"""Test largefile support on system where this makes sense.

"""

import os

import stat

import sys

import unittest

from test.test_support import run_unittest, TESTFN, verbose, requires, \

                              TestSkipped, unlink

try:

    import signal

    # The default handler for SIGXFSZ is to abort the process.

    # By ignoring it, system calls exceeding the file size resource

    # limit will raise IOError instead of crashing the interpreter.

    oldhandler = signal.signal(signal.SIGXFSZ, signal.SIG_IGN)

except (ImportError, AttributeError):

    pass

# create >2GB file (2GB = 2147483648 bytes)

size = 2500000000L

class TestCase(unittest.TestCase):

    """Test that each file function works as expected for a large

    (i.e. > 2GB, do  we have to check > 4GB) files.

    NOTE: the order of execution of the test methods is important! test_seek

    must run first to create the test file. File cleanup must also be handled

    outside the test instances because of this.

    """

    def test_seek(self):

        if verbose:

            print 'create large file via seek (may be sparse file) ...'

        with open(TESTFN, 'wb') as f:

            f.write('z')

            f.seek(0)

            f.seek(size)

            f.write('a')

            f.flush()

            if verbose:

                print 'check file size with os.fstat'

            self.assertEqual(os.fstat(f.fileno())[stat.ST_SIZE], size+1)

    def test_osstat(self):

        if verbose:

            print 'check file size with os.stat'

        self.assertEqual(os.stat(TESTFN)[stat.ST_SIZE], size+1)

    def test_seek_read(self):

        if verbose:

            print 'play around with seek() and read() with the built largefile'

        with open(TESTFN, 'rb') as f:

            self.assertEqual(f.tell(), 0)

            self.assertEqual(f.read(1), 'z')

            self.assertEqual(f.tell(), 1)

            f.seek(0)

            self.assertEqual(f.tell(), 0)

            f.seek(0, 0)

            self.assertEqual(f.tell(), 0)

            f.seek(42)

            self.assertEqual(f.tell(), 42)

            f.seek(42, 0)

            self.assertEqual(f.tell(), 42)

            f.seek(42, 1)

            self.assertEqual(f.tell(), 84)

            f.seek(0, 1)

            self.assertEqual(f.tell(), 84)

            f.seek(0, 2)  # seek from the end

            self.assertEqual(f.tell(), size + 1 + 0)

            f.seek(-10, 2)

            self.assertEqual(f.tell(), size + 1 - 10)

            f.seek(-size-1, 2)

            self.assertEqual(f.tell(), 0)

            f.seek(size)

            self.assertEqual(f.tell(), size)

            # the 'a' that was written at the end of file above

            self.assertEqual(f.read(1), 'a')

            f.seek(-size-1, 1)

            self.assertEqual(f.read(1), 'z')

            self.assertEqual(f.tell(), 1)

    def test_lseek(self):

        if verbose:

            print 'play around with os.lseek() with the built largefile'

        with open(TESTFN, 'rb') as f:

            self.assertEqual(os.lseek(f.fileno(), 0, 0), 0)

            self.assertEqual(os.lseek(f.fileno(), 42, 0), 42)

            self.assertEqual(os.lseek(f.fileno(), 42, 1), 84)

            self.assertEqual(os.lseek(f.fileno(), 0, 1), 84)

            self.assertEqual(os.lseek(f.fileno(), 0, 2), size+1+0)

            self.assertEqual(os.lseek(f.fileno(), -10, 2), size+1-10)

            self.assertEqual(os.lseek(f.fileno(), -size-1, 2), 0)

            self.assertEqual(os.lseek(f.fileno(), size, 0), size)

            # the 'a' that was written at the end of file above

            self.assertEqual(f.read(1), 'a')

    def test_truncate(self):

        if verbose:

            print 'try truncate'

        with open(TESTFN, 'r+b') as f:

            # this is already decided before start running the test suite

            # but we do it anyway for extra protection

            if not hasattr(f, 'truncate'):

                raise TestSkipped, "open().truncate() not available on this system"

            f.seek(0, 2)

            # else we've lost track of the true size

            self.assertEqual(f.tell(), size+1)

            # Cut it back via seek + truncate with no argument.

            newsize = size - 10

            f.seek(newsize)

            f.truncate()

            self.assertEqual(f.tell(), newsize)  # else pointer moved

            f.seek(0, 2)

            self.assertEqual(f.tell(), newsize)  # else wasn't truncated

            # Ensure that truncate(smaller than true size) shrinks

            # the file.

            newsize -= 1

            f.seek(42)

            f.truncate(newsize)

            self.assertEqual(f.tell(), 42)       # else pointer moved

            f.seek(0, 2)

            self.assertEqual(f.tell(), newsize)  # else wasn't truncated

            # XXX truncate(larger than true size) is ill-defined

            # across platform; cut it waaaaay back

            f.seek(0)

            f.truncate(1)

            self.assertEqual(f.tell(), 0)       # else pointer moved

            self.assertEqual(len(f.read()), 1)  # else wasn't truncated

def test_main():

    # On Windows and Mac OSX this test comsumes large resources; It

    # takes a long time to build the >2GB file and takes >2GB of disk

    # space therefore the resource must be enabled to run this test.

    # If not, nothing after this line stanza will be executed.

    if sys.platform[:3] == 'win' or sys.platform == 'darwin':

        requires('largefile',

                 'test requires %s bytes and a long time to run' % str(size))

    else:

        # Only run if the current filesystem supports large files.

        # (Skip this test on Windows, since we now always support

        # large files.)

        f = open(TESTFN, 'wb')

        try:

            # 2**31 == 2147483648

            f.seek(2147483649L)

            # Seeking is not enough of a test: you must write and

            # flush, too!

            f.write("x")

            f.flush()

        except (IOError, OverflowError):

            f.close()

            unlink(TESTFN)

            raise TestSkipped, "filesystem does not have largefile support"

        else:

            f.close()

    suite = unittest.TestSuite()

    suite.addTest(TestCase('test_seek'))

    suite.addTest(TestCase('test_osstat'))

    suite.addTest(TestCase('test_seek_read'))

    suite.addTest(TestCase('test_lseek'))

    with open(TESTFN, 'w') as f:

        if hasattr(f, 'truncate'):

            suite.addTest(TestCase('test_truncate'))

    unlink(TESTFN)

    try:

        run_unittest(suite)

    finally:

        unlink(TESTFN)

if __name__ == '__main__':

    test_main()