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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "net/quic/core/quic_data_writer.h" | 5 #include "net/quic/core/quic_data_writer.h" |
6 | 6 |
7 #include <stdint.h> | 7 #include <stdint.h> |
8 #include <algorithm> | 8 #include <algorithm> |
9 #include <limits> | 9 #include <limits> |
10 | 10 |
11 using base::StringPiece; | 11 using base::StringPiece; |
12 using std::numeric_limits; | |
13 | 12 |
14 namespace net { | 13 namespace net { |
15 | 14 |
16 QuicDataWriter::QuicDataWriter(size_t size, char* buffer) | 15 QuicDataWriter::QuicDataWriter(size_t size, char* buffer) |
17 : buffer_(buffer), capacity_(size), length_(0) {} | 16 : buffer_(buffer), capacity_(size), length_(0) {} |
18 | 17 |
19 QuicDataWriter::~QuicDataWriter() {} | 18 QuicDataWriter::~QuicDataWriter() {} |
20 | 19 |
21 char* QuicDataWriter::data() { | 20 char* QuicDataWriter::data() { |
22 return buffer_; | 21 return buffer_; |
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45 } | 44 } |
46 | 45 |
47 bool QuicDataWriter::WriteUFloat16(uint64_t value) { | 46 bool QuicDataWriter::WriteUFloat16(uint64_t value) { |
48 uint16_t result; | 47 uint16_t result; |
49 if (value < (UINT64_C(1) << kUFloat16MantissaEffectiveBits)) { | 48 if (value < (UINT64_C(1) << kUFloat16MantissaEffectiveBits)) { |
50 // Fast path: either the value is denormalized, or has exponent zero. | 49 // Fast path: either the value is denormalized, or has exponent zero. |
51 // Both cases are represented by the value itself. | 50 // Both cases are represented by the value itself. |
52 result = static_cast<uint16_t>(value); | 51 result = static_cast<uint16_t>(value); |
53 } else if (value >= kUFloat16MaxValue) { | 52 } else if (value >= kUFloat16MaxValue) { |
54 // Value is out of range; clamp it to the maximum representable. | 53 // Value is out of range; clamp it to the maximum representable. |
55 result = numeric_limits<uint16_t>::max(); | 54 result = std::numeric_limits<uint16_t>::max(); |
56 } else { | 55 } else { |
57 // The highest bit is between position 13 and 42 (zero-based), which | 56 // The highest bit is between position 13 and 42 (zero-based), which |
58 // corresponds to exponent 1-30. In the output, mantissa is from 0 to 10, | 57 // corresponds to exponent 1-30. In the output, mantissa is from 0 to 10, |
59 // hidden bit is 11 and exponent is 11 to 15. Shift the highest bit to 11 | 58 // hidden bit is 11 and exponent is 11 to 15. Shift the highest bit to 11 |
60 // and count the shifts. | 59 // and count the shifts. |
61 uint16_t exponent = 0; | 60 uint16_t exponent = 0; |
62 for (uint16_t offset = 16; offset > 0; offset /= 2) { | 61 for (uint16_t offset = 16; offset > 0; offset /= 2) { |
63 // Right-shift the value until the highest bit is in position 11. | 62 // Right-shift the value until the highest bit is in position 11. |
64 // For offset of 16, 8, 4, 2 and 1 (binary search over 1-30), | 63 // For offset of 16, 8, 4, 2 and 1 (binary search over 1-30), |
65 // shift if the bit is at or above 11 + offset. | 64 // shift if the bit is at or above 11 + offset. |
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77 // Hidden bit (position 11) is set. We should remove it and increment the | 76 // Hidden bit (position 11) is set. We should remove it and increment the |
78 // exponent. Equivalently, we just add it to the exponent. | 77 // exponent. Equivalently, we just add it to the exponent. |
79 // This hides the bit. | 78 // This hides the bit. |
80 result = static_cast<uint16_t>(value + (exponent << kUFloat16MantissaBits)); | 79 result = static_cast<uint16_t>(value + (exponent << kUFloat16MantissaBits)); |
81 } | 80 } |
82 | 81 |
83 return WriteBytes(&result, sizeof(result)); | 82 return WriteBytes(&result, sizeof(result)); |
84 } | 83 } |
85 | 84 |
86 bool QuicDataWriter::WriteStringPiece16(StringPiece val) { | 85 bool QuicDataWriter::WriteStringPiece16(StringPiece val) { |
87 if (val.size() > numeric_limits<uint16_t>::max()) { | 86 if (val.size() > std::numeric_limits<uint16_t>::max()) { |
88 return false; | 87 return false; |
89 } | 88 } |
90 if (!WriteUInt16(static_cast<uint16_t>(val.size()))) { | 89 if (!WriteUInt16(static_cast<uint16_t>(val.size()))) { |
91 return false; | 90 return false; |
92 } | 91 } |
93 return WriteBytes(val.data(), val.size()); | 92 return WriteBytes(val.data(), val.size()); |
94 } | 93 } |
95 | 94 |
96 char* QuicDataWriter::BeginWrite(size_t length) { | 95 char* QuicDataWriter::BeginWrite(size_t length) { |
97 if (length_ > capacity_) { | 96 if (length_ > capacity_) { |
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136 void QuicDataWriter::WritePadding() { | 135 void QuicDataWriter::WritePadding() { |
137 DCHECK_LE(length_, capacity_); | 136 DCHECK_LE(length_, capacity_); |
138 if (length_ > capacity_) { | 137 if (length_ > capacity_) { |
139 return; | 138 return; |
140 } | 139 } |
141 memset(buffer_ + length_, 0x00, capacity_ - length_); | 140 memset(buffer_ + length_, 0x00, capacity_ - length_); |
142 length_ = capacity_; | 141 length_ = capacity_; |
143 } | 142 } |
144 | 143 |
145 } // namespace net | 144 } // namespace net |
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