GitHub - ashaduri/csv-parser: Compile-time and runtime CSV parser written in Modern C++ (original) (raw)

Csv::Parser (csv-parser)

Compile-time and runtime CSV parser written in Modern C++

GitHub release (latest SemVer) GitHub Language

Features

API Reference

Automatically generated API reference describes the public API in detail.

Usage Examples

Runtime Parsing into 2D std::vector

Example:

#include "csv_parser.h"

// ...

using namespace std::string_view_literals;

// Data to parse std::string_view data = "abc,def\n5,6"sv;

// Let "cell_refs" be a vector of columns. // After parsing, each element will contain Csv::CellReference object. If the cell data type // is Csv::CellType::String, Csv::CellReference object will reference a part of the original data. // Other Cell* types, as well as floating point and integral types can also be used here. std::vector<std::vectorCsv::CellReference> cell_refs;

Csv::Parser parser;

try { // This throws Csv::ParseError on error. parser.parseTo2DVector(data, cell_refs); } catch(Csv::ParseError& ex) { std::cerr << "CSV parse error: " << ex.what() << std::endl; return EXIT_FAILURE; }

assert(cell_refs.size() == 2); assert(cell_refs[0].size() == 2); assert(cell_refs[1].size() == 2);

assert(cell_refs[0][0].getType() == Csv::CellType::String); assert(cell_refs[1][0].getType() == Csv::CellType::String); assert(cell_refs[0][1].getType() == Csv::CellType::Double); assert(cell_refs[1][1].getType() == Csv::CellType::Double);

std::cout << "Column 0, row 0: " << cell_refs[0][0].getCleanString().value() << std::endl; // abc std::cout << "Column 1, row 0: " << cell_refs[1][0].getCleanString().value() << std::endl; // def std::cout << "Column 0, row 1: " << cell_refs[0][1].getDouble().value() << std::endl; // 5 std::cout << "Column 1, row 1: " << cell_refs[1][1].getDouble().value() << std::endl; // 6

Runtime Parsing of Numeric Matrix Into 1D Vector With Row-Major Order

Example:

#include "csv_parser.h"

// ...

using namespace std::string_view_literals;

// Data to parse std::string_view data = "11,12,13\n21,22,23"sv;

// Let matrix_data be a flat matrix of doubles in row-major order. // Other floating point and integral types, as well as Cell* types can also be used here. std::vector matrix_data;

Csv::Parser parser; Csv::MatrixInformation info;

try { // This throws Csv::ParseError on error. info = parser.parseToVectorRowMajor(data, matrix_data); } catch(Csv::ParseError& ex) { std::cerr << "CSV parse error: " << ex.what() << std::endl; return EXIT_FAILURE; }

assert(matrix_data.size() == 3 * 2); assert(info.getColumns() == 3); assert(info.getRows() == 2);

std::cout << "Row 0, column 0: " << matrix_data[0] << std::endl; // 11 std::cout << "Row 0, column 1: " << matrix_data[1] << std::endl; // 12 std::cout << "Row 0, column 2: " << matrix_data[2] << std::endl; // 13

// matrixIndex(row, column) can be used to avoid accidental mistakes std::cout << "Row 1, column 0: " << matrix_data[info.matrixIndex(1, 0)] << std::endl; // 21 std::cout << "Row 1, column 1: " << matrix_data[info.matrixIndex(1, 1)] << std::endl; // 22 std::cout << "Row 1, column 2: " << matrix_data[info.matrixIndex(1, 2)] << std::endl; // 23

return EXIT_SUCCESS;

Compile-Time Parsing Into 2D std::array

Currently, parsing at compile-time has some restrictions:

One (possibly useful) consequence of compile-time parsing is that a parse error also causes a compilation error.

