cpython/Lib/test/test_mmap.py

from test_support import verify, TESTFN
import mmap
import os, re

PAGESIZE = mmap.PAGESIZE

def test_both():
    "Test mmap module on Unix systems and Windows"

    # Create a file to be mmap'ed.
    if os.path.exists(TESTFN):
        os.unlink(TESTFN)
    f = open(TESTFN, 'w+')

    try:    # unlink TESTFN no matter what
        # Write 2 pages worth of data to the file
        f.write('\0'* PAGESIZE)
        f.write('foo')
        f.write('\0'* (PAGESIZE-3) )

        m = mmap.mmap(f.fileno(), 2 * PAGESIZE)
        f.close()

        # Simple sanity checks

        print type(m)  # SF bug 128713:  segfaulted on Linux
        print '  Position of foo:', m.find('foo') / float(PAGESIZE), 'pages'
        verify(m.find('foo') == PAGESIZE)

        print '  Length of file:', len(m) / float(PAGESIZE), 'pages'
        verify(len(m) == 2*PAGESIZE)

        print '  Contents of byte 0:', repr(m[0])
        verify(m[0] == '\0')
        print '  Contents of first 3 bytes:', repr(m[0:3])
        verify(m[0:3] == '\0\0\0')

        # Modify the file's content
        print "\n  Modifying file's content..."
        m[0] = '3'
        m[PAGESIZE +3: PAGESIZE +3+3] = 'bar'

        # Check that the modification worked
        print '  Contents of byte 0:', repr(m[0])
        verify(m[0] == '3')
        print '  Contents of first 3 bytes:', repr(m[0:3])
        verify(m[0:3] == '3\0\0')
        print '  Contents of second page:',  repr(m[PAGESIZE-1 : PAGESIZE + 7])
        verify(m[PAGESIZE-1 : PAGESIZE + 7] == '\0foobar\0')

        m.flush()

        # Test doing a regular expression match in an mmap'ed file
        match = re.search('[A-Za-z]+', m)
        if match is None:
            print '  ERROR: regex match on mmap failed!'
        else:
            start, end = match.span(0)
            length = end - start

            print '  Regex match on mmap (page start, length of match):',
            print start / float(PAGESIZE), length

            verify(start == PAGESIZE)
            verify(end == PAGESIZE + 6)

        # test seeking around (try to overflow the seek implementation)
        m.seek(0,0)
        print '  Seek to zeroth byte'
        verify(m.tell() == 0)
        m.seek(42,1)
        print '  Seek to 42nd byte'
        verify(m.tell() == 42)
        m.seek(0,2)
        print '  Seek to last byte'
        verify(m.tell() == len(m))

        print '  Try to seek to negative position...'
        try:
            m.seek(-1)
        except ValueError:
            pass
        else:
            verify(0, 'expected a ValueError but did not get it')

        print '  Try to seek beyond end of mmap...'
        try:
            m.seek(1,2)
        except ValueError:
            pass
        else:
            verify(0, 'expected a ValueError but did not get it')

        print '  Try to seek to negative position...'
        try:
            m.seek(-len(m)-1,2)
        except ValueError:
            pass
        else:
            verify(0, 'expected a ValueError but did not get it')

        # Try resizing map
        print '  Attempting resize()'
        try:
            m.resize( 512 )
        except SystemError:
            # resize() not supported
            # No messages are printed, since the output of this test suite
            # would then be different across platforms.
            pass
        else:
            # resize() is supported
            verify(len(m) == 512,
                    "len(m) is %d, but expecting 512" % (len(m),) )
            # Check that we can no longer seek beyond the new size.
            try:
                m.seek(513,0)
            except ValueError:
                pass
            else:
                verify(0, 'Could seek beyond the new size')

        m.close()

    finally:
        try:
            f.close()
        except OSError:
            pass
        try:
            os.unlink(TESTFN)
        except OSError:
            pass

    print ' Test passed'

test_both()