aeron-client/src/main/java/io/aeron/BufferBuilder.java
public BufferBuilder append(final DirectBuffer srcBuffer, final int srcOffset, final int length)
    {
        ensureCapacity(length);

        buffer.putBytes(limit, srcBuffer, srcOffset, length);
        limit += length;

        return this;
    }
public BufferBuilder append(final DirectBuffer srcBuffer, final int srcOffset, final int length)
    {
        ensureCapacity(length);

        buffer.putBytes(limit, srcBuffer, srcOffset, length);
        limit += length;

        return this;
    }
Append a source buffer to the end of the internal buffer, resizing the internal buffer as required.

@param srcBuffer from which to copy.
@param srcOffset in the source buffer from which to copy.
@param length    in bytes to copy from the source buffer.
@return the builder for fluent API usage.