renamed capwap directory to cw.

FossilOrigin-Name: 8a43dd9d05a4cb73210243ddd8df2a26f16c7ef2c4d4e36ab446de1f65d88223

src/cw/lw_checksum.c

@@ -0,0 +1,59 @@
+/*
+    This file is part of libcapwap.
+
+    libcapwap is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    libcapwap is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+/**
+ *@file
+ *@brief Implements lw_checksum.
+ *@addtogroup LWAPPFunctions 
+ *@{
+ */ 
+
+#include "lwapp.h"
+
+/**
+ * Calculate the 16-bit checksum for LWAPP Image Data message 
+ * elements with opcode 3 (see RFC5412) 
+ * This is also used by Cisco in CAPWAP
+ * @param d pointer to data to calulate the checksum for
+ * @param len length of data
+ * @return the calculated checksum.
+ */
+uint16_t lw_checksum(uint8_t * d, int len)
+{
+	int32_t sum = 0;
+	uint16_t *w = (uint16_t *) d;
+
+	while (len > 1) {
+		sum += ntohs(*w++);
+		len -= 2;
+	}
+
+	if (len)
+		sum += (*(uint8_t *) w) << 8;
+
+	sum = (sum >> 16) + (sum & 0xffff);
+	sum += (sum >> 16);
+
+	return (~sum) & 0xffff;
+}
+
+
+/**
+ *@}
+ */
+