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 <sal/config.h>
  12
  13 #include <tools/toolsdllapi.h>
  14 #include <rtl/string.hxx>
  15 #include <rtl/ustring.hxx>
  16
  17 #include <string_view>
  18
  19 /** Simple JSON encoder designed specifically for LibreOfficeKit purposes.
  20  *
  21  * (1) Minimal allocations/re-allocations/copying
  22  * (2) Small/simple JSON documents
  23  * (3) ascii property names
  24  */
  25 namespace tools
  26 {
  27 class TOOLS_DLLPUBLIC JsonWriter
  28 {
  29     // Auto-closes the node.
  30     template <char closing> struct ScopedJsonWriterNode
  31     {
  32         JsonWriter& mrWriter;
  33         ~ScopedJsonWriterNode() { mrWriter.endNode(closing); }
  34     };
  35
  36     rtl_String* mpBuffer;
  37     char* mPos;
  38     int mSpaceAllocated;
  39     int mStartNodeCount;
  40     bool mbFirstFieldInNode;
  41     bool mbClosed; // cannot add to it anymore
  42
  43 public:
  44     JsonWriter();
  45     ~JsonWriter();
  46
  47     [[nodiscard]] ScopedJsonWriterNode<'}'> startNode(std::string_view nodeName);
  48     [[nodiscard]] ScopedJsonWriterNode<']'> startArray(std::string_view nodeName);
  49     [[nodiscard]] ScopedJsonWriterNode<']'> startAnonArray();
  50     [[nodiscard]] ScopedJsonWriterNode<'}'> startStruct();
  51
  52     void put(std::u16string_view pPropName, std::u16string_view rPropValue);
  53
  54     void put(std::string_view pPropName, const OUString& rPropValue);
  55     // Assumes utf-8 property value encoding
  56     void put(std::string_view pPropName, std::string_view rPropValue);
  57     void put(std::string_view pPropName, const char* pPropVal)
  58     {
  59         put(pPropName, std::string_view(pPropVal));
  60     }
  61     template <size_t N> void put(std::string_view pPropName, const char (&pPropVal)[N])
  62     {
  63         put(pPropName, std::string_view(pPropVal, N));
  64     }
  65
  66     template <typename N, std::enable_if_t<std::is_arithmetic_v<N>, int> = 0>
  67     void put(std::string_view pPropName, N n)
  68     {
  69         putLiteral(pPropName, OString::number(n));
  70     }
  71     void put(std::string_view pPropName, bool);
  72
  73     void putSimpleValue(std::u16string_view rPropValue);
  74
  75     /// This assumes that this data belongs at this point in the stream, and is valid, and properly encoded
  76     void putRaw(std::string_view);
  77
  78     /** Closes the tags, and returns data.
  79      * After this no more document modifications may be written. */
  80     OString finishAndGetAsOString();
  81
  82 private:
  83     void endNode(char closing);
  84     void addCommaBeforeField();
  85     void writeEscapedOUString(std::u16string_view rPropVal);
  86     void closeDocument();
  87     void ensureSpace(int noMoreBytesRequired);
  88     void ensureSpaceAndWriteNameColon(std::string_view name, int valSize);
  89     void putLiteral(std::string_view propName, std::string_view propValue);
  90
  91     // overflow validation in debug mode
  92     static constexpr unsigned char JSON_WRITER_DEBUG_MARKER = 0xde;
  93
  94     inline void addValidationMark()
  95     {
  96 #ifndef NDEBUG
  97         *(mpBuffer->buffer + mSpaceAllocated - 1) = JSON_WRITER_DEBUG_MARKER;
  98 #endif
  99     }
 100
 101     inline void validate()
 102     {
 103 #ifndef NDEBUG
 104         unsigned char c = *(mpBuffer->buffer + mSpaceAllocated - 1);
 105         assert(c == JSON_WRITER_DEBUG_MARKER);
 106 #endif
 107     }
 108 };
 109 }
 110 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */