On Thu, Feb 16, 2012 at 9:50 AM, Gary Gregory <garydgreg...@gmail.com>wrote:
> On Wed, Feb 15, 2012 at 11:28 PM, Andreas Menke <asme...@snafu.de> wrote:
>
>> Hi,
>>
>> usage of ensureBufferSize() seems to be 'asymptotic' safe (despite the
>> fact that a line separator might be much bigger than DEFAULT_BUFFER_SIZE,
>> see below, and that no body else use the function as he is told by
>> description..).
>>
>> /** Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}*
>> *. */
>> private void resizeBuffer(int size) {
>> //size = 0;
>> if (buffer == null) {
>> int nSize = getDefaultBufferSize();
>> if(nSize < size )
>> nSize = size;
>> buffer = new byte[nSize];
>> pos = 0;
>> readPos = 0;
>> } else {
>> int nSize = buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR;
>> if( 0 > nSize ) // should be tested with huge data
>> nSize = Integer.MAX_VALUE;
>> else if (nSize < size)
>> nSize = size;
>> byte[] b = new byte[nSize];
>> System.arraycopy(buffer, 0, b, 0, pos);
>> buffer = b;
>> }
>> }
>>
>> /**
>> * Ensure that the buffer has room for <code>size</code> bytes
>> *
>> * @param size minimum spare space required
>> */
>> protected void ensureBufferSize(int size){
>> if ((buffer == null) || (buffer.length < pos + size)){
>> resizeBuffer(pos+size);
>> }
>> }
>>
>> The test case is
>>
>>
>> /**
>> * lineSeparator much bigger than DEFAULT_BUFFER_SIZE.
>> */
>> @Test
>> public void testDEFAULT_BUFFER_SIZE() {
>> byte[] baLineSeparator = new byte[BaseNCodec_DEFAULT_**
>> BUFFER_SIZE*4-3];
>> Base64 b64 = new Base64(Base64_BYTES_PER_**ENCODED_BLOCK,
>> baLineSeparator);
>> String strOriginal = "Hello World";
>> String strDecoded = new String(b64.decode(b64.encode(**
>> StringUtils.getBytesUtf8(**strOriginal))));
>> assertTrue("testDEFAULT_**BUFFER_SIZE",
>> strOriginal.equals(strDecoded)**);
>> }
>> private int BaseNCodec_DEFAULT_BUFFER_SIZE = 8192;
>> private int Base64_BYTES_PER_ENCODED_BLOCK = 4;
>>
>> It's astonishing how big the lineSeparator must be to see the error. I
>> hope I have nothing overseen ('verschlimmbessern'). The code might work
>> with huge data (not tested).
>>
>
> This is an extreme case indeed. I'll expand these two data points from the
> test case below:
>
> - line length is set to 4
> - line separator length is 32765
>
> The line separator length is usually 2 for CRLF.
>
BTW, I added this test with an @Ignore as
org.apache.commons.codec.binary.Base64Test.testHugeLineSeparator()
Gary
>
> Gary
>
>
>
>>
>>
>> My personal view is, that the code is quite complicated. The loop
>>
>> for (int i = 0; i < inAvail; i++) {
>> ensureBufferSize(encodeSize);
>> modulus = (modulus+1) % BYTES_PER_UNENCODED_BLOCK;
>> int b = in[inPos++];
>> if (b < 0) {
>> b += 256;
>> }
>> bitWorkArea = (bitWorkArea << 8) + b; // BITS_PER_BYTE
>> if (0 == modulus) { // 3 bytes = 24 bits = 4 * 6 bits to
>> extract
>>
>> with constant 'encodeSize' might slow down the algorithm. The estimated
>> length is calculated
>>
>> long len = b64.getEncodedLength(**binaryData);
>> if (len > maxResultSize) {
>>
>> but the value is not further used. The result array is doubled
>>
>> byte[] buf = new byte[pos - readPos];
>> readResults(buf, 0, buf.length);
>> return buf;
>>
>> which is memory wasting in case input is very large.
>>
>> Regards
>>
>> Andreas
>>
>> --
>>
>>
>> Andreas Menke
>>
>> Diplom-Informatiker Univ.
>> Software-Entwicklung
>>
>> Fon 0151 5081 1173
>> Mail asme...@snafu.de
>>
>>
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>>
>
>
> --
> E-Mail: garydgreg...@gmail.com | ggreg...@apache.org
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>
--
E-Mail: garydgreg...@gmail.com | ggreg...@apache.org
JUnit in Action, 2nd Ed: <http://goog_1249600977>http://bit.ly/ECvg0
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Blog: http://garygregory.wordpress.com
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