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+QPACK How-To
+============
+
+Using QPACK encoder
+-------------------
+
+Firstly, create QPACK encoder by calling `nghttp3_qpack_encoder_new`.
+It requires *hard_max_dtable_size* parameter. When in doubt, pass
+4096 for this tutorial. Optionally, call
+`nghttp3_qpack_encoder_set_max_dtable_capacity` to set the maximum
+size of dynamic table. You can also call
+`nghttp3_qpack_encoder_set_max_blocked_streams` to set the maximum
+number of streams that can be blocked.
+
+In order to encode HTTP header fields, they must be stored in an array
+of :type:`nghttp3_nv`. Then call `nghttp3_qpack_encoder_encode`. It
+writes 3 buffers; *pbuf*, *rbuf*, and *ebuf*. They are a header block
+prefix, request stream, and encoder stream respectively. A header
+block prefix and request stream must be sent in this order to a stream
+denoted by *stream_id* passed to the function. Encoder stream must be
+sent to the encoder stream you setup.
+
+In order to read decoder stream, call
+`nghttp3_qpack_encoder_read_decoder`.
+
+Once QPACK encoder is no longer used, call `nghttp3_qpack_encoder_del`
+to free up memory allocated for it.
+
+Using QPACK decoder
+-------------------
+
+`nghttp3_qpack_decoder_new` will create new QPACK decoder. It
+requires *hard_max_dtable_size* and *max_blocked* parameters. When in
+doubt, pass 4096 and 0 respectively for this tutorial.
+
+In order to read encoder stream, call
+`nghttp3_qpack_decoder_read_encoder`. This might update dynamic
+table, but does not emit any header fields.
+
+In order to read request stream, call
+`nghttp3_qpack_decoder_read_request`. This is the function to emit
+header fields. *sctx* stores a per-stream decoder state and must be
+created by `nghttp3_qpack_stream_context_new`. It identifies a single
+encoded header block in a particular request stream. *fin* must be
+nonzero if and only if a passed data contains the last part of encoded
+header block.
+
+The scope of :type:`nghttp3_qpack_stream_context` is per header block,
+but `nghttp3_qpack_stream_context_reset` resets its state and can be
+reused for an another header block in the same stream. In general,
+you can reset it when you see that
+:macro:`NGHTTP3_QPACK_DECODE_FLAG_FINAL` is set in *\*pflags*. When
+:type:`nghttp3_qpack_stream_context` is no longer necessary, call
+`nghttp3_qpack_stream_context_del` to free up its resource.
+
+`nghttp3_qpack_decoder_read_request` succeeds, *\*pflags* is assigned.
+If it has :macro:`NGHTTP3_QPACK_DECODE_FLAG_EMIT` set, a header field
+is emitted and stored in the buffer pointed by *nv*. If *\*pflags*
+has :macro:`NGHTTP3_QPACK_DECODE_FLAG_FINAL` set, all header fields
+have been successfully decoded. If *\*pflags* has
+:macro:`NGHTTP3_QPACK_DECODE_FLAG_BLOCKED` set, decoding is blocked
+due to required insert count, which means that more data must be read
+by `nghttp3_qpack_decoder_read_encoder`.
+
+`nghttp3_qpack_decoder_read_request` returns the number of bytes read.
+When a header field is emitted, it might read data partially.
+Applciation has to call the function repeatedly by adjusting the
+pointer to data and its length until the function consumes all data or
+:macro:`NGHTTP3_QPACK_DECODE_FLAG_BLOCKED` is set in *\*pflags*.
+
+If *nv* is assigned, its :member:`nv->name <nghttp3_qpack_nv.name>`
+and :member:`nv->value <nghttp3_qpack_nv.value>` are reference counted
+and already incremented by 1. If application finishes processing
+these values, it must call `nghttp3_rcbuf_decref(nv->name)
+<nghttp3_rcbuf_decref>` and `nghttp3_rcbuf_decref(nv->value)
+<nghttp3_rcbuf_decref>`.
+
+If an application has no interest to decode header fields for a
+particular stream, call `nghttp3_qpack_decoder_cancel_stream`.
+
+In order to tell decoding state to an encoder, QPACK decoder has to
+write decoder stream by calling `nghttp3_qpack_decoder_write_decoder`.
+
+Once QPACK decoder is no longer used, call `nghttp3_qpack_decoder_del`
+to free up memory allocated for it.