xref: /aosp_15_r20/external/cronet/net/third_party/quiche/src/quiche/common/quiche_data_writer.h (revision 6777b5387eb2ff775bb5750e3f5d96f37fb7352b)
1 // Copyright (c) 2020 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_COMMON_QUICHE_DATA_WRITER_H_
6 #define QUICHE_COMMON_QUICHE_DATA_WRITER_H_
7 
8 #include <cstddef>
9 #include <cstdint>
10 #include <cstring>
11 #include <limits>
12 
13 #include "absl/strings/string_view.h"
14 #include "quiche/common/platform/api/quiche_export.h"
15 #include "quiche/common/platform/api/quiche_logging.h"
16 #include "quiche/common/quiche_endian.h"
17 
18 namespace quiche {
19 
20 // Maximum value that can be properly encoded using RFC 9000 62-bit Variable
21 // Length Integer encoding.
22 enum : uint64_t {
23   kVarInt62MaxValue = UINT64_C(0x3fffffffffffffff),
24 };
25 
26 // RFC 9000 62-bit Variable Length Integer encoding masks
27 // If a uint64_t anded with a mask is not 0 then the value is encoded
28 // using that length (or is too big, in the case of kVarInt62ErrorMask).
29 // Values must be checked in order (error, 8-, 4-, and then 2- bytes)
30 // and if none are non-0, the value is encoded in 1 byte.
31 enum : uint64_t {
32   kVarInt62ErrorMask = UINT64_C(0xc000000000000000),
33   kVarInt62Mask8Bytes = UINT64_C(0x3fffffffc0000000),
34   kVarInt62Mask4Bytes = UINT64_C(0x000000003fffc000),
35   kVarInt62Mask2Bytes = UINT64_C(0x0000000000003fc0),
36 };
37 
38 // This class provides facilities for packing binary data.
39 //
40 // The QuicheDataWriter supports appending primitive values (int, string, etc)
41 // to a frame instance.  The internal memory buffer is exposed as the "data"
42 // of the QuicheDataWriter.
43 class QUICHE_EXPORT QuicheDataWriter {
44  public:
45   // Creates a QuicheDataWriter where |buffer| is not owned
46   // using NETWORK_BYTE_ORDER endianness.
47   QuicheDataWriter(size_t size, char* buffer);
48   // Creates a QuicheDataWriter where |buffer| is not owned
49   // using the specified endianness.
50   QuicheDataWriter(size_t size, char* buffer, quiche::Endianness endianness);
51   QuicheDataWriter(const QuicheDataWriter&) = delete;
52   QuicheDataWriter& operator=(const QuicheDataWriter&) = delete;
53 
54   ~QuicheDataWriter();
55 
56   // Returns the size of the QuicheDataWriter's data.
length()57   size_t length() const { return length_; }
58 
59   // Retrieves the buffer from the QuicheDataWriter without changing ownership.
60   char* data();
61 
62   // Methods for adding to the payload.  These values are appended to the end
63   // of the QuicheDataWriter payload.
64 
65   // Writes 8/16/32/64-bit unsigned integers.
66   bool WriteUInt8(uint8_t value);
67   bool WriteUInt16(uint16_t value);
68   bool WriteUInt32(uint32_t value);
69   bool WriteUInt64(uint64_t value);
70 
71   // Writes least significant |num_bytes| of a 64-bit unsigned integer in the
72   // correct byte order.
73   bool WriteBytesToUInt64(size_t num_bytes, uint64_t value);
74 
75   bool WriteStringPiece(absl::string_view val);
76   bool WriteStringPiece16(absl::string_view val);
77   bool WriteBytes(const void* data, size_t data_len);
78   bool WriteRepeatedByte(uint8_t byte, size_t count);
79   // Fills the remaining buffer with null characters.
80   void WritePadding();
81   // Write padding of |count| bytes.
82   bool WritePaddingBytes(size_t count);
83 
84   // Write tag as a 32-bit unsigned integer to the payload. As tags are already
85   // converted to big endian (e.g., CHLO is 'C','H','L','O') in memory by TAG or
86   // MakeQuicTag and tags are written in byte order, so tags on the wire are
87   // in big endian.
88   bool WriteTag(uint32_t tag);
89 
90   // Write a 62-bit unsigned integer using RFC 9000 Variable Length Integer
91   // encoding. Returns false if the value is out of range or if there is no room
92   // in the buffer.
93   bool WriteVarInt62(uint64_t value);
94 
95   // Same as WriteVarInt62(uint64_t), but forces an encoding size to write to.
96   // This is not as optimized as WriteVarInt62(uint64_t). Returns false if the
97   // value does not fit in the specified write_length or if there is no room in
98   // the buffer.
99   bool WriteVarInt62WithForcedLength(
100       uint64_t value, QuicheVariableLengthIntegerLength write_length);
101 
102   // Writes a string piece as a consecutive length/content pair. The
103   // length uses RFC 9000 Variable Length Integer encoding.
104   bool WriteStringPieceVarInt62(const absl::string_view& string_piece);
105 
106   // Utility function to return the number of bytes needed to encode
107   // the given value using IETF VarInt62 encoding. Returns the number
108   // of bytes required to encode the given integer or 0 if the value
109   // is too large to encode.
110   static QuicheVariableLengthIntegerLength GetVarInt62Len(uint64_t value);
111 
112   // Advance the writer's position for writing by |length| bytes without writing
113   // anything. This method only makes sense to be used on a buffer that has
114   // already been written to (and is having certain parts rewritten).
115   bool Seek(size_t length);
116 
capacity()117   size_t capacity() const { return capacity_; }
118 
remaining()119   size_t remaining() const { return capacity_ - length_; }
120 
121   std::string DebugString() const;
122 
123  protected:
124   // Returns the location that the data should be written at, or nullptr if
125   // there is not enough room. Call EndWrite with the returned offset and the
126   // given length to pad out for the next write.
127   char* BeginWrite(size_t length);
128 
endianness()129   quiche::Endianness endianness() const { return endianness_; }
130 
buffer()131   char* buffer() const { return buffer_; }
132 
IncreaseLength(size_t delta)133   void IncreaseLength(size_t delta) {
134     QUICHE_DCHECK_LE(length_, std::numeric_limits<size_t>::max() - delta);
135     QUICHE_DCHECK_LE(length_, capacity_ - delta);
136     length_ += delta;
137   }
138 
139  private:
140   // TODO(fkastenholz, b/73004262) change buffer_, et al, to be uint8_t, not
141   // char.
142   char* buffer_;
143   size_t capacity_;  // Allocation size of payload (or -1 if buffer is const).
144   size_t length_;    // Current length of the buffer.
145 
146   // The endianness to write integers and floating numbers.
147   quiche::Endianness endianness_;
148 };
149 
150 }  // namespace quiche
151 
152 #endif  // QUICHE_COMMON_QUICHE_DATA_WRITER_H_
153