fix: Even better method for generating keys.

shaka-project · Dec 7, 2022 · 8805169 · 8805169
1 parent b446633
commit 8805169
Showing 1 changed file with 36 additions and 33 deletions.
diff --git a/lib/util/stream_utils.js b/lib/util/stream_utils.js
@@ -501,6 +501,40 @@ shaka.util.StreamUtils = class {
   }
 
 
+  /**
+   * Constructs a string out of an object, similar to the JSON.stringify method.
+   * Unlike that method, this guarantees that the order of the keys is
+   * alphabetical, so it can be used as a way to reliably compare two objects.
+   *
+   * @param {!Object} obj
+   * @return {string}
+   * @private
+   */
+  static alphabeticalKeyOrderStringify_(obj) {
+    const keys = [];
+    for (const key in obj) {
+      keys.push(key);
+    }
+    // Alphabetically sort the keys, so they will be in a reliable order.
+    keys.sort();
+
+    const terms = [];
+    for (const key of keys) {
+      const escapedKey = JSON.stringify(key);
+      const value = obj[key];
+      if (value instanceof Object) {
+        const stringifiedValue =
+            shaka.util.StreamUtils.alphabeticalKeyOrderStringify_(value);
+        terms.push(escapedKey + ':' + stringifiedValue);
+      } else {
+        const escapedValue = JSON.stringify(value);
+        terms.push(escapedKey + ':' + escapedValue);
+      }
+    }
+    return '{' + terms.join(',') + '}';
+  }
+
+
   /**
    * Queries mediaCapabilities for the decoding info for that decoding config,
    * and assigns it to the given variant.
@@ -510,39 +544,8 @@ shaka.util.StreamUtils = class {
    * @private
    */
   static async getDecodingInfosForVariant_(variant, decodingConfig) {
-    // Construct a key for that decoding config. By using this instead of plain
-    // JSON.stringify, we ensure that the keys are always in a consistent order.
-    const cacheKeyAr = [decodingConfig.type];
-    if (decodingConfig.video) {
-      cacheKeyAr.push(decodingConfig.video.contentType);
-      cacheKeyAr.push(decodingConfig.video.width);
-      cacheKeyAr.push(decodingConfig.video.height);
-      cacheKeyAr.push(decodingConfig.video.bitrate);
-      cacheKeyAr.push(decodingConfig.video.framerate);
-      cacheKeyAr.push(decodingConfig.video.transferFunction);
-    }
-    if (decodingConfig.audio) {
-      cacheKeyAr.push(decodingConfig.audio.contentType);
-      cacheKeyAr.push(decodingConfig.audio.channels);
-      cacheKeyAr.push(decodingConfig.audio.bitrate);
-      cacheKeyAr.push(decodingConfig.audio.samplerate);
-      cacheKeyAr.push(decodingConfig.audio.spatialRendering);
-    }
-    if (decodingConfig.keySystemConfiguration) {
-      const keyConfig = decodingConfig.keySystemConfiguration;
-      cacheKeyAr.push(keyConfig.keySystem);
-      cacheKeyAr.push(keyConfig.initDataType);
-      cacheKeyAr.push(keyConfig.persistentState);
-      cacheKeyAr.push(keyConfig.distinctiveIdentifier);
-      cacheKeyAr.push(keyConfig.sessionTypes.join(','));
-      if (keyConfig.audio) {
-        cacheKeyAr.push(keyConfig.audio.robustness);
-      }
-      if (keyConfig.video) {
-        cacheKeyAr.push(keyConfig.video.robustness);
-      }
-    }
-    const cacheKey = cacheKeyAr.map((term) => `{${term}}`).join('');
+    const cacheKey =
+        shaka.util.StreamUtils.alphabeticalKeyOrderStringify_(decodingConfig);
 
     try {
       const cache = shaka.util.StreamUtils.decodingConfigCache_;