On 2007-11-08, David Roundy
On Wed, Nov 07, 2007 at 10:10:16PM +0000, Jules Bean wrote:
Joel Reymont wrote:
Is there such a thing as memory-mapped arrays in GHC?
In principle, there could be an IArray instance to memory-mapped files.
(There could also be a mutable version, but just the IArray version would be useful).
The IArray instance would be unsafe, however, because the contents of the file could change after you opened it, breaking referential transparency.
Or even crashing, if the size becomes smaller than the mapped area.
I don't know what all is possible with file open modes, but I don't think you can guarantee that once you've opened a file it won't change (unless you unlink it, and know that noone else has an opened file handle to it).
File open modes won't do it, and I don't think any thing else will do it using just POSIX behavior, either. Linux's mmap() used to support a DENY_WRITE flag, but it enabled DoS attacks, so it's gone.
It may be that by opening it in write mode you could ensure that noone else modifies it (although I don't think this would work e.g. on nfs),
It doesn't even work locally. -- Aaron Denney -><-