sparse-file

问题 I want to copy files from one place to another and the problem is I deal with a lot of sparse files. Is there any (easy) way of copying sparse files without becoming huge at the destination? My basic code: out, err := os.Create(bricks[0] + "/" + fileName) in, err := os.Open(event.Name) io.Copy(out, in) 回答1: Some background theory Note that io.Copy() pipes raw bytes – which is sort of understandable once you consider that it pipes data from an io.Reader to an io.Writer which provide Read([

问题 I have a python3 script that operates with numpy.memmap arrays. It writes an array to newly generated temporary file that is located in /tmp : import numpy, tempfile size = 2 ** 37 * 10 tmp = tempfile.NamedTemporaryFile('w+') array = numpy.memmap(tmp.name, dtype = 'i8', mode = 'w+', shape = size) array[0] = 666 array[size-1] = 777 del array array2 = numpy.memmap(tmp.name, dtype = 'i8', mode = 'r+', shape = size) print('File: {}. Array size: {}. First cell value: {}. Last cell value: {}'.\

问题 Given a file descriptor or file name, how do I know if I can write to an arbitrary location without waiting for the intervening part be explicitly zeroed out on disk? 回答1: You can stat() the file to obtain file size and number of disk blocks, seek a relatively small number of disk blocks past the end of the file, write a known number of blocks, then stat the file again. Compare the original number of disk blocks to the final number. Just a few disk blocks shouldn't take too long to write if

问题 I'm creating sparse files in python as follows: >>> f = open('testfile', 'ab') >>> f.truncate(1024000) >>> f.close() when the file is done, it takes up 0 disk space, but its inode size is set to my truncated value (1000K): igor47@piglet:~/test$ ls -lh testfile -rw-r--r-- 1 igor47 igor47 1000K 2010-07-09 04:02 testfile igor47@piglet:~/test$ du -hs testfile 0 testfile How do I get the file's real space usage (allocated size) inside python? The stat call returns the file's apparent size, and I

问题 I'm creating sparse files in python as follows: >>> f = open('testfile', 'ab') >>> f.truncate(1024000) >>> f.close() when the file is done, it takes up 0 disk space, but its inode size is set to my truncated value (1000K): igor47@piglet:~/test$ ls -lh testfile -rw-r--r-- 1 igor47 igor47 1000K 2010-07-09 04:02 testfile igor47@piglet:~/test$ du -hs testfile 0 testfile How do I get the file's real space usage (allocated size) inside python? The stat call returns the file's apparent size, and I

问题 how can i create a pre-allocated file on android? something like a sparse file ? i need to make an applicaton that will download a large file , and i want to avoid having an out-of-space error while the download is commencing . my solution needs to support resuming and writing to both internal and external storage. i've tried what is written here: Create file with given size in Java but for some reason, none of those solutions worked. 回答1: this is odd. it works fine now . perhaps i've tested

问题 how can i create a pre-allocated file on android? something like a sparse file ? i need to make an applicaton that will download a large file , and i want to avoid having an out-of-space error while the download is commencing . my solution needs to support resuming and writing to both internal and external storage. i've tried what is written here: Create file with given size in Java but for some reason, none of those solutions worked. 回答1: this is odd. it works fine now . perhaps i've tested

问题 What is a sparse file and why do we need it? The only thing that I am able to get is that it is a very large file and it is efficient(in gigabytes). How is it efficient ? 回答1: Say you have a file with many empty bytes \x00 . These many empty bytes \x00 are called holes. Storing empty bytes is just not efficient, we know there are many of them in the file, so why store them on the storage device? We could instead store metadata describing those zeros. When a process reads the file those zero

问题 I want to fetch image from table 1 to update image in table 2 on parse here is my code ParseFile image= ParseUser.getCurrentUser().getParseFile("image"); if(image==null) { } else { try { byte[] data=image.getData(); Bitmap bmp = BitmapFactory .decodeByteArray( data, 0, data.length); // Set the Bitmap into the // ImageView image1.setImageBitmap(bmp); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } This code is working perfect it retrieves and set image

问题 I got a sparse file of 1TB which stores actually 32MB data on Linux. Is it possible to "efficiently" make a package to store the sparse file? The package should be unpacked to be a 1TB sparse file on another computer. Ideally, the "package" should be around 32MB. Note: On possible solution is to use 'tar': https://wiki.archlinux.org/index.php/Sparse_file#Archiving_with_.60tar.27 However, for a 1TB sparse file, although the tar ball may be small, archiving the sparse file will take too long a