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Diffstat (limited to 'src/s3select/rapidjson/example/tutorial/tutorial.cpp')
-rw-r--r-- | src/s3select/rapidjson/example/tutorial/tutorial.cpp | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/src/s3select/rapidjson/example/tutorial/tutorial.cpp b/src/s3select/rapidjson/example/tutorial/tutorial.cpp new file mode 100644 index 000000000..d6021c668 --- /dev/null +++ b/src/s3select/rapidjson/example/tutorial/tutorial.cpp @@ -0,0 +1,151 @@ +// 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; +} |