRAME_HEADER_LEN 9

length of the fixed frame header in bytes

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 53 of file n_http2.h.

Referenced by h2_client_get(), n_http2_frame_build_header(), n_http2_frame_parse(), peer_frame(), srv_send(), test_boundaries(), and test_roundtrip().

◆ N_H2_GOAWAY

#define N_H2_GOAWAY 0x7

GOAWAY.

Examples: ex_http2_server.c.

Definition at line 66 of file n_http2.h.

Referenced by n_http2_server_goaway(), srv_handle_frame(), test_callback_stop(), test_get(), and test_ping_goaway().

◆ N_H2_HEADERS

#define N_H2_HEADERS 0x1

HEADERS.

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 60 of file n_http2.h.

Referenced by h2_client_get(), n_http2_server_respond(), peer_headers(), srv_apply_headers(), srv_handle_frame(), test_continuation(), test_get(), test_multiplex(), and test_roundtrip().

◆ N_H2_HPACK_DEFAULT_TABLE_SIZE

#define N_H2_HPACK_DEFAULT_TABLE_SIZE 4096

the default HPACK dynamic table size (SETTINGS_HEADER_TABLE_SIZE default)

Definition at line 120 of file n_http2.h.

Referenced by n_http2_hpack_new().

◆ N_H2_MAX_FRAME_PAYLOAD

#define N_H2_MAX_FRAME_PAYLOAD 16384

largest frame payload the parser accepts (the default SETTINGS_MAX_FRAME_SIZE)

Definition at line 55 of file n_http2.h.

Referenced by n_http2_frame_parse(), and srv_apply_settings().

◆ N_H2_PING

#define N_H2_PING 0x6

PING.

Examples: ex_http2.c, and ex_http2_server.c.

Definition at line 65 of file n_http2.h.

Referenced by srv_handle_frame(), test_boundaries(), test_continuation(), test_handshake_errors(), and test_ping_goaway().

◆ N_H2_PREFACE

#define N_H2_PREFACE "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"

the client connection preface sent before any HTTP/2 frame (RFC 7540 3.5)

Examples: ex_http2.c, ex_http2_server.c, and ex_network_alpn.c.

Definition at line 51 of file n_http2.h.

Referenced by h2_client_get(), n_http2_server_handshake(), peer_prologue(), test_handshake_errors(), and test_preface().

◆ N_H2_PRIORITY

#define N_H2_PRIORITY 0x2

PRIORITY.

Definition at line 61 of file n_http2.h.

Referenced by srv_handle_frame().

◆ N_H2_PUSH_PROMISE

#define N_H2_PUSH_PROMISE 0x5

PUSH_PROMISE.

Definition at line 64 of file n_http2.h.

Referenced by srv_handle_frame().

◆ N_H2_RST_STREAM

#define N_H2_RST_STREAM 0x3

RST_STREAM.

Examples: ex_http2_server.c.

Definition at line 62 of file n_http2.h.

Referenced by n_http2_server_rst_stream(), srv_handle_frame(), and test_rst_stream().

◆ N_H2_SETTINGS

#define N_H2_SETTINGS 0x4

SETTINGS.

Examples: ex_http2_server.c, and ex_network_alpn.c.

Definition at line 63 of file n_http2.h.

Referenced by h2_client_get(), n_http2_server_handshake(), peer_prologue(), srv_apply_settings(), srv_handle_frame(), and test_handshake().

◆ N_H2_SETTINGS_ENABLE_PUSH

#define N_H2_SETTINGS_ENABLE_PUSH 0x2

Definition at line 83 of file n_http2.h.

Referenced by n_http2_server_handshake().

◆ N_H2_SETTINGS_HEADER_TABLE_SIZE

#define N_H2_SETTINGS_HEADER_TABLE_SIZE 0x1

Definition at line 82 of file n_http2.h.

◆ N_H2_SETTINGS_INITIAL_WINDOW_SIZE

#define N_H2_SETTINGS_INITIAL_WINDOW_SIZE 0x4

Examples: ex_http2.c, and ex_http2_server.c.

Definition at line 85 of file n_http2.h.

Referenced by n_http2_server_handshake(), srv_apply_settings(), test_handshake(), and test_settings().

◆ N_H2_SETTINGS_MAX_CONCURRENT_STREAMS

#define N_H2_SETTINGS_MAX_CONCURRENT_STREAMS 0x3

Examples: ex_http2.c.

