I have this C++ code, and am having trouble json serializing it.
string uInput;
string const& retInput;
while(!std::cin.eof()) {
getline(cin, uInput);
JSONExample source; //JSON enabled class from jsonserialize.h
source.text = uInput;
//create JSON from producer
std::string json = JSON::producer<JSONExample>::convert(source); //string -> returns {"JSONExample":{"text":"hi"}}
//then create new instance from a consumer...
JSONExample sink = JSON::consumer<JSONExample>::convert(json);
//retInput = serialize(sink);
// Json::FastWriter fastWriter;
// retInput = fastWriter.write(uInput);
retInput = static_cast<string const&>(uInput);
pubnub::futres fr_2 = pb_2.publish(chan, retInput);
cout << "user input as json which should be published is " << retInput<< std::endl;
while(!cin.eof()) {
getline(cin, uInput);
newInput = "\"\\\"";
newInput += uInput;
newInput += "\\\"\"";
Instead of typing in the message like "\"hi\"", this code takes "hi" and does it.
If the change you described made the "Invalid JSON" disappear, then a "more correct" solution would be, AFAICT, to change the publish() line to:
pubnub::futres fr_2 = pb_2.publish(chan, json);
Because json already has JSON serialized data. Of course, if that JSON is what you want to publish.
Related
I'm trying to incorporate Protocol buffers in my project. I have created the following very simple schema:
syntax = "proto3";
message Document{
string title = 1;
int64 size = 2;
int64 data = 3;
}
Then in my C++ code (after compiling with the protobufc compiler) I use this as:
Document document;
document.set_title(random_string(20));
document.set_data(300);
document.set_size(500);
std::string docString = document.SerializeAsString();
std::string compressedString;
google::protobuf::io::StringOutputStream stream(&compressedString);
google::protobuf::io::GzipOutputStream gStream(&stream);
document.SerializeToZeroCopyStream(&gStream);
std::cout << docString.size() << std::endl;
std::cout << compressedString.size() << std::endl;
The output of the code above is:
28 0
Thus the compressed string is empty, while the normal string is 28. What is the correct way of using GzipOutputStream and compress the serialised data of a protocol buffer.
I am developing a quick DICOM viewer using DCMTK library and I am following the example provided in this link.
The buffer from the API always returns null for any tag ID, eg: DCM_PatientName.
But the findAndGetOFString() API works fine but returns only the first character of the tag in ASCII, is this how this API should work?
Can someone let me know why the buffer is empty the former API?
Also the DicomImage API also the same issue.
Snippet 1:
DcmFileFormat fileformat;
OFCondition status = fileformat.loadFile(test_data_file_path.toStdString().c_str());
if (status.good())
{
OFString patientName;
char* name;
if (fileformat.getDataset()->findAndGetOFString(DCM_PatientName, patientName).good())
{
name = new char[patientName.length()];
strcpy(name, patientName.c_str());
}
else
{
qDebug() << "Error: cannot access Patient's Name!";
}
}
else
{
qDebug() << "Error: cannot read DICOM file (" << status.text() << ")";
}
In the above snippet name has the ASCII value "50" and the actual name is "PATIENT".
Snippet 2:
DcmFileFormat file_format;
OFCondition status = file_format.loadFile(test_data_file_path.toStdString().c_str());
std::shared_ptr<DcmDataset> dataset(file_format.getDataset());
qDebug() << "\nInformation extracted from DICOM file: \n";
const char* buffer = nullptr;
DcmTagKey key = DCM_PatientName;
dataset->findAndGetString(key,buffer);
std::string tag_value = buffer;
qDebug() << "Patient name: " << tag_value.c_str();
In the above snippet, the buffer is null. It doesn't read the name.
NOTE:
This is only a sample. I am just playing around the APIs for learning
purpose.
The following sample method reads the patient name from a DcmDataset object:
std::string getPatientName(DcmDataset& dataset)
{
// Get the tag's value in ofstring
OFString ofstring;
OFCondition condition = dataset.findAndGetOFString(DCM_PatientName, ofstring);
if(condition.good())
{
// Tag found. Put it in a std::string and return it
return std::string(ofstring.c_str());
}
// Tag not found
return ""; // or throw if you need the tag
}
I have tried your code with your datasets. I just replaced the output to QT console classes to std::cout. It works for me - i.e. it prints the correct patient name (e.g. "PATIENT2" for scan2.dcm). Everything seems correct, except for the fact that you apparently want to transfer the ownership for the dataset to a smart pointer.
To obtain the ownership for the DcmDataset from the DcmFileFormat, you must call getAndRemoveDataset() instead of getDataset(). However, I do not think that your issue is related that. You may want to try my modified snippet:
DcmFileFormat file_format;
OFCondition status = file_format.loadFile("d:\\temp\\StackOverflow\\scan2.dcm");
std::shared_ptr<DcmDataset> dataset(file_format.getAndRemoveDataset());
std::cout << "\nInformation extracted from DICOM file: \n";
const char* buffer = nullptr;
DcmTagKey key = DCM_PatientName;
dataset->findAndGetString(key, buffer);
std::string tag_value = buffer;
std::cout << "Patient name: " << tag_value.c_str();
It probably helps you to know that your code and the dcmtk methods you use are correct, but that does not solve your problem. Another thing I would recommend is to verify the result returned by file_format.loadFile(). Maybe there is a surprise in there.
