mpi: Add an API for EC math.
* src/context.c, src/context.h: New. * src/Makefile.am (libgcrypt_la_SOURCES): Add new files. * src/gcrypt.h.in (struct gcry_context, gcry_ctx_t): New types. (gcry_ctx_release): New prototype. (gcry_mpi_ec_p_new, gcry_mpi_ec_get_affine, gcry_mpi_ec_dup) (gcry_mpi_ec_add, gcry_mpi_ec_mul): New prototypes. * mpi/ec.c: Include errno.h and context.h. (_gcry_mpi_ec_init): Rename to .. (ec_p_init): this, make static, remove allocation and add arg CTX. (_gcry_mpi_ec_p_internal_new): New; to replace _gcry_mpi_ec_init. Change all callers to use this func. (_gcry_mpi_ec_free): Factor code out to .. (ec_deinit): New func. (gcry_mpi_ec_p_new): New. * src/visibility.c: Include context.h and mpi.h. (gcry_mpi_ec_p_new, gcry_mpi_ec_get_affine, gcry_mpi_ec_dup) (gcry_mpi_ec_add, gcry_mpi_ec_mul) (gcry_ctx_release): New wrapper functions. * src/visibility.h: Mark new wrapper functions visible. * src/libgcrypt.def, src/libgcrypt.vers: Add new symbols. * tests/t-mpi-point.c (print_mpi, hex2mpi, cmp_mpihex): New. (context_alloc): New. (make_point, basic_ec_math): New.
This part finishes the basic API to do EC math. It provides a wrapper
around all internal functions. tests/t-mpi-point.c may be useful as
sample code. Eventually we will add function to retrieve curve
parameters etc.