ReadStream.h

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#ifndef _utl_ReadStream_h_
#define _utl_ReadStream_h_

#include <utl/ShadowPtrPolicy.h>
#include <boost/lexical_cast.hpp>
#include <boost/algorithm/string/trim.hpp>
#include <vector>
#include <iostream>
#include <string>


namespace utl {

  /*
    \brief Read simple structured data from stream sources

    The only requirement for reading a colon-structured data is that
    is is described by some type T with the operator>> implemented.

    Example:
    File contains columns: int time, double pressure, bool flag

    The structure is described by the following class:
    \code
    struct Data {
      int fTime;
      double fPressure;
      bool fFlag;
    };

    inline
    std::istream&
    operator>>(std::istream& is, Data& d)
    {
      return is >> d.fTime >> std::ws >> d.fPressure >> std::ws >> d.fFlag;
    }
    \endcode

    Having that, the whole file is read as
    \code
    ifstream file("foo.txt");
    vector<Data> v;
    ReadStream(file).GetLines(v);
    \endcode

    By default, the GetLines() method does whitespace and comment stripping before
    the string is passed to the boost::lexical_cast (which uses operator>>). If not
    desired, this white-space compression and comment stripping can be switched off
    by adding 'false' to the GetLines() call.

    The following types of input is stripped:
    <ul>
    <li> empty lines or lines with only white-space characters (this is done even
         when 'false' is passed)
    <li> shell-like comments: all the rest of the line after '#' is discarded
    <li> C-like comments: all characters between inclusive '&47;*' and '*&47;' are removed
    <li> C++-like comments: all characters after and including '//' are discarded
    </ul>

    If your file contain more columns which you don't want to parse, issue
    is.setstate(ios_base::eofbit) after you've read all the needed columns.
    boost::lexical_cast namely checks for the state of the stream after operator>>
    is called and requires the EOF state to be set.

    \author Darko Veberic
  */

  class ReadStream {

  public:
    ReadStream() = default;

    ReadStream(std::istream& is) : fStream(&is) { }

    void SetStream(std::istream& is) { fStream = &is; }

    std::istream& GetStream() const
    { ThrowOnZeroDereference::Examine(fStream); return *fStream; }

    void Clear() { fStream = nullptr; }

    template<typename T> bool Get(T& t)
    { ThrowOnZeroDereference::Examine(fStream); return (GetStream() >> t); }

    template<typename T>
    bool
    GetLine(T& t, const bool trim = false)
    {
      ThrowOnZeroDereference::Examine(fStream);
      std::string line;
      if (!std::getline(*fStream, line))
        return false;
      if (trim)
        boost::algorithm::trim(line);
      t = boost::lexical_cast<T>(line);
      return true;
    }

    template<typename T>
    void
    GetLines(std::vector<T>& v, const bool filterComments = true, const bool trim = false)
    {
      ThrowOnZeroDereference::Examine(fStream);
      std::string line;
      while (std::getline(*fStream, line)) {
        if (filterComments)
          line = FilterComments(line);
        if (trim)
          boost::algorithm::trim(line);
        if (!line.empty())
          v.push_back(boost::lexical_cast<T>(line));
      }
    }

    explicit operator bool() const { return fStream && *fStream; }

  private:
    ReadStream(const ReadStream&);
    ReadStream& operator=(const ReadStream&);

    static std::string FilterComments(const std::string& line);

    std::istream* fStream = nullptr;

  };

}


#endif