github.com/ashaduri/csv-parser

Csv::Parser (csv-parser)

Compile-time and runtime CSV parser written in C++17

Features

• Header-only.
• Requires only standard C++ (C++17).
• Supports reading CSV data from std::string_view during compilation (using constexpr).
• Fully supports RFC 4180, including quoted values, escaped quotes, and newlines in field values.
• Liberal in terms of accepting not-quite-standard CSV files, but detects errors when needed.
• Supports Excel CSV variations.
• Supports reading data as different types (string, double, empty field) (runtime only).
• Extensively tested using Catch2.

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::vector<Csv::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<double> 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

Currently, parsing at compile-time has some restrictions:

• Only string_views are supported for output (no doubles).
• To collapse consecutive double-quotes in strings, a compile-time-allocated buffer has to be used.

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::string_view data =
R"(abc, "def"
"with ""quote inside",6)";

constexpr std::size_t columns = 2, rows = 2;

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 an uncollapsed string value.
// If the buffer is too small, the code will simply not compile.
constexpr auto buffer_size = matrix[0][1].getRequiredBufferSize();  // uncollapsed size
constexpr auto buffer = matrix[0][1].getCleanStringBuffer<buffer_size>();
static_assert(buffer.getStringView() == R"(with "quote inside)"sv);

Copyright

Copyright: Alexander Shaduri [e-mail]
License: Zlib