aeron-client/src/main/java/io/aeron/logbuffer/ExclusiveTermAppender.java
public int appendFragmentedMessage(
        final int termId,
        final int termOffset,
        final HeaderWriter header,
        final DirectBufferVector[] vectors,
        final int length,
        final int maxPayloadLength,
        final ReservedValueSupplier reservedValueSupplier)
    {
        final int numMaxPayloads = length / maxPayloadLength;
        final int remainingPayload = length % maxPayloadLength;
        final int lastFrameLength = remainingPayload > 0 ? align(remainingPayload + HEADER_LENGTH, FRAME_ALIGNMENT) : 0;
        final int requiredLength = (numMaxPayloads * (maxPayloadLength + HEADER_LENGTH)) + lastFrameLength;
        final UnsafeBuffer termBuffer = this.termBuffer;
        final int termLength = termBuffer.capacity();

        int resultingOffset = termOffset + requiredLength;
        putRawTailOrdered(termId, resultingOffset);

        if (resultingOffset > termLength)
        {
            resultingOffset = handleEndOfLogCondition(termBuffer, termOffset, header, termLength, termId);
        }
        else
        {
            int frameOffset = termOffset;
            byte flags = BEGIN_FRAG_FLAG;
            int remaining = length;
            int vectorIndex = 0;
            int vectorOffset = 0;

            do
            {
                final int bytesToWrite = Math.min(remaining, maxPayloadLength);
                final int frameLength = bytesToWrite + HEADER_LENGTH;
                final int alignedLength = align(frameLength, FRAME_ALIGNMENT);

                header.write(termBuffer, frameOffset, frameLength, termId);

                int bytesWritten = 0;
                int payloadOffset = frameOffset + HEADER_LENGTH;
                do
                {
                    final DirectBufferVector vector = vectors[vectorIndex];
                    final int vectorRemaining = vector.length - vectorOffset;
                    final int numBytes = Math.min(bytesToWrite - bytesWritten, vectorRemaining);

                    termBuffer.putBytes(payloadOffset, vector.buffer, vector.offset + vectorOffset, numBytes);

                    bytesWritten += numBytes;
                    payloadOffset += numBytes;
                    vectorOffset += numBytes;

                    if (vectorRemaining <= numBytes)
                    {
                        vectorIndex++;
                        vectorOffset = 0;
                    }
                }
                while (bytesWritten < bytesToWrite);

                if (remaining <= maxPayloadLength)
                {
                    flags |= END_FRAG_FLAG;
                }

                frameFlags(termBuffer, frameOffset, flags);

                if (null != reservedValueSupplier)
                {
                    final long reservedValue = reservedValueSupplier.get(termBuffer, frameOffset, frameLength);
                    termBuffer.putLong(frameOffset + RESERVED_VALUE_OFFSET, reservedValue, LITTLE_ENDIAN);
                }

                frameLengthOrdered(termBuffer, frameOffset, frameLength);

                flags = 0;
                frameOffset += alignedLength;
                remaining -= bytesToWrite;
            }
            while (remaining > 0);
        }

        return resultingOffset;
    }
public int appendFragmentedMessage(
        final int termId,
        final int termOffset,
        final HeaderWriter header,
        final DirectBufferVector[] vectors,
        final int length,
        final int maxPayloadLength,
        final ReservedValueSupplier reservedValueSupplier)
    {
        final int numMaxPayloads = length / maxPayloadLength;
        final int remainingPayload = length % maxPayloadLength;
        final int lastFrameLength = remainingPayload > 0 ? align(remainingPayload + HEADER_LENGTH, FRAME_ALIGNMENT) : 0;
        final int requiredLength = (numMaxPayloads * (maxPayloadLength + HEADER_LENGTH)) + lastFrameLength;
        final UnsafeBuffer termBuffer = this.termBuffer;
        final int termLength = termBuffer.capacity();

        int resultingOffset = termOffset + requiredLength;
        putRawTailOrdered(termId, resultingOffset);

        if (resultingOffset > termLength)
        {
            resultingOffset = handleEndOfLogCondition(termBuffer, termOffset, header, termLength, termId);
        }
        else
        {
            int frameOffset = termOffset;
            byte flags = BEGIN_FRAG_FLAG;
            int remaining = length;
            int vectorIndex = 0;
            int vectorOffset = 0;

            do
            {
                final int bytesToWrite = Math.min(remaining, maxPayloadLength);
                final int frameLength = bytesToWrite + HEADER_LENGTH;
                final int alignedLength = align(frameLength, FRAME_ALIGNMENT);

                header.write(termBuffer, frameOffset, frameLength, termId);

                int bytesWritten = 0;
                int payloadOffset = frameOffset + HEADER_LENGTH;
                do
                {
                    final DirectBufferVector vector = vectors[vectorIndex];
                    final int vectorRemaining = vector.length - vectorOffset;
                    final int numBytes = Math.min(bytesToWrite - bytesWritten, vectorRemaining);

                    termBuffer.putBytes(payloadOffset, vector.buffer, vector.offset + vectorOffset, numBytes);

                    bytesWritten += numBytes;
                    payloadOffset += numBytes;
                    vectorOffset += numBytes;

                    if (vectorRemaining <= numBytes)
                    {
                        vectorIndex++;
                        vectorOffset = 0;
                    }
                }
                while (bytesWritten < bytesToWrite);

                if (remaining <= maxPayloadLength)
                {
                    flags |= END_FRAG_FLAG;
                }

                frameFlags(termBuffer, frameOffset, flags);

                if (null != reservedValueSupplier)
                {
                    final long reservedValue = reservedValueSupplier.get(termBuffer, frameOffset, frameLength);
                    termBuffer.putLong(frameOffset + RESERVED_VALUE_OFFSET, reservedValue, LITTLE_ENDIAN);
                }

                frameLengthOrdered(termBuffer, frameOffset, frameLength);

                flags = 0;
                frameOffset += alignedLength;
                remaining -= bytesToWrite;
            }
            while (remaining > 0);
        }

        return resultingOffset;
    }
Append a fragmented message to the the term buffer.
The message will be split up into fragments of MTU length minus header.

@param termId                for the current term.
@param termOffset            in the term at which to append.
@param header                for writing the default header.
@param vectors               to the buffers.
@param length                of the message in the source buffer.
@param maxPayloadLength      that the message will be fragmented into.
@param reservedValueSupplier {@link ReservedValueSupplier} for the frame.
@return the resulting offset of the term after the append on success otherwise {@link #FAILED}.