"""
libc, csum etc.
"""

# 	Copyright (c) 2008 Peter V. Saveliev
#
# 	This file is part of Connexion project.
#
# 	Connexion is free software; you can redistribute it and/or modify
# 	it under the terms of the GNU General Public License as published by
# 	the Free Software Foundation; either version 3 of the License, or
# 	(at your option) any later version.
#
# 	Connexion is distributed in the hope that it will be useful,
# 	but WITHOUT ANY WARRANTY; without even the implied warranty of
# 	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# 	GNU General Public License for more details.
#
# 	You should have received a copy of the GNU General Public License
# 	along with Connexion; if not, write to the Free Software
# 	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

__all__ = [
	"cx_int",
	"libc",
	"hdump",
	"hprint",
	"csum",
	"csum_words",
	"csum_complement",
]

from ctypes import *

from sys import maxint
if maxint == 2147483647:
	cx_int = c_uint32
else:
	cx_int = c_uint64

libc = CDLL("libc.so.6")

def hdump(name,msg,size=0):
	"""
	Dump a packet into a file
	"""
	if not size:
		size = sizeof(msg)
	fd = libc.open(name,577,384)
	libc.write(fd,byref(msg),size)
	libc.close(fd)

def hline(msg,size=0):
	"""
	Format packet into a string
	"""
	if not size:
		size = sizeof(msg)
	length = size
	offset = 0
	ptr = addressof(msg)
	line = ""
	result = ""
	
	while offset < length:
		a = c_ubyte.from_address(ptr).value
		result += "%02x " % (a)
		if 31 < a and a < 127:
			line += chr(a)
		else:
			line += '.'

		if offset:
			if not (offset + 1) % 8:
				result += ": "
			if not (offset + 1) % 16:
				result += "\t %s\n" % (str(line))
				line = ""

		offset += 1
		ptr += 1

	if line:
		result += "\t\t\t\t %s\n" % (str(line))
	return result


def hprint(msg,size=0):
	"""
	Dump a packet onto stdout
	"""
	print hline(msg,size)

class be16 (BigEndianStructure):
	_fields_ = [
		("c",	c_uint16),
	]

def csum_words(msg,l):
	odd = False
	if (l%2):
		l -= 1
		odd = True

	# l is in bytes. We need 16-bit words
	a = addressof(msg)
	x = 0

	for i in xrange(0,l,2):
		c = be16.from_address(a + i)
		x += c.c

	if odd:
		last = c_uint16(c_uint8.from_address(a + l).value << 8)
		x += last.value

	return x

def csum_complement(x):
	x = c_uint32(x)
	x1 = c_uint16.from_address(addressof(x))
	x2 = c_uint16.from_address(addressof(x) + 2)
	return ~c_uint16(x1.value + x2.value).value

def csum(msg,l):
	##
	# details: rfc 1071
	# a simple description: http://www.netfor2.com/checksum.html
	##
	return csum_complement(csum_words(msg,l))