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 #ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__ 32 #define GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__ 33 34 #include <memory> 35 36 #include <google/protobuf/stubs/casts.h> 37 #include <google/protobuf/stubs/common.h> 38 #include <google/protobuf/util/internal/object_writer.h> 39 40 #include <google/protobuf/port_def.inc> 41 42 namespace google { 43 namespace protobuf { 44 namespace util { 45 namespace converter { 46 47 // An StructuredObjectWriter is an ObjectWriter for writing 48 // tree-structured data in a stream of events representing objects 49 // and collections. Implementation of this interface can be used to 50 // write an object stream to an in-memory structure, protobufs, 51 // JSON, XML, or any other output format desired. The ObjectSource 52 // interface is typically used as the source of an object stream. 53 // 54 // See JsonObjectWriter for a sample implementation of 55 // StructuredObjectWriter and its use. 56 // 57 // Derived classes could be thread-unsafe. 58 class PROTOBUF_EXPORT StructuredObjectWriter : public ObjectWriter { 59 public: ~StructuredObjectWriter()60 virtual ~StructuredObjectWriter() {} 61 62 protected: 63 // A base element class for subclasses to extend, makes tracking state easier. 64 // 65 // StructuredObjectWriter behaves as a visitor. BaseElement represents a node 66 // in the input tree. Implementation of StructuredObjectWriter should also 67 // extend BaseElement to keep track of the location in the input tree. 68 class PROTOBUF_EXPORT BaseElement { 69 public: 70 // Takes ownership of the parent Element. BaseElement(BaseElement * parent)71 explicit BaseElement(BaseElement* parent) 72 : parent_(parent), level_(parent == NULL ? 0 : parent->level() + 1) {} ~BaseElement()73 virtual ~BaseElement() {} 74 75 // Releases ownership of the parent and returns a pointer to it. 76 template <typename ElementType> pop()77 ElementType* pop() { 78 return down_cast<ElementType*>(parent_.release()); 79 } 80 81 // Returns true if this element is the root. is_root()82 bool is_root() const { return parent_ == nullptr; } 83 84 // Returns the number of hops from this element to the root element. level()85 int level() const { return level_; } 86 87 protected: 88 // Returns pointer to parent element without releasing ownership. parent()89 virtual BaseElement* parent() const { return parent_.get(); } 90 91 private: 92 // Pointer to the parent Element. 93 std::unique_ptr<BaseElement> parent_; 94 95 // Number of hops to the root Element. 96 // The root Element has nullptr parent_ and a level_ of 0. 97 const int level_; 98 99 GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(BaseElement); 100 }; 101 StructuredObjectWriter()102 StructuredObjectWriter() {} 103 104 // Returns the current element. Used for indentation and name overrides. 105 virtual BaseElement* element() = 0; 106 107 private: 108 // Do not add any data members to this class. 109 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StructuredObjectWriter); 110 }; 111 112 } // namespace converter 113 } // namespace util 114 } // namespace protobuf 115 } // namespace google 116 117 #include <google/protobuf/port_undef.inc> 118 119 #endif // GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__ 120