Add new HTTP/2 and HPACK decoder in net/http2/.

net/http2/decoder/frame_decoder_state.h

Index: net/http2/decoder/frame_decoder_state.h
diff --git a/net/http2/decoder/frame_decoder_state.h b/net/http2/decoder/frame_decoder_state.h
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index 0000000000000000000000000000000000000000..ddf64d1f3a1b956216e06a6d3289bbcb1219d855
--- /dev/null
+++ b/net/http2/decoder/frame_decoder_state.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_HTTP2_DECODER_FRAME_DECODER_STATE_H_
+#define NET_HTTP2_DECODER_FRAME_DECODER_STATE_H_
+
+// FrameDecoderState provides state and behaviors in support of decoding
+// the common frame header and the payload of all frame types.
+// It is an input to all of the payload decoders.
+
+// TODO(jamessynge): Since FrameDecoderState has far more than state in it,
+// rename to FrameDecoderHelper, or similar.
+
+#include <stddef.h>
+
+#include "base/logging.h"
+#include "net/base/net_export.h"
+#include "net/http2/decoder/decode_buffer.h"
+#include "net/http2/decoder/decode_status.h"
+#include "net/http2/decoder/http2_frame_decoder_listener.h"
+#include "net/http2/decoder/http2_structure_decoder.h"
+#include "net/http2/http2_constants.h"
+#include "net/http2/http2_structures.h"
+
+namespace net {
+namespace test {
+class FrameDecoderStatePeer;
+}  // namespace test
+
+class NET_EXPORT_PRIVATE FrameDecoderState {
+ public:
+  FrameDecoderState() {}
+
+  // Sets the listener which the decoders should call as they decode HTTP/2
+  // frames. The listener can be changed at any time, which allows for replacing
+  // it with a no-op listener when an error is detected, either by the payload
+  // decoder (OnPaddingTooLong or OnFrameSizeError) or by the "real" listener.
+  // That in turn allows us to define Http2FrameDecoderListener such that all
+  // methods have return type void, with no direct way to indicate whether the
+  // decoder should stop, and to eliminate from the decoder all checks of the
+  // return value. Instead the listener/caller can simply replace the current
+  // listener with a no-op listener implementation.
+  // TODO(jamessynge): Make set_listener private as only Http2FrameDecoder
+  // and tests need to set it, so it doesn't need to be public.
+  void set_listener(Http2FrameDecoderListener* listener) {
+    listener_ = listener;
+  }
+  Http2FrameDecoderListener* listener() const { return listener_; }
+
+  // The most recently decoded frame header.
+  const Http2FrameHeader& frame_header() const { return frame_header_; }
+
+  // Decode a structure in the payload, adjusting remaining_payload_ to account
+  // for the consumed portion of the payload. Returns kDecodeDone when fully
+  // decoded, kDecodeError if it ran out of payload before decoding completed,
+  // and kDecodeInProgress if the decode buffer didn't have enough of the
+  // remaining payload.
+  template <class S>
+  DecodeStatus StartDecodingStructureInPayload(S* out, DecodeBuffer* db) {
+    DVLOG(2) << __func__ << "\n\tdb->Remaining=" << db->Remaining()
+             << "\n\tremaining_payload_=" << remaining_payload_
+             << "\n\tneed=" << S::EncodedSize();
+    DecodeStatus status =
+        structure_decoder_.Start(out, db, &remaining_payload_);
+    if (status != DecodeStatus::kDecodeError) {
+      return status;
+    }
+    DVLOG(2) << "StartDecodingStructureInPayload: detected frame size error";
+    return ReportFrameSizeError();
+  }
+
+  // Resume decoding of a structure that has been split across buffers,
+  // adjusting remaining_payload_ to account for the consumed portion of
+  // the payload. Returns values are as for StartDecodingStructureInPayload.
