1 // Protocol Buffers - Google's data interchange format 2 // Copyright 2008 Google Inc. All rights reserved. 3 // https://developers.google.com/protocol-buffers/ 4 // 5 // Redistribution and use in source and binary forms, with or without 6 // modification, are permitted provided that the following conditions are 7 // met: 8 // 9 // * Redistributions of source code must retain the above copyright 10 // notice, this list of conditions and the following disclaimer. 11 // * Redistributions in binary form must reproduce the above 12 // copyright notice, this list of conditions and the following disclaimer 13 // in the documentation and/or other materials provided with the 14 // distribution. 15 // * Neither the name of Google Inc. nor the names of its 16 // contributors may be used to endorse or promote products derived from 17 // this software without specific prior written permission. 18 // 19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31 // Authors: wink@google.com (Wink Saville), 32 // kenton@google.com (Kenton Varda) 33 // Based on original Protocol Buffers design by 34 // Sanjay Ghemawat, Jeff Dean, and others. 35 // 36 // Defines MessageLite, the abstract interface implemented by all (lite 37 // and non-lite) protocol message objects. 38 39 #ifndef GOOGLE_PROTOBUF_MESSAGE_LITE_H__ 40 #define GOOGLE_PROTOBUF_MESSAGE_LITE_H__ 41 42 #include <google/protobuf/stubs/common.h> 43 44 45 namespace google { 46 namespace protobuf { 47 class Arena; 48 namespace io { 49 class CodedInputStream; 50 class CodedOutputStream; 51 class ZeroCopyInputStream; 52 class ZeroCopyOutputStream; 53 } 54 55 // Interface to light weight protocol messages. 56 // 57 // This interface is implemented by all protocol message objects. Non-lite 58 // messages additionally implement the Message interface, which is a 59 // subclass of MessageLite. Use MessageLite instead when you only need 60 // the subset of features which it supports -- namely, nothing that uses 61 // descriptors or reflection. You can instruct the protocol compiler 62 // to generate classes which implement only MessageLite, not the full 63 // Message interface, by adding the following line to the .proto file: 64 // 65 // option optimize_for = LITE_RUNTIME; 66 // 67 // This is particularly useful on resource-constrained systems where 68 // the full protocol buffers runtime library is too big. 69 // 70 // Note that on non-constrained systems (e.g. servers) when you need 71 // to link in lots of protocol definitions, a better way to reduce 72 // total code footprint is to use optimize_for = CODE_SIZE. This 73 // will make the generated code smaller while still supporting all the 74 // same features (at the expense of speed). optimize_for = LITE_RUNTIME 75 // is best when you only have a small number of message types linked 76 // into your binary, in which case the size of the protocol buffers 77 // runtime itself is the biggest problem. 78 class LIBPROTOBUF_EXPORT MessageLite { 79 public: MessageLite()80 inline MessageLite() {} 81 virtual ~MessageLite(); 82 83 // Basic Operations ------------------------------------------------ 84 85 // Get the name of this message type, e.g. "foo.bar.BazProto". 86 virtual string GetTypeName() const = 0; 87 88 // Construct a new instance of the same type. Ownership is passed to the 89 // caller. 90 virtual MessageLite* New() const = 0; 91 92 // Construct a new instance on the arena. Ownership is passed to the caller 93 // if arena is a NULL. Default implementation for backwards compatibility. 94 virtual MessageLite* New(::google::protobuf::Arena* arena) const; 95 96 // Get the arena, if any, associated with this message. Virtual method 97 // required for generic operations but most arena-related operations should 98 // use the GetArenaNoVirtual() generated-code method. Default implementation 99 // to reduce code size by avoiding the need for per-type implementations when 100 // types do not implement arena support. GetArena()101 virtual ::google::protobuf::Arena* GetArena() const { return NULL; } 102 103 // Get a pointer that may be equal to this message's arena, or may not be. If 104 // the value returned by this method is equal to some arena pointer, then this 105 // message is on that arena; however, if this message is on some arena, this 106 // method may or may not return that arena's pointer. As a tradeoff, this 107 // method may be more efficient than GetArena(). The intent is to allow 108 // underlying representations that use e.g. tagged pointers to sometimes store 109 // the arena pointer directly, and sometimes in a more indirect way, and allow 110 // a fastpath comparison against the arena pointer when it's easy to obtain. GetMaybeArenaPointer()111 virtual void* GetMaybeArenaPointer() const { return GetArena(); } 112 113 // Clear all fields of the message and set them to their default values. 