private void ensureCapacity(int inLen) {
        int minLen = cipher.getOutputSize(inLen);
        if (obuffer == null || obuffer.length < minLen) {
            obuffer = new byte[minLen];
        }
        ostart = 0;
        ofinish = 0;
    }
Ensure obuffer is big enough for the next update or doFinal
operation, given the input length <code>inLen</code> (in bytes)
The ostart and ofinish indices are reset to 0.

@param inLen the input length (in bytes)
src/main/java/org/gaul/s3proxy/crypto/DecryptionInputStream.java