Add ol.array utility functions

src/ol/base/array.js

@@ -0,0 +1,59 @@
+goog.provide('ol.array');
+
+goog.require('goog.array');
+
+
+/**
+ * @param {Array.<number>} arr Array.
+ * @param {number} target Target.
+ * @return {number} Index.
+ */
+ol.array.binaryFindNearest = function(arr, target) {
+  var index = goog.array.binarySearch(arr, target, function(a, b) {
+    return b - a;
+  });
+  if (index >= 0) {
+    return index;
+  } else if (index == -1) {
+    return 0;
+  } else if (index == -arr.length - 1) {
+    return arr.length - 1;
+  } else {
+    var left = -index - 2;
+    var right = -index - 1;
+    if (arr[left] - target < target - arr[right]) {
+      return left;
+    } else {
+      return right;
+    }
+  }
+};
+
+
+/**
+ * @param {Array.<number>} arr Array.
+ * @param {number} target Target.
+ * @return {number} Index.
+ */
+ol.array.linearFindNearest = function(arr, target) {
+  var n = arr.length;
+  if (arr[0] <= target) {
+    return 0;
+  } else if (target <= arr[n - 1]) {
+    return n - 1;
+  } else {
+    var i;
+    for (i = 1; i < n; ++i) {
+      if (arr[i] == target) {
+        return i;
+      } else if (arr[i] < target) {
+        if (arr[i - 1] - target < target - arr[i]) {
+          return i - 1;
+        } else {
+          return i;
+        }
+      }
+    }
+    return n - 1;
+  }
+};

src/ol/base/array_test.js

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+goog.require('goog.testing.jsunit');
+goog.require('ol.array');
+
+
+function testBinaryFindNearest() {
+  var arr = [1000, 500, 100];
+
+  assertEquals(0, ol.array.binaryFindNearest(arr, 10000));
+  assertEquals(0, ol.array.binaryFindNearest(arr, 1000));
+  assertEquals(0, ol.array.binaryFindNearest(arr, 900));
+
+  assertEquals(1, ol.array.binaryFindNearest(arr, 750));
+
+  assertEquals(1, ol.array.binaryFindNearest(arr, 550));
+  assertEquals(1, ol.array.binaryFindNearest(arr, 500));
+  assertEquals(1, ol.array.binaryFindNearest(arr, 450));
+
+  assertEquals(2, ol.array.binaryFindNearest(arr, 300));
+
+  assertEquals(2, ol.array.binaryFindNearest(arr, 200));
+  assertEquals(2, ol.array.binaryFindNearest(arr, 100));
+  assertEquals(2, ol.array.binaryFindNearest(arr, 50));
+
+}
+
+
+function testLinearFindNearest() {
+  var arr = [1000, 500, 100];
+
+  assertEquals(0, ol.array.linearFindNearest(arr, 10000));
+  assertEquals(0, ol.array.linearFindNearest(arr, 1000));
+  assertEquals(0, ol.array.linearFindNearest(arr, 900));
+
+  assertEquals(1, ol.array.linearFindNearest(arr, 750));
+
+  assertEquals(1, ol.array.linearFindNearest(arr, 550));
+  assertEquals(1, ol.array.linearFindNearest(arr, 500));
+  assertEquals(1, ol.array.linearFindNearest(arr, 450));
+
+  assertEquals(2, ol.array.linearFindNearest(arr, 300));
+
+  assertEquals(2, ol.array.linearFindNearest(arr, 200));
+  assertEquals(2, ol.array.linearFindNearest(arr, 100));
+  assertEquals(2, ol.array.linearFindNearest(arr, 50));
+
+}