#include "Base64.h"

// 来源于阿里IOT代码  base64.c

static const unsigned char base64_enc_map[64] =
{
    '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 base64_dec_map[128] =
{
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
    127, 127, 127,  62, 127, 127, 127,  63,  52,  53,
     54,  55,  56,  57,  58,  59,  60,  61, 127, 127,
    127,  64, 127, 127, 127,   0,   1,   2,   3,   4,
      5,   6,   7,   8,   9,  10,  11,  12,  13,  14,
     15,  16,  17,  18,  19,  20,  21,  22,  23,  24,
     25, 127, 127, 127, 127, 127, 127,  26,  27,  28,
     29,  30,  31,  32,  33,  34,  35,  36,  37,  38,
     39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
     49,  50,  51, 127, 127, 127, 127, 127
};

/* SIZE_T_MAX is not standard */
#define BASE64_SIZE_T_MAX   ( (int) -1 ) 


/*
 * Encode a buffer into base64 format
 */

int Base64Encode(byte* dst, int dlen, int* olen, byte* src, int slen)
// int mbedtls_base64_encode(unsigned char* dst, int dlen, int* olen, const unsigned char* src, int slen)
{
    int i, n;
    int C1, C2, C3;
    byte* p;

    if (slen == 0)
    {
        *olen = 0;
        return(0);
    }

    n = slen / 3 + (slen % 3 != 0);

    // if (n > (BASE64_SIZE_T_MAX - 1) / 4)
    // {
    //     *olen = BASE64_SIZE_T_MAX;
    //     return(MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL);
    // }

    n *= 4;

    if ((dlen < n + 1) || (NULL == dst))
    {
        *olen = n + 1;
        return(MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL);
    }

    n = (slen / 3) * 3;

    for (i = 0, p = dst; i < n; i += 3)
    {
        C1 = *src++;
        C2 = *src++;
        C3 = *src++;

        *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
        *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];
        *p++ = base64_enc_map[(((C2 & 15) << 2) + (C3 >> 6)) & 0x3F];
        *p++ = base64_enc_map[C3 & 0x3F];
    }

    if (i < slen)
    {
        C1 = *src++;
        C2 = ((i + 1) < slen) ? *src++ : 0;

        *p++ = base64_enc_map[(C1 >> 2) & 0x3F];
        *p++ = base64_enc_map[(((C1 & 3) << 4) + (C2 >> 4)) & 0x3F];

        if ((i + 1) < slen)
            *p++ = base64_enc_map[((C2 & 15) << 2) & 0x3F];
        else *p++ = '=';

        *p++ = '=';
    }

    *olen = p - dst;
    *p = 0;

    return(0);
}

/*
 * Decode a base64-formatted buffer
 */

int Base64Decode(byte* dst, int dlen, int* olen, byte* src, int slen)
// int mbedtls_base64_decode(unsigned char* dst, int dlen, int* olen, const unsigned char* src, int slen)
{
    int i, n;
    uint j, x;
    byte* p;

    /* First pass: check for validity and get output length */
    for (i = n = j = 0; i < slen; i++)
    {
        /* Skip spaces before checking for EOL */
        x = 0;
        while (i < slen && src[i] == ' ')
        {
            ++i;
            ++x;
        }

        /* Spaces at end of buffer are OK */
        if (i == slen)
            break;

        if ((slen - i) >= 2 &&
            src[i] == '\r' && src[i + 1] == '\n')
            continue;

        if (src[i] == '\n')
            continue;

        /* Space inside a line is an error */
        if (x != 0)
            return(MBEDTLS_ERR_BASE64_INVALID_CHARACTER);

        if (src[i] == '=' && ++j > 2)
            return(MBEDTLS_ERR_BASE64_INVALID_CHARACTER);

        if (src[i] > 127 || base64_dec_map[src[i]] == 127)
            return(MBEDTLS_ERR_BASE64_INVALID_CHARACTER);

        if (base64_dec_map[src[i]] < 64 && j != 0)
            return(MBEDTLS_ERR_BASE64_INVALID_CHARACTER);

        n++;
    }

    if (n == 0)
    {
        *olen = 0;
        return(0);
    }

    /* The following expression is to calculate the following formula without
     * risk of integer overflow in n:
     *     n = ( ( n * 6 ) + 7 ) >> 3;
     */
    n = (6 * (n >> 3)) + ((6 * (n & 0x7) + 7) >> 3);
    n -= j;

    if (dst == NULL || dlen < n)
    {
        *olen = n;
        return(MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL);
    }

    for (j = 3, n = x = 0, p = dst; i > 0; i--, src++)
    {
        if (*src == '\r' || *src == '\n' || *src == ' ')
            continue;

        j -= (base64_dec_map[*src] == 64);
        x = (x << 6) | (base64_dec_map[*src] & 0x3F);

        if (++n == 4)
        {
            n = 0;
            if (j > 0) *p++ = (unsigned char)(x >> 16);
            if (j > 1) *p++ = (unsigned char)(x >> 8);
            if (j > 2) *p++ = (unsigned char)(x);
        }
    }

    *olen = p - dst;

    return(0);
}