X-Git-Url: http://source.jalview.org/gitweb/?a=blobdiff_plain;f=src%2Fjalview%2Fext%2Fandroid%2FSparseIntArray.java;h=fcd4f1fc512e196f3f21cd760063d56e742f8f3c;hb=ffa5c07d90b4a933762a5d9faa0578c11693d63a;hp=e286cb478d621afac153775db50fb2798555d1c9;hpb=1c757dc1e6ee864277825c1ebd9c6a9fbe0da7b2;p=jalview.git

diff --git a/src/jalview/ext/android/SparseIntArray.java b/src/jalview/ext/android/SparseIntArray.java
index e286cb4..fcd4f1f 100644
--- a/src/jalview/ext/android/SparseIntArray.java
+++ b/src/jalview/ext/android/SparseIntArray.java
@@ -40,6 +40,13 @@ package jalview.ext.android;
  * order in the case of <code>valueAt(int)<code>.
  * </p>
  */
+
+/*
+ * Imported into Jalview September 2016
+ * Change log:
+ *   Sep 2016 method add(int, int) added for more efficient increment of counts
+ *            (a single binary search, rather than one on read and one on write)
+ */
 public class SparseIntArray implements Cloneable
 {
   private int[] mKeys;
@@ -355,6 +362,8 @@ public class SparseIntArray implements Cloneable
    * @param key
    * @oparam toAdd
    * @return the new value of the count for the key
+   * @throw ArithmeticException if the result would exceed the maximum value of
+   *        an int
    */
   public int add(int key, int toAdd)
   {
@@ -362,6 +371,7 @@ public class SparseIntArray implements Cloneable
     int i = ContainerHelpers.binarySearch(mKeys, mSize, key);
     if (i >= 0)
     {
+      checkOverflow(mValues[i], toAdd);
       mValues[i] += toAdd;
       newValue = mValues[i];
     }
@@ -389,4 +399,34 @@ public class SparseIntArray implements Cloneable
     }
     return newValue;
   }
+
+  /**
+   * Throws ArithmeticException if adding addend to value would exceed the range
+   * of int
+   * 
+   * @param value
+   * @param addend
+   */
+  static void checkOverflow(int value, int addend)
+  {
+    /*
+     * test cases being careful to avoid overflow while testing!
+     */
+    if (addend > 0)
+    {
+      if (value > 0 && Integer.MAX_VALUE - value < addend)
+      {
+        throw new ArithmeticException("Integer overflow adding " + addend
+                + " to  " + value);
+      }
+    }
+    else if (addend < 0)
+    {
+      if (value < 0 && Integer.MIN_VALUE - value > addend)
+      {
+        throw new ArithmeticException("Integer underflow adding " + addend
+                + " to  " + value);
+      }
+    }
+  }
 }