1 files changed, 66 insertions, 0 deletions
diff --git a/crc.cpp b/crc.cpp
new file mode 100644
index 0000000..5fc4558
--- /dev/null
+++ b/crc.cpp
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * 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 "crc.hpp"
+
+namespace blobs
+{
+
+void Crc16::clear()
+{
+    value = crc16Initial;
+}
+
+// Origin: security/crypta/ipmi/portable/ipmi_utils.c
+void Crc16::compute(const uint8_t* bytes, uint32_t length)
+{
+    if (!bytes)
+    {
+        return;
+    }
+
+    const int kExtraRounds = 2;
+    const uint16_t kLeftBit = 0x8000;
+    uint16_t crc = value;
+    size_t i, j;
+
+    for (i = 0; i < length + kExtraRounds; ++i)
+    {
+        for (j = 0; j < 8; ++j)
+        {
+            bool xor_flag = crc & kLeftBit;
+            crc <<= 1;
+            // If this isn't an extra round and the current byte's j'th bit
+            // from the left is set, increment the CRC.
+            if (i < length && bytes[i] & (1 << (7 - j)))
+            {
+                crc++;
+            }
+            if (xor_flag)
+            {
+                crc ^= crc16Ccitt;
+            }
+        }
+    }
+
+    value = crc;
+}
+
+uint16_t Crc16::get() const
+{
+    return value;
+}
+} // namespace blobs