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C++ read line from file with comma-separated values

This function reads a line from a comma-separated values (CSV) file. Parses each entry into a string, long int, or double and stores each in a separate vector. Also stores information on the order of the entries so the original line can be reconstructed, or so particular elements can be extracted.

Submitted By: jjhaag

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Views: 31,930

Language: C++

Last Modified: October 9, 2007

Instructions: Copy and paste into file. Detailed description and usage are given in the comments. Requires string, fstream, and vector headers.

Snippet

#include <string>
#include <fstream>
#include <vector>
/******************************************************************************/
/* void readCSV()
*
* Function to read a line from a comma-separated value text file and interpret
* the entries. Assumes that there are three potential data types - string,
* long/integer, and double/float. The entries are stored in separate vectors
* that are passed to the function by reference.
*
* Arguments:
*
* fstream& infile -file stream from which to read. must already be
* open with read access
*
* vector<string>& stringArray -vector of strings in which to store the strings
* that are found in the line
*
* vector<double>& doubleArray -vector of doubles in which to store the doubles
* or floats that are found in the line
*
* vector<long>& longArray -vector of longs in which to store the longs or ints
* that are found in the line
*
* vector<long>& order -vector of longs in which to store the ordering of
* elements in the original line. 0=long, 1=double,
* 2=string.
*
* The ordering of the original elements can be reconstructed and outputted
* using:
*
* vector<string>::iterator striter=stringArray.begin();
vector<double>::iterator dbliter=doubleArray.begin();
vector<long>::iterator longiter=longArray.begin();
for (long i=0; i<order.size(); ++i) {
if (order.at(i)==0) {
cout << *longiter << endl;
longiter++;
} else if (order.at(i)==1) {
cout << *dbliter << endl;
dbliter++;
} else if (order.at(i)==2) {
cout << *striter << endl;
striter++;
}
}
*
* The function stores entries in the line from the CSV file based their data
* type, which is decided with a few simple rules:
*
* If an entry contains only numerical characters, it is considered to be an
* integer (stored as long integers). Floating point numbers (stored as
* doubles) must consist entirely of numerical characters, except for a single
* period located anywhere within the entry. Any entry containing more than one
* period, or any other non-numerical characters, is stored as a string (sorry,
* no support for hex numbers).
*
* Dependencies: requires the string, vector, and fstream standard C++ headers.
*/
void readCSV(std::fstream& infile,
std::vector<std::string>& stringArray,
std::vector<double>& doubleArray,
std::vector<long>& longArray,
std::vector<long>& order) {
// declare string buffer
std::string buffer;
// get line from file
getline(infile, buffer, '\n');
// read through buffer searching for commas or end of string. the start of
// each entry is the first element of the string (first word), or the
// position after the last comma encountered (all other words). the end
// of the entry is the last element of the string (last word), or the
// position before the next comma (all other words)
std::string temp;
unsigned long start=0;
unsigned long end=0;
while (end<=buffer.size()) {
// increment end counter
end++;
// check if position of 'end' in the string a comma, past the end of
// the string, or just another character. if at a non-comma character,
// skip to the start of the next loop
if (end<buffer.size() && buffer[end]!=',') {
continue;
}
// assign comma-free token to a temporary string
temp.assign(buffer,start,end-start);
// run through each character of the token to determine if it is a
// string, floating-point, or integer, based on number of periods and
// presence of non-numeric characters
int containsPeriod=0;
int containsAlpha=0;
for (long i=0; i<(long)temp.size(); ++i) {
if (temp[i]=='.') {
// token contains a '.' character - either a string or a floating point
containsPeriod++;
} else if ( temp[i]<48 || 57<temp[i] ) {
// token contains non-numeric characters - string (sorry no hex)
containsAlpha++;
}
}
// based on alphabetical/numerical content and the presence of period/
// decimals, determine whether the entry is an integer, floating-point
// number, or a string
if (containsAlpha==0 && containsPeriod==0) {
longArray.push_back(atoi(temp.c_str()));
order.push_back(0);
} else if (containsPeriod==1 && containsAlpha==0) {
doubleArray.push_back(atof(temp.c_str()));
order.push_back(1);
} else {
stringArray.push_back(temp);
order.push_back(2);
}
// set the start and end to the proper next position
end++;
start=end;
}
}

