Package dev.relism.flash.http2.frame

Class FrameWriteBuffer

java.lang.Object

dev.relism.flash.http2.frame.FrameWriteBuffer

public final class FrameWriteBuffer
extends Object

Serializes HTTP/2 frames into a ByteWriter scratch buffer with the standard length-back-patching technique: beginFrame(dev.relism.flash.http2.frame.FrameType, int, int) writes a 9-byte header with a placeholder length, the caller writes the payload directly through writer() (the same ByteWriter), and endFrame() rewrites the length once it is known — the payload size is rarely known before it is serialized (an HPACK-encoded header block, in particular, has no cheap way to be measured in advance). issues one bulk write, rather than streaming bytes as they are produced: streaming would require knowing the length before the first byte goes out, which back-patching deliberately avoids needing.

Usage

 FrameWriteBuffer out = new FrameWriteBuffer(new ByteWriter(4096));
 out.beginFrame(FrameType.SETTINGS, 0, 0);
 out.writer().writeUInt16(SETTINGS_MAX_CONCURRENT_STREAMS);
 out.writer().writeUInt32(100);
 out.endFrame();
 // out.writer().array()[0, out.writer().length()) now holds one complete, correctly-lengthed frame
 

Multiple frames, one buffer

beginFrame(dev.relism.flash.http2.frame.FrameType, int, int)/endFrame() pairs may be repeated on the same instance without a ByteWriter.reset() between them — each pair appends one more complete frame after whatever was already written, which is exactly what Http2FrameWriter.write(dev.relism.flash.http2.frame.WriteIntent) wants for a single bulk write covering several frames (e.g. HEADERS followed immediately by its first DATA frame).

Thread-safety

Not thread-safe — exactly one writer at a time, the same convention every other per-connection scratch object in this codebase follows.

Constructor Summary

Constructors

Constructor	Description
FrameWriteBuffer(ByteWriter writer)

Method Summary

Modifier and Type	Method	Description
void	beginFrame(FrameType type, int flags, int streamId)	Writes a 9-byte frame header with a placeholder length, to be filled in by endFrame().
void	endFrame()	Back-patches the length field written by beginFrame(dev.relism.flash.http2.frame.FrameType, int, int) now that the payload's size is known.
ByteWriter	writer()	The underlying ByteWriter — write the frame's payload directly through this between beginFrame(dev.relism.flash.http2.frame.FrameType, int, int) and endFrame().

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

FrameWriteBuffer

public FrameWriteBuffer(ByteWriter writer)

Method Details

writer

public ByteWriter writer()

The underlying ByteWriter — write the frame's payload directly through this between beginFrame(dev.relism.flash.http2.frame.FrameType, int, int) and endFrame().

beginFrame

public void beginFrame(FrameType type,
 int flags,
 int streamId)

Writes a 9-byte frame header with a placeholder length, to be filled in by endFrame().

endFrame

public void endFrame()

Back-patches the length field written by beginFrame(dev.relism.flash.http2.frame.FrameType, int, int) now that the payload's size is known.