Sources_For_Win/ParaView/Lib/site-packages/win32/Demos/mmapfile_demo.py

import win32api, mmapfile
import winerror
import tempfile, os
from pywin32_testutil import str2bytes

system_info=win32api.GetSystemInfo()
page_size=system_info[1]
alloc_size=system_info[7]

fname=tempfile.mktemp()
mapping_name=os.path.split(fname)[1]
fsize=8*page_size
print(fname, fsize, mapping_name)

m1=mmapfile.mmapfile(File=fname, Name=mapping_name, MaximumSize=fsize)
m1.seek(100)
m1.write_byte(str2bytes('?'))
m1.seek(-1,1)
assert m1.read_byte()==str2bytes('?')

## A reopened named mapping should have exact same size as original mapping
m2=mmapfile.mmapfile(Name=mapping_name, File=None, MaximumSize=fsize*2)
assert m2.size()==m1.size()
m1.seek(0,0)
m1.write(fsize*str2bytes('s'))
assert m2.read(fsize)==fsize*str2bytes('s')

move_src=100
move_dest=500
move_size=150

m2.seek(move_src,0)
assert m2.tell()==move_src
m2.write(str2bytes('m')*move_size)
m2.move(move_dest, move_src, move_size)
m2.seek(move_dest, 0)
assert m2.read(move_size) ==  str2bytes('m') * move_size
##    m2.write('x'* (fsize+1))

m2.close()
m1.resize(fsize*2)
assert m1.size()==fsize * 2
m1.seek(fsize)
m1.write(str2bytes('w') * fsize)
m1.flush()
m1.close()
os.remove(fname)



## Test a file with size larger than 32 bits
## need 10 GB free on drive where your temp folder lives
fname_large=tempfile.mktemp()
mapping_name='Pywin32_large_mmap'
offsetdata=str2bytes('This is start of offset')

## Deliberately use odd numbers to test rounding logic
fsize = (1024*1024*1024*10) + 333
offset = (1024*1024*32) + 42
view_size = (1024*1024*16) + 111

## round mapping size and view size up to multiple of system page size
if fsize%page_size:
    fsize += page_size - (fsize%page_size)
if view_size%page_size:
    view_size += page_size - (view_size%page_size)
## round offset down to multiple of allocation granularity
offset -= offset%alloc_size

m1=None
m2=None
try:
    try:
        m1=mmapfile.mmapfile(fname_large, mapping_name, fsize, 0, offset*2)
    except mmapfile.error as exc:
        # if we don't have enough disk-space, that's OK.
        if exc.winerror!=winerror.ERROR_DISK_FULL:
            raise
        print("skipping large file test - need", fsize, "available bytes.")
    else:
        m1.seek(offset)
        m1.write(offsetdata)
    
        ## When reopening an existing mapping without passing a file handle, you have
        ##  to specify a positive size even though it's ignored
        m2=mmapfile.mmapfile(File=None, Name=mapping_name, MaximumSize=1,
            FileOffset=offset, NumberOfBytesToMap=view_size)
        assert m2.read(len(offsetdata))==offsetdata
finally:
    if m1 is not None:
        m1.close()
    if m2 is not None:
        m2.close()
    if os.path.exists(fname_large):
        os.remove(fname_large)