MPILIB: Provide a function to read raw data into an MPI

[karo-tx-linux.git] / lib / mpi / mpicoder.c

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index f0fa659958002ca824d47144e6ecba3fdcdc7e38..3962b7f7fe3f08ec4b639e328ddc6dcf4baa05fd 100644 (file)
--- 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;