1 files changed, 59 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/common/TimeUtils.java b/api/src/main/java/io/opencensus/common/TimeUtils.java
new file mode 100644
index 00000000..db119e2e
--- /dev/null
+++ b/api/src/main/java/io/opencensus/common/TimeUtils.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017, OpenCensus Authors
+ *
+ * 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.
+ */
+
+package io.opencensus.common;
+
+import java.math.BigInteger;
+
+/** Util class for {@link Timestamp} and {@link Duration}. */
+final class TimeUtils {
+  static final long MAX_SECONDS = 315576000000L;
+  static final int MAX_NANOS = 999999999;
+  static final long MILLIS_PER_SECOND = 1000L;
+  static final long NANOS_PER_MILLI = 1000 * 1000;
+  static final long NANOS_PER_SECOND = NANOS_PER_MILLI * MILLIS_PER_SECOND;
+
+  private TimeUtils() {}
+
+  /**
+   * Compares two longs. This functionality is provided by {@code Long.compare(long, long)} in Java
+   * 7.
+   */
+  static int compareLongs(long x, long y) {
+    if (x < y) {
+      return -1;
+    } else if (x == y) {
+      return 0;
+    } else {
+      return 1;
+    }
+  }
+
+  private static final BigInteger MAX_LONG_VALUE = BigInteger.valueOf(Long.MAX_VALUE);
+  private static final BigInteger MIN_LONG_VALUE = BigInteger.valueOf(Long.MIN_VALUE);
+
+  /**
+   * Adds two longs and throws an {@link ArithmeticException} if the result overflows. This
+   * functionality is provided by {@code Math.addExact(long, long)} in Java 8.
+   */
+  static long checkedAdd(long x, long y) {
+    BigInteger sum = BigInteger.valueOf(x).add(BigInteger.valueOf(y));
+    if (sum.compareTo(MAX_LONG_VALUE) > 0 || sum.compareTo(MIN_LONG_VALUE) < 0) {
+      throw new ArithmeticException("Long sum overflow: x=" + x + ", y=" + y);
+    }
+    return x + y;
+  }
+}