crc32 polynomial documentation

Bug #1519207 reported by Luke A. Perkins
10
This bug affects 2 people
Affects Status Importance Assigned to Milestone
libarchive-zip-perl (Ubuntu)
Confirmed
Undecided
Unassigned

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)

Revision history for this message
Luke A. Perkins (public-a) wrote :
Revision history for this message
Launchpad Janitor (janitor) wrote :

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

Changed in libarchive-zip-perl (Ubuntu):
status: New → Confirmed
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