b64.cpp

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#include "b64.h"
#include "Exception.h"
 
#include <limits>
#include <stdio.h>
 
namespace eve
{
 
// Translation table as described in RFC1113
static const char cb64[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
// Translation table to decode (created by Bob Trower)
static const char cd64[]="|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\\]^_`abcdefghijklmnopq";
 
static void b64_encode_block(char in[3], char out[4], int len)
{
    out[0] = (char) cb64[(int)((in[0] & 0xfc) >> 2)];
    out[1] = (char) cb64[(int)(((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4))];
    out[2] = (char) (len > 1 ? cb64[(int)(((in[1] & 0x0f) << 2) | ((in[2] & 0xc0) >> 6))] : '=');
    out[3] = (char) (len > 2 ? cb64[(int)(in[2] & 0x3f)] : '=');
}
 
char *b64_encode(const char *src, size_t srclen, size_t linelen, size_t &dstlen)
{
    if (linelen == 0)
        linelen = std::numeric_limits<size_t>::max();
 
    size_t blocksout = 0;
    size_t srcpos = 0;
 
    size_t adjustment = (srclen % 3) ? (3 - (srclen % 3)) : 0;
    size_t paddedlen = ((srclen + adjustment) / 3) * 4;
 
    dstlen = paddedlen + paddedlen / linelen;
 
    if (dstlen == 0)
        return nullptr;
 
    char *dst = nullptr;
    try
    {
        dst = new char[dstlen + 1];
    }
    catch (std::exception &)
    {
        throw eve::Exception("Out of memory.");
    }
 
    size_t dstpos = 0;
 
    while (srcpos < srclen)
    {
        char in[3]  = {0};
        char out[4] = {0};
 
        int len = 0;
 
        for (int i = 0; i < 3; i++)
        {
            if (srcpos >= srclen)
                break;
 
            in[i] = src[srcpos++];
            len++;
        }
 
        if (len > 0)
        {
            b64_encode_block(in, out, len);
 
            for (int i = 0; i < 4 && dstpos < dstlen; i++, dstpos++)
                dst[dstpos] = out[i];
 
            blocksout++;
        }
 
        if (blocksout >= linelen / 4 || srcpos >= srclen)
        {
            if (blocksout > 0 && dstpos < dstlen)
                dst[dstpos++] = '\n';
 
            blocksout = 0;
        }
    }
 
    dst[dstpos] = '\0';
    return dst;
}
 
static void b64_decode_block(char in[4], char out[3])
{
    out[0] = (char)(in[0] << 2 | in[1] >> 4);
    out[1] = (char)(in[1] << 4 | in[2] >> 2);
    out[2] = (char)(((in[2] << 6) & 0xc0) | in[3]);
}
 
char *b64_decode(const char *src, size_t srclen, size_t &size)
{
    size_t paddedsize = (srclen / 4) * 3;
 
    char *dst = nullptr;
    try
    {
        dst = new char[paddedsize];
    }
    catch (std::exception &)
    {
        throw eve::Exception("Out of memory.");
    }
 
    char *d = dst;
 
    char in[4]  = {0};
    char out[3] = {0};
    size_t i, len, srcpos = 0;
 
    while (srcpos <= srclen)
    {
        for (len = 0, i = 0; i < 4 && srcpos <= srclen; i++)
        {
            char v = 0;
 
            while (srcpos <= srclen && v == 0)
            {
                v = src[srcpos++];
                v = (char)((v < 43 || v > 122) ? 0 : cd64[v - 43]);
                if (v != 0)
                    v = (char)((v == '$') ? 0 : v - 61);
            }
 
            if (srcpos <= srclen)
            {
                len++;
                if (v != 0)
                    in[i] = (char)(v - 1);
            }
            else
                in[i] = 0;
        }
 
        if (len)
        {
            b64_decode_block(in, out);
            for (i = 0; i < len - 1; i++)
                 *(d++) = out[i];
        }
    }
 
    size = (size_t)(ptrdiff_t) (d - dst);
    return dst;
}
 
} // eve