1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef QUICHE_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_ 6 #define QUICHE_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_ 7 8 // HpackDecoderStringBuffer helps an HPACK decoder to avoid copies of a string 9 // literal (name or value) except when necessary (e.g. when split across two 10 // or more HPACK block fragments). 11 12 #include <stddef.h> 13 14 #include <ostream> 15 #include <string> 16 17 #include "absl/strings/string_view.h" 18 #include "quiche/http2/hpack/huffman/hpack_huffman_decoder.h" 19 #include "quiche/common/platform/api/quiche_export.h" 20 21 namespace http2 { 22 23 class QUICHE_EXPORT HpackDecoderStringBuffer { 24 public: 25 enum class State : uint8_t { RESET, COLLECTING, COMPLETE }; 26 enum class Backing : uint8_t { RESET, UNBUFFERED, BUFFERED, STATIC }; 27 28 HpackDecoderStringBuffer(); 29 ~HpackDecoderStringBuffer(); 30 31 HpackDecoderStringBuffer(const HpackDecoderStringBuffer&) = delete; 32 HpackDecoderStringBuffer& operator=(const HpackDecoderStringBuffer&) = delete; 33 34 void Reset(); 35 void Set(absl::string_view value, bool is_static); 36 37 // Note that for Huffman encoded strings the length of the string after 38 // decoding may be larger (expected), the same or even smaller; the latter 39 // are unlikely, but possible if the encoder makes odd choices. 40 void OnStart(bool huffman_encoded, size_t len); 41 bool OnData(const char* data, size_t len); 42 bool OnEnd(); 43 void BufferStringIfUnbuffered(); 44 bool IsBuffered() const; 45 size_t BufferedLength() const; 46 47 // Accessors for the completely collected string (i.e. Set or OnEnd has just 48 // been called, and no reset of the state has occurred). 49 50 // Returns a string_view pointing to the backing store for the string, 51 // either the internal buffer or the original transport buffer (e.g. for a 52 // literal value that wasn't Huffman encoded, and that wasn't split across 53 // transport buffers). 54 absl::string_view str() const; 55 56 // Same as str() if state_ is COMPLETE. Otherwise, returns empty string piece. 57 absl::string_view GetStringIfComplete() const; 58 59 // Returns the completely collected string by value, using std::move in an 60 // effort to avoid unnecessary copies. ReleaseString() must not be called 61 // unless the string has been buffered (to avoid forcing a potentially 62 // unnecessary copy). ReleaseString() also resets the instance so that it can 63 // be used to collect another string. 64 std::string ReleaseString(); 65 state_for_testing()66 State state_for_testing() const { return state_; } backing_for_testing()67 Backing backing_for_testing() const { return backing_; } 68 void OutputDebugStringTo(std::ostream& out) const; 69 70 private: 71 // Storage for the string being buffered, if buffering is necessary 72 // (e.g. if Huffman encoded, buffer_ is storage for the decoded string). 73 std::string buffer_; 74 75 // The string_view to be returned by HpackDecoderStringBuffer::str(). If 76 // a string has been collected, but not buffered, value_ points to that 77 // string. 78 absl::string_view value_; 79 80 // The decoder to use if the string is Huffman encoded. 81 HpackHuffmanDecoder decoder_; 82 83 // Count of bytes not yet passed to OnData. 84 size_t remaining_len_; 85 86 // Is the HPACK string Huffman encoded? 87 bool is_huffman_encoded_; 88 89 // State of the string decoding process. 90 State state_; 91 92 // Where is the string stored? 93 Backing backing_; 94 }; 95 96 QUICHE_EXPORT std::ostream& operator<<(std::ostream& out, 97 const HpackDecoderStringBuffer& v); 98 99 } // namespace http2 100 101 #endif // QUICHE_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_ 102