Remember that the memory-allocation mechanism is crucial. How does BN
do that?
BN uses a structure called "CTX"--OpenSSL calls all such structures
"CTX"--to hold the local static variables for reentrancy. CTX
structures do not affect memory allocation, though they *do* require
malloc'd memory. For my purposes, the BN-CTX structure does give me
an easy way to handle thread local storage. Otherwise, BN uses
standard malloc'd memory. Creating a BN-MP (called a BIGNUM; really
a struct), you either do:
BIGNUM x;
BN_init(&x); // defined in bn_lib.c; uses memset
or,
// uses OpenSSL-named checked malloc:
// OPENSSL_malloc == CRYPTO_malloc
BIGNUM* y = BN_new();
It would be easy to change the definition of OPENSSL_malloc to call
RTS-memory as necessary. It would be more efficient for BN to be
garbage collected (these bignum libraries allocate and delete a lot
of small memory blocks (~1-2KB for large integers)). Since
ForeignPtr is simply too slow I am bringing BN value allocations into
the rts as close as possible to how you did it with GMP.
Making a single word contain either a pointer or a non-pointer
(depending on the setting of some bit) would have some quite global
implications, as would losing 32 bit precision from Int#. I suggest
that you do not couple these two projects together! Do the GMP thing
first, then investigate this later. We have quite a few bit-twidding
ideas that we have never followed up.
The original idea was to create a specialized Int30# for that
purpose. In any case implementing it would certainly make my
intended job--getting this done in time for the next release--a bit
more difficult.
Best regards,
Peter
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