a few tar.xz packages are bigger than their uncompressed tar

a few tar.xz packages are bigger than their uncompressed tar

[Jérôme Bouat]

Hello,

I looked into the local folder where the downloaded packages are saved before they are installed. I noticed that a few compressed archives files are using more size than their uncompressed form. For example, the libstdc++6-6.4.0-1.tar.xz file uses more space than its uncompressed tar file (on cygwin x86_64).

That is not surprising. All compression methods may sometimes inflate the final amount of data.

Would it be a way to keep the tar archive file uncompressed if the compressed form needs more space ?

Regards.

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: a few tar.xz packages are bigger than their uncompressed tar

[Marco Atzeri]

On 24/09/2017 20:46, Jérôme Bouat wrote:
> Hello,
> 
> I looked into the local folder where the downloaded packages are saved 
> before they are installed. I noticed that a few compressed archives 
> files are using more size than their uncompressed form. For example, the 
> libstdc++6-6.4.0-1.tar.xz file uses more space than its uncompressed tar 
> file (on cygwin x86_64).

I do not see it

$ ls -s  libstdc++6-6.4.0-1.tar.xz
280K libstdc++6-6.4.0-1.tar.xz

$ ls -s usr/bin/cygstdc++-6.dll
1.4M usr/bin/cygstdc++-6.dll

Regards
Marco

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: a few tar.xz packages are bigger than their uncompressed tar

[Andrey Repin]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=utf-8, Size: 1544 bytes --]

Greetings, Jérôme Bouat!

> Hello,

> I looked into the local folder where the downloaded packages are saved
> before they are installed. I noticed that a few compressed archives files
> are using more size than their uncompressed form. For example, the
> libstdc++6-6.4.0-1.tar.xz file uses more space than its uncompressed tar file (on cygwin x86_64).

$ ls -ld "libstdc++6-6.4.0-1.tar.xz" ; tar tf "libstdc++6-6.4.0-1.tar.xz"  -v
-rw-r--r-- 1 anrdaemon None 282724 сен 18 20:17 libstdc++6-6.4.0-1.tar.xz
-rwxr-xr-x Blue/None   1367059 2017-09-10 01:23 usr/bin/cygstdc++-6.dll

$ sha512sum.exe libstdc++6-6.4.0-1.tar.xz
734f6f91003588c82bccfc016d89414cd25ea6560484391c1424513f053b3e0f3e9932e317740804c10d90e6f9fd99d4d198cf8ea953da22969aab50182f4c74 *libstdc++6-6.4.0-1.tar.xz
# Matches the one in setup.ini

> That is not surprising. All compression methods may sometimes inflate the final amount of data.

> Would it be a way to keep the tar archive file uncompressed if the compressed form needs more space ?

Compression MAY inflate the file, but never by an order of magnitude.
At worst, it will be inflated by the size of metadata describing all blocks in
order.


-- 
With best regards,
Andrey Repin
Wednesday, September 27, 2017 07:43:04

Sorry for my terrible english...\x03B‹KCB”\x1c›Ø›\x19[H\x1c™\^[ܝ\x1cΈ\b\b\b\b\b\b\x1a\x1d\x1d\x1c\x0e‹ËØÞYÝÚ[‹˜ÛÛKÜ\x1c›Ø›\x19[\Ëš\x1d^[[\x03B‘TNˆ\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\x1a\x1d\x1d\x1c\x0e‹ËØÞYÝÚ[‹˜ÛÛKÙ˜\KÃB‘^[ØÝ[Y[\x18]\x1a[ÛŽˆ\b\b\b\b\b\b\b\b\x1a\x1d\x1d\x1c\x0e‹ËØÞYÝÚ[‹˜ÛÛKÙ^[ØÜËš\x1d^[[\x03B•[œÝXœØÜšX™H\x1a[™›Îˆ\b\b\b\b\b\x1a\x1d\x1d\x1c\x0e‹ËØÞYÝÚ[‹˜ÛÛKÛ[\vÈÝ[œÝXœØÜšX™K\Ú[\^[\x19CBƒB

Re: a few tar.xz packages are bigger than their uncompressed tar

[Kaz Kylheku]

On 24.09.2017 11:46, Jérôme Bouat wrote:
> Hello,
> 
> I looked into the local folder where the downloaded packages are saved
> before they are installed. I noticed that a few compressed archives
> files are using more size than their uncompressed form. For example,
> the libstdc++6-6.4.0-1.tar.xz file uses more space than its
> uncompressed tar file (on cygwin x86_64).
> 
> That is not surprising. All compression methods may sometimes inflate
> the final amount of data.

No compression method need ever increase the
size of the datum by more than one bit.

The compressed representation can begin with a header
bit which is 1 to indicate "compressed" and 0 to indicate
"stored without compression".


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: a few tar.xz packages are bigger than their uncompressed tar

[Jérôme Bouat]

Hello

> No compression method need ever increase the
> size of the datum by more than one bit.
> 
> The compressed representation can begin with a header
> bit which is 1 to indicate "compressed" and 0 to indicate
> "stored without compression".

Does the xz format provide a checksum even if the file is stored without compression ?

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: a few tar.xz packages are bigger than their uncompressed tar

[Jérôme Bouat]

Hello

> No compression method need ever increase the
> size of the datum by more than one bit.
> 
> The compressed representation can begin with a header
> bit which is 1 to indicate "compressed" and 0 to indicate
> "stored without compression".

Does the xz format provide a checksum even if the file is stored without compression ?

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple