summaryrefslogtreecommitdiff
path: root/graphics/asymptote/LspCpp/third_party/rapidjson/example/tutorial/tutorial.cpp
blob: f97b0be86ead568036432c976b2efe1cd59a0ee2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
// Hello World example
// This example shows basic usage of DOM-style API.

#include "rapidjson/document.h"     // rapidjson's DOM-style API
#include "rapidjson/prettywriter.h" // for stringify JSON
#include <cstdio>

using namespace rapidjson;
using namespace std;

int main(int, char*[]) {
    ////////////////////////////////////////////////////////////////////////////
    // 1. Parse a JSON text string to a document.

    const char json[] = " { \"hello\" : \"world\", \"t\" : true , \"f\" : false, \"n\": null, \"i\":123, \"pi\": 3.1416, \"a\":[1, 2, 3, 4] } ";
    printf("Original JSON:\n %s\n", json);

    Document document;  // Default template parameter uses UTF8 and MemoryPoolAllocator.

#if 0
    // "normal" parsing, decode strings to new buffers. Can use other input stream via ParseStream().
    if (document.Parse(json).HasParseError())
        return 1;
#else
    // In-situ parsing, decode strings directly in the source string. Source must be string.
    char buffer[sizeof(json)];
    memcpy(buffer, json, sizeof(json));
    if (document.ParseInsitu(buffer).HasParseError())
        return 1;
#endif

    printf("\nParsing to document succeeded.\n");

    ////////////////////////////////////////////////////////////////////////////
    // 2. Access values in document.

    printf("\nAccess values in document:\n");
    assert(document.IsObject());    // Document is a JSON value represents the root of DOM. Root can be either an object or array.

    assert(document.HasMember("hello"));
    assert(document["hello"].IsString());
    printf("hello = %s\n", document["hello"].GetString());

    // Since version 0.2, you can use single lookup to check the existing of member and its value:
    Value::MemberIterator hello = document.FindMember("hello");
    assert(hello != document.MemberEnd());
    assert(hello->value.IsString());
    assert(strcmp("world", hello->value.GetString()) == 0);
    (void)hello;

    assert(document["t"].IsBool());     // JSON true/false are bool. Can also uses more specific function IsTrue().
    printf("t = %s\n", document["t"].GetBool() ? "true" : "false");

    assert(document["f"].IsBool());
    printf("f = %s\n", document["f"].GetBool() ? "true" : "false");

    printf("n = %s\n", document["n"].IsNull() ? "null" : "?");

    assert(document["i"].IsNumber());   // Number is a JSON type, but C++ needs more specific type.
    assert(document["i"].IsInt());      // In this case, IsUint()/IsInt64()/IsUint64() also return true.
    printf("i = %d\n", document["i"].GetInt()); // Alternative (int)document["i"]

    assert(document["pi"].IsNumber());
    assert(document["pi"].IsDouble());
    printf("pi = %g\n", document["pi"].GetDouble());

    {
        const Value& a = document["a"]; // Using a reference for consecutive access is handy and faster.
        assert(a.IsArray());
        for (SizeType i = 0; i < a.Size(); i++) // rapidjson uses SizeType instead of size_t.
            printf("a[%d] = %d\n", i, a[i].GetInt());

        int y = a[0].GetInt();
        (void)y;

        // Iterating array with iterators
        printf("a = ");
        for (Value::ConstValueIterator itr = a.Begin(); itr != a.End(); ++itr)
            printf("%d ", itr->GetInt());
        printf("\n");
    }

    // Iterating object members
    static const char* kTypeNames[] = { "Null", "False", "True", "Object", "Array", "String", "Number" };
    for (Value::ConstMemberIterator itr = document.MemberBegin(); itr != document.MemberEnd(); ++itr)
        printf("Type of member %s is %s\n", itr->name.GetString(), kTypeNames[itr->value.GetType()]);

    ////////////////////////////////////////////////////////////////////////////
    // 3. Modify values in document.

    // Change i to a bigger number
    {
        uint64_t f20 = 1;   // compute factorial of 20
        for (uint64_t j = 1; j <= 20; j++)
            f20 *= j;
        document["i"] = f20;    // Alternate form: document["i"].SetUint64(f20)
        assert(!document["i"].IsInt()); // No longer can be cast as int or uint.
    }

    // Adding values to array.
    {
        Value& a = document["a"];   // This time we uses non-const reference.
        Document::AllocatorType& allocator = document.GetAllocator();
        for (int i = 5; i <= 10; i++)
            a.PushBack(i, allocator);   // May look a bit strange, allocator is needed for potentially realloc. We normally uses the document's.

        // Fluent API
        a.PushBack("Lua", allocator).PushBack("Mio", allocator);
    }

    // Making string values.

    // This version of SetString() just store the pointer to the string.
    // So it is for literal and string that exists within value's life-cycle.
    {
        document["hello"] = "rapidjson";    // This will invoke strlen()
        // Faster version:
        // document["hello"].SetString("rapidjson", 9);
    }

    // This version of SetString() needs an allocator, which means it will allocate a new buffer and copy the the string into the buffer.
    Value author;
    {
        char buffer2[10];
        int len = sprintf(buffer2, "%s %s", "Milo", "Yip");  // synthetic example of dynamically created string.

        author.SetString(buffer2, static_cast<SizeType>(len), document.GetAllocator());
        // Shorter but slower version:
        // document["hello"].SetString(buffer, document.GetAllocator());

        // Constructor version:
        // Value author(buffer, len, document.GetAllocator());
        // Value author(buffer, document.GetAllocator());
        memset(buffer2, 0, sizeof(buffer2)); // For demonstration purpose.
    }
    // Variable 'buffer' is unusable now but 'author' has already made a copy.
    document.AddMember("author", author, document.GetAllocator());

    assert(author.IsNull());        // Move semantic for assignment. After this variable is assigned as a member, the variable becomes null.

    ////////////////////////////////////////////////////////////////////////////
    // 4. Stringify JSON

    printf("\nModified JSON with reformatting:\n");
    StringBuffer sb;
    PrettyWriter<StringBuffer> writer(sb);
    document.Accept(writer);    // Accept() traverses the DOM and generates Handler events.
    puts(sb.GetString());

    return 0;
}