base64.c

См. документацию.

 
#include <kernel.h>
 
static const char encoding_table[] = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
    'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
    'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', '0', '1', '2', '3',
    '4', '5', '6', '7', '8', '9', '+', '/' };
 
static const unsigned char decoding_table[256] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3e, 0x00, 0x00, 0x00, 0x3f,
    0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
    0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
    0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
 
uint8_t* b64e(const char *string){
    uint32_t len = ((strlen(string)));
    int i;
    uint8_t *p = nullptr;
    uint8_t *encoded = nullptr;
    p = encoded;
    for (i = 0; i < len - 2; i += 3) {
        *p++ = encoding_table[(string[i] >> 2) & 0x3F];
        *p++ = encoding_table[((string[i] & 0x3) << 4) | ((int) (string[i + 1] & 0xF0) >> 4)];
        *p++ = encoding_table[((string[i + 1] & 0xF) << 2) | ((int) (string[i + 2] & 0xC0) >> 6)];
        *p++ = encoding_table[string[i + 2] & 0x3F];
    }
    if (i < len) {
        *p++ = encoding_table[(string[i] >> 2) & 0x3F];
        if (i == (len - 1)) {
            *p++ = encoding_table[((string[i] & 0x3) << 4)];
            *p++ = '=';
        } else {
            *p++ = encoding_table[((string[i] & 0x3) << 4) |
                        ((int) (string[i + 1] & 0xF0) >> 4)];
            *p++ = encoding_table[((string[i + 1] & 0xF) << 2)];
        }
        *p++ = '=';
    }
    *p++ = '\0';
    return encoded;
}
 
uint8_t* b64d(const char *data) {
    size_t decode_size = strlen(data);
 
    if (decode_size % 4 != 0){
        return 0;
    }
 
    size_t output_length = decode_size / 4 * 3;
    
    if (data[decode_size - 1] == '=') (output_length)--;
    if (data[decode_size - 2] == '=') (output_length)--;
    
    uint8_t* decoded_data = (uint8_t*)kmalloc(output_length*3);
    
    if (decoded_data == 0){
        return 0;
    }
 
    for (size_t i = 0, j = 0; i < decode_size;) {
        uint32_t sextet_a = data[i] == '=' ? 0 & i++ : decoding_table[(uint8_t)data[i++]];
        uint32_t sextet_b = data[i] == '=' ? 0 & i++ : decoding_table[(uint8_t)data[i++]];
        uint32_t sextet_c = data[i] == '=' ? 0 & i++ : decoding_table[(uint8_t)data[i++]];
        uint32_t sextet_d = data[i] == '=' ? 0 & i++ : decoding_table[(uint8_t)data[i++]];
        uint32_t triple = (sextet_a << 3 * 6)
                    + (sextet_b << 2 * 6)
                    + (sextet_c << 1 * 6)
                    + (sextet_d << 0 * 6);
 
        if (j < output_length) decoded_data[j++] = (triple >> 2 * 8) & 0xFF;
        if (j < output_length) decoded_data[j++] = (triple >> 1 * 8) & 0xFF;
        if (j < output_length) decoded_data[j++] = (triple >> 0 * 8) & 0xFF;
    }
    decoded_data[output_length] = '\0';
    return decoded_data;
}