libbase64

Библиотека на C для кодирования и декодирования base64
по умолчанию используется вариант RFC4648, но имеется
возможность задать любой иной вариант алфавита кодирования

Не использует выделения памяти, работает с входным и выходным
буферами, кодирует и декодирует данные целиком

Можно использовать не как библиотеку, а просто расположить
base64.c и base64.h в дереве исходников вашего проекта.

Зависимости

• Заголовки
  • stdint.h
  • stddef.h
• C компилятор
  • C99 или C11

Установка и удаление

Глобально

make
sudo make install
sudo make uninstall

Локально

make
make PREFIX=$HOME/.local install
make PREFIX=$HOME/.local uninstall

Независимо

make
make DESTDIR=$HOME/some_you_dir install
make DESTDIR=$HOME/some_you_dir uninstall

Использование

Минимальный пример кодирования

/* This example code licensed as Public Domain CC0 */
/* https://creativecommons.org/public-domain/cc0/  */
#include <stdio.h>
#include <string.h>
#include "base64.h"
int main(int argc, char **argv)
{
    /* prepare input */
    unsigned char inp[] = "Hello World!";
    size_t        inp_size = strlen(inp);
    /* prepare ouput */
    size_t        out_size = inp_size * 1.5; // or ((inp_size / 3) * 4) + 4
    unsigned char out[out_size];
    /* prepare variable to save data len (can ignore it and set NULL) */
    size_t        written = 0;
    /* set data, if last parametr is NULL used RFC4648 base64 alphabet */
    int status = base64_encode(inp,inp_size,out,out_size,&written,NULL);
    if(status != BASE64_SUCCESS)
    {
        fprintf(stderr,"Error: code = %d\n",status);
        return status;
    }
    /* out_size > written size, in this case need set '\0' */
    out[written] = '\0';
    /* show result */
    printf("data = %s  size = %d\n",out, written);
    return 0;
}

make && cc encode.c -o app libbase64.a
./app
data = SGVsbG8gV29ybGQh  size = 16

Минимальный пример декодирования

/* This example code licensed as Public Domain CC0 */
/* https://creativecommons.org/public-domain/cc0/  */
#include <stdio.h>
#include <string.h>
#include "base64.h"
int main(int argc, char **argv)
{
    /* prepare input */
    unsigned char inp[] = "SGVsbG8gV29ybGQh";
    size_t        inp_size = strlen(inp);
    /* prepare ouput */
    size_t        out_size = inp_size; /* or calculate own*/
    unsigned char out[out_size];
    /* prepare variable to save data len (can ignore it and set NULL) */
    size_t        written = 0;
    /* set data, if last parametr is NULL used RFC4648 base64 alphabet */
    int status = base64_decode(inp,inp_size,out,out_size,&written,NULL);
    if(status != BASE64_SUCCESS)
    {
        fprintf(stderr,"Error: code = %d\n",status);
        return status;
    }
    /*out_size > written size, in this case need set '\0' */
    out[written] = '\0';
    /* show result */
    printf("data = %s  size = %d\n",out, written);
    return 0;
}

make && cc encode.c -o app libbase64.a
./app
data = Hello World!  size = 12

Пример использования альтернативного кодирования

/* This example code licensed as Public Domain CC0 */
/* https://creativecommons.org/public-domain/cc0/  */
#include <stdio.h>
#include <string.h>
#include "base64.h"
int main(int argc, char **argv)
{
    /* create you own base64 */
    unsigned char alphabet[] =
    "ABCDEFGcdefghijHIJKLMN0123456789*?abkOPQRSTUVWXYZlmnopqrstuvwxyz";
    unsigned char endcode    = '@';
    struct base64 mybase;
    int reg_status =  base64_register(alphabet,endcode,&mybase);
    if(reg_status != BASE64_SUCCESS)
    {
        fprintf(stderr,"Error: code = %d\n",reg_status);
        return reg_status;
    }
    /* prepare input */
    unsigned char inp[] = "Hello World!";
    size_t        inp_size = strlen(inp);
    /* prepare ouput */
    size_t        out_size = inp_size * 1.5; // or ((inp_size / 3) * 4) + 4
    unsigned char out[out_size];
    /* prepare variable to save data len (can ignore it and set NULL) */
    size_t        written = 0;
    /* set data, if last parametr is NULL used RFC4648 base64 alphabet */
    int status = base64_encode(inp,inp_size,out,out_size,&written,&mybase);
    if(status != BASE64_SUCCESS)
    {
        fprintf(stderr,"Error: code = %d\n",status);
        return status;
    }
    /*out_size > written size, in this case need set '\0' */
    out[written] = '\0';
    printf("data = %s  size = %d\n",out, written);
    return 0;
}

make && cc custom.c -o app libbase64.a
./app
data = KGNV5Gw*Nqxm5GI?  size = 16

Различные варианты Base64 существующие в реальности. Этот список не претендует на полноту, есть полные совпадения с rfc4648.

----------
basename = "rfc4648"
endcode  = '='
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
----------
baename  = "rfc1421"
endcode  = '='
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
----------
baename  = "rfc2045"
endcode  = '='
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
----------
basename = "freenet"
endcode  = '='
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789~-";
----------
basename = "rfc3548"
endcode  = '='
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
----------
basename = "rfc4880"
endcode  = '='
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
----------
basename = "y64"
endcode  = '-'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._";
----------
basename = "rfc1642"
endcode  = '\0'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
----------
basename = "xmltoken"
endcode  = '\0'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-";
----------
basename = "xmlname"
endcode  = '\0'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_:";
----------
basename = "pident1"
endcode  = '\0'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-";
----------
basename = "pident2"
endcode  = '\0'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._";
----------
basename = "rfc3501"
endcode  = '\0'
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

На заметку

Кажется всё работает правильно. Потоковый механизм кодирования и декодирования base64 в планах.