Converting from Java to C++ Reading a File, and parsing - c++

The Text file looks like this:
Apple,Itunes,1,7.3
Microsoft,Windows Media Player,1,10
.... and so on.....
The parse method is:
private IApplication parseLineToApp(String lineFromTxtFile) {
Scanner lineScanner = new Scanner(lineFromTxtFile);
lineScanner.useDelimiter(",");
return new Application(lineScanner.next(), lineScanner.next(), lineScanner.nextInt(), lineScanner.next());
}
I want to do the same thing in c++ to create a new application().
Note: I already have an application class, and need to add that application to a repository which is a collection of applications
Thanks in advance :)

You can create a vector of strings using Boost and the STL.
// given std::string lineFromTxtFile
std::vector<std::string> scanner;
boost::split (scanner, lineFromTxtFile, boost::is_any_of(","));
return new Application (scanner[0], scanner[1], scanner[2], scanner[3]);
If you want scanner[2] to be an integer, there's
boost::lexical_cast<int> (scanner[2])

File operations can be done a few different ways in C/C++. A C++-style approach could look like the following:
std::vector<Application> ApplicationList;
std::ifstream fin("myapplist.txt"); // open a file stream
while (!fin.eof()) // while this isn't the end of the file
{
char buffer[256] = {0};
fin.getline(buffer, 256); // read the current line of text into the buffer
std::vector<std::string> scanner;
boost::split(scanner, buffer, boost::is_any_of(",")); // split the buffer and store the results in the scanner vector
ApplicationList.push_back(Application(scanner[0], scanner[1], scanner[2], scanner[3]); // add the application to the application list
}
fin.close();
Assuming your Application struct/class is copyable (otherwise you'd want to use pointers in your ApplicationList).

There is no Scanner class in the C++ standard library, the direct translation is not possible. Of course, you can always implement your own.
Alas, you could create a split function:
unsigned int split(const std::string &txt, std::vector<std::string> &strs, char ch)
{
size_t pos = txt.find( ch );
size_t initialPos = 0;
strs.clear();
if ( pos != std::string::npos ) {
// Decompose each statement
strs.push_back( txt.substr( initialPos, pos - initialPos + 1 ) );
initialPos = pos + 1;
pos = txt.find( ch, initialPos );
while( pos != std::string::npos ) {
strs.push_back( txt.substr( initialPos, pos - initialPos + 1 ) );
initialPos = pos + 1;
pos = txt.find( ch, initialPos );
}
}
else strs.push_back( txt );
return strs.size();
}
Then you could rewrite your code as:
std::vector<std::string> scanner;
split( lineFromTxtFile, scanner, ',' );
return new Application (scanner[0], scanner[1], scanner[2], scanner[3]);
Hope this helps.

