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+#include <tommath.h>
+#ifdef BN_MP_LSHD_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis
+ *
+ * LibTomMath is a library that provides multiple-precision
+ * integer arithmetic as well as number theoretic functionality.
+ *
+ * The library was designed directly after the MPI library by
+ * Michael Fromberger but has been written from scratch with
+ * additional optimizations in place.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
+ */
+
+/* shift left a certain amount of digits */
+int mp_lshd (mp_int * a, int b)
+{
+ int x, res;
+
+ /* if its less than zero return */
+ if (b <= 0) {
+ return MP_OKAY;
+ }
+
+ /* grow to fit the new digits */
+ if (a->alloc < a->used + b) {
+ if ((res = mp_grow (a, a->used + b)) != MP_OKAY) {
+ return res;
+ }
+ }
+
+ {
+ register mp_digit *top, *bottom;
+
+ /* increment the used by the shift amount then copy upwards */
+ a->used += b;
+
+ /* top */
+ top = a->dp + a->used - 1;
+
+ /* base */
+ bottom = a->dp + a->used - 1 - b;
+
+ /* much like mp_rshd this is implemented using a sliding window
+ * except the window goes the otherway around. Copying from
+ * the bottom to the top. see bn_mp_rshd.c for more info.
+ */
+ for (x = a->used - 1; x >= b; x--) {
+ *top-- = *bottom--;
+ }
+
+ /* zero the lower digits */
+ top = a->dp;
+ for (x = 0; x < b; x++) {
+ *top++ = 0;
+ }
+ }
+ return MP_OKAY;
+}
+#endif