Some cleanups (removed unused files, split i15 code into per-function files).

[BearSSL] / src / int / i15_reduce.c

diff --git a/src/int/i15_reduce.c b/src/int/i15_reduce.c
new file mode 100644 (file)
index 0000000..0931b10
--- /dev/null
+++ b/src/int/i15_reduce.c
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see inner.h */
+void
+br_i15_reduce(uint16_t *x, const uint16_t *a, const uint16_t *m)
+{
+       uint32_t m_bitlen, a_bitlen;
+       size_t mlen, alen, u;
+
+       m_bitlen = m[0];
+       mlen = (m_bitlen + 15) >> 4;
+
+       x[0] = m_bitlen;
+       if (m_bitlen == 0) {
+               return;
+       }
+
+       /*
+        * If the source is shorter, then simply copy all words from a[]
+        * and zero out the upper words.
+        */
+       a_bitlen = a[0];
+       alen = (a_bitlen + 15) >> 4;
+       if (a_bitlen < m_bitlen) {
+               memcpy(x + 1, a + 1, alen * sizeof *a);
+               for (u = alen; u < mlen; u ++) {
+                       x[u + 1] = 0;
+               }
+               return;
+       }
+
+       /*
+        * The source length is at least equal to that of the modulus.
+        * We must thus copy N-1 words, and input the remaining words
+        * one by one.
+        */
+       memcpy(x + 1, a + 2 + (alen - mlen), (mlen - 1) * sizeof *a);
+       x[mlen] = 0;
+       for (u = 1 + alen - mlen; u > 0; u --) {
+               br_i15_muladd_small(x, a[u], m);
+       }
+}