`http.h2.frames`

import http

http exposes this as http.h2.frames, so import http is enough and the names are called as http.h2.frames.*. import http.h2.frames reaches the same definitions directly.

The HTTP/2 frame layer (RFC 9113 §4 and §6): a nine-octet header - a 24-bit length, a type, a flags byte, and a 31-bit stream identifier - followed by a payload.

Constants

`PREFACE`

http.h2.frames.PREFACE: string = 'PRI * HTTP/2.0

SM

'

The connection preface every HTTP/2 client sends before anything else. A server that reads these exact bytes knows it is speaking HTTP/2 and not an HTTP/1.1 request that happens to start with PRI.

`DATA`

http.h2.frames.DATA = 0

DATA frame. @type int

`HEADERS`

http.h2.frames.HEADERS = 1

HEADERS frame. @type int

`PRIORITY`

http.h2.frames.PRIORITY = 2

PRIORITY frame; deprecated by RFC 9113 and ignored here. @type int

`RST_STREAM`

http.h2.frames.RST_STREAM = 3

RST_STREAM frame. @type int

`SETTINGS`

http.h2.frames.SETTINGS = 4

SETTINGS frame. @type int

`PUSH_PROMISE`

http.h2.frames.PUSH_PROMISE = 5

PUSH_PROMISE frame. @type int

`PING`

http.h2.frames.PING = 6

PING frame. @type int

`GOAWAY`

http.h2.frames.GOAWAY = 7

GOAWAY frame. @type int

`WINDOW_UPDATE`

http.h2.frames.WINDOW_UPDATE = 8

WINDOW_UPDATE frame. @type int

`CONTINUATION`

http.h2.frames.CONTINUATION = 9

CONTINUATION frame. @type int

`FLAG_END_STREAM`

http.h2.frames.FLAG_END_STREAM = 1

END_STREAM flag, on DATA and HEADERS. @type int

`FLAG_ACK`

http.h2.frames.FLAG_ACK = 1

ACK flag, on SETTINGS and PING. @type int

`FLAG_END_HEADERS`

http.h2.frames.FLAG_END_HEADERS = 4

END_HEADERS flag, on HEADERS, PUSH_PROMISE and CONTINUATION. @type int

`FLAG_PADDED`

http.h2.frames.FLAG_PADDED = 8

PADDED flag, on DATA, HEADERS and PUSH_PROMISE. @type int

`FLAG_PRIORITY`

http.h2.frames.FLAG_PRIORITY = 32

PRIORITY flag, on HEADERS. @type int

`SETTINGS_HEADER_TABLE_SIZE`

http.h2.frames.SETTINGS_HEADER_TABLE_SIZE = 1

SETTINGS_HEADER_TABLE_SIZE. @type int

`SETTINGS_ENABLE_PUSH`

http.h2.frames.SETTINGS_ENABLE_PUSH = 2

SETTINGS_ENABLE_PUSH. @type int

`SETTINGS_MAX_CONCURRENT_STREAMS`

http.h2.frames.SETTINGS_MAX_CONCURRENT_STREAMS = 3

SETTINGS_MAX_CONCURRENT_STREAMS. @type int

`SETTINGS_INITIAL_WINDOW_SIZE`

http.h2.frames.SETTINGS_INITIAL_WINDOW_SIZE = 4

SETTINGS_INITIAL_WINDOW_SIZE. @type int

`SETTINGS_MAX_FRAME_SIZE`

http.h2.frames.SETTINGS_MAX_FRAME_SIZE = 5

SETTINGS_MAX_FRAME_SIZE. @type int

`SETTINGS_MAX_HEADER_LIST_SIZE`

http.h2.frames.SETTINGS_MAX_HEADER_LIST_SIZE = 6

SETTINGS_MAX_HEADER_LIST_SIZE. @type int

`NO_ERROR`

http.h2.frames.NO_ERROR = 0

NO_ERROR. @type int

`PROTOCOL_ERROR`

http.h2.frames.PROTOCOL_ERROR = 1

PROTOCOL_ERROR. @type int

`INTERNAL_ERROR`

http.h2.frames.INTERNAL_ERROR = 2

INTERNAL_ERROR. @type int

`FLOW_CONTROL_ERROR`

http.h2.frames.FLOW_CONTROL_ERROR = 3

FLOW_CONTROL_ERROR. @type int

`SETTINGS_TIMEOUT`

http.h2.frames.SETTINGS_TIMEOUT = 4

SETTINGS_TIMEOUT. @type int

`STREAM_CLOSED`

http.h2.frames.STREAM_CLOSED = 5

STREAM_CLOSED. @type int

`FRAME_SIZE_ERROR`

http.h2.frames.FRAME_SIZE_ERROR = 6

FRAME_SIZE_ERROR. @type int

`REFUSED_STREAM`

http.h2.frames.REFUSED_STREAM = 7

REFUSED_STREAM. @type int

`CANCEL`

http.h2.frames.CANCEL = 8

CANCEL. @type int

`COMPRESSION_ERROR`

http.h2.frames.COMPRESSION_ERROR = 9

COMPRESSION_ERROR. @type int

`CONNECT_ERROR`

http.h2.frames.CONNECT_ERROR = 10

