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Commit f00fa241 authored by Nicolai Stange's avatar Nicolai Stange Committed by Herbert Xu
Browse files

lib/mpi: mpi_read_buffer(): optimize skipping of leading zero limbs 



Currently, if the number of leading zeros is greater than fits into a
complete limb, mpi_read_buffer() skips them by iterating over them
limb-wise.

Instead of skipping the high order zero limbs within the loop as shown
above, adjust the copying loop's bounds.

Signed-off-by: default avatarNicolai Stange <nicstange@gmail.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent d7552906

lib/mpi/mpicoder.c

+8 −10
Original line number Original line Diff line number Diff line
@@ -184,7 +184,9 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, 
	p = buf;

	p = buf;

	*nbytes = n - lzeros;

	*nbytes = n - lzeros;





	for (i = a->nlimbs - 1; i >= 0; i--) {

	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,

			lzeros %= BYTES_PER_MPI_LIMB;

		i >= 0; i--) {

		alimb = a->d[i];

		alimb = a->d[i];

#if BYTES_PER_MPI_LIMB == 4

#if BYTES_PER_MPI_LIMB == 4

		*p++ = alimb >> 24;

		*p++ = alimb >> 24;
@@ -205,15 +207,11 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, 
#endif

#endif





		if (lzeros > 0) {

		if (lzeros > 0) {

			if (lzeros >= sizeof(alimb)) {

				p -= sizeof(alimb);

			} else {

			mpi_limb_t *limb1 = (void *)p - sizeof(alimb);

			mpi_limb_t *limb1 = (void *)p - sizeof(alimb);

			mpi_limb_t *limb2 = (void *)p - sizeof(alimb)

			mpi_limb_t *limb2 = (void *)p - sizeof(alimb)

				+ lzeros;

				+ lzeros;

			*limb1 = *limb2;

			*limb1 = *limb2;

			p -= lzeros;

			p -= lzeros;

			}

			lzeros -= sizeof(alimb);

			lzeros -= sizeof(alimb);

		}

		}

	}

	}