Http2CodecUtil (Netty API Reference (4.1.11.Final))

java.lang.Object
- io.netty.handler.codec.http2.Http2CodecUtil

```
@UnstableApi
public final class Http2CodecUtil
extends Object
```
Constants and utility method used for encoding/decoding HTTP2 frames.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`CONNECTION_STREAM_ID`
`static int`	`CONTINUATION_FRAME_HEADER_LENGTH`
`static int`	`DATA_FRAME_HEADER_LENGTH`
`static long`	`DEFAULT_HEADER_LIST_SIZE` The initial value of this setting is unlimited.
`static int`	`DEFAULT_HEADER_TABLE_SIZE`
`static int`	`DEFAULT_MAX_FRAME_SIZE`
`static short`	`DEFAULT_PRIORITY_WEIGHT`
`static int`	`DEFAULT_WINDOW_SIZE`
`static int`	`FRAME_HEADER_LENGTH`
`static int`	`GO_AWAY_FRAME_HEADER_LENGTH`
`static int`	`HEADERS_FRAME_HEADER_LENGTH`
`static CharSequence`	`HTTP_UPGRADE_PROTOCOL_NAME`
`static CharSequence`	`HTTP_UPGRADE_SETTINGS_HEADER`
`static int`	`HTTP_UPGRADE_STREAM_ID`
`static int`	`INT_FIELD_LENGTH`
`static long`	`MAX_CONCURRENT_STREAMS`
`static int`	`MAX_FRAME_SIZE_LOWER_BOUND`
`static int`	`MAX_FRAME_SIZE_UPPER_BOUND`
`static long`	`MAX_HEADER_LIST_SIZE`
`static long`	`MAX_HEADER_TABLE_SIZE`
`static int`	`MAX_INITIAL_WINDOW_SIZE`
`static int`	`MAX_PADDING` The maximum number of padding bytes.
`static short`	`MAX_UNSIGNED_BYTE`
`static long`	`MAX_UNSIGNED_INT`
`static short`	`MAX_WEIGHT`
`static long`	`MIN_CONCURRENT_STREAMS`
`static long`	`MIN_HEADER_LIST_SIZE`
`static long`	`MIN_HEADER_TABLE_SIZE`
`static int`	`MIN_INITIAL_WINDOW_SIZE`
`static short`	`MIN_WEIGHT`
`static int`	`NUM_STANDARD_SETTINGS`
`static int`	`PING_FRAME_PAYLOAD_LENGTH`
`static int`	`PRIORITY_ENTRY_LENGTH`
`static int`	`PRIORITY_FRAME_LENGTH`
`static int`	`PUSH_PROMISE_FRAME_HEADER_LENGTH`
`static int`	`RST_STREAM_FRAME_LENGTH`
`static int`	`SETTING_ENTRY_LENGTH`
`static char`	`SETTINGS_ENABLE_PUSH`
`static char`	`SETTINGS_HEADER_TABLE_SIZE`
`static char`	`SETTINGS_INITIAL_WINDOW_SIZE`
`static char`	`SETTINGS_MAX_CONCURRENT_STREAMS`
`static char`	`SETTINGS_MAX_FRAME_SIZE`
`static char`	`SETTINGS_MAX_HEADER_LIST_SIZE`
`static int`	`SMALLEST_MAX_CONCURRENT_STREAMS` The assumed minimum value for `SETTINGS_MAX_CONCURRENT_STREAMS` as recommended by the HTTP/2 spec.
`static CharSequence`	`TLS_UPGRADE_PROTOCOL_NAME`
`static int`	`WINDOW_UPDATE_FRAME_LENGTH`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static long`	`calculateMaxHeaderListSizeGoAway(long maxHeaderListSize)` Calculate the threshold in bytes which should trigger a `GO_AWAY` if a set of headers exceeds this amount.
`static ByteBuf`	`connectionPrefaceBuf()` Returns a buffer containing the the `CONNECTION_PREFACE`.
`static ByteBuf`	`emptyPingBuf()` Returns a buffer filled with all zeros that is the appropriate length for a PING frame.
`static Http2Exception`	`getEmbeddedHttp2Exception(Throwable cause)` Iteratively looks through the causality chain for the given exception and returns the first `Http2Exception` or `null` if none.
`static void`	`headerListSizeExceeded(int streamId, long maxHeaderListSize, boolean onDecode)` Results in a RST_STREAM being sent for `streamId` due to violating SETTINGS_MAX_HEADER_LIST_SIZE.
`static void`	`headerListSizeExceeded(long maxHeaderListSize)` Results in a GO_AWAY being sent due to violating SETTINGS_MAX_HEADER_LIST_SIZE in an unrecoverable manner.
`static boolean`	`isMaxFrameSizeValid(int maxFrameSize)` Indicates whether or not the given value for max frame size falls within the valid range.
`static boolean`	`isOutboundStream(boolean server, int streamId)` Returns `true` if the stream is an outbound stream.
`static boolean`	`isStreamIdValid(int streamId)` Returns true if the `streamId` is a valid HTTP/2 stream identifier.
`static int`	`readUnsignedInt(ByteBuf buf)` Reads a big-endian (31-bit) integer from the buffer.
`static int`	`streamableBytes(StreamByteDistributor.StreamState state)` Calculate the amount of bytes that can be sent by `state`.
`static ByteBuf`	`toByteBuf(ChannelHandlerContext ctx, Throwable cause)` Creates a buffer containing the error message from the given exception.
`static void`	`verifyPadding(int padding)`
`static void`	`writeFrameHeader(ByteBuf out, int payloadLength, byte type, Http2Flags flags, int streamId)` Writes an HTTP/2 frame header to the output buffer.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - CONNECTION_STREAM_ID
```
public static final int CONNECTION_STREAM_ID
```
    See Also:
    
