planning

node_modules/@mapbox/mapbox-gl-style-spec/expression/stops.js

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+// @flow
+
+import RuntimeError from './runtime_error.js';
+
+import type {Expression} from './expression.js';
+
+export type Stops = Array<[number, Expression]>;
+
+/**
+ * Returns the index of the last stop <= input, or 0 if it doesn't exist.
+ * @private
+ */
+export function findStopLessThanOrEqualTo(stops: Array<number>, input: number): number {
+    const lastIndex = stops.length - 1;
+    let lowerIndex = 0;
+    let upperIndex = lastIndex;
+    let currentIndex = 0;
+    let currentValue, nextValue;
+
+    while (lowerIndex <= upperIndex) {
+        currentIndex = Math.floor((lowerIndex + upperIndex) / 2);
+        currentValue = stops[currentIndex];
+        nextValue = stops[currentIndex + 1];
+
+        if (currentValue <= input) {
+            if (currentIndex === lastIndex || input < nextValue) { // Search complete
+                return currentIndex;
+            }
+
+            lowerIndex = currentIndex + 1;
+        } else if (currentValue > input) {
+            upperIndex = currentIndex - 1;
+        } else {
+            throw new RuntimeError('Input is not a number.');
+        }
+    }
+
+    return 0;
+}