| OLD | NEW |
| (Empty) |
| 1 // Copyright 2013 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 NET_QUIC_IOVECTOR_H_ | |
| 6 #define NET_QUIC_IOVECTOR_H_ | |
| 7 | |
| 8 #include <stddef.h> | |
| 9 #include <algorithm> | |
| 10 #include <vector> | |
| 11 | |
| 12 #include "base/basictypes.h" | |
| 13 #include "base/logging.h" | |
| 14 #include "net/base/iovec.h" | |
| 15 #include "net/base/net_export.h" | |
| 16 | |
| 17 namespace net { | |
| 18 | |
| 19 // Calculate the total number of bytes in an array of iovec structures. | |
| 20 inline size_t TotalIovecLength(const struct iovec* iov, size_t iovcnt) { | |
| 21 size_t length = 0; | |
| 22 if (iov != NULL) { | |
| 23 for (size_t i = 0; i < iovcnt; ++i) { | |
| 24 length += iov[i].iov_len; | |
| 25 } | |
| 26 } | |
| 27 return length; | |
| 28 } | |
| 29 | |
| 30 // IOVector is a helper class that makes it easier to work with POSIX vector I/O | |
| 31 // struct. It is a thin wrapper by design and thus has no virtual functions and | |
| 32 // all inlined methods. This class makes no assumptions about the ordering of | |
| 33 // the pointer values of the blocks appended, it simply counts bytes when asked | |
| 34 // to consume bytes. | |
| 35 // | |
| 36 // IOVector is a bookkeeping object that collects a description of buffers to | |
| 37 // be read or written together and in order. It does not take ownership of the | |
| 38 // blocks appended. | |
| 39 // | |
| 40 // Because it is used for scatter-gather operations, the order in which the | |
| 41 // buffer blocks are added to the IOVector is important to the client. The | |
| 42 // intended usage pattern is: | |
| 43 // | |
| 44 // iovector.Append(p0, len0); | |
| 45 // ... | |
| 46 // iovector.Append(pn, lenn); | |
| 47 // int bytes_written = writev(fd, iovector.iovec(), iovector.Size()); | |
| 48 // if (bytes_written > 0) | |
| 49 // iovector.Consume(bytes_written); | |
| 50 // | |
| 51 // The sequence is the same for readv, except that Consume() in this case is | |
| 52 // used to change the IOVector to only keep track of description of blocks of | |
| 53 // memory not yet written to. | |
| 54 // | |
| 55 // IOVector does not have any method to change the iovec entries that it | |
| 56 // accumulates. This is due to the block merging nature of Append(): we'd like | |
| 57 // to avoid accidentally change an entry that is assembled by two or more | |
| 58 // Append()'s by simply an index access. | |
| 59 // | |
| 60 class NET_EXPORT_PRIVATE IOVector { | |
| 61 public: | |
| 62 // Provide a default constructor so it'll never be inhibited by adding other | |
| 63 // constructors. | |
| 64 IOVector(); | |
| 65 ~IOVector(); | |
| 66 | |
| 67 // Provides a way to convert system call-like iovec representation to | |
| 68 // IOVector. | |
| 69 void AppendIovec(const struct iovec* iov, size_t iovcnt) { | |
| 70 for (size_t i = 0; i < iovcnt; ++i) | |
| 71 Append(static_cast<char*>(iov[i].iov_base), iov[i].iov_len); | |
| 72 } | |
| 73 | |
| 74 // Appends at most max_bytes from iovec to the IOVector. | |
| 75 size_t AppendIovecAtMostBytes(const struct iovec* iov, | |
| 76 size_t iovcnt, | |
| 77 size_t max_bytes) { | |
| 78 size_t bytes_appended = 0; | |
| 79 for (size_t i = 0; i < iovcnt && max_bytes > 0; ++i) { | |
| 80 const size_t length = std::min(max_bytes, iov[i].iov_len); | |
| 81 Append(static_cast<char*>(iov[i].iov_base), length); | |
| 82 max_bytes -= length; | |
| 83 bytes_appended += length; | |
| 84 } | |
| 85 return bytes_appended; | |
| 86 } | |
| 87 | |
| 88 // Append another block to the IOVector. Since IOVector can be used for read | |
| 89 // and write, it always takes char*. Clients that writes will need to cast | |
| 90 // away the constant of the pointer before appending a block. | |
| 91 void Append(char* buffer, size_t length) { | |
| 92 if (buffer != NULL && length > 0) { | |
| 93 if (iovec_.size() > 0) { | |
| 94 struct iovec& last = iovec_.back(); | |
| 95 // If the new block is contiguous with the last block, just extend. | |
| 96 if (static_cast<char*>(last.iov_base) + last.iov_len == buffer) { | |
| 97 last.iov_len += length; | |
| 98 return; | |
| 99 } | |
| 100 } | |
| 101 struct iovec tmp = {buffer, length}; | |
| 102 iovec_.push_back(tmp); | |
| 103 } | |
| 104 } | |
| 105 | |
