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1 // Copyright (c) 2012 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 #include "net/quic/quic_data_writer.h" | |
6 | |
7 #include <algorithm> | |
8 #include <limits> | |
9 #include <string> | |
10 | |
11 #include "base/basictypes.h" | |
12 #include "base/logging.h" | |
13 | |
14 using base::StringPiece; | |
15 using std::numeric_limits; | |
16 | |
17 namespace net { | |
18 | |
19 QuicDataWriter::QuicDataWriter(size_t size, char* buffer) | |
20 : buffer_(buffer), capacity_(size), length_(0) { | |
21 } | |
22 | |
23 QuicDataWriter::~QuicDataWriter() { | |
24 } | |
25 | |
26 char* QuicDataWriter::data() { | |
27 return buffer_; | |
28 } | |
29 | |
30 bool QuicDataWriter::WriteUInt8(uint8 value) { | |
31 return WriteBytes(&value, sizeof(value)); | |
32 } | |
33 | |
34 bool QuicDataWriter::WriteUInt16(uint16 value) { | |
35 return WriteBytes(&value, sizeof(value)); | |
36 } | |
37 | |
38 bool QuicDataWriter::WriteUInt32(uint32 value) { | |
39 return WriteBytes(&value, sizeof(value)); | |
40 } | |
41 | |
42 bool QuicDataWriter::WriteUInt48(uint64 value) { | |
43 uint16 hi = static_cast<uint16>(value >> 32); | |
44 uint32 lo = static_cast<uint32>(value); | |
45 return WriteUInt32(lo) && WriteUInt16(hi); | |
46 } | |
47 | |
48 bool QuicDataWriter::WriteUInt64(uint64 value) { | |
49 return WriteBytes(&value, sizeof(value)); | |
50 } | |
51 | |
52 bool QuicDataWriter::WriteUFloat16(uint64 value) { | |
53 uint16 result; | |
54 if (value < (GG_UINT64_C(1) << kUFloat16MantissaEffectiveBits)) { | |
55 // Fast path: either the value is denormalized, or has exponent zero. | |
56 // Both cases are represented by the value itself. | |
57 result = static_cast<uint16>(value); | |
58 } else if (value >= kUFloat16MaxValue) { | |
59 // Value is out of range; clamp it to the maximum representable. | |
60 result = numeric_limits<uint16>::max(); | |
61 } else { | |
62 // The highest bit is between position 13 and 42 (zero-based), which | |
63 // corresponds to exponent 1-30. In the output, mantissa is from 0 to 10, | |
64 // hidden bit is 11 and exponent is 11 to 15. Shift the highest bit to 11 | |
65 // and count the shifts. | |
66 uint16 exponent = 0; | |
67 for (uint16 offset = 16; offset > 0; offset /= 2) { | |
68 // Right-shift the value until the highest bit is in position 11. | |
69 // For offset of 16, 8, 4, 2 and 1 (binary search over 1-30), | |
70 // shift if the bit is at or above 11 + offset. | |
71 if (value >= (GG_UINT64_C(1) << (kUFloat16MantissaBits + offset))) { | |
72 exponent += offset; | |
73 value >>= offset; | |
74 } | |
75 } | |
76 | |
77 DCHECK_GE(exponent, 1); | |
78 DCHECK_LE(exponent, kUFloat16MaxExponent); | |
79 DCHECK_GE(value, GG_UINT64_C(1) << kUFloat16MantissaBits); | |
80 DCHECK_LT(value, GG_UINT64_C(1) << kUFloat16MantissaEffectiveBits); | |
81 | |
82 // Hidden bit (position 11) is set. We should remove it and increment the | |
83 // exponent. Equivalently, we just add it to the exponent. | |
84 // This hides the bit. | |
85 result = static_cast<uint16>(value + (exponent << kUFloat16MantissaBits)); | |
86 } | |
87 | |
