zeroinstall/injector/arch.py

   1 """
   2 Information about the current system's architecture.
   3
   4 This module provides information about the current system. It is used to determine
   5 whether an implementation is suitable for this machine, and to compare different implementations.
   6
   7 For example, it will indicate that:
   8
   9  - An i486 machine cannot run an i686 binary.
  10  - An i686 machine can run an i486 binary, but would prefer an i586 one.
  11  - A Windows binary cannot run on a Linux machine.
  12
  13 Each dictionary maps from a supported architecture type to a preference level. Lower numbers are
  14 better, Unsupported architectures are not listed at all.
  15 """
  16
  17 # Copyright (C) 2006, Thomas Leonard
  18 # See the README file for details, or visit http://0install.net.
  19
  20 import os
  21
  22 # os_ranks and mapping are mappings from names to how good they are.
  23 # 1 => Native (best)
  24 # Higher numbers are worse but usable.
  25 _uname = os.uname()
  26
  27 os_ranks = {
  28 #       'Linux' : 3,            # Linux (lots of systems support emulation)
  29         None : 2,               # Any OS
  30         _uname[0] : 1,          # Current OS
  31 }
  32
  33 def _get_machine_ranks():
  34         # Binaries compiled for _this_machine are best...
  35         this_machine = _uname[-1]
  36         machine_ranks = {this_machine : 0}
  37
  38         # If this_machine appears in the first column of this table, all
  39         # following machine types on the line will also run on this one
  40         # (earlier ones preferred):
  41         _machine_matrix = {
  42                 'i486': ['i386'],
  43                 'i586': ['i486', 'i386'],
  44                 'i686': ['i586', 'i486', 'i386'],
  45                 'ppc64': ['ppc32'],
  46         }
  47         for supported in _machine_matrix.get(this_machine, []):
  48                 machine_ranks[supported] = len(machine_ranks)
  49
  50         # At the lowest priority, try a machine-independant implementation
  51         machine_ranks[None] = len(machine_ranks)
  52         return machine_ranks
  53
  54 machine_ranks = _get_machine_ranks()
  55 #print machine_ranks
  56
  57 class Architecture:
  58         """A description of an architecture. Use by L{solver} to make sure it chooses
  59         compatible versions.
  60         @ivar os_ranks: supported operating systems and their desirability
  61         @type os_ranks: {str: int}
  62         @ivar machine_ranks: supported CPU types and their desirability
  63         @type machine_ranks: {str: int}
  64         @ivar child_arch: architecture for dependencies (usually C{self})
  65         @type child_arch: L{Architecture}"""
  66         def __init__(self, os_ranks, machine_ranks):
  67                 self.os_ranks = os_ranks
  68                 self.machine_ranks = machine_ranks
  69                 self.child_arch = self
  70
  71         def __str__(self):
  72                 return "<Arch: %s %s>" % (self.os_ranks, self.machine_ranks)
  73
  74 class SourceArchitecture(Architecture):
  75         """Matches source code that creates binaries for a particular architecture.
  76         Note that the L{child_arch} here is the binary; source code depends on binary tools,
  77         not on other source packages.
  78         """
  79         def __init__(self, binary_arch):
  80                 Architecture.__init__(self, binary_arch.os_ranks, {'src': 1})
  81                 self.child_arch = binary_arch
  82
  83 def get_host_architecture():
  84         """Get an Architecture that matches implementations that will run on the host machine.
  85         @rtype: L{Architecture}"""
  86         return Architecture(os_ranks, machine_ranks)