114 // Clear() avoids freeing memory, assuming that any memory allocated 115 // to hold parts of the message will be needed again to hold the next 116 // message. If you actually want to free the memory used by a Message, 117 // you must delete it. 118 virtual void Clear() = 0; 119 120 // Quickly check if all required fields have values set. 121 virtual bool IsInitialized() const = 0; 122 123 // This is not implemented for Lite messages -- it just returns "(cannot 124 // determine missing fields for lite message)". However, it is implemented 125 // for full messages. See message.h. 126 virtual string InitializationErrorString() const; 127 128 // If |other| is the exact same class as this, calls MergeFrom(). Otherwise, 129 // results are undefined (probably crash). 130 virtual void CheckTypeAndMergeFrom(const MessageLite& other) = 0; 131 132 // Parsing --------------------------------------------------------- 133 // Methods for parsing in protocol buffer format. Most of these are 134 // just simple wrappers around MergeFromCodedStream(). Clear() will be called 135 // before merging the input. 136 137 // Fill the message with a protocol buffer parsed from the given input stream. 138 // Returns false on a read error or if the input is in the wrong format. A 139 // successful return does not indicate the entire input is consumed, ensure 140 // you call ConsumedEntireMessage() to check that if applicable. 141 bool ParseFromCodedStream(io::CodedInputStream* input); 142 // Like ParseFromCodedStream(), but accepts messages that are missing 143 // required fields. 144 bool ParsePartialFromCodedStream(io::CodedInputStream* input); 145 // Read a protocol buffer from the given zero-copy input stream. If 146 // successful, the entire input will be consumed. 147 bool ParseFromZeroCopyStream(io::ZeroCopyInputStream* input); 148 // Like ParseFromZeroCopyStream(), but accepts messages that are missing 149 // required fields. 150 bool ParsePartialFromZeroCopyStream(io::ZeroCopyInputStream* input); 151 // Read a protocol buffer from the given zero-copy input stream, expecting 152 // the message to be exactly "size" bytes long. If successful, exactly 153 // this many bytes will have been consumed from the input. 154 bool ParseFromBoundedZeroCopyStream(io::ZeroCopyInputStream* input, int size); 155 // Like ParseFromBoundedZeroCopyStream(), but accepts messages that are 156 // missing required fields. 157 bool ParsePartialFromBoundedZeroCopyStream(io::ZeroCopyInputStream* input, 158 int size); 159 // Parses a protocol buffer contained in a string. Returns true on success. 160 // This function takes a string in the (non-human-readable) binary wire 161 // format, matching the encoding output by MessageLite::SerializeToString(). 162 // If you'd like to convert a human-readable string into a protocol buffer 163 // object, see google::protobuf::TextFormat::ParseFromString(). 164 bool ParseFromString(const string& data); 165 // Like ParseFromString(), but accepts messages that are missing 166 // required fields. 167 bool ParsePartialFromString(const string& data); 168 // Parse a protocol buffer contained in an array of bytes. 169 bool ParseFromArray(const void* data, int size); 170 // Like ParseFromArray(), but accepts messages that are missing 171 // required fields. 172 bool ParsePartialFromArray(const void* data, int size); 173 174 175 // Reads a protocol buffer from the stream and merges it into this 176 // Message. Singular fields read from the input overwrite what is 177 // already in the Message and repeated fields are appended to those 178 // already present. 179 // 180 // It is the responsibility of the caller to call input->LastTagWas() 181 // (for groups) or input->ConsumedEntireMessage() (for non-groups) after 182 // this returns to verify that the message's end was delimited correctly. 183 // 184 // ParsefromCodedStream() is implemented as Clear() followed by 185 // MergeFromCodedStream(). 186 bool MergeFromCodedStream(io::CodedInputStream* input); 187 188 // Like MergeFromCodedStream(), but succeeds even if required fields are 189 // missing in the input. 