How to unzip large zip file & write to SDCARD in less time

Question

To unzip zip file I've used classes from package java.util.zip* by refering this and it works correctly however to unzip a file of 40MB it takes 59 seconds. When I tried same zip file on iPhone project (we are developing app for both platforms - Android & iPone & that have functionality to unzip zip file & save unzipped content to SDCARD-Android or document directory - iPhone ), it takes only 14 seconds. The iphone app uses ziparchive.

So my question are:

1.From above experiment it clears that unzipping & file write operation to SDCARD in Java consumes more time as compared to iPhone app, so I decided to use C/C++ level unzipping & file write operation using NDK. Is this right choice ?

2.I have searched on google, stackoverflow & some suggested to use minizip but there no sufficient help on how to use minizip in android. Is anyboday have tried minizip for android ?

3.I also tried NDK development for libz to achieve my goal, as Libz is added in NDK but not getting how to use it. Is anybody tried libz in NDK?

4.Is there any other Framework in Java or C/C++ that unzip large zip file & write them to SDCARD in less time ?

Please help me.

Here is my Java Unzip Code :

public String unzip() {

    String result;

    try {

        FileInputStream fin = new FileInputStream(this.filePath);
        ZipInputStream zin = new ZipInputStream(fin);
        ZipEntry ze = null;

        while ((ze = zin.getNextEntry()) != null) {

            Log.v("Unzip", "Unzipping " + ze.getName());

            if (ze.isDirectory()) {
                _dirChecker(ze.getName());
            } else {

                // Read 16 k at a time 
                byte[] buffer = new byte[16*1024];
                 int read;

                FileOutputStream fout = new FileOutputStream(this.location+ "/" + ze.getName());

                while ((read = zin.read(buffer)) != -1)
                {
                    fout.write(buffer, 0, read);
                }


                zin.closeEntry();
                fout.close();
            }

        }

        zin.close();
        result = "success";

    } catch (Exception e) {
        Log.e("unzip", "unzip", e);
        result = "failure";
    }

    return result;
}

Answer 1

Why don't you try this code.It works awesome

    String zipname = "data.zip";
FileInputStream fis = new FileInputStream(zipname);
ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
ZipEntry entry;

while ((entry = zis.getNextEntry()) != null) {
  System.out.println("Unzipping: " + entry.getName());

  int size;
  byte[] buffer = new byte[2048];

  FileOutputStream fos = new FileOutputStream(entry.getName());
  BufferedOutputStream bos = new BufferedOutputStream(fos, buffer.length);

  while ((size = zis.read(buffer, 0, buffer.length)) != -1) {
    bos.write(buffer, 0, size);
  }
  bos.flush();
  bos.close();
}
zis.close();
fis.close();

}

Answer 2

All of the unzip code eventually ends up in zlib. There is no Java implementation of "deflate" compression in Android core libs.

The only reason java.util.Zip should be slower than a "native" unzip is if the file I/O is done badly, e.g. something is using really small buffers. Looking at the code linked from the question, this is exactly what's happening -- it's operating on individual bytes.

One of the comments on the solution provided a patch that uses a 4K buffer. Drop that in and see what happens to your performance.

Answer 3

Try to just write 40Mb file to SDCard and measure time spent. (Almost) all free (or even paid) implementations of zip archive support libraries are based on the same zlib code, which takes most processing speed during the unzipping. Java code should be much slower than native one, so I'd suggest to try NDK unzipping. Also, trying to unzip archive with zero compression level will give you a guess how much time unzipping code takes and how much time is spend on just data copying.

Answer 4

public boolean unzip(String zipfilepath, String destinationdir) {

            try {
                FileInputStream fis = new FileInputStream(zipfilepath);
                ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
                ZipEntry entry;

                while ((entry = zis.getNextEntry()) != null) {
                  System.out.println("Unzipping: " + entry.getName());

                  int size;
                  byte[] buffer = new byte[2048];

                  FileOutputStream fos = new FileOutputStream(destinationdir+ "/" + entry.getName());
                  BufferedOutputStream bos = new BufferedOutputStream(fos, buffer.length);

                  while ((size = zis.read(buffer, 0, buffer.length)) != -1) {
                    bos.write(buffer, 0, size);
                  }
                  bos.flush();
                  bos.close();
                }
                zis.close();
                fis.close();
                return true;
                }catch(Exception e){
                    return false;
                }
        }



String zipfilepath = context.getFilesDir().getPath()+"/"+myfile.zip;
String  destinationdir = context.getFilesDir().getPath();


unzip(zipfilepath, destinationdir);