Program Listing for File Base64.cpp

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#include "Base64.h"

namespace util {

static const char BASE64_ALPHABET[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                      "abcdefghijklmnopqrstuvwxyz"
                                      "0123456789+/";

static void a3_to_a4(std::uint8_t* a4, std::uint8_t* a3)
{
    a4[0] = (a3[0] & 0xfc) >> 2;
    a4[1] = ((a3[0] & 0x03) << 4) + ((a3[1] & 0xf0) >> 4);
    a4[2] = ((a3[1] & 0x0f) << 2) + ((a3[2] & 0xc0) >> 6);
    a4[3] = (a3[2] & 0x3f);
}

bool base64Encode(const std::string& in, std::string* out)
{
    int i = 0;
    int j = 0;
    size_t enc_len = 0;

    std::uint8_t a3[3] = {0};
    std::uint8_t a4[4] = {0};

    out->resize(base64EncodedLength(in));

    int input_len = in.size();
    std::string::const_iterator input = in.begin();

    while (input_len--) {
        a3[i++] = *(input++);
        if (i == 3) {
            a3_to_a4(a4, a3);

            for (i = 0; i < 4; i++) {
                (*out)[enc_len++] = BASE64_ALPHABET[a4[i]];
            }

            i = 0;
        }
    }

    if (i) {
        for (j = i; j < 3; j++) {
            a3[j] = '\0';
        }

        a3_to_a4(a4, a3);

        for (j = 0; j < i + 1; j++) {
            (*out)[enc_len++] = BASE64_ALPHABET[a4[j]];
        }

        while ((i++ < 3)) {
            (*out)[enc_len++] = '=';
        }
    }

    return (enc_len == out->size());
}

} // namespace util