Diff: source/mbed_trace_ip6tos.c

Revision:

1:506ad37c6bd7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/mbed_trace_ip6tos.c	Thu Mar 31 18:10:53 2016 +0300
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2014-2015 ARM Limited. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <stdio.h>
+#include <inttypes.h>
+#include "mbed-trace/mbed_trace_ip6tos.h"
+
+/**
+ * Print binary IPv6 address to a string.
+ * String must contain enough room for full address, 40 bytes exact.
+ * IPv4 tunneling addresses are not covered.
+ * \param addr IPv6 address.
+ * \p buffer to write string to.
+ */
+void mbed_trace_ip6tos(const void *ip6addr, char *p)
+{
+    uint_fast8_t zero_start = 255, zero_len = 1;
+    const uint8_t *addr = ip6addr;
+    uint_fast16_t part;
+
+    /* Follow RFC 5952 - pre-scan for longest run of zeros */
+    for (uint_fast8_t n = 0; n < 8; n++) {
+        part = *addr++;
+        part = (part << 8) | *addr++;
+        if (part != 0) {
+            continue;
+        }
+
+        /* We're at the start of a run of zeros - scan to non-zero (or end) */
+        uint_fast8_t n0 = n;
+        for (n = n0 + 1; n < 8; n++) {
+            part = *addr++;
+            part = (part << 8) | *addr++;
+            if (part != 0) {
+                break;
+            }
+        }
+
+        /* Now n0->initial zero of run, n->after final zero in run. Is this the
+         * longest run yet? If equal, we stick with the previous one - RFC 5952
+         * S4.2.3. Note that zero_len being initialised to 1 stops us
+         * shortening a 1-part run (S4.2.2.)
+         */
+        if (n - n0 > zero_len) {
+            zero_start = n0;
+            zero_len = n - n0;
+        }
+
+        /* Continue scan for initial zeros from part n+1 - we've already
+         * consumed part n, and know it's non-zero. */
+    }
+
+    /* Now go back and print, jumping over any zero run */
+    addr = ip6addr;
+    for (uint_fast8_t n = 0; n < 8;) {
+        if (n == zero_start) {
+            if (n == 0) {
+                *p++ = ':';
+            }
+            *p++ = ':';
+            addr += 2 * zero_len;
+            n += zero_len;
+            continue;
+        }
+
+        part = *addr++;
+        part = (part << 8) | *addr++;
+        n++;
+
+        p += sprintf(p, "%"PRIxFAST16, part);
+
+        /* One iteration writes "part:" rather than ":part", and has the
+         * explicit check for n == 8 below, to allow easy extension for
+         * IPv4-in-IPv6-type addresses ("xxxx::xxxx:a.b.c.d"): we'd just
+         * run the same loop for 6 parts, and output would then finish with the
+         * required : or ::, ready for "a.b.c.d" to be tacked on.
+         */
+        if (n != 8) {
+            *p++ = ':';
+        }
+    }
+    *p++ = '\0';
+}