"""
Information about the current system's architecture.

This module provides information about the current system. It is used to determine
whether an implementation is suitable for this machine, and to compare different implementations.

For example, it will indicate that:

 - An i486 machine cannot run an i686 binary.
 - An i686 machine can run an i486 binary, but would prefer an i586 one.
 - A Windows binary cannot run on a Linux machine.

Each dictionary maps from a supported architecture type to a preference level. Lower numbers are
better, Unsupported architectures are not listed at all.
"""

# Copyright (C) 2006, Thomas Leonard
# See the README file for details, or visit http://0install.net.

import os

# os_ranks and mapping are mappings from names to how good they are.
# 1 => Native (best)
# Higher numbers are worse but usable.
_uname = os.uname()

os_ranks = {
#	'Linux' : 3,		# Linux (lots of systems support emulation)
	None : 2,		# Any OS
	_uname[0] : 1,		# Current OS
}

def _get_machine_ranks():
	# Binaries compiled for _this_machine are best...
	this_machine = _uname[-1]
	machine_ranks = {this_machine : 0}

	# If this_machine appears in the first column of this table, all
	# following machine types on the line will also run on this one
	# (earlier ones preferred):
	_machine_matrix = {
		'i486': ['i386'],
		'i586': ['i486', 'i386'],
		'i686': ['i586', 'i486', 'i386'],
		'ppc64': ['ppc32'],
	}
	for supported in _machine_matrix.get(this_machine, []):
		machine_ranks[supported] = len(machine_ranks)

	# At the lowest priority, try a machine-independant implementation
	machine_ranks[None] = len(machine_ranks)
	return machine_ranks

machine_ranks = _get_machine_ranks()
#print machine_ranks