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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.
// HpackDecoderStringBuffer helps an HPACK decoder to avoid copies of a string
// literal (name or value) except when necessary (e.g. when split across two
// or more HPACK block fragments).
#include <stddef.h>
#include <ostream>
#include <string>
#include "absl/strings/string_view.h"
#include "http2/hpack/huffman/hpack_huffman_decoder.h"
#include "common/platform/api/quiche_export.h"
namespace http2 {
class QUICHE_EXPORT_PRIVATE HpackDecoderStringBuffer {
enum class State : uint8_t { RESET, COLLECTING, COMPLETE };
enum class Backing : uint8_t { RESET, UNBUFFERED, BUFFERED, STATIC };
HpackDecoderStringBuffer(const HpackDecoderStringBuffer&) = delete;
HpackDecoderStringBuffer& operator=(const HpackDecoderStringBuffer&) = delete;
void Reset();
void Set(absl::string_view value, bool is_static);
// Note that for Huffman encoded strings the length of the string after
// decoding may be larger (expected), the same or even smaller; the latter
// are unlikely, but possible if the encoder makes odd choices.
void OnStart(bool huffman_encoded, size_t len);
bool OnData(const char* data, size_t len);
bool OnEnd();
void BufferStringIfUnbuffered();
bool IsBuffered() const;
size_t BufferedLength() const;
// Accessors for the completely collected string (i.e. Set or OnEnd has just
// been called, and no reset of the state has occurred).
// Returns a string_view pointing to the backing store for the string,
// either the internal buffer or the original transport buffer (e.g. for a
// literal value that wasn't Huffman encoded, and that wasn't split across
// transport buffers).
absl::string_view str() const;
// Same as str() if state_ is COMPLETE. Otherwise, returns empty string piece.
absl::string_view GetStringIfComplete() const;
// Returns the completely collected string by value, using std::move in an
// effort to avoid unnecessary copies. ReleaseString() must not be called
// unless the string has been buffered (to avoid forcing a potentially
// unnecessary copy). ReleaseString() also resets the instance so that it can
// be used to collect another string.
std::string ReleaseString();
State state_for_testing() const { return state_; }
Backing backing_for_testing() const { return backing_; }
void OutputDebugStringTo(std::ostream& out) const;
// Storage for the string being buffered, if buffering is necessary
// (e.g. if Huffman encoded, buffer_ is storage for the decoded string).
std::string buffer_;
// The string_view to be returned by HpackDecoderStringBuffer::str(). If
// a string has been collected, but not buffered, value_ points to that
// string.
absl::string_view value_;
// The decoder to use if the string is Huffman encoded.
HpackHuffmanDecoder decoder_;
// Count of bytes not yet passed to OnData.
size_t remaining_len_;
// Is the HPACK string Huffman encoded?
bool is_huffman_encoded_;
// State of the string decoding process.
State state_;
// Where is the string stored?
Backing backing_;
QUICHE_EXPORT_PRIVATE std::ostream& operator<<(
std::ostream& out,
const HpackDecoderStringBuffer& v);
} // namespace http2