Related

`fgetpos` Not Returning the Correct Position

Update: To get around the problem below, I have done
if (ftell(m_pFile) != m_strLine.size())
fseek(m_pFile, m_strLine.size(), SEEK_SET);
fpos_t position;
fgetpos(m_pFile, &position);
this then returns the correct position for my file. However, I would still like to understand why this is occurring?
I want to get the position in a text file. For most files I have been reading the first line, storing the position, doing some other stuff and returning to the position afterwards...
m_pFile = Utils::OpenFile(m_strBaseDir + "\\" + Source + "\\" + m_strFile, "r");
m_strLine = Utils::ReadLine(m_pFile);
bEOF = feof(m_pFile) != 0;
if (bEOF)
{
Utils::CompilerError(m_ErrorCallback,
(boost::format("File '%1%' is empty.") % m_strFile).str());
return false;
}
// Open.
pFileCode = Utils::OpenFile(strGenCode + "\\" + m_strFile, options.c_str());
m_strLine = Utils::Trim(m_strLine);
Utils::WriteLine(pFileCode, m_strLine);
// Store location and start passes.
unsigned int nLineCount = 1;
fpos_t position;
fgetpos(m_pFile, &position);
m_strLine = Utils::ReadLine(m_pFile);
...
fsetpos(m_pFile, &position);
m_strLine = Utils::ReadLine(m_pFile);
With all files provided to me the storage of the fgetpos and fsetpos works correctly. The problem is with a file that I have created which looks like
which is almost identical to the supplied files. The problem is that for the file above fgetpos(m_pFile, &position); is not returning the correct position (I am aware that the fpos_t position is implementation specific). After the first ReadLine I get a position of 58 (edited from 60) so that when I attempt to read the second line with
fsetpos(m_pFile, &position);
m_strLine = Utils::ReadLine(m_pFile);
I get
on 700
instead of
Selection: Function ADJEXCL
Why is fgetpos not returning the position of the end of the first line?
_Note. The Utils.ReadLine method is:
std::string Utils::ReadLine(FILE* file)
{
if (file == NULL)
return NULL;
char buffer[MAX_READLINE];
if (fgets(buffer, MAX_READLINE, file) != NULL)
{
if (buffer != NULL)
{
std::string str(buffer);
Utils::TrimNewLineChar(str);
return str;
}
}
std::string str(buffer);
str.clear();
return str;
}
with
void Utils::TrimNewLineChar(std::string& s)
{
if (!s.empty() && s[s.length() - 1] == '\n')
s.erase(s.length() - 1);
}
Edit. Following the debugging suggestions in the comments I have added the following code
m_pFile = Utils::OpenFile(m_strBaseDir + "\\" + Source + "\\" + m_strFile, "r");
m_strLine = Utils::ReadLine(m_pFile);
// Here m-strLine = " Logic Definition Report Chart Version: New Version 700" (64 chars).
long vv = ftell(m_pFile); // Here vv = 58!?
fpos_t pos;
vv = ftell(m_pFile);
fgetpos(m_pFile, &pos); // pos = 58.
fsetpos(m_pFile, &pos);
m_strLine = Utils::ReadLine(m_pFile);
Sorry, but your Utils functions have clearly been written by an incompetent. Some issues are just a matter of style. For trimming:
void Utils::TrimNewLineChar(std::string& s)
{
if (!s.empty() && *s.rbegin() == '\n')
s.resize(s.size() - 1); // resize, not erase
}
or in C++11
void Utils::TrimNewLineChar(std::string& s)
{
if (!s.empty() && s.back() == '\n')
s.pop_back();
}
ReadLine is even worse, replace it with:
std::string Utils::ReadLine(FILE* file)
{
std::string str;
char buffer[MAX_READLINE];
if (file != NULL && fgets(buffer, MAX_READLINE, file) != NULL)
{
// it is guaranteed that buffer != NULL, since it is an automatic array
str.assign(buffer);
Utils::TrimNewLineChar(str);
}
// copying buffer into str is useless here
return str;
}
That last str(buffer) in the original worries me especially. If fgets reaches a newline, fills the buffer, or reaches end of file, you're guaranteed to get a properly terminated string in your buffer. If some other I/O error occurs? Who knows? It might be undefined behavior.
Best not to rely on the value of buffer when fgets fails.

cocos2d-x JSON file parsing

I have a .json file, containing an array of dictionaries. Can you show me a good way of parsing it? I'm using the cocos2d-x 3.0-alpha version and the json classes, placed in the external/json directory.
I tried:
Array* items = Array::createWithContentsOfFile("test.json");
and
string fullPath = CCFileUtils::getInstance()->fullPathForFilename("test.json");
long bufferSize = 0;
const char* mFileData = (const char*)FileUtils::getInstance()->getFileData(fullPath.c_str(), "r", &bufferSize);
string clearData(mFileData);
size_t pos = clearData.rfind("}");
clearData = clearData.substr(0, pos+1);
string data = clearData.c_str();
log("%s", clearData.c_str());
Json::Value _root;
Json::Reader reader;
reader.parse(data, _root);
but none of them work - the first method returns an empty array, the second one results a _root variable, containing the whole json, but I can't make it into an array and create a separate dictionary object for each of the array's elements ( which is what I'm trying to do ).
Use JsonCPP you mentioned above but with CCFileUtils class
unsigned long filesize = 0;
std::string content;
std::string fullPath = "path relative to your androidmanifest.xml/index.json"
unsigned char* fileData = CCFileUtils::sharedFileUtils()->getFileData(fullPath.c_str(), "r", &filesize);
content.append((char*)fileData);
delete[] fileData;
Json::Value jsonresult;
Json::Reader reader;
bool parsingSuccessful = reader.parse( content, jsonresult );
if ( !parsingSuccessful )
{
// report to the user the failure
return false;
}

