blob: f627f4d863673a008c75835602723c9518fcdbcb [file] [log] [blame]
#include "rapidjson/reader.h"
#include "rapidjson/document.h"
#include <iostream>
RAPIDJSON_DIAG_PUSH
#ifdef __GNUC__
RAPIDJSON_DIAG_OFF(effc++)
#endif
// This example demonstrates JSON token-by-token parsing with an API that is
// more direct; you don't need to design your logic around a handler object and
// callbacks. Instead, you retrieve values from the JSON stream by calling
// GetInt(), GetDouble(), GetString() and GetBool(), traverse into structures
// by calling EnterObject() and EnterArray(), and skip over unwanted data by
// calling SkipValue(). When you know your JSON's structure, this can be quite
// convenient.
//
// If you aren't sure of what's next in the JSON data, you can use PeekType() and
// PeekValue() to look ahead to the next object before reading it.
//
// If you call the wrong retrieval method--e.g. GetInt when the next JSON token is
// not an int, EnterObject or EnterArray when there isn't actually an object or array
// to read--the stream parsing will end immediately and no more data will be delivered.
//
// After calling EnterObject, you retrieve keys via NextObjectKey() and values via
// the normal getters. When NextObjectKey() returns null, you have exited the
// object, or you can call SkipObject() to skip to the end of the object
// immediately. If you fetch the entire object (i.e. NextObjectKey() returned null),
// you should not call SkipObject().
//
// After calling EnterArray(), you must alternate between calling NextArrayValue()
// to see if the array has more data, and then retrieving values via the normal
// getters. You can call SkipArray() to skip to the end of the array immediately.
// If you fetch the entire array (i.e. NextArrayValue() returned null),
// you should not call SkipArray().
//
// This parser uses in-situ strings, so the JSON buffer will be altered during the
// parse.
using namespace rapidjson;
class LookaheadParserHandler {
public:
bool Null() { st_ = kHasNull; v_.SetNull(); return true; }
bool Bool(bool b) { st_ = kHasBool; v_.SetBool(b); return true; }
bool Int(int i) { st_ = kHasNumber; v_.SetInt(i); return true; }
bool Uint(unsigned u) { st_ = kHasNumber; v_.SetUint(u); return true; }
bool Int64(int64_t i) { st_ = kHasNumber; v_.SetInt64(i); return true; }
bool Uint64(uint64_t u) { st_ = kHasNumber; v_.SetUint64(u); return true; }
bool Double(double d) { st_ = kHasNumber; v_.SetDouble(d); return true; }
bool RawNumber(const char*, SizeType, bool) { return false; }
bool String(const char* str, SizeType length, bool) { st_ = kHasString; v_.SetString(str, length); return true; }
bool StartObject() { st_ = kEnteringObject; return true; }
bool Key(const char* str, SizeType length, bool) { st_ = kHasKey; v_.SetString(str, length); return true; }
bool EndObject(SizeType) { st_ = kExitingObject; return true; }
bool StartArray() { st_ = kEnteringArray; return true; }
bool EndArray(SizeType) { st_ = kExitingArray; return true; }
protected:
LookaheadParserHandler(char* str);
void ParseNext();
protected:
enum LookaheadParsingState {
kInit,
kError,
kHasNull,
kHasBool,
kHasNumber,
kHasString,
kHasKey,
kEnteringObject,
kExitingObject,
kEnteringArray,
kExitingArray
};
Value v_;
LookaheadParsingState st_;
Reader r_;
InsituStringStream ss_;
static const int parseFlags = kParseDefaultFlags | kParseInsituFlag;
};
LookaheadParserHandler::LookaheadParserHandler(char* str) : v_(), st_(kInit), r_(), ss_(str) {
r_.IterativeParseInit();
ParseNext();
}
void LookaheadParserHandler::ParseNext() {
if (r_.HasParseError()) {
st_ = kError;
return;
}
r_.IterativeParseNext<parseFlags>(ss_, *this);
}
class LookaheadParser : protected LookaheadParserHandler {
public:
LookaheadParser(char* str) : LookaheadParserHandler(str) {}
bool EnterObject();
bool EnterArray();
const char* NextObjectKey();
bool NextArrayValue();
int GetInt();
double GetDouble();
const char* GetString();
bool GetBool();
void GetNull();