+  template <class S>
+  DecodeStatus ResumeDecodingStructureInPayload(S* out, DecodeBuffer* db) {
+    DVLOG(2) << __func__ << "\n\tdb->Remaining=" << db->Remaining()
+             << "\n\tremaining_payload_=" << remaining_payload_;
+    if (structure_decoder_.Resume(out, db, &remaining_payload_)) {
+      return DecodeStatus::kDecodeDone;
+    } else if (remaining_payload_ > 0) {
+      return DecodeStatus::kDecodeInProgress;
+    } else {
+      DVLOG(2) << "ResumeDecodingStructureInPayload: detected frame size error";
+      return ReportFrameSizeError();
+    }
+  }
+
+  // Initializes the two remaining* fields, which is needed if the frame's
+  // payload is split across buffers, or the decoder calls ReadPadLength or
+  // StartDecodingStructureInPayload, and of course the methods below which
+  // read those fields, as their names imply.
+  void InitializeRemainders() {
+    remaining_payload_ = frame_header().payload_length;
+    // Note that remaining_total_payload() relies on remaining_padding_ being
+    // zero for frames that have no padding.
+    remaining_padding_ = 0;
+  }
+
+  // Returns the number of bytes of the frame's payload that remain to be
+  // decoded, including any trailing padding. This method must only be called
+  // after the variables have been initialized, which in practice means once a
+  // payload decoder has called InitializeRemainders and/or ReadPadLength.
+  size_t remaining_total_payload() const {
+    DCHECK(IsPaddable() || remaining_padding_ == 0) << frame_header();
+    return remaining_payload_ + remaining_padding_;
+  }
+
+  // Returns the number of bytes of the frame's payload that remain to be
+  // decoded, excluding any trailing padding. This method must only be called
+  // after the variable has been initialized, which in practice means once a
+  // payload decoder has called InitializeRemainders; ReadPadLength will deduct
+  // the total number of padding bytes from remaining_payload_, including the
+  // size of the Pad Length field itself (1 byte).
+  size_t remaining_payload() const { return remaining_payload_; }
+
+  // Returns the number of bytes of the frame's payload that remain to be
+  // decoded, including any trailing padding. This method must only be called if
+  // the frame type allows padding, and after the variable has been initialized,
+  // which in practice means once a payload decoder has called
+  // InitializeRemainders and/or ReadPadLength.
+  size_t remaining_payload_and_padding() const {
+    DCHECK(IsPaddable()) << frame_header();
+    return remaining_payload_ + remaining_padding_;
+  }
+
+  // Returns the number of bytes of trailing padding after the payload that
+  // remain to be decoded. This method must only be called if the frame type
+  // allows padding, and after the variable has been initialized, which in
+  // practice means once a payload decoder has called InitializeRemainders,
+  // and isn't set to a non-zero value until ReadPadLength has been called.
+  uint32_t remaining_padding() const {
+    DCHECK(IsPaddable()) << frame_header();
+    return remaining_padding_;
+  }
+
+  // Returns the amount of trailing padding after the payload that remains to be
+  // decoded.
+  uint32_t remaining_padding_for_test() const { return remaining_padding_; }
+
+  // How many bytes of the remaining payload are in db?
+  size_t AvailablePayload(DecodeBuffer* db) const {
+    return db->MinLengthRemaining(remaining_payload_);
+  }
+
+  // How many bytes of the remaining payload and padding are in db?
+  // Call only for frames whose type is paddable.
+  size_t AvailablePayloadAndPadding(DecodeBuffer* db) const {
+    DCHECK(IsPaddable()) << frame_header();
+    return db->MinLengthRemaining(remaining_payload_ + remaining_padding_);
+  }
+
+  // How many bytes of the padding that have not yet been skipped are in db?
+  // Call only after remaining_padding_ has been set (for padded frames), or
+  // been cleared (for unpadded frames); and after all of the non-padding
+  // payload has been decoded.
+  size_t AvailablePadding(DecodeBuffer* db) const {
+    DCHECK(IsPaddable()) << frame_header();
+    DCHECK_EQ(remaining_payload_, 0u);
+    return db->MinLengthRemaining(remaining_padding_);
+  }
+
+  // Reduces remaining_payload_ by amount. To be called by a payload decoder
+  // after it has passed a variable length portion of the payload to the
+  // listener; remaining_payload_ will be automatically reduced when fixed
+  // size structures and padding, including the Pad Length field, are decoded.
