Function b64decode

Plugins/UnLuaExtensions/LuaSocket/Source/src/mime.cpp:318–341

-------------------------------------------------------------------------*\ * Acumulates bytes in input buffer until 4 bytes are available. * Translate the 4 bytes from Base64 form and append to buffer. * Returns new number of bytes in buffer. \*-------------------------------------------------------------------------*/

* Returns new number of bytes in buffer.
\*-------------------------------------------------------------------------*/
static size_t b64decode(UC c, UC *input, size_t size,
        luaL_Buffer *buffer)
{
    /* ignore invalid characters */
    if (b64unbase[c] > 64) return size;
    input[size++] = c;
    /* decode atom */
    if (size == 4) {
        UC decoded[3];
        int valid, value = 0;
        value =  b64unbase[input[0]]; value <<= 6;
        value |= b64unbase[input[1]]; value <<= 6;
        value |= b64unbase[input[2]]; value <<= 6;
        value |= b64unbase[input[3]];
        decoded[2] = (UC) (value & 0xff); value >>= 8;
        decoded[1] = (UC) (value & 0xff); value >>= 8;
        decoded[0] = (UC) value;
        /* take care of paddding */
        valid = (input[2] == '=') ? 1 : (input[3] == '=') ? 2 : 3;
        luaL_addlstring(buffer, (char *) decoded, valid);
        return 0;
    /* need more data */
    } else return size;
}

/*-------------------------------------------------------------------------*\
* Incrementally applies the Base64 transfer content encoding to a string