    Constant Field Values
  - HTTP_UPGRADE_STREAM_ID
```
public static final int HTTP_UPGRADE_STREAM_ID
```
    See Also:
    
    Constant Field Values
  - HTTP_UPGRADE_SETTINGS_HEADER
```
public static final CharSequence HTTP_UPGRADE_SETTINGS_HEADER
```
  - HTTP_UPGRADE_PROTOCOL_NAME
```
public static final CharSequence HTTP_UPGRADE_PROTOCOL_NAME
```
  - TLS_UPGRADE_PROTOCOL_NAME
```
public static final CharSequence TLS_UPGRADE_PROTOCOL_NAME
```
  - PING_FRAME_PAYLOAD_LENGTH
```
public static final int PING_FRAME_PAYLOAD_LENGTH
```
    See Also:
    
    Constant Field Values
  - MAX_UNSIGNED_BYTE
```
public static final short MAX_UNSIGNED_BYTE
```
    See Also:
    
    Constant Field Values
  - MAX_PADDING
```
public static final int MAX_PADDING
```
    The maximum number of padding bytes. That is the 255 padding bytes appended to the end of a frame and the 1 byte pad length field.
    
    See Also:
    
    Constant Field Values
  - MAX_UNSIGNED_INT
```
public static final long MAX_UNSIGNED_INT
```
    See Also:
    
    Constant Field Values
  - FRAME_HEADER_LENGTH
```
public static final int FRAME_HEADER_LENGTH
```
    See Also:
    
    Constant Field Values
  - SETTING_ENTRY_LENGTH
```
public static final int SETTING_ENTRY_LENGTH
```
    See Also:
    
    Constant Field Values
  - PRIORITY_ENTRY_LENGTH
```
public static final int PRIORITY_ENTRY_LENGTH
```
    See Also:
    
    Constant Field Values
  - INT_FIELD_LENGTH
```
public static final int INT_FIELD_LENGTH
```
    See Also:
    
    Constant Field Values
  - MAX_WEIGHT
```
public static final short MAX_WEIGHT
```
    See Also:
    
    Constant Field Values
  - MIN_WEIGHT
```
public static final short MIN_WEIGHT
```
    See Also:
    
