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