+  void ConsumePayload(size_t amount) {
+    DCHECK_LE(amount, remaining_payload_);
+    remaining_payload_ -= amount;
+  }
+
+  // Reads the Pad Length field into remaining_padding_, and appropriately sets
+  // remaining_payload_. When present, the Pad Length field is always the first
+  // field in the payload, which this method relies on so that the caller need
+  // not set remaining_payload_ before calling this method.
+  // If report_pad_length is true, calls the listener's OnPadLength method when
+  // it decodes the Pad Length field.
+  // Returns kDecodeDone if the decode buffer was not empty (i.e. because the
+  // field is only a single byte long, it can always be decoded if the buffer is
+  // not empty).
+  // Returns kDecodeError if the buffer is empty because the frame has no
+  // payload (i.e. payload_length() == 0).
+  // Returns kDecodeInProgress if the buffer is empty but the frame has a
+  // payload.
+  DecodeStatus ReadPadLength(DecodeBuffer* db, bool report_pad_length);
+
+  // Skip the trailing padding bytes; only call once remaining_payload_==0.
+  // Returns true when the padding has been skipped.
+  // Does NOT check that the padding is all zeroes.
+  bool SkipPadding(DecodeBuffer* db);
+
+  // Calls the listener's OnFrameSizeError method and returns kDecodeError.
+  DecodeStatus ReportFrameSizeError();
+
+ private:
+  friend class Http2FrameDecoder;
+  friend class test::FrameDecoderStatePeer;
+
+  // Starts the decoding of a common frame header. Returns true if completed the
+  // decoding, false if the decode buffer didn't have enough data in it, in
+  // which case the decode buffer will have been drained and the caller should
+  // call ResumeDecodingFrameHeader when more data is available. This is called
+  // from Http2FrameDecoder, a friend class.
+  bool StartDecodingFrameHeader(DecodeBuffer* db) {
+    return structure_decoder_.Start(&frame_header_, db);
+  }
+
+  // Resumes decoding the common frame header after the preceding call to
+  // StartDecodingFrameHeader returned false, as did any subsequent calls to
+  // ResumeDecodingFrameHeader. This is called from Http2FrameDecoder,
+  // a friend class.
+  bool ResumeDecodingFrameHeader(DecodeBuffer* db) {
+    return structure_decoder_.Resume(&frame_header_, db);
+  }
+
+  // Clear any of the flags in the frame header that aren't set in valid_flags.
+  void RetainFlags(uint8_t valid_flags) {
+    frame_header_.RetainFlags(valid_flags);
+  }
+
+  // Clear all of the flags in the frame header; for use with frame types that
+  // don't define any flags, such as WINDOW_UPDATE.
+  void ClearFlags() { frame_header_.flags = Http2FrameFlag(); }
+
+  // Returns true if the type of frame being decoded can have padding.
+  bool IsPaddable() const {
+    return frame_header().type == Http2FrameType::DATA ||
+           frame_header().type == Http2FrameType::HEADERS ||
+           frame_header().type == Http2FrameType::PUSH_PROMISE;
+  }
+
+  Http2FrameDecoderListener* listener_ = nullptr;
+  Http2FrameHeader frame_header_;
+
+  // Number of bytes remaining to be decoded, if set; does not include the
+  // trailing padding once the length of padding has been determined.
+  // See ReadPadLength.
+  uint32_t remaining_payload_;
+
+  // The amount of trailing padding after the payload that remains to be
+  // decoded. See ReadPadLength.
+  uint32_t remaining_padding_;
+
+  // Generic decoder of structures, which takes care of buffering the needed
+  // bytes if the encoded structure is split across decode buffers.
+  Http2StructureDecoder structure_decoder_;
+};
+
+}  // namespace net
+
+#endif  // NET_HTTP2_DECODER_FRAME_DECODER_STATE_H_