simdplayground/encoder.cpp at main · morm24/simdplayground · GitHub

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//
// Created by mo on 4/11/23.
//
#include "encoder.h"

//#include <string>


void Encoder::encodeString(const std::string &in, std::string &out) {
    //out.clear();
    out.resize(ceil((in.size() / 3.0)) * 5);
    const char* inPtr = &in[0];
    char* outPtr = &out[0];

    //char c = * (inPtr +12);


    const size_t loop = !(in.size()%12) ? (in.size() / 12) : (in.size() / 12) +1;


    uint padding = 3-(in.size()%3);


    for(int i = 0; i < loop; i++){
        //everytime the last 4 out of 16 byte string data get lost through processing, therefore 12 byte jumps
        simde__m128i data = simde_mm_lddqu_si128((simde__m128i*) (inPtr + i*12) );
        data = simde_mm_shuffle_epi8(data, shuffleMask);
        //by shuffling every 3 8bit ASCII Letters now take up 4 bytes, "ABC" gets shuffled to "CCBA" to match the 4 bytes of the Base64 Encoding, and deal with little Endianness.

        data =   simde_mm_srli_epi32(data, 2 ) & mask1 |
                        simde_mm_srli_epi32(data, 4 ) & mask2 |
                        simde_mm_srli_epi32(data, 6 ) & mask3 |
                        data & mask4;

        data = simde_mm_shuffle_epi8(data, shuffleMask2);


        simde__m128i bigLetterMask= simde_mm_cmplt_epi8(data, _mm_set1_epi8(26)); // (a < b) ? 0xFF : 0x00
        simde__m128i allMask= bigLetterMask;
        simde__m128i smallLetterMask = simde_mm_andnot_si128(allMask, simde_mm_cmplt_epi8(data,simde_mm_set1_epi8(52))); //not allMask and  b where b is 0xFF if binaries are smaller than 52
        allMask |= smallLetterMask;
        simde__m128i numberMask = simde_mm_andnot_si128(allMask, simde_mm_cmplt_epi8(data, simde_mm_set1_epi8(62)));
        allMask |= numberMask;
        simde__m128i plusMask = simde_mm_andnot_si128(allMask, simde_mm_cmplt_epi8(data, simde_mm_set1_epi8(63)));
        allMask |= plusMask;
        simde__m128i & slashAntiMask = allMask;

        data =  bigLetterMask   & simde_mm_add_epi8(data, allA)|
                smallLetterMask & simde_mm_add_epi8(data, alla)|
                numberMask      & simde_mm_add_epi8(data, all0)|
                plusMask        & allPlus                      |
                simde_mm_andnot_si128(slashAntiMask, allSlash);

        simde_mm_storeu_si128((simde__m128*) (outPtr + i * 16), data);

    }
    out.resize(ceil((in.size() / 3.0) * 4));


    out.resize((((4 * in.size() / 3) + 3) & ~3), '=');


}