| 106 // Same as Append, but doesn't do the tail merge optimization. | |
| 107 // Intended for testing. | |
| 108 void AppendNoCoalesce(char* buffer, size_t length) { | |
| 109 if (buffer != NULL && length > 0) { | |
| 110 struct iovec tmp = {buffer, length}; | |
| 111 iovec_.push_back(tmp); | |
| 112 } | |
| 113 } | |
| 114 | |
| 115 // Remove a number of bytes from the beginning of the IOVector. Since vector | |
| 116 // I/O operations always occur at the beginning of the block list, a method | |
| 117 // to remove bytes at the end is not provided. | |
| 118 // It returns the number of bytes actually consumed (it'll only be smaller | |
| 119 // than the requested number if the IOVector contains less data). | |
| 120 size_t Consume(size_t length) { | |
| 121 if (length == 0) return 0; | |
| 122 | |
| 123 size_t bytes_to_consume = length; | |
| 124 std::vector<struct iovec>::iterator iter = iovec_.begin(); | |
| 125 std::vector<struct iovec>::iterator end = iovec_.end(); | |
| 126 for (; iter < end && bytes_to_consume >= iter->iov_len; ++iter) { | |
| 127 bytes_to_consume -= iter->iov_len; | |
| 128 } | |
| 129 iovec_.erase(iovec_.begin(), iter); | |
| 130 if (iovec_.size() > 0 && bytes_to_consume != 0) { | |
| 131 iovec_[0].iov_base = | |
| 132 static_cast<char*>(iovec_[0].iov_base) + bytes_to_consume; | |
| 133 iovec_[0].iov_len -= bytes_to_consume; | |
| 134 return length; | |
| 135 } | |
| 136 if (iovec_.size() == 0 && bytes_to_consume > 0) { | |
| 137 LOG(DFATAL) << "Attempting to consume " << bytes_to_consume | |
| 138 << " non-existent bytes."; | |
| 139 } | |
| 140 // At this point bytes_to_consume is the number of wanted bytes left over | |
| 141 // after walking through all the iovec entries. | |
| 142 return length - bytes_to_consume; | |
| 143 } | |
| 144 | |
| 145 // TODO(joechan): If capacity is large, swap out for a blank one. | |
| 146 // Clears the IOVector object to contain no blocks. | |
| 147 void Clear() { iovec_.clear(); } | |
| 148 | |
| 149 // Swap the guts of two IOVector. | |
| 150 void Swap(IOVector* other) { iovec_.swap(other->iovec_); } | |
| 151 | |
| 152 // Returns the number of valid blocks in the IOVector (not the number of | |
| 153 // bytes). | |
| 154 size_t Size() const { return iovec_.size(); } | |
| 155 | |
| 156 // Returns the total storage used by the IOVector in number of blocks (not | |
| 157 // the number of bytes). | |
| 158 size_t Capacity() const { return iovec_.capacity(); } | |
| 159 | |
| 160 // Returns true if there are no blocks in the IOVector. | |
| 161 bool Empty() const { return iovec_.empty(); } | |
| 162 | |
| 163 // Returns the pointer to the beginning of the iovec to be used for vector | |
| 164 // I/O operations. If the IOVector has no blocks appened, this function | |
| 165 // returns NULL. | |
| 166 struct iovec* iovec() { return !Empty() ? &iovec_[0] : NULL; } | |
| 167 | |
| 168 // Const version. | |
| 169 const struct iovec* iovec() const { return !Empty() ? &iovec_[0] : NULL; } | |
| 170 | |
| 171 // Returns a pointer to one past the last byte of the last block. If the | |
| 172 // IOVector is empty, NULL is returned. | |
| 173 const char* LastBlockEnd() const { | |
| 174 return iovec_.size() > 0 ? | |
| 175 static_cast<char *>(iovec_.back().iov_base) + iovec_.back().iov_len : | |
| 176 NULL; | |
| 177 } | |
| 178 | |
| 179 // Returns the total number of bytes in the IOVector. | |
| 180 size_t TotalBufferSize() const { return TotalIovecLength(iovec(), Size()); } | |
| 181 | |
| 182 void Resize(size_t count) { | |
| 183 iovec_.resize(count); | |
| 184 } | |
| 185 | |
| 186 private: | |
| 187 std::vector<struct iovec> iovec_; | |
| 188 | |
| 189 // IOVector has value-semantics; copy and assignment are allowed. | |
| 190 // This class does not explicitly define copy/move constructors or the | |
| 191 // assignment operator to preserve compiler-generated copy/move constructors | |
| 192 // and assignment operators. Note that since IOVector does not own the | |
| 193 // actual buffers that the struct iovecs point to, copies and assignments | |
| 194 // result in a shallow copy of the buffers; resulting IOVectors will point | |
| 195 // to the same copy of the underlying data. | |
| 196 }; | |
| 197 | |
| 198 } // namespace net | |
| 199 | |
| 200 #endif // NET_QUIC_IOVECTOR_H_ | |
| OLD | NEW |