[Bug 1519207] Re: crc32 polynomial documentation

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: libarchive-zip-perl (Ubuntu)
       Status: New => Confirmed

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Title:
  crc32 polynomial documentation

Status in libarchive-zip-perl package in Ubuntu:
  Confirmed

Bug description:
  The crc32 polynomial needs to be documented in the man page. There are
  multiple CRC polynomials that are defined in the community for 32-bit
  calculations. It is my understanding that the polynomial is the ANSI
  X3.66 CRC-32 or 0x104C11DB7. Another deficiency in the documentation
  is the initial value of the CRC and the Endean-ness of the binary
  data.

  Changing this library function will be next to impossible; however,
  documentation of these items will enable us to correlate results on
  other platforms.

  Other unexplainable results:

  1) Providing a 4 byte binary file with all zeros reports a value of "2144df1c". This implies an initial value of 0x2144df1c.
  2) Providing a 4 byte binary file with the value of 0x1c, 0xdf, 0x44, 0x21 reports a value of "6522df69".
  3) Providing a 4 byte binary file with the value of 0x21, 0x44, 0xdf, 0x1c reports a value of "5cf8b7c4".

  Since neither #2 or #3 cause crc32 to report a value of "00000000",
  the CRC calculator inside this utility is inconsistent with all of the
  CRC algorithms I know of.

  Release: Ubuntu 14.04.3 LTS Release:  14.04

  libarchive-zip-perl:
    Installed: 1.30-7
    Candidate: 1.30-7
    Version table:
   *** 1.30-7 0
          500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
          100 /var/lib/dpkg/status

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: libarchive-zip-perl 1.30-7
  ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
  Uname: Linux 3.13.0-32-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.16
  Architecture: amd64
  Date: Mon Nov 23 21:08:00 2015
  InstallationDate: Installed on 2015-01-23 (305 days ago)
  InstallationMedia: Ubuntu-Server 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.3)
  PackageArchitecture: all
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/usr/bin/tcsh
  SourcePackage: libarchive-zip-perl
  UpgradeStatus: No upgrade log present (probably fresh install)

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