I had a simular situation when I was writing Python routines to access the the storage (SCSIPASSTHROUGH) layer provided by Windows XP. My solution was to develope an extention in C that allocated all storage buffers within the extension. Then I added access extensions to controll reading and writing to and from these buffers. I would guess that you can write a vxworks extension that provides this linkage. Bengt Richter wrote: > On 14 Dec 2005 14:30:34 -0800, "Greg Copeland" <[EMAIL PROTECTED]> wrote: > > >I am running python on VxWorks. In the course of operation, a vxworks > >tasks writes to a reserved area of memory. I need access to this chunk > >of memory from within python. Initially I thought I could simply > >access it as a string but a string would reallocate and copy this chunk > >of memory; which is not something I can have as it would waste a huge > >amount of memory. We're talking about something like 40MB on a device > >with limited RAM. I have been looking at array. It looks promising. > >What's the best route to go here? Ideally, I would like to simply pass > >in the address of the reserved block and a length, and have the memory > >accessible. > > > >Is there some existing python object/facility I can use or will I need > >to create a custom module? Any tips, hints, or pointers would > >certainly be appreciated! > > What have you gathered from people who have gone before? googling python > vxworks > gives about 50k hits ;-) > > Your post does not have enough info about your environment, but for > the sake of eliciting same, suppose you had a custom extension module > written in C that would give you the access to the "reserved area of memory" > that you want. So e.g. from the point of view of your python program, it looks > like a module you can import, e.g., > > import vxreservedmem > > Ok, how does the module know where the "reserved area" is? Would you link > the C to some vx library interface to establish location and size? Or? > Is there already a python interface to provide some access? > Can there be more than one instance, so the module should be able to > give you multiple objects that you can use to access different areas? > > Once you have an access-providing object, what kind of access do you require? > What is represented within the "memory area" besides an array of bytes? Do the > bytes represent C structs and primitive types? Are there access locks that > determine when it's safe to touch the bytes? A single lock for the whole area, > or individual locks for structs/subregions within the whole? Do you just need > read access or do you want to store info? How would you like to select > chunks of info? Just slices of byte arrays, or are there meaningful arrays > of numbers -- integer, floats, etc. or bit fields etc? > > You could define a pure python vxresrvedmem module that just simulates the > real > thing, to test ideas -- and to communicate more clearly to us what the > problem is. > > What modules/libraries do you have to give you access now from python to the > vxworks > environment? A file system? /dev/magic_stuff? or /proc/magic_stuff or ? > > > Regards, > Bengt Richter
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