QPACKDecoder.h

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/*
 *  Copyright (c) 2015-present, Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 *
 */
#pragma once

#include <folly/io/Cursor.h>
#include <folly/io/IOBuf.h>
#include <proxygen/lib/http/codec/compress/HeaderCodec.h>
#include <proxygen/lib/http/codec/compress/HPACKDecoderBase.h>
#include <proxygen/lib/http/codec/compress/HPACKDecodeBuffer.h>
#include <proxygen/lib/http/codec/compress/QPACKContext.h>
#include <folly/io/async/DestructorCheck.h>

namespace proxygen {

class QPACKDecoder : public HPACKDecoderBase,
                     public QPACKContext,
                     public folly::DestructorCheck {
 public:
  explicit QPACKDecoder(
    uint32_t tableSize=HPACK::kTableSize,
    uint32_t maxUncompressed=HeaderCodec::kMaxUncompressed)
      : HPACKDecoderBase(tableSize, maxUncompressed),
        QPACKContext(tableSize, false /* don't track references */) {}

  void decodeStreaming(
      uint64_t streamId,
      std::unique_ptr<folly::IOBuf> block,
      uint32_t totalBytes,
      HPACK::StreamingCallback* streamingCb);

  HPACK::DecodeError decodeEncoderStream(std::unique_ptr<folly::IOBuf> buf);

  std::unique_ptr<folly::IOBuf> encodeTableStateSync();

  std::unique_ptr<folly::IOBuf> encodeHeaderAck(uint64_t streamId) const;

  std::unique_ptr<folly::IOBuf> encodeCancelStream(uint64_t streamId);

  uint64_t getHolBlockCount() const {
    return holBlockCount_;
  }

  uint64_t getQueuedBytes() const {
    return queuedBytes_;
  }

  void setMaxBlocking(uint32_t maxBlocking) {
    maxBlocking_ = maxBlocking;
  }

 private:
  bool isValid(bool isStatic, uint32_t index, bool aboveBase);

  uint32_t handleBaseIndex(HPACKDecodeBuffer& dbuf);

  void decodeStreamingImpl(uint32_t largestReference,
                           uint32_t consumed,
                           HPACKDecodeBuffer& dbuf,
                           HPACK::StreamingCallback* streamingCb);

  uint32_t decodeHeaderQ(
      HPACKDecodeBuffer& dbuf,
      HPACK::StreamingCallback* streamingCb);

  uint32_t decodeIndexedHeaderQ(
      HPACKDecodeBuffer& dbuf,
      uint32_t prefixLength,
      bool aboveBase,
      HPACK::StreamingCallback* streamingCb,
      headers_t* emitted);

  uint32_t decodeLiteralHeaderQ(
      HPACKDecodeBuffer& dbuf,
      bool indexing,
      bool nameIndexed,
      uint8_t prefixLength,
      bool aboveBase,
      HPACK::StreamingCallback* streamingCb);

  void decodeEncoderStreamInstruction(HPACKDecodeBuffer& dbuf);

  void enqueueHeaderBlock(
      uint64_t streamId,
      uint32_t largestReference,
      uint32_t baseIndex,
      uint32_t consumed,
      std::unique_ptr<folly::IOBuf> block,
      size_t length,
      HPACK::StreamingCallback* streamingCb);

  struct PendingBlock {
    PendingBlock(
        uint64_t sid,
        uint32_t bi, uint32_t l, uint32_t cons,
        std::unique_ptr<folly::IOBuf> b,
        HPACK::StreamingCallback* c)
        : streamID(sid), baseIndex(bi), length(l), consumed(cons),
          block(std::move(b)), cb(c)
      {}
    uint64_t streamID;
    uint32_t baseIndex;
    uint32_t length;
    uint32_t consumed;
    std::unique_ptr<folly::IOBuf> block;
    HPACK::StreamingCallback* cb;
  };

  // Returns true if this object was destroyed by its callback.  Callers
  // should check the result and immediately return.
  bool decodeBlock(uint32_t largestReference, const PendingBlock& pending);

  void drainQueue();

  uint32_t maxBlocking_{HPACK::kDefaultBlocking};
  uint32_t baseIndex_{0};
  uint32_t lastAcked_{0};
  uint32_t holBlockCount_{0};
  uint64_t queuedBytes_{0};
  std::multimap<uint32_t, PendingBlock> queue_;

  // This holds the state of a partially decoded literal insert on the control
  // stream
  struct Partial {
    enum { NAME, VALUE } state{NAME};
    uint32_t consumed;
    HPACKHeader header;
  };
  Partial partial_;
  folly::IOBufQueue ingress_{folly::IOBufQueue::cacheChainLength()};
};

}