Actually, there is documentation, it's linked in CFFI's main page: http://common-lisp.net/gitweb?p=projects/cffi/cffi.git;a=blob_plain;f=doc/shareable-vectors.txt
<http://common-lisp.net/gitweb?p=projects/cffi/cffi.git;a=blob_plain;f=doc/shareable-vectors.txt>You seem to need to use CFFI:MAKE-SHAREABLE-BYTE-VECTOR to create the array. Em 12 de setembro de 2010 20:39, Gustavo <gugamil...@gmail.com> escreveu: > Hello, > > What about CFFI:WITH-POINTER-TO-VECTOR-DATA? Or did you just miss it? > Documentation is missing, but it pines the array within its body (which > means the array won't be moved, but garbage collector might still run) and > grabs the foreign pointer of the array, at least on SBCL. > > Regards, > Gustavo. > > 2010/9/11 JTK <jetm...@gmail.com> > > >> >> Hello, >> >> I'm using cffi, and I need to perform the common task of passing Lisp >> arrays to foreign code. >> >> This task comes up a lot in scientific code, matrix math, image >> processing, etc. >> >> Normally, it involves a lot of boilerplate to allocate a pointer, copy >> data Lisp to foreign >> memory, copy the data back, and deallocate the memory. Getting the >> copying to run >> fast can be tricky. >> >> Hence I wrote a package to automate it. It maintains a set of >> specialized copying >> functions to copy from array of Lisp type X to foreign memory of type Y. >> On SBCL, copying >> doesn't cons and is reasonably fast (~200 MB a second, there and back) >> >> I've put the package here: >> >> http://www.megaupload.com/?d=CX1XFMU6 >> >> Sorry for the megaupload, and its imposed delay, but I didn't want to spam >> the list with a 100K file. >> >> The package includes a MANUAL.txt and a test package. >> >> I'd be happy to have this included in a user contrib section of CFFI, if >> the maintainers >> think it would be useful. >> >> >> >> >> Here's an example the main macro does: >> >> >> (LET ((U (MAKE-ARRAY 100 :ELEMENT-TYPE 'SINGLE-FLOAT :INITIAL-ELEMENT >> 1.0))) >> ;; >> (WITH-ARRAY-AS-FOREIGN-POINTER >> (U PU :FLOAT ;; LISP-VAR POINTER-VAR >> CFFI-FOREIGN-TYPE >> :LISP-TYPE SINGLE-FLOAT ;; promise U is a single-float array >> :START 2 ;; begin at index 2 of of Lisp array >> :END 7 ;; last index used is 6 >> :COPY-TO-FOREIGN T ;; put contents of Lisp into foreign >> memory >> :COPY-FROM-FOREIGN T) ;; copy back from FFI space to lisp >> array >> ;; >> ;; at this point, PU is a foreign pointer containing data copied >> ;; from the array starting at element 1 and ending at 6, of type >> :FLOAT. >> >> (SOME-FOREIGN-FUNCTION PU)) >> ;; >> ;; at end, all foreign memory is deallocated, and U has been copied >> ;; back from foreign space, but the 0th element of U is untouched >> ;; because START was 1, not 0 >> ) >> >> >> -John >> _______________________________________________ >> cffi-devel mailing list >> cffi-devel@common-lisp.net >> http://common-lisp.net/cgi-bin/mailman/listinfo/cffi-devel >> > >
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