cwcsv

CSV reading and writing

No allocation on traversing cells and rows
Supports arbitrary separator, quote and newline symbols
Support embedded separator, quote and newline symbols in quoted fields
Reading and writing iterators are compatible with standard algorithms
Header only
Unit tested using Catch
Single-threaded

Benchmark

A benchmark is included that counts the number of cells and rows in a given file.

Running this on a 758 MB file containing 20 million rows with 6 cells each gives:

rows: 20239829
cells: 121438974
cells/row: 6
time: 0.798856 s
rate: 152 cells/us

A smaller version of the file is included, bench/sample.csv, which yields similar performance of 150 cells per microsecond.

Note this excludes the time taken to load the file into memory.

Reading

Cells and rows are iterated over using standard range-based for loops.

The cell object contains the methods:

to_string()
to_int()
to_long()
to_longlong()
to_double()

which convert the cell value to the respective type.

It is also possible to get a string view into the raw data:

to_string_view()

which allows you to avoid allocation if no conversion is required.

Example: from a string literal

auto& text = "a,b,c,d,e\n"
             "1,2,3,4,5";

auto parser = csv::make_parser( text );

for( auto&& row : parser ) {
	for( auto&& cell : row ) {
		cout << '[' << cell.to_string_view() << ']';
	}
	cout << '\n';
}

Example: from a file

// first load the file into a std::string
auto str = csv::load_file("test.csv");

auto parser = csv::make_parser( str );

for( auto&& row : parser ) {
	for( auto&& cell : row ) {
		cout << '[' << cell.to_string() << ']';
	}
	cout << '\n';
}

We can also use standard algorithms:

auto row = parser.begin();
++row; // skip header

std::vector<int> data;

std::transform( row.begin(), row.end(), std::back_inserter(data), []( auto&& x ){ return x.to_int(); });

for( auto&& x : data ) {
	cout << '[' << x << ']';
}
cout << '\n';

Writing

Example: to string

std::string out;

auto writer = csv::make_writer( std::back_inserter(out) );

writer.write_row( "Open", "High", "Low", "Close" );
writer.write_row( 101, 102.5, 99.8, 102 );

auto vals = { 100.2, 103.1, 98.6, 101.5 };

writer.write_row_range( vals.begin(), vals.end() );

Example: to file

std::ofstream out("test.csv");

auto writer = csv::make_writer( out );

writer.write_row( "Open", "High", "Low", "Close" );
writer.write_row( 101, 102.5, 99.8, 102 );

auto vals = { 100.2, 103.1, 98.6, 101.5 };

writer.write_row_range( vals.begin(), vals.end() );

cwzx/cwcsv