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+// 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;
+}