Copy & Paste

#include <string>
#include <fstream>
#include <vector>

/******************************************************************************/
/* void readCSV()
 * 
 * Function to read a line from a comma-separated value text file and interpret 
 * the entries.  Assumes that there are three potential data types - string, 
 * long/integer, and double/float.  The entries are stored in separate vectors
 * that are passed to the function by reference.
 * 
 * Arguments:
 * 
 * 		fstream& infile		-file stream from which to read.  must already be 
 * 							open with read access
 * 
 * vector<string>& stringArray	-vector of strings in which to store the strings
 * 							that are found in the line
 * 
 * vector<double>& doubleArray	-vector of doubles in which to store the doubles
 * 							or floats that are found in the line
 * 
 * vector<long>& longArray	-vector of longs in which to store the longs or ints
 * 							that are found in the line
 * 
 * vector<long>& order		-vector of longs in which to store the ordering of
 * 							elements in the original line.  0=long, 1=double, 
 * 							2=string.
 * 
 * The ordering of the original elements can be reconstructed and outputted 
 * using:
 * 
 * 	vector<string>::iterator striter=stringArray.begin();
	vector<double>::iterator dbliter=doubleArray.begin();
	vector<long>::iterator longiter=longArray.begin();
	for (long i=0; i<order.size(); ++i) {
		if (order.at(i)==0) {
			cout << *longiter << endl;
			longiter++;
		} else if (order.at(i)==1) {
			cout << *dbliter << endl;
			dbliter++;
		} else if (order.at(i)==2) {
			cout << *striter << endl;
			striter++;
		}
	}
 * 
 * The function stores entries in the line from the CSV file based their data
 * type, which is decided with a few simple rules:
 * 
 * If an entry contains only numerical characters, it is considered to be an 
 * integer (stored as long integers).  Floating point numbers (stored as 
 * doubles) must consist entirely of numerical characters, except for a single 
 * period located anywhere within the entry.  Any entry containing more than one
 * period, or any other non-numerical characters, is stored as a string (sorry, 
 * no support for hex numbers).
 * 
 * Dependencies:  requires the string, vector, and fstream standard C++ headers.
 */

void readCSV(std::fstream& infile,
		std::vector<std::string>& stringArray,
		std::vector<double>& doubleArray,
		std::vector<long>& longArray,
		std::vector<long>& order) {
	
	//	declare string buffer
	std::string buffer;
	
	//	get line from file
	getline(infile, buffer, '\n');
	
	//	read through buffer searching for commas or end of string. the start of 
	//	each entry is the first element of the string (first word), or the 
	//	position after the last comma encountered (all other words).  the end
	//	of the entry is the last element of the string (last word), or the 
	//	position before the next comma (all other words)
	std::string temp;
	unsigned long start=0;
	unsigned long end=0;
	while (end<=buffer.size()) {
		
		//	increment end counter
		end++;
		
		//	check if position of 'end' in the string a comma, past the end of 
		//	the string, or just another character.  if at a non-comma character,
		//	skip to the start of the next loop
		if (end<buffer.size() && buffer[end]!=',') {
			continue;
		}
		
		//	assign comma-free token to a temporary string
		temp.assign(buffer,start,end-start);
		
		
		//	run through each character of the token to determine if it is a 
		//	string, floating-point, or integer, based on number of periods and
		//	presence of non-numeric characters
		int containsPeriod=0;
		int containsAlpha=0;
		
		for (long i=0; i<(long)temp.size(); ++i) {
			if (temp[i]=='.') {
				//	token contains a '.' character - either a string or a floating point
				containsPeriod++;
			} else if ( temp[i]<48 || 57<temp[i] ) {
				//	token contains non-numeric characters - string (sorry no hex)
				containsAlpha++;
			}
		}
		
		
		//	based on alphabetical/numerical content and the presence of period/
		//	decimals, determine whether the entry is an integer, floating-point
		//	number, or a string
		if (containsAlpha==0 && containsPeriod==0) {
			longArray.push_back(atoi(temp.c_str()));
			order.push_back(0);
			
		} else if (containsPeriod==1 && containsAlpha==0) {
			doubleArray.push_back(atof(temp.c_str()));
			order.push_back(1);
		} else {
			stringArray.push_back(temp);
			order.push_back(2);
		}

//	set the start and end to the proper next position
		end++;
		start=end;
	}
}

Comments
C++21 2008-09-21 10:35:03
Hi, I am a beginner on C++ and I want to implement a C++ program to read CSV files on vectors and matrices so I can manipulate. I copied and pasted the above code but I received the following error in my VC++ 6.0 comp�ler: --------------------Configuration: ReadingTextFiles_2 - Win32 Debug-------------------- Compiling... ReadingTextFile_2_Main.cpp C:\CONFIN DEL MUNDO\FINANCE\Software\MySoftware\C++\DifferentExamples\Arrays\ReadingTextFiles_2\ReadingTextFile_2_Main.cpp(81) : error C2065: 'getline' : undeclared identifier Error executing cl.exe. ReadingTextFile_2_Main.obj - 1 error(s), 0 warning(s) could you help me to fix my error. Thanks. my email is jhleonjy@yahoo.es