190 // 191 // MergeFromCodedStream() is just implemented as MergePartialFromCodedStream() 192 // followed by IsInitialized(). 193 virtual bool MergePartialFromCodedStream(io::CodedInputStream* input) = 0; 194 195 196 // Serialization --------------------------------------------------- 197 // Methods for serializing in protocol buffer format. Most of these 198 // are just simple wrappers around ByteSize() and SerializeWithCachedSizes(). 199 200 // Write a protocol buffer of this message to the given output. Returns 201 // false on a write error. If the message is missing required fields, 202 // this may GOOGLE_CHECK-fail. 203 bool SerializeToCodedStream(io::CodedOutputStream* output) const; 204 // Like SerializeToCodedStream(), but allows missing required fields. 205 bool SerializePartialToCodedStream(io::CodedOutputStream* output) const; 206 // Write the message to the given zero-copy output stream. All required 207 // fields must be set. 208 bool SerializeToZeroCopyStream(io::ZeroCopyOutputStream* output) const; 209 // Like SerializeToZeroCopyStream(), but allows missing required fields. 210 bool SerializePartialToZeroCopyStream(io::ZeroCopyOutputStream* output) const; 211 // Serialize the message and store it in the given string. All required 212 // fields must be set. 213 bool SerializeToString(string* output) const; 214 // Like SerializeToString(), but allows missing required fields. 215 bool SerializePartialToString(string* output) const; 216 // Serialize the message and store it in the given byte array. All required 217 // fields must be set. 218 bool SerializeToArray(void* data, int size) const; 219 // Like SerializeToArray(), but allows missing required fields. 220 bool SerializePartialToArray(void* data, int size) const; 221 222 // Make a string encoding the message. Is equivalent to calling 223 // SerializeToString() on a string and using that. Returns the empty 224 // string if SerializeToString() would have returned an error. 225 // Note: If you intend to generate many such strings, you may 226 // reduce heap fragmentation by instead re-using the same string 227 // object with calls to SerializeToString(). 228 string SerializeAsString() const; 229 // Like SerializeAsString(), but allows missing required fields. 230 string SerializePartialAsString() const; 231 232 // Like SerializeToString(), but appends to the data to the string's existing 233 // contents. All required fields must be set. 234 bool AppendToString(string* output) const; 235 // Like AppendToString(), but allows missing required fields. 236 bool AppendPartialToString(string* output) const; 237 238 // Computes the serialized size of the message. This recursively calls 239 // ByteSize() on all embedded messages. If a subclass does not override 240 // this, it MUST override SetCachedSize(). 241 // 242 // ByteSize() is generally linear in the number of fields defined for the 243 // proto. 244 virtual int ByteSize() const = 0; 245 246 // Serializes the message without recomputing the size. The message must 247 // not have changed since the last call to ByteSize(); if it has, the results 248 // are undefined. 249 virtual void SerializeWithCachedSizes( 250 io::CodedOutputStream* output) const = 0; 251 252 // Like SerializeWithCachedSizes, but writes directly to *target, returning 253 // a pointer to the byte immediately after the last byte written. "target" 254 // must point at a byte array of at least ByteSize() bytes. 255 virtual uint8* SerializeWithCachedSizesToArray(uint8* target) const; 256 257 // Returns the result of the last call to ByteSize(). An embedded message's 258 // size is needed both to serialize it (because embedded messages are 259 // length-delimited) and to compute the outer message's size. Caching 260 // the size avoids computing it multiple times. 261 // 262 // ByteSize() does not automatically use the cached size when available 263 // because this would require invalidating it every time the message was 264 // modified, which would be too hard and expensive. (E.g. if a deeply-nested 265 // sub-message is changed, all of its parents' cached sizes would need to be 266 // invalidated, which is too much work for an otherwise inlined setter 267 // method.) 268 virtual int GetCachedSize() const = 0; 269 270 private: 271 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageLite); 272 }; 273 274 } // namespace protobuf 275 276 } // namespace google 277 #endif // GOOGLE_PROTOBUF_MESSAGE_LITE_H__ 278