fix: fix reference searching when search time = segment.endTime

Fixes shaka-project#3191

Change-Id: I4f2c6b3e2e67a6db1bfb71815a5ce80a3584e41e

lib/media/segment_index.js

@@ -116,10 +116,18 @@ shaka.media.SegmentIndex = class {
     // For live streams, searching from the end is faster.  For VOD, it balances
     // out either way.  In both cases, references.length is small enough that
     // the difference isn't huge.
-    for (let i = this.references.length - 1; i >= 0; --i) {
+    const lastReferenceIndex = this.references.length - 1;
+    for (let i = lastReferenceIndex; i >= 0; --i) {
       const r = this.references[i];
+      const start = r.startTime;
+      // A rounding error can cause /time/ to equal e.endTime or fall in between
+      // the references by a fraction of a second. To account for this, we use
+      // the start of the next segment as /end/, unless this is the last
+      // reference, in which case we use its end time as /end/.
+      const end = i < lastReferenceIndex ?
+        this.references[i + 1].startTime : r.endTime;
       // Note that a segment ends immediately before the end time.
-      if ((time >= r.startTime) && (time < r.endTime)) {
+      if ((time >= start) && (time < end)) {
         return i + this.numEvicted;
       }
     }

test/media/segment_index_unit.js

@@ -60,6 +60,28 @@ describe('SegmentIndex', /** @suppress {accessControls} */ () => {
       expect(ref).toBe(actual2);
     });
 
+    it('works with two references if time == first end time', () => {
+      const actual1 = makeReference(uri(10), 10, 20.12);
+      const actual2 = makeReference(uri(20), 20.13, 30);
+      const index = new shaka.media.SegmentIndex([actual1, actual2]);
+
+      const pos = index.find(20.12);
+      goog.asserts.assert(pos != null, 'Null position!');
+      const ref = index.get(pos);
+      expect(ref).toBe(actual1);
+    });
+
+    it('works with time is between first endTime and second startTime', () => {
+      const actual1 = makeReference(uri(10), 10, 20.12111);
+      const actual2 = makeReference(uri(20), 20.12113, 30);
+      const index = new shaka.media.SegmentIndex([actual1, actual2]);
+
+      const pos = index.find(20.12112);
+      goog.asserts.assert(pos != null, 'Null position!');
+      const ref = index.get(pos);
+      expect(ref).toBe(actual1);
+    });
+
     it('returns the first segment if time < first start time', () => {
       const actual = makeReference(uri(10), 10, 20);
       const index = new shaka.media.SegmentIndex([actual]);
@@ -85,15 +107,6 @@ describe('SegmentIndex', /** @suppress {accessControls} */ () => {
       const pos = index.find(21);
       expect(pos).toBeNull();
     });
-
-    it('returns null if time is within a gap', () => {
-      const actual1 = makeReference(uri(10), 10, 20);
-      const actual2 = makeReference(uri(25), 25, 30);
-      const index = new shaka.media.SegmentIndex([actual1, actual2]);
-
-      const pos = index.find(23);
-      expect(pos).toBeNull();
-    });
   });
 
   describe('get', () => {