#!/usr/bin/env python
# -*- coding: iso-8859-1 -*-

# This is jcfilesize.
# For more information, see http://www.lysator.liu.se/~jc/jcfilesize.html

# Copyright (C) 2005  Jörgen Cederlöf <jc@lysator.liu.se>
# 
# This program 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 2
# of the License, or (at your option) any later version.
# 
# This program 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 this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.

from __future__ import division

VERSION = 0.5

import sys

def l2h(l):
    prefixes = ["B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"]
    s, i = [], 0
    while l:
        if l%1024:
            if i < len(prefixes):
                p = prefixes[i]
            else:
                p = "*1024^%d" % i
            s.append("%d %s" % (l%1024, p))
        l //= 1024
        i  += 1
    return " + ".join(s[::-1])

def l2hn(l):
    i = 1
    while l > i:
        i *= 2
    return "%s - ( %s )" % (l2h(i), l2h(i-l) or 0)

def prettyl(l):
    return "%d bytes == 0x%X bytes == %s == %s" % (l, l, l2h(l), l2hn(l))

def testlen(f, l, test):
    """Return True if position l in file f is not the end of the file."""
    try:
        f.seek(l)
        if f.read(1) == "":
            return False
    except IOError:
        return False
    except OverflowError:
        print "File is too large to measure."
        sys.exit(2)
    if   test[0] == "zeros":
        # Consider this the end of file if we find a single non-zero
        # byte.
        for c in f.read(test[1]):
            if c != '\x00':
                return False
    elif test[0] == "notzeros":
        # Consider this the end of file if all bytes are zero.
        for c in f.read(test[1]):
            if c != '\x00':
                return True
        return False
    return True


def main(argv):
    def usage(e=0):
        print 'This is jcfilesize version %s.' % VERSION
        print 'Usage: %s filename ["zeros"|"notzeros" [blocksize]]' % argv[0]
        sys.exit(e)

    if len(argv) == 2 and argv[1] in ('--help', '-h'):
        usage()

    if len(argv) >= 2:
        filename = argv[1]
        if filename == '-':
            f = sys.stdin
        else:
            f = open(filename)
    else:
        usage(1)
        
    t = "File length"
    if len(argv) >= 3:
        test=argv[2]
        if   test == "zeros":
            t = "Length of zeros at beginning of file"
        elif test == "notzeros":
            t = "Length before all zeros"
        else:
            usage(1)
    else:
        test = "end"
    if len(argv) >= 4:
        test = (test, int(argv[3]))
    else:
        test = (test, 1024)

    if not testlen(f, 0, test):
        print t + " is exactly zero."
        sys.exit(0)
    l = 1
    while True:
        if not testlen(f, l, test):
            break
        l *= 2
    toohigh, toolow = l, l//2
    while toolow+1 < toohigh:
        middle = (toohigh+toolow)//2
        if not testlen(f, middle, test):
            toohigh = middle
        else:
            toolow  = middle
    print t + ": %s" % prettyl(toohigh)
          

if __name__ == "__main__":
    main(sys.argv)