Not sure if I can help you more, but my next step would be to verify your build environment, e.g. the options that you use for building dcmtk. Are you using CMake to build dcmtk?
I am using jsonc-libjson to create a json string like below.
{ "author-details": {
"name" : "Joys of Programming",
"Number of Posts" : 10
}
}
My code looks like below
json_object *jobj = json_object_new_object();
json_object *jStr1 = json_object_new_string("Joys of Programming");
json_object *jstr2 = json_object_new_int("10");
json_object_object_add(jobj,"name", jStr1 );
json_object_object_add(jobj,"Number of Posts", jstr2 );
this gives me json string
{
"name" : "Joys of Programming",
"Number of Posts" : 10
}
How do I add the top part associated with author details?
To paraphrase an old advertisement, "libjson users would rather fight than switch."
At least I assume you must like fighting with the library. Using nlohmann's JSON library, you could use code like this:
nlohmann::json j {
{ "author-details", {
{ "name", "Joys of Programming" },
{ "Number of Posts", 10 }
}
}
};
At least to me, this seems somewhat simpler and more readable.
Parsing is about equally straightforward. For example, let's assume we had a file named somefile.json that contained the JSON data shown above. To read and parse it, we could do something like this:
nlohmann::json j;
std::ifstream in("somefile.json");
in >> j; // Read the file and parse it into a json object
// Let's start by retrieving and printing the name.
std::cout << j["author-details"]["name"];
Or, let's assume we found a post, so we want to increment the count of posts. This is one place that things get...less tasteful--we can't increment the value as directly as we'd like; we have to obtain the value, add one, then assign the result (like we would in lesser languages that lack ++):
j["author-details"]["Number of Posts"] = j["author-details"]["Number of Posts"] + 1;
Then we want to write out the result. If we want it "dense" (e.g., we're going to transmit it over a network for some other machine to read it) we can just use <<:
somestream << j;
On the other hand, we might want to pretty-print it so a person can read it more easily. The library respects the width we set with setw, so to have it print out indented with 4-column tab stops, we can do:
somestream << std::setw(4) << j;
Create a new JSON object and add the one you already created as a child.
Just insert code like this after what you've already written:
json_object* root = json_object_new_object();
json_object_object_add(root, "author-details", jobj); // This is the same "jobj" as original code snippet.
Based on the comment from Dominic, I was able to figure out the correct answer.
json_object *jobj = json_object_new_object();
json_object* root = json_object_new_object();
json_object_object_add(jobj, "author-details", root);
json_object *jStr1 = json_object_new_string("Joys of Programming");
json_object *jstr2 = json_object_new_int(10);
json_object_object_add(root,"name", jStr1 );
json_object_object_add(root,"Number of Posts", jstr2 );
Is it possible to obtain the string equivalent of protobuf enums in C++?
e.g.:
The following is the message description:
package MyPackage;
message MyMessage
{
enum RequestType
{
Login = 0;
Logout = 1;
}
optional RequestType requestType = 1;
}
In my code I wish to do something like this:
MyMessage::RequestType requestType = MyMessage::RequestType::Login;
// requestTypeString will be "Login"
std::string requestTypeString = ProtobufEnumToString(requestType);
The EnumDescriptor and EnumValueDescriptor classes can be used for this kind of manipulation, and the
the generated .pb.h and .pb.cc names are easy enough to read, so you can look through them to get details on the functions they offer.
In this particular case, the following should work (untested):
std::string requestTypeString = MyMessage_RequestType_Name(requestType);
See the answer of Josh Kelley, use the EnumDescriptor and EnumValueDescriptor.
The EnumDescriptor documentation says:
To get a EnumDescriptor
To get the EnumDescriptor for a generated enum type, call
TypeName_descriptor(). Use DescriptorPool to construct your own
descriptors.
To get the string value, use FindValueByNumber(int number)
const EnumValueDescriptor * EnumDescriptor::FindValueByNumber(int number) const
Looks up a value by number.
Returns NULL if no such value exists. If multiple values have this >number,the first one defined is returned.
Example, get the protobuf enum:
enum UserStatus {
AWAY = 0;
ONLINE = 1;
OFFLINE = 2;
}
The code to read the string name from a value and the value from a string name:
const google::protobuf::EnumDescriptor *descriptor = UserStatus_descriptor();
std::string name = descriptor->FindValueByNumber(UserStatus::ONLINE)->name();
int number = descriptor->FindValueByName("ONLINE")->number();
std::cout << "Enum name: " << name << std::endl;
std::cout << "Enum number: " << number << std::endl;
I have been writing a wrapper for the Cassandra cppdriver for CQL3.0 and I have come across some odd behavior, and I am not sure if it is typical or a bug.
