[Haskell-cafe] mapping large structures into memory

Warren Harris warrensomebody at gmail.com
Fri Sep 25 15:10:37 EDT 2009

I've dabbled in haskell, but am by no means an expert. I was hoping  
someone here could help me settle this debate so that we can more  
seriously consider haskell for a next version of an application we're  

I would like to understand better what its capabilities are for  
directly mapping and managing memory. For instance, I would like mmap  
many large files into memory and mutate their internals directly...  
without needing to reallocate them (or chunks of them) in the haskell  
heap, and without resorting to a byte-array and byte-offset  
representation. Furthermore, I might also like to map intrinsic  
haskell data structures into this mmap'd memory such that standard  
library functions can manipulate them (perhaps in a purely functional  
way, e.g. treating them as haskell arrays of smaller foreign  

I understand that the foreign function interface has the ability to  
marshall/unmarshall C structs, but I'm unsure of the memory  
implications of using this mechanism. Our application has a very large  
footprint, and reallocating some or all of these mapped files is a non- 
starter. Thanks,


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