    Constant Field Values
  - DATA_FRAME_HEADER_LENGTH
```
public static final int DATA_FRAME_HEADER_LENGTH
```
    See Also:
    
    Constant Field Values
  - HEADERS_FRAME_HEADER_LENGTH
```
public static final int HEADERS_FRAME_HEADER_LENGTH
```
    See Also:
    
    Constant Field Values
  - PRIORITY_FRAME_LENGTH
```
public static final int PRIORITY_FRAME_LENGTH
```
    See Also:
    
    Constant Field Values
  - RST_STREAM_FRAME_LENGTH
```
public static final int RST_STREAM_FRAME_LENGTH
```
    See Also:
    
    Constant Field Values
  - PUSH_PROMISE_FRAME_HEADER_LENGTH
```
public static final int PUSH_PROMISE_FRAME_HEADER_LENGTH
```
    See Also:
    
    Constant Field Values
  - GO_AWAY_FRAME_HEADER_LENGTH
```
public static final int GO_AWAY_FRAME_HEADER_LENGTH
```
    See Also:
    
    Constant Field Values
  - WINDOW_UPDATE_FRAME_LENGTH
```
public static final int WINDOW_UPDATE_FRAME_LENGTH
```
    See Also:
    
    Constant Field Values
  - CONTINUATION_FRAME_HEADER_LENGTH
```
public static final int CONTINUATION_FRAME_HEADER_LENGTH
```
    See Also:
    
    Constant Field Values
  - SETTINGS_HEADER_TABLE_SIZE
```
public static final char SETTINGS_HEADER_TABLE_SIZE
```
    See Also:
    
    Constant Field Values
  - SETTINGS_ENABLE_PUSH
```
public static final char SETTINGS_ENABLE_PUSH
```
    See Also:
    
    Constant Field Values
  - SETTINGS_MAX_CONCURRENT_STREAMS
```
public static final char SETTINGS_MAX_CONCURRENT_STREAMS
```
    See Also:
    
    Constant Field Values
  - SETTINGS_INITIAL_WINDOW_SIZE
```
public static final char SETTINGS_INITIAL_WINDOW_SIZE
```
    See Also:
    
    Constant Field Values
  - SETTINGS_MAX_FRAME_SIZE
```
public static final char SETTINGS_MAX_FRAME_SIZE
```
    See Also:
    
    Constant Field Values
  - SETTINGS_MAX_HEADER_LIST_SIZE
```
public static final char SETTINGS_MAX_HEADER_LIST_SIZE
```
    See Also:
    
    Constant Field Values
  - NUM_STANDARD_SETTINGS
```
public static final int NUM_STANDARD_SETTINGS
```
    See Also:
    
    Constant Field Values
  - MAX_HEADER_TABLE_SIZE
```
public static final long MAX_HEADER_TABLE_SIZE
```
    See Also:
    
    Constant Field Values
  - MAX_CONCURRENT_STREAMS
```
public static final long MAX_CONCURRENT_STREAMS
```
    See Also:
    
    Constant Field Values
  - MAX_INITIAL_WINDOW_SIZE
```
public static final int MAX_INITIAL_WINDOW_SIZE
```
    See Also:
    
    Constant Field Values
  - MAX_FRAME_SIZE_LOWER_BOUND
```
public static final int MAX_FRAME_SIZE_LOWER_BOUND
```
    See Also:
    
    Constant Field Values
  - MAX_FRAME_SIZE_UPPER_BOUND
```
public static final int MAX_FRAME_SIZE_UPPER_BOUND
```
    See Also:
    
    Constant Field Values
  - MAX_HEADER_LIST_SIZE
```
public static final long MAX_HEADER_LIST_SIZE
```
    See Also:
    
    Constant Field Values
  - MIN_HEADER_TABLE_SIZE
```
public static final long MIN_HEADER_TABLE_SIZE
```
    See Also:
    
    Constant Field Values
  - MIN_CONCURRENT_STREAMS
```
public static final long MIN_CONCURRENT_STREAMS
```
    See Also:
    