88 return WriteBytes(&result, sizeof(result)); | |
89 } | |
90 | |
91 bool QuicDataWriter::WriteStringPiece16(StringPiece val) { | |
92 if (val.size() > numeric_limits<uint16>::max()) { | |
93 return false; | |
94 } | |
95 if (!WriteUInt16(static_cast<uint16>(val.size()))) { | |
96 return false; | |
97 } | |
98 return WriteBytes(val.data(), val.size()); | |
99 } | |
100 | |
101 bool QuicDataWriter::WriteIOVector(const IOVector& data) { | |
102 char *dest = BeginWrite(data.TotalBufferSize()); | |
103 if (!dest) { | |
104 return false; | |
105 } | |
106 for (size_t i = 0; i < data.Size(); ++i) { | |
107 WriteBytes(data.iovec()[i].iov_base, data.iovec()[i].iov_len); | |
108 } | |
109 | |
110 return true; | |
111 } | |
112 | |
113 char* QuicDataWriter::BeginWrite(size_t length) { | |
114 if (length_ > capacity_) { | |
115 return nullptr; | |
116 } | |
117 | |
118 if (capacity_ - length_ < length) { | |
119 return nullptr; | |
120 } | |
121 | |
122 #ifdef ARCH_CPU_64_BITS | |
123 DCHECK_LE(length, std::numeric_limits<uint32>::max()); | |
124 #endif | |
125 | |
126 return buffer_ + length_; | |
127 } | |
128 | |
129 bool QuicDataWriter::WriteBytes(const void* data, size_t data_len) { | |
130 char* dest = BeginWrite(data_len); | |
131 if (!dest) { | |
132 return false; | |
133 } | |
134 | |
135 memcpy(dest, data, data_len); | |
136 | |
137 length_ += data_len; | |
138 return true; | |
139 } | |
140 | |
141 bool QuicDataWriter::WriteRepeatedByte(uint8 byte, size_t count) { | |
142 char* dest = BeginWrite(count); | |
143 if (!dest) { | |
144 return false; | |
145 } | |
146 | |
147 memset(dest, byte, count); | |
148 | |
149 length_ += count; | |
150 return true; | |
151 } | |
152 | |
153 void QuicDataWriter::WritePadding() { | |
154 DCHECK_LE(length_, capacity_); | |
155 if (length_ > capacity_) { | |
156 return; | |
157 } | |
158 memset(buffer_ + length_, 0x00, capacity_ - length_); | |
159 length_ = capacity_; | |
160 } | |
161 | |
162 bool QuicDataWriter::WriteUInt8ToOffset(uint8 value, size_t offset) { | |
163 if (offset >= capacity_) { | |
164 LOG(DFATAL) << "offset: " << offset << " >= capacity: " << capacity_; | |
165 return false; | |
166 } | |
167 size_t latched_length = length_; | |
168 length_ = offset; | |
169 bool success = WriteUInt8(value); | |
170 DCHECK_LE(length_, latched_length); | |
171 length_ = latched_length; | |
172 return success; | |
173 } | |
174 | |
175 bool QuicDataWriter::WriteUInt32ToOffset(uint32 value, size_t offset) { | |
176 DCHECK_LT(offset, capacity_); | |
177 size_t latched_length = length_; | |
178 length_ = offset; | |
179 bool success = WriteUInt32(value); | |
180 DCHECK_LE(length_, latched_length); | |
181 length_ = latched_length; | |
182 return success; | |
183 } | |
184 | |
185 bool QuicDataWriter::WriteUInt48ToOffset(uint64 value, size_t offset) { | |
186 DCHECK_LT(offset, capacity_); | |
187 size_t latched_length = length_; | |
188 length_ = offset; | |
189 bool success = WriteUInt48(value); | |
190 DCHECK_LE(length_, latched_length); | |
191 length_ = latched_length; | |
192 return success; | |
193 } | |
194 | |
195 } // namespace net | |
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