For reference, I am working with with the cppdriver code release on 4 September (from the repository), libuv0.10 and off of the songs / playlist example posted on the datastax website (http://www.datastax.com/documentation/cql/3.1/cql/ddl/ddl_music_service_c.html)
The problem that I am having is with executing query strings. There seems to be some threshold of characters after which the query string being sent to Cassandra becomes garbage. The code that I am using to construct and send the string to the cppdriver library (and parse the results) is provided below. I added a function (cass_session_print_query) to the cassandra.h and session.cpp files to print out generated statement.
map<string, vector<string> > retresults;
int i = 0, ccount;
stringstream ss;
vector<string> keys = get.GetList();
vector<string>::iterator kit = keys.begin();
map<int, pair<string, string> > primkeys = get.GetMap();
map<int, pair<string, string> >::iterator mit = primkeys.begin();
if (!keys.empty())
{
ss << "SELECT " << (*kit);
++kit;
for ( ; kit != keys.end(); ++kit)
ss << "," << (*kit);
ss << " FROM " << tablename;
if (!primkeys.empty())
{
ss << " WHERE ";
ss << mit->second.first << " = ?";
++mit;
for ( ; mit != primkeys.end(); ++mit)
ss << " and " << mit->second.first << " = ?";
mit = primkeys.begin();
}
ss << ";";
cass_bool_t has_more_pages = cass_false;
const CassResult* result = NULL;
CassString query = cass_string_init(ss.str().c_str());
CassStatement* statement = cass_statement_new(query, primkeys.size());
for ( ; mit != primkeys.end(); ++mit)
cass_statement_bind_string(statement, i++, cass_string_init(mit->second.second.c_str()));
cass_statement_set_paging_size(statement, 100);
do
{
cass_session_print_query(statement);
CassIterator* iterator;
CassFuture* future = cass_session_execute(session_, statement);
if (cass_future_error_code(future) != 0)
{
CassString message = cass_future_error_message(future);
fprintf(stderr, "Error: %.*s\n", (int)message.length, message.data);
break;
}
result = cass_future_get_result(future);
ccount = cass_result_column_count(result);
vector<string> cnames;
for (i = 0; i < ccount; i++)
cnames.push_back(cass_result_column_name(result, i).data);
iterator = cass_iterator_from_result(result);
ListVector::iterator vit;
while (cass_iterator_next(iterator))
{
const CassRow* row = cass_iterator_get_row(iterator);
for (vit = cnames.begin(); vit != cnames.end(); ++vit)
{
CassString value;
char value_buffer[256];
cass_value_get_string(cass_row_get_column_by_name(row, (*vit).c_str()), &value);
if (value.length == 0 || value.data == NULL)
continue;
memcpy(value_buffer, value.data, value.length);
value_buffer[value.length] = '\0';
retresults[(*vit)].push_back(value_buffer);
}
}
has_more_pages = cass_result_has_more_pages(result);
if (has_more_pages)
cass_statement_set_paging_state(statement, result);
cass_iterator_free(iterator);
cass_result_free(result);
} while (has_more_pages);
}
return retresults;
With this, an initial query string of SELECT id,album,title,artist,data FROM songs; results in a Cassandra query string of SELECT id,album,title,artist,data FROM songs;. However, if I add one more column to the SELECT portion SELECT id,album,title,artist,data,tags FROM songs; the query string in the Cassandra cppdriver library becomes something like: ,ar����,dat�� jOM songX. This results in the following error from Cassandra / library: Error: line 1:49 no viable alternative at character '�'.
I have also tried fewer columns, but with a WHERE clause, and that results in the same problem.
Is this a bug? Or am I building and sending strings to the cppdriver library incorrectly?
You should cass_future_wait() on the execute future before testing the error code.
Unrelated: there are also a couple of things that should be freed (future, statement), but I'm assuming that was omitted to keep this concise.
So, it looks like (for whatever reason) I HAVE to parse out the row key from the results. I checked the example, and I was able to not parse out the row key information and everything still worked. I am not yet entirely sure what is forcing me to do this (compared to the provided paging example), but for others, you need to include the following within the while (cass_iterator_nex(iterator)) block to "magically" fix my code above.
CassUuid key;
char key_buffer[CASS_UUID_STRING_LENGTH];
const CassRow* row = cass_iterator_get_row(iterator);
cass_value_get_uuid(cass_row_get_column(row, 0), key);
cass_uuid_string(key, key_buffer);
This is really a long shot, but since you mentioned the Music Service example, did you possibly download and use cql_collections.zip query strings? If so, the strings (now fixed) had minor syntax errors:
-use music
-CREATE TABLE music.songs ( id uuid PRIMARY KEY, album text, artist text, data blob, reviews list, tags set, title text, venue map
+use music;
+CREATE TABLE music.songs ( id uuid PRIMARY KEY, album text, artist text, data blob, reviews list, tags set, title text, venue map);
AeroBuffalo's code worked for me except that I had to put '&' in front of the second parameter of cass_value_get_uuid() function. It required reference type.
cass_value_get_uuid(cass_row_get_column(row, 0), &key);