1// Hello World example
2// This example shows basic usage of DOM-style API.
3
4#include "rapidjson/document.h"     // rapidjson's DOM-style API
5#include "rapidjson/prettywriter.h" // for stringify JSON
6#include <cstdio>
7
8using namespace rapidjson;
9using namespace std;
10
11int main(int, char*[]) {
12    ////////////////////////////////////////////////////////////////////////////
13    // 1. Parse a JSON text string to a document.
14
15    const char json[] = " { \"hello\" : \"world\", \"t\" : true , \"f\" : false, \"n\": null, \"i\":123, \"pi\": 3.1416, \"a\":[1, 2, 3, 4] } ";
16    printf("Original JSON:\n %s\n", json);
17
18    Document document;  // Default template parameter uses UTF8 and MemoryPoolAllocator.
19
20#if 0
21    // "normal" parsing, decode strings to new buffers. Can use other input stream via ParseStream().
22    if (document.Parse(json).HasParseError())
23        return 1;
24#else
25    // In-situ parsing, decode strings directly in the source string. Source must be string.
26    char buffer[sizeof(json)];
27    memcpy(buffer, json, sizeof(json));
28    if (document.ParseInsitu(buffer).HasParseError())
29        return 1;
30#endif
31
32    printf("\nParsing to document succeeded.\n");
33
34    ////////////////////////////////////////////////////////////////////////////
35    // 2. Access values in document.
36
37    printf("\nAccess values in document:\n");
38    assert(document.IsObject());    // Document is a JSON value represents the root of DOM. Root can be either an object or array.
39
40    assert(document.HasMember("hello"));
41    assert(document["hello"].IsString());
42    printf("hello = %s\n", document["hello"].GetString());
43
44    // Since version 0.2, you can use single lookup to check the existing of member and its value:
45    Value::MemberIterator hello = document.FindMember("hello");
46    assert(hello != document.MemberEnd());
47    assert(hello->value.IsString());
48    assert(strcmp("world", hello->value.GetString()) == 0);
49    (void)hello;
50
51    assert(document["t"].IsBool());     // JSON true/false are bool. Can also uses more specific function IsTrue().
52    printf("t = %s\n", document["t"].GetBool() ? "true" : "false");
53
54    assert(document["f"].IsBool());
55    printf("f = %s\n", document["f"].GetBool() ? "true" : "false");
56
57    printf("n = %s\n", document["n"].IsNull() ? "null" : "?");
58
59    assert(document["i"].IsNumber());   // Number is a JSON type, but C++ needs more specific type.
60    assert(document["i"].IsInt());      // In this case, IsUint()/IsInt64()/IsUInt64() also return true.
61    printf("i = %d\n", document["i"].GetInt()); // Alternative (int)document["i"]
62
63    assert(document["pi"].IsNumber());
64    assert(document["pi"].IsDouble());
65    printf("pi = %g\n", document["pi"].GetDouble());
66
67    {
68        const Value& a = document["a"]; // Using a reference for consecutive access is handy and faster.
69        assert(a.IsArray());
70        for (SizeType i = 0; i < a.Size(); i++) // rapidjson uses SizeType instead of size_t.
71            printf("a[%d] = %d\n", i, a[i].GetInt());
72
73        int y = a[0].GetInt();
74        (void)y;
75
76        // Iterating array with iterators
77        printf("a = ");
78        for (Value::ConstValueIterator itr = a.Begin(); itr != a.End(); ++itr)
79            printf("%d ", itr->GetInt());
80        printf("\n");
81    }
82
83    // Iterating object members
84    static const char* kTypeNames[] = { "Null", "False", "True", "Object", "Array", "String", "Number" };
85    for (Value::ConstMemberIterator itr = document.MemberBegin(); itr != document.MemberEnd(); ++itr)
86        printf("Type of member %s is %s\n", itr->name.GetString(), kTypeNames[itr->value.GetType()]);
87
88    ////////////////////////////////////////////////////////////////////////////
89    // 3. Modify values in document.
90
91    // Change i to a bigger number
92    {
93        uint64_t f20 = 1;   // compute factorial of 20
94        for (uint64_t j = 1; j <= 20; j++)
95            f20 *= j;
96        document["i"] = f20;    // Alternate form: document["i"].SetUint64(f20)
97        assert(!document["i"].IsInt()); // No longer can be cast as int or uint.
98    }
99
100    // Adding values to array.
101    {
102        Value& a = document["a"];   // This time we uses non-const reference.
103        Document::AllocatorType& allocator = document.GetAllocator();
104        for (int i = 5; i <= 10; i++)
105            a.PushBack(i, allocator);   // May look a bit strange, allocator is needed for potentially realloc. We normally uses the document's.
106
107        // Fluent API
108        a.PushBack("Lua", allocator).PushBack("Mio", allocator);
109    }
110
111    // Making string values.
112
113    // This version of SetString() just store the pointer to the string.
114    // So it is for literal and string that exists within value's life-cycle.
115    {
116        document["hello"] = "rapidjson";    // This will invoke strlen()
117        // Faster version:
118        // document["hello"].SetString("rapidjson", 9);
119    }
120
121    // This version of SetString() needs an allocator, which means it will allocate a new buffer and copy the the string into the buffer.
122    Value author;
123    {
124        char buffer[10];
125        int len = sprintf(buffer, "%s %s", "Milo", "Yip");  // synthetic example of dynamically created string.
126
127        author.SetString(buffer, static_cast<size_t>(len), document.GetAllocator());
128        // Shorter but slower version:
129        // document["hello"].SetString(buffer, document.GetAllocator());
130
131        // Constructor version:
132        // Value author(buffer, len, document.GetAllocator());
133        // Value author(buffer, document.GetAllocator());
134        memset(buffer, 0, sizeof(buffer)); // For demonstration purpose.
135    }
136    // Variable 'buffer' is unusable now but 'author' has already made a copy.
137    document.AddMember("author", author, document.GetAllocator());
138
139    assert(author.IsNull());        // Move semantic for assignment. After this variable is assigned as a member, the variable becomes null.
140
141    ////////////////////////////////////////////////////////////////////////////
142    // 4. Stringify JSON
143
144    printf("\nModified JSON with reformatting:\n");
145    StringBuffer sb;
146    PrettyWriter<StringBuffer> writer(sb);
147    document.Accept(writer);    // Accept() traverses the DOM and generates Handler events.
148    puts(sb.GetString());
149
150    return 0;
151}
152