On Tue, Mar 18, 2008 at 01:46:28PM +0000, Gracjan Polak wrote:
I just uploaded mmap to hackage:
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/mmap
The package provides memory mapping abstractions for both POSIX and Windows systems like Vista, Linux and Mac OSX. This library provides a wrapper to mmap(2) or MapViewOfFile, allowing files or devices to be lazily loaded into memory as strict or lazy ByteStrings, ForeignPtrs or even plain Ptrs, using the virtual memory subsystem to do on-demand loading. Modifications are also supported.
Package includes a cp-like copy utility that uses different mechanisms to copy contents of file. Here come some statistics from using it on 90MB file:
Incidentally, you'll probably find that for large files, using mmap on Windows is a huge loser when compared with lazy bytestrings. As far as I understand, on Windows when a file is mmapped, its entire contents are immediately loaded into memory, so if you mmap a file that is larger than your memory, you pay a huge penalty on Windows. I'm not sure what the target audience for this library is, but I'd be surprised if it turns out to be useful for much more than toy projects (or posix-only projects), just because the Windows file system semantics are so screwed up. :( -- David Roundy Department of Physics Oregon State University