Definition at line 84 of file n_http2.h.

Referenced by n_http2_server_handshake(), and test_settings().

◆ N_H2_SETTINGS_MAX_FRAME_SIZE

#define N_H2_SETTINGS_MAX_FRAME_SIZE 0x5

Definition at line 86 of file n_http2.h.

Referenced by srv_apply_settings().

◆ N_H2_SETTINGS_MAX_HEADER_LIST_SIZE

#define N_H2_SETTINGS_MAX_HEADER_LIST_SIZE 0x6

Definition at line 87 of file n_http2.h.

◆ N_H2_WINDOW_UPDATE

#define N_H2_WINDOW_UPDATE 0x8

WINDOW_UPDATE.

Examples: ex_http2.c, and ex_http2_server.c.

Definition at line 67 of file n_http2.h.

Referenced by peer_window_update(), srv_handle_frame(), srv_window_update(), test_handshake(), test_post_body(), and test_roundtrip().

Function Documentation

◆ n_http2_frame_build_header()

size_t n_http2_frame_build_header	(	unsigned char *	out,
		size_t	out_cap,
		uint32_t	length,
		int	type,
		int	flags,
		uint32_t	stream_id )

write a 9-byte HTTP/2 frame header into out.

Returns N_H2_FRAME_HEADER_LEN, or 0 when out_cap is too small or length exceeds 24 bits.

Definition at line 52 of file n_http2.c.

References N_H2_FRAME_HEADER_LEN, and type().

Referenced by h2_client_get(), peer_frame(), srv_send(), test_boundaries(), and test_roundtrip().

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◆ n_http2_frame_parse()

int n_http2_frame_parse	(	const unsigned char *	buf,
		size_t	len,
		N_H2_FRAME *	frame,
		size_t *	consumed )

parse one HTTP/2 frame from a byte buffer (stateless).

Returns 1 and fills frame + *consumed (header + payload) on a complete frame, 0 when more bytes are needed, -1 when the payload exceeds N_H2_MAX_FRAME_PAYLOAD.

Definition at line 32 of file n_http2.c.

References N_H2_FRAME::flags, N_H2_FRAME::length, N_H2_FRAME_HEADER_LEN, N_H2_MAX_FRAME_PAYLOAD, N_H2_FRAME::payload, N_H2_FRAME::stream_id, and N_H2_FRAME::type.

Referenced by h2_client_get(), out_count(), out_find(), srv_next_frame(), test_boundaries(), test_post_body(), and test_roundtrip().

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◆ n_http2_hpack_decode()

int n_http2_hpack_decode	(	N_H2_HPACK *	ctx,
		const unsigned char *	block,
		size_t	len,
		N_H2_HEADER *	out,
		size_t	max_out,
		size_t *	count )

decode an HPACK header block into out[] (owned name/value strings).

Handles indexed fields (static and dynamic table), the three literal forms (with/without/never indexing), Huffman-coded and literal strings, and dynamic table size updates. On success *count holds the number of headers written (<= max_out) and the dynamic table is updated. Returns 0 on success, -1 on a malformed block or when more than max_out headers are produced. Free the decoded headers with n_http2_hpack_headers_free.

Parameters

ctx	codec context (its dynamic table is read and updated)
block	the header block fragment bytes
len	length of block
out	array receiving the decoded headers
max_out	capacity of out
count	receives the number of headers decoded

Returns: 0 on success, -1 on error

Definition at line 472 of file n_http2.c.

References hpack_dyn_add(), hpack_evict(), hpack_int_decode(), hpack_lookup(), hpack_str_decode(), N_H2_HPACK::limit, N_H2_HPACK::max_size, n_http2_hpack_headers_free(), N_H2_HEADER::name, and N_H2_HEADER::value.

Referenced by h2_client_get(), srv_finish_headers(), test_hpack_guards(), test_hpack_overflow(), test_hpack_rfc_huffman(), test_hpack_rfc_requests(), and test_hpack_roundtrip().

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◆ n_http2_hpack_encode()

size_t n_http2_hpack_encode	(	const N_H2_HEADER *	headers,
		size_t	n,
		unsigned char *	out,
		size_t	out_cap )

encode a header list into a block using literal representations without indexing and without Huffman (a valid, interoperable, self-contained encoding that needs no dynamic-table state).

Returns the number of bytes written, or 0 when out_cap is too small or an argument is invalid.

Parameters