void SkipObject();
void SkipArray();
void SkipValue();
Value* PeekValue();
int PeekType(); // returns a rapidjson::Type, or -1 for no value (at end of object/array)
bool IsValid() { return st_ != kError; }
protected:
void SkipOut(int depth);
};
bool LookaheadParser::EnterObject() {
if (st_ != kEnteringObject) {
st_ = kError;
return false;
}
ParseNext();
return true;
}
bool LookaheadParser::EnterArray() {
if (st_ != kEnteringArray) {
st_ = kError;
return false;
}
ParseNext();
return true;
}
const char* LookaheadParser::NextObjectKey() {
if (st_ == kHasKey) {
const char* result = v_.GetString();
ParseNext();
return result;
}
if (st_ != kExitingObject) {
st_ = kError;
return 0;
}
ParseNext();
return 0;
}
bool LookaheadParser::NextArrayValue() {
if (st_ == kExitingArray) {
ParseNext();
return false;
}
if (st_ == kError || st_ == kExitingObject || st_ == kHasKey) {
st_ = kError;
return false;
}
return true;
}
int LookaheadParser::GetInt() {
if (st_ != kHasNumber || !v_.IsInt()) {
st_ = kError;
return 0;
}
int result = v_.GetInt();
ParseNext();
return result;
}
double LookaheadParser::GetDouble() {
if (st_ != kHasNumber) {
st_ = kError;
return 0.;
}
double result = v_.GetDouble();
ParseNext();
return result;
}
bool LookaheadParser::GetBool() {
if (st_ != kHasBool) {
st_ = kError;
return false;
}
bool result = v_.GetBool();
ParseNext();
return result;
}
void LookaheadParser::GetNull() {
if (st_ != kHasNull) {
st_ = kError;
return;
}
ParseNext();
}
const char* LookaheadParser::GetString() {
if (st_ != kHasString) {
st_ = kError;
return 0;
}
const char* result = v_.GetString();
ParseNext();
return result;
}
void LookaheadParser::SkipOut(int depth) {
do {
if (st_ == kEnteringArray || st_ == kEnteringObject) {
++depth;
}
else if (st_ == kExitingArray || st_ == kExitingObject) {
--depth;
}
else if (st_ == kError) {
return;
}
ParseNext();
}
while (depth > 0);
}
void LookaheadParser::SkipValue() {
SkipOut(0);
}
void LookaheadParser::SkipArray() {
SkipOut(1);
}
void LookaheadParser::SkipObject() {
SkipOut(1);
}
Value* LookaheadParser::PeekValue() {
if (st_ >= kHasNull && st_ <= kHasKey) {
return &v_;
}
return 0;
}
int LookaheadParser::PeekType() {
if (st_ >= kHasNull && st_ <= kHasKey) {
return v_.GetType();
}
if (st_ == kEnteringArray) {
return kArrayType;
}
if (st_ == kEnteringObject) {
return kObjectType;
}
return -1;
}
//-------------------------------------------------------------------------
int main() {
using namespace std;
char json[] = " { \"hello\" : \"world\", \"t\" : true , \"f\" : false, \"n\": null,"
"\"i\":123, \"pi\": 3.1416, \"a\":[-1, 2, 3, 4, \"array\", []], \"skipArrays\":[1, 2, [[[3]]]], "
"\"skipObject\":{ \"i\":0, \"t\":true, \"n\":null, \"d\":123.45 }, "
"\"skipNested\":[[[[{\"\":0}, {\"\":[-9.87]}]]], [], []], "
"\"skipString\":\"zzz\", \"reachedEnd\":null, \"t\":true }";
LookaheadParser r(json);
RAPIDJSON_ASSERT(r.PeekType() == kObjectType);
r.EnterObject();
while (const char* key = r.NextObjectKey()) {
if (0 == strcmp(key, "hello")) {
RAPIDJSON_ASSERT(r.PeekType() == kStringType);
cout << key << ":" << r.GetString() << endl;
}
else if (0 == strcmp(key, "t") || 0 == strcmp(key, "f")) {
RAPIDJSON_ASSERT(r.PeekType() == kTrueType || r.PeekType() == kFalseType);
cout << key << ":" << r.GetBool() << endl;
continue;
}
else if (0 == strcmp(key, "n")) {
RAPIDJSON_ASSERT(r.PeekType() == kNullType);
r.GetNull();
cout << key << endl;
continue;
}
else if (0 == strcmp(key, "pi")) {
RAPIDJSON_ASSERT(r.PeekType() == kNumberType);
cout << key << ":" << r.GetDouble() << endl;
continue;
}
else if (0 == strcmp(key, "a")) {
RAPIDJSON_ASSERT(r.PeekType() == kArrayType);
r.EnterArray();
cout << key << ":[ ";
while (r.NextArrayValue()) {
if (r.PeekType() == kNumberType) {
cout << r.GetDouble() << " ";
}
else if (r.PeekType() == kStringType) {
cout << r.GetString() << " ";
}
else {
r.SkipArray();
break;
}
}
cout << "]" << endl;
}
else {
cout << key << ":skipped" << endl;
r.SkipValue();
}
}
return 0;
}
RAPIDJSON_DIAG_POP