X-Git-Url: http://source.jalview.org/gitweb/?a=blobdiff_plain;f=src%2Fjalview%2Fext%2Fandroid%2FSparseIntArray.java;h=fcd4f1fc512e196f3f21cd760063d56e742f8f3c;hb=51728d3951398f9c12d7017c776953f17322cc68;hp=0602d503903d5cc4f3a8592292fa93a868fd5009;hpb=d1e9d0331c7bd5b73130f63f5b1447a05f166549;p=jalview.git

diff --git a/src/jalview/ext/android/SparseIntArray.java b/src/jalview/ext/android/SparseIntArray.java
index 0602d50..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;
@@ -346,4 +353,80 @@ public class SparseIntArray implements Cloneable
     buffer.append('}');
     return buffer.toString();
   }
+
+  /**
+   * Method (copied from put) added for Jalview to efficiently increment a key's
+   * value if present, else add it with the given value. This avoids a double
+   * binary search (once to get the value, again to put the updated value).
+   * 
+   * @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)
+  {
+    int newValue = toAdd;
+    int i = ContainerHelpers.binarySearch(mKeys, mSize, key);
+    if (i >= 0)
+    {
+      checkOverflow(mValues[i], toAdd);
+      mValues[i] += toAdd;
+      newValue = mValues[i];
+    }
+    else
+    {
+      i = ~i;
+      if (mSize >= mKeys.length)
+      {
+        int n = idealIntArraySize(mSize + 1);
+        int[] nkeys = new int[n];
+        int[] nvalues = new int[n];
+        System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length);
+        System.arraycopy(mValues, 0, nvalues, 0, mValues.length);
+        mKeys = nkeys;
+        mValues = nvalues;
+      }
+      if (mSize - i != 0)
+      {
+        System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i);
+        System.arraycopy(mValues, i, mValues, i + 1, mSize - i);
+      }
+      mKeys[i] = key;
+      mValues[i] = toAdd;
+      mSize++;
+    }
+    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);
+      }
+    }
+  }
 }