C++ equivalent of MATLAB's "fileparts" function

In MATLAB there's a nice function called fileparts that takes a full file path and parses it into path, filename (without extension), and extension as in the following example from the documentation:
file = 'H:\user4\matlab\classpath.txt';
[pathstr, name, ext] = fileparts(file)
>> pathstr = H:\user4\matlab
>> name = classpath
>> ext = .txt
So I was wondering if there's an equivalent function in any standard C++ or C libraries that I could use? Or would I have to implement this myself? I realize it's fairly simple, but I figured if there's already something pre-made that would be preferable.
Thanks.
The boost library has a file system component "basic_path" that allows you use iterators to discover each component in the filename. Such a component would be OS specific, and I believe you need to compile boost separately for Windows, Linux etc.
I just wrote this simple function. It behaves similar as Matlab's fileparts and works independent of platform.
struct FileParts
{
string path;
string name;
string ext;
};
FileParts fileparts(string filename)
{
int idx0 = filename.rfind("/");
int idx1 = filename.rfind(".");
FileParts fp;
fp.path = filename.substr(0,idx0+1);
fp.name = filename.substr(idx0+1,idx1-idx0-1);
fp.ext = filename.substr(idx1);
return fp;
}
A platform-independent way with C++11/14.
#include <experimental/filesystem>
namespace fs = std::experimental::filesystem;
void fileparts(string full, string& fpath, string& fname, string& fext)
{
auto source = fs::path(full);
fpath = source.parent_path().string();
fname = source.stem().string();
fext = source.extension().string();
}
...
string fpath, fname, fext;
fileparts(full_file_path,fpath,fname,fext);
Some possible solutions, depending on your OS:
Visual C++ _splitpath function
Win32 Shell Path Handling Functions such as PathFindExtension, PathFindFileName, PathStripPath, PathRemoveExtension, PathRemoveFileSpec
Ekalic's text-only approach is useful, but it didn't check for errors. Here's one that does, and also works with both / and \
struct FileParts
{
std::string path; //!< containing folder, if provided, including trailing slash
std::string name; //!< base file name, without extension
std::string ext; //!< extension, including '.'
};
//! Using only text manipulation, splits a full path into component file parts
FileParts fileparts(const std::string &fullpath)
{
using namespace std;
size_t idxSlash = fullpath.rfind("/");
if (idxSlash == string::npos) {
idxSlash = fullpath.rfind("\\");
}
size_t idxDot = fullpath.rfind(".");
FileParts fp;
if (idxSlash != string::npos && idxDot != string::npos) {
fp.path = fullpath.substr(0, idxSlash + 1);
fp.name = fullpath.substr(idxSlash + 1, idxDot - idxSlash - 1);
fp.ext = fullpath.substr(idxDot);
} else if (idxSlash == string::npos && idxDot == string::npos) {
fp.name = fullpath;
} else if (/* only */ idxSlash == string::npos) {
fp.name = fullpath.substr(0, idxDot);
fp.ext = fullpath.substr(idxDot);
} else { // only idxDot == string::npos
fp.path = fullpath.substr(0, idxSlash + 1);
fp.name = fullpath.substr(idxSlash + 1);
}
return fp;
}

