include/tools/json_writer.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9 #pragma once
  10
  11 #include <tools/toolsdllapi.h>
  12 #include <rtl/ustring.hxx>
  13 #include <memory>
  14 #include <algorithm>
  15
  16 namespace rtl
  17 {
  18 class OStringBuffer;
  19 }
  20
  21 /** Simple JSON encoder designed specifically for LibreOfficeKit purposes.
  22  *
  23  * (1) Minimal allocations/re-allocations/copying
  24  * (2) Small/simple JSON documents
  25  * (3) ascii property names
  26  */
  27 namespace tools
  28 {
  29 class ScopedJsonWriterNode;
  30 class ScopedJsonWriterArray;
  31 class ScopedJsonWriterStruct;
  32
  33 class TOOLS_DLLPUBLIC JsonWriter
  34 {
  35     friend class ScopedJsonWriterNode;
  36     friend class ScopedJsonWriterArray;
  37     friend class ScopedJsonWriterStruct;
  38
  39     int mSpaceAllocated;
  40     char* mpBuffer;
  41     int mStartNodeCount;
  42     char* mPos;
  43     bool mbFirstFieldInNode;
  44
  45 public:
  46     JsonWriter();
  47     ~JsonWriter();
  48
  49     [[nodiscard]] ScopedJsonWriterNode startNode(const char*);
  50     [[nodiscard]] ScopedJsonWriterArray startArray(const char*);
  51     [[nodiscard]] ScopedJsonWriterStruct startStruct();
  52
  53     void put(const char* pPropName, const OUString& rPropValue);
  54     void put(const char* pPropName, const OString& rPropValue);
  55     void put(const char* pPropName, const char* pPropVal);
  56     void put(const char*, int);
  57
  58     /// This assumes that this data belongs at this point in the stream, and is valid, and properly encoded
  59     void putRaw(const rtl::OStringBuffer&);
  60
  61     /** Hands ownership of the underlying storage buffer to the caller,
  62      * after this no more document modifications may be written. */
  63     char* extractData();
  64     OString extractAsOString();
  65
  66 private:
  67     void endNode();
  68     void endArray();
  69     void endStruct();
  70     void addCommaBeforeField();
  71     void reallocBuffer(int noMoreBytesRequired);
  72
  73     // this part inline to speed up the fast path
  74     inline void ensureSpace(int noMoreBytesRequired)
  75     {
  76         assert(mpBuffer && "already extracted data");
  77         int currentUsed = mPos - mpBuffer;
  78         if (currentUsed + noMoreBytesRequired >= mSpaceAllocated)
  79             reallocBuffer(noMoreBytesRequired);
  80     }
  81 };
  82
  83 /**
  84  * Auto-closes the node.
  85  */
  86 class ScopedJsonWriterNode
  87 {
  88     friend class JsonWriter;
  89
  90     JsonWriter& mrWriter;
  91
  92     ScopedJsonWriterNode(JsonWriter& rWriter)
  93         : mrWriter(rWriter)
  94     {
  95     }
  96
  97 public:
  98     ~ScopedJsonWriterNode() { mrWriter.endNode(); }
  99 };
 100
 101 /**
 102  * Auto-closes the node.
 103  */
 104 class ScopedJsonWriterArray
 105 {
 106     friend class JsonWriter;
 107
 108     JsonWriter& mrWriter;
 109
 110     ScopedJsonWriterArray(JsonWriter& rWriter)
 111         : mrWriter(rWriter)
 112     {
 113     }
 114
 115 public:
 116     ~ScopedJsonWriterArray() { mrWriter.endArray(); }
 117 };
 118
 119 /**
 120  * Auto-closes the node.
 121  */
 122 class ScopedJsonWriterStruct
 123 {
 124     friend class JsonWriter;
 125
 126     JsonWriter& mrWriter;
 127
 128     ScopedJsonWriterStruct(JsonWriter& rWriter)
 129         : mrWriter(rWriter)
 130     {
 131     }
 132
 133 public:
 134     ~ScopedJsonWriterStruct() { mrWriter.endStruct(); }
 135 };
 136 };
 137 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */