// 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;

}