    Constant Field Values
  - MIN_INITIAL_WINDOW_SIZE
```
public static final int MIN_INITIAL_WINDOW_SIZE
```
    See Also:
    
    Constant Field Values
  - MIN_HEADER_LIST_SIZE
```
public static final long MIN_HEADER_LIST_SIZE
```
    See Also:
    
    Constant Field Values
  - DEFAULT_WINDOW_SIZE
```
public static final int DEFAULT_WINDOW_SIZE
```
    See Also:
    
    Constant Field Values
  - DEFAULT_PRIORITY_WEIGHT
```
public static final short DEFAULT_PRIORITY_WEIGHT
```
    See Also:
    
    Constant Field Values
  - DEFAULT_HEADER_TABLE_SIZE
```
public static final int DEFAULT_HEADER_TABLE_SIZE
```
    See Also:
    
    Constant Field Values
  - DEFAULT_HEADER_LIST_SIZE
```
public static final long DEFAULT_HEADER_LIST_SIZE
```
    The initial value of this setting is unlimited. However in practice we don't want to allow our peers to use unlimited memory by default. So we take advantage of the For any given request, a lower limit than what is advertised MAY be enforced. loophole.
    
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_FRAME_SIZE
```
public static final int DEFAULT_MAX_FRAME_SIZE
```
    See Also:
    
    Constant Field Values
  - SMALLEST_MAX_CONCURRENT_STREAMS
```
public static final int SMALLEST_MAX_CONCURRENT_STREAMS
```
    The assumed minimum value for SETTINGS_MAX_CONCURRENT_STREAMS as recommended by the HTTP/2 spec.
    
    See Also:
    
    Constant Field Values
- Method Detail
  - calculateMaxHeaderListSizeGoAway
```
public static long calculateMaxHeaderListSizeGoAway(long maxHeaderListSize)
```
    Calculate the threshold in bytes which should trigger a GO_AWAY if a set of headers exceeds this amount.
    
    Parameters:
    
    maxHeaderListSize - SETTINGS_MAX_HEADER_LIST_SIZE for the local endpoint.
    
    Returns:
    
    the threshold in bytes which should trigger a GO_AWAY if a set of headers exceeds this amount.
  - isOutboundStream
```
public static boolean isOutboundStream(boolean server,
                                       int streamId)
```
    Returns true if the stream is an outbound stream.
    
    Parameters:
    
    server - true if the endpoint is a server, false otherwise.
    
    streamId - the stream identifier
  - isStreamIdValid
```
public static boolean isStreamIdValid(int streamId)
```
    Returns true if the streamId is a valid HTTP/2 stream identifier.
  - isMaxFrameSizeValid
```
public static boolean isMaxFrameSizeValid(int maxFrameSize)
```
    Indicates whether or not the given value for max frame size falls within the valid range.
  - connectionPrefaceBuf
```
public static ByteBuf connectionPrefaceBuf()
```
    Returns a buffer containing the the CONNECTION_PREFACE.
  - emptyPingBuf
```
public static ByteBuf emptyPingBuf()
```
    Returns a buffer filled with all zeros that is the appropriate length for a PING frame.
  - getEmbeddedHttp2Exception
```
public static Http2Exception getEmbeddedHttp2Exception(Throwable cause)
```
    Iteratively looks through the causality chain for the given exception and returns the first Http2Exception or null if none.
  - toByteBuf
```
public static ByteBuf toByteBuf(ChannelHandlerContext ctx,
                                Throwable cause)
```
    Creates a buffer containing the error message from the given exception. If the cause is null returns an empty buffer.
  - readUnsignedInt
```
public static int readUnsignedInt(ByteBuf buf)
```
    Reads a big-endian (31-bit) integer from the buffer.
  - writeFrameHeader
```
public static void writeFrameHeader(ByteBuf out,
                                    int payloadLength,
                                    byte type,
                                    Http2Flags flags,
                                    int streamId)
```
    Writes an HTTP/2 frame header to the output buffer.
  - streamableBytes
```
public static int streamableBytes(StreamByteDistributor.StreamState state)
```
    Calculate the amount of bytes that can be sent by state. The lower bound is 0.
  - headerListSizeExceeded
```
public static void headerListSizeExceeded(int streamId,
                                          long maxHeaderListSize,
                                          boolean onDecode)
                                   throws Http2Exception
```
    Results in a RST_STREAM being sent for streamId due to violating SETTINGS_MAX_HEADER_LIST_SIZE.
    
