Home/ Questions/Q 6555261
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-25T12:47:53+00:00

Does any one know what the cache map hash function that generates a hash

  • 0

Does any one know what the cache map hash function that generates a hash from a URL that mozilla firefox uses? I have allready found this http://benlast.livejournal.com/29164.html where it gives a pretty good example code, unfortunately I think it is outdated and not used anymore in the current version of Firefox.
Any help would be much appreciated.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    You can see the hash algorithm used by Firefox here: http://hg.mozilla.org/mozilla-central/file/09935ede3c77/netwerk/cache/nsDiskCacheDevice.cpp#l272. It is pretty simple but rather different from the one you linked to (I checked and the change happened between Firefox 3.5 and Firefox 3.6). Essentially, it seems to treat the URL as a sequence of unsigned integers (little-endian, padded with zeros as necessary) and adds them up to the variables a, b and c (first and forth number to a, second and fifth to b, third and sixth to c). The three variables are then combined in function hashmix().

    The initial value for a and b is 0x9e3779b9, the value for c is somewhat more complicated – it comes in as parameter. All callers use the default value of this parameter however which is 0 (see nsDiskCache.h).

    I guess that http://burtleburtle.net/bob/hash/evahash.html might provide more info on the algorithm used.

    • 0