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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 QUICHE_HTTP2_DECODER_HTTP2_STRUCTURE_DECODER_H_
#define QUICHE_HTTP2_DECODER_HTTP2_STRUCTURE_DECODER_H_
// Http2StructureDecoder is a class for decoding the fixed size structures in
// the HTTP/2 spec, defined in net/third_party/quiche/src/http2/http2_structures.h. This class
// is in aid of deciding whether to keep the SlowDecode methods which I
// (jamessynge) now think may not be worth their complexity. In particular,
// if most transport buffers are large, so it is rare that a structure is
// split across buffer boundaries, than the cost of buffering upon
// those rare occurrences is small, which then simplifies the callers.
#include <cstdint>
#include "net/third_party/quiche/src/http2/decoder/decode_buffer.h"
#include "net/third_party/quiche/src/http2/decoder/decode_http2_structures.h"
#include "net/third_party/quiche/src/http2/decoder/decode_status.h"
#include "net/third_party/quiche/src/http2/http2_structures.h"
#include "net/third_party/quiche/src/http2/platform/api/http2_logging.h"
#include "net/third_party/quiche/src/common/platform/api/quiche_export.h"
namespace http2 {
namespace test {
class Http2StructureDecoderPeer;
} // namespace test
class QUICHE_EXPORT_PRIVATE Http2StructureDecoder {
public:
// The caller needs to keep track of whether to call Start or Resume.
//
// Start has an optimization for the case where the DecodeBuffer holds the
// entire encoded structure; in that case it decodes into *out and returns
// true, and does NOT touch the data members of the Http2StructureDecoder
// instance because the caller won't be calling Resume later.
//
// However, if the DecodeBuffer is too small to hold the entire encoded
// structure, Start copies the available bytes into the Http2StructureDecoder
// instance, and returns false to indicate that it has not been able to
// complete the decoding.
//
template <class S>
bool Start(S* out, DecodeBuffer* db) {
static_assert(S::EncodedSize() <= sizeof buffer_, "buffer_ is too small");
HTTP2_DVLOG(2) << __func__ << "@" << this
<< ": db->Remaining=" << db->Remaining()
<< "; EncodedSize=" << S::EncodedSize();
if (db->Remaining() >= S::EncodedSize()) {
DoDecode(out, db);
return true;
}
IncompleteStart(db, S::EncodedSize());
return false;
}
template <class S>
bool Resume(S* out, DecodeBuffer* db) {
HTTP2_DVLOG(2) << __func__ << "@" << this << ": offset_=" << offset_
<< "; db->Remaining=" << db->Remaining();
if (ResumeFillingBuffer(db, S::EncodedSize())) {
// We have the whole thing now.
HTTP2_DVLOG(2) << __func__ << "@" << this << " offset_=" << offset_
<< " Ready to decode from buffer_.";
DecodeBuffer buffer_db(buffer_, S::EncodedSize());
DoDecode(out, &buffer_db);
return true;
}
DCHECK_LT(offset_, S::EncodedSize());
return false;
}
// A second pair of Start and Resume, where the caller has a variable,
// |remaining_payload| that is both tested for sufficiency and updated
// during decoding. Note that the decode buffer may extend beyond the
// remaining payload because the buffer may include padding.
template <class S>
DecodeStatus Start(S* out, DecodeBuffer* db, uint32_t* remaining_payload) {
static_assert(S::EncodedSize() <= sizeof buffer_, "buffer_ is too small");
HTTP2_DVLOG(2) << __func__ << "@" << this
<< ": *remaining_payload=" << *remaining_payload
<< "; db->Remaining=" << db->Remaining()
<< "; EncodedSize=" << S::EncodedSize();
if (db->MinLengthRemaining(*remaining_payload) >= S::EncodedSize()) {
DoDecode(out, db);
*remaining_payload -= S::EncodedSize();
return DecodeStatus::kDecodeDone;
}
return IncompleteStart(db, remaining_payload, S::EncodedSize());
}
template <class S>
bool Resume(S* out, DecodeBuffer* db, uint32_t* remaining_payload) {
HTTP2_DVLOG(3) << __func__ << "@" << this << ": offset_=" << offset_
<< "; *remaining_payload=" << *remaining_payload
<< "; db->Remaining=" << db->Remaining()
<< "; EncodedSize=" << S::EncodedSize();
if (ResumeFillingBuffer(db, remaining_payload, S::EncodedSize())) {
// We have the whole thing now.
HTTP2_DVLOG(2) << __func__ << "@" << this << ": offset_=" << offset_
<< "; Ready to decode from buffer_.";
DecodeBuffer buffer_db(buffer_, S::EncodedSize());
DoDecode(out, &buffer_db);
return true;
}
DCHECK_LT(offset_, S::EncodedSize());
return false;
}
uint32_t offset() const { return offset_; }
private:
friend class test::Http2StructureDecoderPeer;
uint32_t IncompleteStart(DecodeBuffer* db, uint32_t target_size);
DecodeStatus IncompleteStart(DecodeBuffer* db,
uint32_t* remaining_payload,
uint32_t target_size);
bool ResumeFillingBuffer(DecodeBuffer* db, uint32_t target_size);
bool ResumeFillingBuffer(DecodeBuffer* db,
uint32_t* remaining_payload,
uint32_t target_size);
uint32_t offset_;
char buffer_[Http2FrameHeader::EncodedSize()];
};
} // namespace http2
#endif // QUICHE_HTTP2_DECODER_HTTP2_STRUCTURE_DECODER_H_