access memory mapped file created on .net via python

Question

I made a memory mapped file using MemoryMappedFile.CreateNew(mapName, capacity) of .net 4

Can i access this mmf by the mapName from cpython ?

I tried like below.

import mmap
map = mmap.mmap(-1, 0, mapName, 1)

but it returns WindowsError [error 87] saying the parameter is incorrect.

I'm using windows vista.

@Matt, I also think i'm confused. But i made a mmf in system memory using the .net function above, and access it from another process (another .net app) efficiently. So, i just guess that it may be possible to access that system memory from python too, bcz the shared data is a plain old data. — tk.
– tk., Commented Jul 15, 2010 at 15:47

Matt Joiner · Accepted Answer · 2010-07-16 11:13:32Z

2

I have absolutely no experience with C#, but I'll attempt to answer your question.

CreateNew should create a mapping to a file that doesn't reside in the filesystem. Note that this isn't cross platform in any way. On Windows, the tagname parameter of mmap.mmap should allow you to map these tagged mappings. Since the mapping is not backed by a file, the -1 for fileno is correct also. The length of 0 will obtain the entire mapping. The issue then lies with access. There is a mention that not providing the access parameter will give write-through mapping on Windows, you might try experimenting with this.

If all else fails, try falling back to using a file-backed memory mapping, it's more portable, and far more common. The C# MemoryMappedFile class provides the CreateFromFile method for this.

answered Jul 16, 2010 at 11:13

Matt Joiner

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3 Comments

tk. Over a year ago

Thnx Matt.. It still fails with different accessing options, but i got that this 'non file-backed' is windows only function.

Matt Joiner Over a year ago

I mean, try not providing the access parameter at all. That seems to be what the doco suggests.

ephraim Over a year ago

@tk. did you find a sollution?

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