axmol/external/fastlib/fast_csv.hpp

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 Copyright (c) 2020 Simdsoft Limited.

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#ifndef SIMDSOFT_FAST_CSV_HPP
#define SIMDSOFT_FAST_CSV_HPP

#include <type_traits>

/* The usage of fastl::fast_csv_parse_line
std::string buffer = read_file("xxx.csv");
const char* cursor = buffer.c_str();
while(*cursor) {
   cursor = fastl::fast_csv_parse_line(cursor, [&](const char* v_start, const char* v_end) {
       // do somethings, store or parse the column value
       // std::string value(v_start, v_end);
   });
}
*/

namespace fastl {
    /*
    * The common xsv fwd, the delimiter could be any other
    */
    template <int _Delimiter, typename _CStr, typename _Fty> inline _CStr fast_xsv_parse_line(_CStr s, _Fty&& op);

    /*
     * op prototype: op(const char* v_start, const char* v_end)
     */
    template <typename _CStr, typename _Fty> inline _CStr fast_csv_parse_line(_CStr s, _Fty&& op)
    {
        return fast_xsv_parse_line<(int)','>(s, std::forward<_Fty>(op));
    }

    /*
     * op prototype: op(const char* v_start, const char* v_end)
     */
    template <int _Delimiter, typename _CStr, typename _Fty> inline _CStr fast_xsv_parse_line(_CStr s, _Fty&& op)
    {
        // FSM
        enum
        {
            normal, // new field
            quote_field,
            quote_field_try_end,
            quote_field_end,
        } state;

        state = normal;

        _CStr _Start = s; // the start of every string
        _CStr _Ptr = s; // source string iterator
        _CStr _Quote = nullptr;
        int skipCRLF = 1;

    _L_loop:
        {
            switch ((int)*_Ptr)
            {
            case _Delimiter:
                switch (state)
                {
                case normal:
                    if (_Start <= _Ptr)
                        op(_Start, _Ptr);
                    _Start = _Ptr + 1;
                    break;
                case quote_field_try_end:
                    if (_Start < _Ptr)
                        op(_Start, _Ptr - 1);
                case quote_field_end:
                    state = normal;
                    _Start = _Ptr + 1; // skip the field end '\"'
                    break;
                default:; // quote_field, do nothing
                }

                break;
            case (int)'\"':
                switch (state)
                {
                case normal:
                    state = quote_field;
                    ++_Start; // skip left '\"'
                    break;
                case quote_field: // field end by right '\"'
                    _Quote = _Ptr;
                    state = quote_field_try_end; // delay 1 loop to detect whether is a
                                                  // inner quote, not end for field
                    break;
                case quote_field_try_end:
                    if (_Ptr - _Quote > 1)
                    {
                        state = quote_field_end;
                        op(_Start, _Ptr);
                    }
                    else
                    {
                        state = quote_field;
                    }
                    break;
                default:;
                }
                break;
            case (int)'\r':
                skipCRLF = 2;
            case (int)'\n':
                if (quote_field == state)
                {
                    skipCRLF = 0;
                    break;
                }
            case (int)'\0':
                switch (state)
                {
                case normal:
                    if (_Start <= _Ptr)
                        op(_Start, _Ptr);
                    break;
                case quote_field_try_end:
                    if (_Start < _Ptr)
                        op(_Start, _Ptr - 1);
                    break;
                default:; // other state, do nothing, quote_field, invalid csv format
                }
                goto _L_end;
            }
            ++_Ptr;

            goto _L_loop;
        }

    _L_end:
        return _Ptr + skipCRLF; // pointer to next line or after of
                                // null-termainted-charactor
    }
}

#endif