Save all file names in a directory to a vector

I need to save all ".xml" file names in a directory to a vector. To make a long story short, I cannot use the dirent API. It seems as if C++ does not have any concept of "directories".
Once I have the filenames in a vector, I can iterate through and "fopen" these files.
Is there an easy way to get these filenames at runtime?
Easy way is to use Boost.Filesystem library.
namespace fs = boost::filesystem;
// ...
std::string path_to_xml = CUSTOM_DIR_PATH;
std::vector<string> xml_files;
fs::directory_iterator dir_iter( static_cast<fs::path>(path_to_xml) ), dir_end;
for (; dir_iter != dir_end; ++dir_iter ) {
if ( boost::iends_with( boost::to_lower_copy( dir_iter->filename() ), ".xml" ) )
xml_files.push_back( dir_iter->filename() );
}
I suggest having a look at boost::filesystem if it should be portable and bringing boost in isn't too heavy.
If you don't like boost, try Poco. It has a DirectoryIterator. http://pocoproject.org/
Something like this (Note, Format is a sprintf:ish funciton you can replace)
bool MakeFileList(const wchar_t* pDirectory,vector<wstring> *pFileList)
{
wstring sTemp = Format(L"%s\\*.%s",pDirectory,L"xml");
_wfinddata_t first_file;
long hFile = _wfindfirst(sTemp.c_str(),&first_file);
if(hFile != -1)
{
wstring sFile = first_file.name;
wstring sPath = Format(L"%s%s",pDirectory,sFile.c_str());
pFileList->push_back(sPath);
while(_wfindnext(hFile,&first_file) != -1)
{
wstring sFile = first_file.name;
wstring sPath = Format(L"%s%s",pDirectory,sFile.c_str());
pFileList->push_back(sPath);
}
_findclose(hFile);
}else
return false;
return true;
}

Remove '\n.\n' C++

If i have a string as such
"I am not here... \n..Hello\n.\n....Whats happening"
I want to replace the above string so:
"I am not here... \n..Hello\n. \n....Whats happening"
^ Space added
Just a bit of a background on what im doing. Im using sendmail in C++ and \n.\n is End Of Message Equivalent of sendmail. I just created a class that uses sendmail to send mails. but obviously if the user from the outsite gives sendmail that command i want it to be removed. Here is my message function just incase.:
//Operator to add to the message
void operator<<(string imessage){
if (imessage != ""){ message += imessage; }
}
How would i go about doing this. Thanks in advance :D
This is my last version :)
This code handles the case mentioned by #Greg Hewgill
string& format_text(string& str)
{
const string::size_type dot_offset = 2;
string::size_type found_at_start = str.find("\n.\n"),
found_at = str.find("\n.\n");
if(found_at_start != string::npos)
str.insert(0, " ");
while(found_at != string::npos)
{
str.insert(found_at+dot_offset+1, " ");
found_at = str.find("\n.\n", found_at+1);
}
return str;
}
int main()
{
string text = ".\nn\n.\nn";
std::cout << format_text(text);
}
Look up String.find and String.replace
For example (not tested)
string endOfMessage = "\n.\n";
string replacement = "\n. \n";
size_t position;
while (position = message.find(endOfMessage))
{
message.replace(position, endOfMessage.length(), replacement);
}
This is derived from Dan McG's answer so upvote him ;)
string endOfMessage = "\n.\n";
string replacement = "\n. \n";
size_t position;
while (position = message.find(endOfMessage, position) != message.npos)
{
message.replace(position, endOfMessage.length(), replacement);
position += replacement.length();
}
Boost has Boost.Regex (a regular expression module). Might be overkill if this is the only replacement you need to do.
Use std::search and the insert method of sequence containers such as string, deque, or whatever you use to store the message text.
typedef std::string::iterator SIter; // or whatever container you use
static const char *end_seq = "\n.\n";
for ( SIter tricky_begin = msg.begin();
tricky_begin = std::search( tricky_begin, msg.end(), end_seq, end_seq+3 ),
tricky_begin != msg.end(); ) {
tricky_begin = msg.insert( tricky_begin + 2, ' ' );
}