/**
* Method used to rewrap a GTSWrapper, typically to change the compression settings.
*
* @param wrapper
* @param compress
* @param compratio
* @return
*/
public static GTSWrapper rewrap(GTSWrapper wrapper, boolean compress, double compratio) {
byte[] unwrapped = unwrapEncoded(wrapper);
GTSEncoder encoder = new GTSEncoder(wrapper.getBase(), null, unwrapped);
GTSWrapper tmp = fromGTSEncoderToGTSWrapper(encoder, compress, compratio);
GTSWrapper rewrapped = new GTSWrapper(wrapper);
rewrapped.setCompressed(tmp.isCompressed());
rewrapped.setCompressionPasses(tmp.getCompressionPasses());
rewrapped.setEncoded(tmp.getEncoded());
return rewrapped;
}
public static GTSWrapper fromGTSEncoderToGTSWrapper(
GTSEncoder encoder, boolean compress, double compratio) {
if (compratio < 1.0D) {
compratio = 1.0D;
}
GTSWrapper wrapper = new GTSWrapper();
try {
if (!compress) {
wrapper.setEncoded(encoder.getBytes());
} else {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] bytes = encoder.getBytes();
double ratio = 0.0D;
int pass = 0;
//
// We compress the data once, if the compression ratio is greater
// than 'compratio', we consider that the resulting compressed data will
// probably still have lots of repetitions since we will have
// overflowed the gzip sliding window several times, we therefore
// enter a loop to compress the data until the compression ratio
// falls below 'compratio'
// We then store the number of compression passes in the GTSWrapper
// so we can apply a matching number of decompression ops
//
// For ultimate compression, set 'compratio' to 1.0
//
byte[] encoded = null;
do {
encoded = bytes;
ratio = bytes.length;
GZIPOutputStream gzos = new GZIPOutputStream(baos);
gzos.write(bytes);
gzos.close();
bytes = baos.toByteArray();
baos.reset();
ratio = ratio / bytes.length;
pass++;
} while (ratio > compratio);
if (ratio > 1.0D) {
// The last compression pass improved the footprint, so use the compressed data
wrapper.setEncoded(bytes);
} else {
// The last pass added some overhead, ignore it
pass = pass - 1;
wrapper.setEncoded(encoded);
}
if (pass > 0) {
wrapper.setCompressed(true);
if (pass > 1) {
// Only store number of passes if it is > 1 as 1 is the default value
wrapper.setCompressionPasses(pass);
}
} else {
wrapper.setCompressed(false);
}
}
wrapper.setBase(encoder.getBaseTimestamp());
wrapper.setCount(encoder.getCount());
wrapper.setMetadata(encoder.getMetadata());
} catch (IOException e) {
e.printStackTrace();
}
return wrapper;
}
