1 files changed, 88 insertions, 0 deletions
diff --git a/libtommath/bn_mp_export.c b/libtommath/bn_mp_export.c
new file mode 100644
index 0000000..ac4c2f9
--- /dev/null
+++ b/libtommath/bn_mp_export.c
@@ -0,0 +1,88 @@
+#include <tommath_private.h>
+#ifdef BN_MP_EXPORT_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, tstdenis82@gmail.com, http://libtom.org
+ */
+
+/* based on gmp's mpz_export.
+ * see http://gmplib.org/manual/Integer-Import-and-Export.html
+ */
+int mp_export(void* rop, size_t* countp, int order, size_t size, 
+                                int endian, size_t nails, mp_int* op) {
+	int result;
+	size_t odd_nails, nail_bytes, i, j, bits, count;
+	unsigned char odd_nail_mask;
+
+	mp_int t;
+
+	if ((result = mp_init_copy(&t, op)) != MP_OKAY) {
+		return result;
+	}
+
+	if (endian == 0) {
+		union {
+			unsigned int i;
+			char c[4];
+		} lint;
+		lint.i = 0x01020304;
+
+		endian = (lint.c[0] == 4) ? -1 : 1;
+	}
+
+	odd_nails = (nails % 8);
+	odd_nail_mask = 0xff;
+	for (i = 0; i < odd_nails; ++i) {
+		odd_nail_mask ^= (1 << (7 - i));
+	}
+	nail_bytes = nails / 8;
+
+	bits = mp_count_bits(&t);
+	count = (bits / ((size * 8) - nails)) + (((bits % ((size * 8) - nails)) != 0) ? 1 : 0);
+
+	for (i = 0; i < count; ++i) {
+		for (j = 0; j < size; ++j) {
+			unsigned char* byte = (
+				(unsigned char*)rop + 
+				(((order == -1) ? i : ((count - 1) - i)) * size) +
+				((endian == -1) ? j : ((size - 1) - j))
+			);
+
+			if (j >= (size - nail_bytes)) {
+				*byte = 0;
+				continue;
+			}
+
+			*byte = (unsigned char)((j == ((size - nail_bytes) - 1)) ? (t.dp[0] & odd_nail_mask) : (t.dp[0] & 0xFF));
+
+			if ((result = mp_div_2d(&t, ((j == ((size - nail_bytes) - 1)) ? (8 - odd_nails) : 8), &t, NULL)) != MP_OKAY) {
+				mp_clear(&t);
+				return result;
+			}
+		}
+	}
+
+	mp_clear(&t);
+
+	if (countp != NULL) {
+		*countp = count;
+	}
+
+	return MP_OKAY;
+}
+
+#endif
+
+/* $Source$ */
+/* $Revision$ */
+/* $Date$ */