    Parameters:
    
    streamId - The stream ID that was being processed when the exceptional condition occurred.
    
    maxHeaderListSize - The max allowed size for a list of headers in bytes which was exceeded.
    
    onDecode - true if the exception was encountered during decoder. false for encode.
    
    Throws:
    
    Http2Exception - a stream error.
  - headerListSizeExceeded
```
public static void headerListSizeExceeded(long maxHeaderListSize)
                                   throws Http2Exception
```
    Results in a GO_AWAY being sent due to violating SETTINGS_MAX_HEADER_LIST_SIZE in an unrecoverable manner.
    
    Parameters:
    
    maxHeaderListSize - The max allowed size for a list of headers in bytes which was exceeded.
    
    Throws:
    
    Http2Exception - a connection error.
  - verifyPadding
```
public static void verifyPadding(int padding)
```

Class Http2CodecUtil

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

CONNECTION_STREAM_ID

HTTP_UPGRADE_STREAM_ID

HTTP_UPGRADE_SETTINGS_HEADER

HTTP_UPGRADE_PROTOCOL_NAME

TLS_UPGRADE_PROTOCOL_NAME

PING_FRAME_PAYLOAD_LENGTH

MAX_UNSIGNED_BYTE

MAX_PADDING

MAX_UNSIGNED_INT

FRAME_HEADER_LENGTH

SETTING_ENTRY_LENGTH

PRIORITY_ENTRY_LENGTH

INT_FIELD_LENGTH

MAX_WEIGHT

MIN_WEIGHT

DATA_FRAME_HEADER_LENGTH

HEADERS_FRAME_HEADER_LENGTH

PRIORITY_FRAME_LENGTH

RST_STREAM_FRAME_LENGTH

PUSH_PROMISE_FRAME_HEADER_LENGTH

GO_AWAY_FRAME_HEADER_LENGTH

WINDOW_UPDATE_FRAME_LENGTH

CONTINUATION_FRAME_HEADER_LENGTH

SETTINGS_HEADER_TABLE_SIZE

SETTINGS_ENABLE_PUSH

SETTINGS_MAX_CONCURRENT_STREAMS

SETTINGS_INITIAL_WINDOW_SIZE

SETTINGS_MAX_FRAME_SIZE

SETTINGS_MAX_HEADER_LIST_SIZE

NUM_STANDARD_SETTINGS

MAX_HEADER_TABLE_SIZE

MAX_CONCURRENT_STREAMS

MAX_INITIAL_WINDOW_SIZE

MAX_FRAME_SIZE_LOWER_BOUND

MAX_FRAME_SIZE_UPPER_BOUND

MAX_HEADER_LIST_SIZE

MIN_HEADER_TABLE_SIZE

MIN_CONCURRENT_STREAMS

MIN_INITIAL_WINDOW_SIZE

MIN_HEADER_LIST_SIZE

DEFAULT_WINDOW_SIZE

DEFAULT_PRIORITY_WEIGHT

DEFAULT_HEADER_TABLE_SIZE

DEFAULT_HEADER_LIST_SIZE

DEFAULT_MAX_FRAME_SIZE

SMALLEST_MAX_CONCURRENT_STREAMS

Method Detail

calculateMaxHeaderListSizeGoAway

isOutboundStream

isStreamIdValid

isMaxFrameSizeValid

connectionPrefaceBuf

emptyPingBuf

getEmbeddedHttp2Exception

toByteBuf

readUnsignedInt

writeFrameHeader

streamableBytes

headerListSizeExceeded

headerListSizeExceeded

verifyPadding