diff
< DecodeBase64Block(dptr, b64);
---
> if (*decoded_bytes + numDecoded_blk <= dest_size) {
>     DecodeBase64Block(dest + *decoded_bytes, b64);
>     *decoded_bytes += numDecoded_blk;
> } else {
>     ecode = BASE64_ECODE_BUF;
>     break;
> }
