Mailinglist Archive: zypp-devel (56 mails)

[Michael Matz <matz@xxxxxxx>]

Hi,

On Tue, 18 Dec 2007, mlandres@xxxxxxxxxxxxxxxx wrote:

> Author: mlandres
> Date: Tue Dec 18 21:49:35 2007
> New Revision: 8127
>
> URL: http://svn.opensuse.org/viewcvs/zypp?rev=8127&view=rev
> Log:
> - Changed ResKind implementation to use IdStr.
> - split Solvable ident into kind/name
> - map src/nosrc Solvables to kind(SrcPackage) and arch(noarch)

I think it would be better if either libzypp would do away with the 
Solvable kind altogether, or implement this so that it doesn't take up any 
space in the libzypp wrapper of the sat Solvable structure.

I can't really see how fantastically usefull the kind is to deserve it 
having an own member.  The only uses I can imagine are of the type "give 
me only Patches" or "don't search Patterns" and the like.  The old solver 
also uses them in Dependencies, but let's ignore that, as it's going away.

So, in all cases you already have a Solvable, hence the complete SAT Name, 
which includes the "type".  I think it would be better to compute the kind 
from that whenever it's necessary, instead of storing it.  It can be done 
quite fast when we assume that ':' doesn't occur normally in a name (we 
can assume that):

int solv2kind (Solvable *s)
{
  if (s->arch == ARCH_SRC || s->arch == ARCH_NOSRC)
    return KIND_SOURCEPACK;
  const char *name = id2str(s->name);
  // make sure we have four characters
  if (!(name[0] && name[1] && name[2] && name[3]))
    return KIND_PACKAGE;
  int len = 0;
  int kind = 0;
  switch (name[3])
    {
      // we look at the fourth character              --------v
      case 'm': len = 4; kind = KIND_ATOM;      break;  // atom
      case 'g': len = 8; kind = KIND_LANGUAGE;  break;  // language
      case 's': len = 7; kind = KIND_MESSAGE;   break;  // message
      case 'c': len = 5; kind = KIND_PATCH;     break;  // patch
      case 't': len = 7; kind = KIND_PATTERN;   break;  // pattern
      case 'd': len = 7; kind = KIND_PRODUCT;   break;  // product
      case 'e': len = 9; kind = KIND_SELECTION; break;  // selection
      case 'i': len = 6; kind = KIND_SCRIPT;    break;  // script
      default:
        return KIND_PACKAGE;
    }
  int i;
  // make sure string doesn't end before the position of the ':'
  for (i = 4; i < len && name[i]; i++)
    ;
  if (i == len && name[i] == ':')
    return kind;
  return KIND_PACKAGE;
}

This needs to touch just one cache line of something which most probably 
is in cache already (the name) and hence is only slower by a couple of 
cycles compared to directly having the kind stored away.  But it saves 
half the size of Solvables.


Ciao,
Michael.
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