Example:

#include "csv_parser.h"

// ...

using namespace std::string_view_literals;

constexpr std::size_t columns = 2, rows = 2; constexpr std::string_view data = R"(abc, "def" "with ""quote inside",6)";

constexpr Csv::Parser parser;

// parse into std::array<std::array<CellStringReference, rows>, columns> constexpr auto matrix = parser.parseTo2DArray<rows, columns>(data);

// Verify the data at compile time. // Note that consecutive double-quotes are not collapsed when using // getOriginalStringView(). To collapse them, use the getCleanStringBuffer() // approach below. static_assert(matrix[0][0].getOriginalStringView() == "abc"sv); static_assert(matrix[1][0].getOriginalStringView() == "def"sv); static_assert(matrix[1][1].getOriginalStringView() == "6"sv);

// To support consecutive double-quote collapsing at compile-time, allocate a compile-time // buffer to place the clean string inside. The buffer size has to be at least that // of a collapsed string value. // If the buffer is too small, the code will simply not compile. constexpr auto buffer_size = matrix[0][1].getRequiredBufferSize(); // collapsed size constexpr auto buffer = matrix[0][1].getCleanStringBuffer(); static_assert(buffer.getStringView() == R"(with "quote inside)"sv);

Compile-Time Parsing of Integral Matrix Into 1D Vector

The library can be used to parse CSV data at compile-time into a 1D vector, in row-major or column-major order. Additionally, compile-time parsing of integral types is supported since C++23.

Example:

#include "csv_parser.h"

// ...

using namespace std::string_view_literals;

constexpr std::size_t columns = 2, rows = 3; constexpr std::string_view data = R"(11, -12 21, 4 60, -10)";

// Use Csv::LocaleUnawareBehaviorPolicy to avoid locale issues and allow compile-time integer parsing. constexpr Csv::ParserCsv::LocaleUnawareBehaviorPolicy parser;

// Parse into std::array<CellStringReference, rows * columns> in row-major order { constexpr auto matrix = parser.parseToArray<rows, columns>(data, Csv::MatrixOrder::RowMajor);

static_assert(matrix[0].getOriginalStringView() == "11"sv);
static_assert(matrix[2].getOriginalStringView() == "21"sv);

}

// Parse into std::array<std::int64_t, rows * columns> in column-major order. // Compile-time parsing to integers is supported since C++23. #if __cplusplus >= 202300L { constexpr auto matrix = parser.parseToArray<rows, columns, std::int64_t>(data, Csv::MatrixOrder::ColumnMajor);

static_assert(matrix[0] == 11);
static_assert(matrix[2] == 60);

} #endif

Compile-Time Parsing of Numeric Matrix Using External Library for Floating Point Numbers

A library like fast_float can be used to parse floating point numbers at compile-time. This is done by creating a custom policy that implements the readNumber andcreate methods. This approach also allows for improving the performance of parsing floating point numbers compared to the standard library.

Example:

#include "csv_parser.h" #include "fast_float/fast_float.h"

// Custom policy which uses fast_float library for parsing to floating point. struct CustomPolicy : Csv::LocaleUnawareBehaviorPolicy { template static constexpr std::optional readNumber(std::string_view cell) { Number parsed_value = 0; auto [ptr, ec] = fast_float::from_chars(cell.begin(), cell.end(), parsed_value); if (ec == std::errc() && ptr == (cell.end())) { return parsed_value; } return std::nullopt; }

template<typename CellT>
static constexpr CellT create(std::string_view cell, Csv::CellTypeHint hint)
{
    return readNumber<CellT>(cell).value_or(std::numeric_limits<CellT>::quiet_NaN());
}

};

void parse() { constexpr std::string_view data = R"(11.6, -12.3 2e5, -inf nan, inf)";

// Use custom policy which uses fast_float library for parsing to floating point.
constexpr Csv::Parser<CustomPolicy> parser;
constexpr std::size_t columns = 2, rows = 3;

// Parse into std::array<double, rows * columns> in row-major order
constexpr auto matrix = parser.parseToArray<rows, columns, double>(data, Csv::MatrixOrder::RowMajor);

static_assert(matrix[0] == 11.6);
static_assert(matrix[3] == -std::numeric_limits<double>::infinity());

}

Copyright: Alexander Shaduri ashaduri@gmail.com
License: Zlib