New functions mpn_set_base256_le and mpn_get_base256_le.

ChangeLog

+2014-08-06  Niels Möller  <nisse@lysator.liu.se>
+
+	* gmp-glue.c (mpn_set_base256_le, mpn_get_base256_le): New functions.
+	* gmp-glue.h: Declare them.
+
 2014-08-02  Niels Möller  <nisse@lysator.liu.se>
 
 	* testsuite/curve25519-dh-test.c (curve25519_sqrt): Fixed memory

gmp-glue.c

@@ -227,6 +227,68 @@ mpn_set_base256 (mp_limb_t *rp, mp_size_t rn,
     }
 }
 
+void
+mpn_set_base256_le (mp_limb_t *rp, mp_size_t rn,
+		    const uint8_t *xp, size_t xn)
+{
+  size_t xi;
+  mp_limb_t out;
+  unsigned bits;
+  for (xi = 0, out = bits = 0; xi < xn && rn > 0; )
+    {
+      mp_limb_t in = xp[xi++];
+      out |= (in << bits) & GMP_NUMB_MASK;
+      bits += 8;
+      if (bits >= GMP_NUMB_BITS)
+	{
+	  *rp++ = out;
+	  rn--;
+
+	  bits -= GMP_NUMB_BITS;
+	  out = in >> (8 - bits);
+	}
+    }
+  if (rn > 0)
+    {
+      *rp++ = out;
+      if (--rn > 0)
+	mpn_zero (rp, rn);
+    }
+}
+
+void
+mpn_get_base256_le (uint8_t *rp, size_t rn,
+		    const mp_limb_t *xp, mp_size_t xn)
+{
+  unsigned bits;
+  mp_limb_t in;
+  for (bits = in = 0; xn > 0 && rn > 0; )
+    {
+      if (bits >= 8)
+	{
+	  *rp++ = in;
+	  rn--;
+	  in >>= 8;
+	  bits -= 8;
+	}
+      else
+	{
+	  uint8_t old = in;
+	  in = *xp++;
+	  xn--;
+	  *rp++ = old | (in << bits);
+	  in >>= (8 - bits);
+	  bits += GMP_NUMB_BITS - 8;
+	}
+    }
+  while (rn > 0)
+    {
+      *rp++ = in;
+      rn--;
+      in >>= 8;
+    }
+}
+
 mp_limb_t *
 gmp_alloc_limbs (mp_size_t n)
 {

gmp-glue.h

@@ -71,6 +71,8 @@
 #define mpz_limbs_copy _nettle_mpz_limbs_copy
 #define mpz_set_n _nettle_mpz_set_n
 #define mpn_set_base256 _nettle_mpn_set_base256
+#define mpn_set_base256_le _nettle_mpn_set_base256_le
+#define mpn_get_base256_le _nettle_mpn_get_base256_le
 #define gmp_alloc_limbs _nettle_gmp_alloc_limbs
 #define gmp_free_limbs _nettle_gmp_free_limbs
 #define gmp_free _nettle_gmp_free
@@ -153,7 +155,7 @@ mpz_limbs_read_n (mpz_ptr x, mp_size_t n);
 
 /* Copy limbs, with zero-padding. */
 /* FIXME: Reorder arguments, on the theory that the first argument of
-   an _mpz_* fucntion should be an mpz_t? Or rename to _mpz_get_limbs,
+   an _mpz_* function should be an mpz_t? Or rename to _mpz_get_limbs,
    with argument order consistent with mpz_get_*. */
 void
 mpz_limbs_copy (mp_limb_t *xp, mpz_srcptr x, mp_size_t n);
@@ -167,6 +169,14 @@ void
 mpn_set_base256 (mp_limb_t *rp, mp_size_t rn,
 		 const uint8_t *xp, size_t xn);
 
+void
+mpn_set_base256_le (mp_limb_t *rp, mp_size_t rn,
+		    const uint8_t *xp, size_t xn);
+
+void
+mpn_get_base256_le (uint8_t *rp, size_t rn,
+		    const mp_limb_t *xp, mp_size_t xn);
+
 
 mp_limb_t *
 gmp_alloc_limbs (mp_size_t n);