hpack_varint_decoder.h | Explore in Territory

// 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.

// HpackVarintDecoder decodes HPACK variable length unsigned integers. In HPACK,
// these integers are used to identify static or dynamic table index entries, to
// specify string lengths, and to update the size limit of the dynamic table.
// In QPACK, in addition to these uses, these integers also identify streams.
//
// The caller will need to validate that the decoded value is in an acceptable
// range.
//
// For details of the encoding, see:
//        http://httpwg.org/specs/rfc7541.html#integer.representation
//
// HpackVarintDecoder supports decoding any integer that can be represented on
// uint64_t, thereby exceeding the requirements for QPACK: "QPACK
// implementations MUST be able to decode integers up to 62 bits long."  See
// https://quicwg.org/base-drafts/draft-ietf-quic-qpack.html#rfc.section.5.1.1
//
// This decoder supports at most 10 extension bytes (bytes following the prefix,
// also called continuation bytes).  An encoder is allowed to zero pad the
// encoded integer on the left, thereby increasing the number of extension
// bytes.  If an encoder uses so much padding that the number of extension bytes
// exceeds the limit, then this decoder signals an error.

#ifndef QUICHE_HTTP2_HPACK_VARINT_HPACK_VARINT_DECODER_H_
#define QUICHE_HTTP2_HPACK_VARINT_HPACK_VARINT_DECODER_H_

#include <cstdint>
#include <limits>
#include <string>

#include "quiche/http2/decoder/decode_buffer.h"
#include "quiche/http2/decoder/decode_status.h"
#include "quiche/common/platform/api/quiche_export.h"
#include "quiche/common/platform/api/quiche_logging.h"

namespace http2 {

// Sentinel value for |HpackVarintDecoder::offset_| to signify that decoding is
// completed.  Only used in debug builds.
#ifndef NDEBUG
const uint8_t kHpackVarintDecoderOffsetDone = …;
#endif

// Decodes an HPACK variable length unsigned integer, in a resumable fashion
// so it can handle running out of input in the DecodeBuffer. Call Start or
// StartExtended the first time (when decoding the byte that contains the
// prefix), then call Resume later if it is necessary to resume. When done,
// call value() to retrieve the decoded value.
//
// No constructor or destructor. Holds no resources, so destruction isn't
// needed. Start and StartExtended handles the initialization of member
// variables. This is necessary in order for HpackVarintDecoder to be part
// of a union.
class QUICHE_EXPORT HpackVarintDecoder { … };

}  // namespace http2

#endif  // QUICHE_HTTP2_HPACK_VARINT_HPACK_VARINT_DECODER_H_
chromium/net/third_party/quiche/src/quiche/http2/hpack/varint/hpack_varint_decoder.h
