use 64-bit integer for granule position

anthumchris · Nov 2, 2018 · 315293d · 315293d
1 parent 4d0fda6
commit 315293d
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Showing 2 changed files with 32 additions and 4 deletions.
diff --git a/dist/test-seekable-opus-stream-decoder.html b/dist/test-seekable-opus-stream-decoder.html
@@ -256,8 +256,7 @@
         this.filePos = posFromFileStart;
         this.filePosHex = posFromFileStart.toString(16); // used for debugging
 
-        // TODO this shoudl be read as 64-bit, which isn't supported
-        this.granule = view.getUint32(viewOffset+6, true);
+        this.granule = view.getUint64(viewOffset+6, true);
 
         this.serial = view.getUint32(viewOffset+14, true);
         this.page = view.getUint32(viewOffset+18, true);
@@ -280,6 +279,21 @@
           channelMappingFamily: dataView.getUint8(14, true),
         };
       }
+
+      // getUint64() polyfill from https://stackoverflow.com/questions/53103695/
+      DataView.prototype.getUint64 = function(byteOffset, littleEndian) {
+        // split 64-bit number into two 32-bit parts
+        const left =  this.getUint32(byteOffset, littleEndian);
+        const right = this.getUint32(byteOffset+4, littleEndian);
+
+        // combine the two 32-bit values
+        const combined = littleEndian? left + 2**32*right : 2**32*left + right;
+
+        if (!Number.isSafeInteger(combined))
+          console.warn(combined, 'exceeds MAX_SAFE_INTEGER. Precision may be lost');
+
+        return combined;
+      }
     </script>
   </body>
 </html>
diff --git a/src/test-seekable-opus-stream-decoder.html b/src/test-seekable-opus-stream-decoder.html
@@ -256,8 +256,7 @@
         this.filePos = posFromFileStart;
         this.filePosHex = posFromFileStart.toString(16); // used for debugging
 
-        // TODO this shoudl be read as 64-bit, which isn't supported
-        this.granule = view.getUint32(viewOffset+6, true);
+        this.granule = view.getUint64(viewOffset+6, true);
 
         this.serial = view.getUint32(viewOffset+14, true);
         this.page = view.getUint32(viewOffset+18, true);
@@ -280,6 +279,21 @@
           channelMappingFamily: dataView.getUint8(14, true),
         };
       }
+
+      // getUint64() polyfill from https://stackoverflow.com/questions/53103695/
+      DataView.prototype.getUint64 = function(byteOffset, littleEndian) {
+        // split 64-bit number into two 32-bit parts
+        const left =  this.getUint32(byteOffset, littleEndian);
+        const right = this.getUint32(byteOffset+4, littleEndian);
+
+        // combine the two 32-bit values
+        const combined = littleEndian? left + 2**32*right : 2**32*left + right;
+
+        if (!Number.isSafeInteger(combined))
+          console.warn(combined, 'exceeds MAX_SAFE_INTEGER. Precision may be lost');
+
+        return combined;
+      }
     </script>
   </body>
 </html>