Initial import.

src/int/i31_encode.c

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2016 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_i31_encode(void *dst, size_t len, const uint32_t *x)
+{
+	unsigned char *buf;
+	size_t k, xlen;
+	uint32_t acc;
+	int acc_len;
+
+	xlen = (x[0] + 31) >> 5;
+	if (xlen == 0) {
+		memset(dst, 0, len);
+		return;
+	}
+	buf = (unsigned char *)dst + len;
+	k = 1;
+	acc = 0;
+	acc_len = 0;
+	while (len != 0) {
+		uint32_t w;
+
+		w = (k <= xlen) ? x[k] : 0;
+		k ++;
+		if (acc_len == 0) {
+			acc = w;
+			acc_len = 31;
+		} else {
+			uint32_t z;
+
+			z = acc | (w << acc_len);
+			acc_len --;
+			acc = w >> (31 - acc_len);
+			if (len >= 4) {
+				buf -= 4;
+				len -= 4;
+				br_enc32be(buf, z);
+			} else {
+				switch (len) {
+				case 3:
+					buf[-3] = (unsigned char)(z >> 16);
+					/* fall through */
+				case 2:
+					buf[-2] = (unsigned char)(z >> 8);
+					/* fall through */
+				case 1:
+					buf[-1] = (unsigned char)z;
+					break;
+				}
+				return;
+			}
+		}
+	}
+}