CONNECT_ERROR. @type int

`ENHANCE_YOUR_CALM`

http.h2.frames.ENHANCE_YOUR_CALM = 11

ENHANCE_YOUR_CALM. @type int

`INADEQUATE_SECURITY`

http.h2.frames.INADEQUATE_SECURITY = 12

INADEQUATE_SECURITY. @type int

`HTTP_1_1_REQUIRED`

http.h2.frames.HTTP_1_1_REQUIRED = 13

HTTP_1_1_REQUIRED. @type int

Functions

`read_u32()`

http.h2.frames.read_u32(data, offset: number) -> number

Reads a 32-bit big-endian integer from data at offset.

Parameters

data (bytes)
offset (number)

Returns number

`write_u32()`

http.h2.frames.write_u32(out, value: number)

Appends a 32-bit big-endian integer to out.

Parameters

out (bytes)
value (number)

`read_u24()`

http.h2.frames.read_u24(data, offset: number) -> number

Reads a 24-bit big-endian integer from data at offset.

Parameters

data (bytes)
offset (number)

Returns number

`read_frame()`

http.h2.frames.read_frame(connection, max_frame_size: number) -> Frame

Reads one frame off a connection.

Padding is stripped here, so a caller never has to think about it, and a pad length that does not fit inside the frame is rejected - that mismatch is a connection error, not a frame to salvage.

Parameters

connection (Connection)
max_frame_size (number) — refuse anything larger

Returns Frame

Raises ProtocolError on a malformed or over-large frame

`write_frame()`

http.h2.frames.write_frame(connection, type: int, flags: int, stream_id: int, payload)

Writes one frame to a connection.

Parameters

connection (Connection)
type (int)
flags (int)
stream_id (int)
payload (?bytes)

`encode_settings()`

http.h2.frames.encode_settings(values: dict) -> bytes

Builds a SETTINGS payload from a dictionary of identifier to value.

Parameters

values (dict)

Returns bytes

`decode_settings()`

http.h2.frames.decode_settings(payload) -> dict

Parses a SETTINGS payload into a dictionary.

Unknown identifiers are kept rather than dropped - an endpoint must ignore settings it does not understand, and keeping them makes that the caller’s decision rather than a silent one here.

Parameters

payload (bytes)

Returns dict

Raises ProtocolError if the payload is not a whole number of six-octet entries

`encode_goaway()`

http.h2.frames.encode_goaway(last_stream_id: int, error_code: int, debug_message: ?string) -> bytes

Builds a GOAWAY payload.

Parameters

last_stream_id (int) — the highest stream this endpoint acted on
error_code (int)
debug_message (?string) — for humans reading a packet capture; never interpreted by the peer

Returns bytes

`encode_error()`

http.h2.frames.encode_error(error_code: int) -> bytes

Builds an RST_STREAM payload.

Parameters

error_code (int)

Returns bytes

Classes

`Frame`

class http.h2.frames.Frame

One frame, as read off the wire.

printable — has a @to_string(), so echo and print() show something useful

Fields

Field	Type	Description
`type`	`int`	The frame type - one of the constants above.
`flags`	`int`	The flags byte.
`stream_id`	`int`	The stream this frame belongs to; `0` for connection-level frames.
`payload`	`bytes`	The payload, with any padding already removed.

Constructor

http.h2.frames.Frame(type, flags, stream_id, payload)

`Frame.has_flag()`

http.h2.frames.Frame.has_flag(flag: int) -> bool

Whether flag is set.

Parameters

flag (int)

Returns bool

`Frame.to_string()`

http.h2.frames.Frame.to_string()

2026, Richard Ore and Zuri contributors

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