vectorAsText.hh

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#ifndef NPSTAT_VECTORASTEXT_HH_
#define NPSTAT_VECTORASTEXT_HH_
 
/*!
// \file vectorAsText.hh
//
// \brief Utilities for reading/writing std::vector objects from/to text files 
//
// Author: I. Volobouev
//
// January 2023
*/
 
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <climits>
 
namespace npstat {
    /**
    // Function for dumping vectors into text files, one element per line.
    //
    // Note that, while this function will work with T objects that do
    // not have default constructors, it will not be possible to read
    // such objects back.
    //
    // "true" is returned on success, "false" on failure.
    // Dumping less than "nElementsToDump" elements is considered
    // a success.
    */
    template <typename T>
    bool dumpVectorAsText(const std::vector<T>& v,
                          std::ostream& asciiStream,
                          const unsigned long firstElementToDump=0,
                          const unsigned long nElementsToDump=ULONG_MAX)
    {
        if (nElementsToDump)
        {
            const unsigned long sz = v.size();
            if (firstElementToDump < sz)
            {
                unsigned long ndumped = 0;
                for (unsigned long i=firstElementToDump;
                     i<sz && ndumped<nElementsToDump; ++i, ++ndumped)
                    asciiStream << v[i] << '\n';
                if (asciiStream.fail())
                    return false;
            }
        }
        return true;
    }
 
    /**
    // Function for filling vectors from text files, one element per line.
    // Will only work with T objects that have default constructors.
    // "true" is returned on success, "false" on failure.
    //
    // Empty lines, lines which consist of pure white space, and lines
    // which start with an arbitrary amount of white space (including
    // none) followed by '#' are ignored (considered comments).
    */
    template <typename T>    
    bool fillVectorFromText(std::istream& asciiStream,
                            std::vector<T>* v,
                            const unsigned long maxElementsToFill=ULONG_MAX)
    {
        bool status = true;
        if (maxElementsToFill && asciiStream)
        {
            assert(v);
            std::string linebuf;
            std::istringstream is;
            unsigned long nfilled = 0;
            T buffer;
 
            while (asciiStream && status && nfilled<maxElementsToFill)
            {
                std::getline(asciiStream, linebuf);
                const unsigned long len = linebuf.size();
                if (len == 0UL)
                    continue;
 
                // Ignore lines which are pure white space
                // or which start with an arbitrary number
                // of white space characters followed by #.
                bool isComment = false;
                bool allSpace = true;
                char* line = &linebuf[0];
 
                for (unsigned long i=0; i<len && allSpace; ++i)
                {
                    if (isspace(line[i]))
                        continue;
                    if (line[i] == '#')
                        isComment = true;
                    allSpace = false;
                }
                if (isComment || allSpace)
                    continue;
 
                is.str(linebuf);
                is.clear();
                is >> buffer;
                if (is.fail())
                    status = false;
                else
                    v->push_back(buffer);
 
                if ((asciiStream.fail() && !asciiStream.eof()) || 
                    asciiStream.bad())
                    status = false;
             }
        }
        return status;        
    }
}
 
#endif // NPSTAT_VECTORASTEXT_HH_