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authorDavid Howells <dhowells@redhat.com>2012-09-24 17:11:27 +0100
committerRusty Russell <rusty@rustcorp.com.au>2012-10-08 13:50:21 +1030
commite1045992949160b56309b730b8bdc428f2f8b69e (patch)
treeca0e00fcd4502cb66df19f4e1aecbb1b4544908c /lib/mpi
parent42d5ec27f873c654a68f7f865dcd7737513e9508 (diff)
downloadlinux-linaro-stable-e1045992949160b56309b730b8bdc428f2f8b69e.tar.gz
MPILIB: Provide a function to read raw data into an MPI
Provide a function to read raw data of a predetermined size into an MPI rather than expecting the size to be encoded within the data. The data is assumed to represent an unsigned integer, and the resulting MPI will be positive. The function looks like this: MPI mpi_read_raw_data(const void *, size_t); This is useful for reading ASN.1 integer primitives where the length is encoded in the ASN.1 metadata. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'lib/mpi')
-rw-r--r--lib/mpi/mpicoder.c55
1 files changed, 55 insertions, 0 deletions
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index f0fa65995800..3962b7f7fe3f 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -18,10 +18,65 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
+#include <linux/bitops.h>
+#include <asm-generic/bitops/count_zeros.h>
#include "mpi-internal.h"
#define MAX_EXTERN_MPI_BITS 16384
+/**
+ * mpi_read_raw_data - Read a raw byte stream as a positive integer
+ * @xbuffer: The data to read
+ * @nbytes: The amount of data to read
+ */
+MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
+{
+ const uint8_t *buffer = xbuffer;
+ int i, j;
+ unsigned nbits, nlimbs;
+ mpi_limb_t a;
+ MPI val = NULL;
+
+ while (nbytes >= 0 && buffer[0] == 0) {
+ buffer++;
+ nbytes--;
+ }
+
+ nbits = nbytes * 8;
+ if (nbits > MAX_EXTERN_MPI_BITS) {
+ pr_info("MPI: mpi too large (%u bits)\n", nbits);
+ return NULL;
+ }
+ if (nbytes > 0)
+ nbits -= count_leading_zeros(buffer[0]);
+ else
+ nbits = 0;
+
+ nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+ val = mpi_alloc(nlimbs);
+ if (!val)
+ return NULL;
+ val->nbits = nbits;
+ val->sign = 0;
+ val->nlimbs = nlimbs;
+
+ if (nbytes > 0) {
+ i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+ i %= BYTES_PER_MPI_LIMB;
+ for (j = nlimbs; j > 0; j--) {
+ a = 0;
+ for (; i < BYTES_PER_MPI_LIMB; i++) {
+ a <<= 8;
+ a |= *buffer++;
+ }
+ i = 0;
+ val->d[j - 1] = a;
+ }
+ }
+ return val;
+}
+EXPORT_SYMBOL_GPL(mpi_read_raw_data);
+
MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
{
const uint8_t *buffer = xbuffer;