Bug 761076 - FileHandle: Add optional location parameter to LockedFile.truncate(). r=sicking

dom/file/LockedFile.cpp

@@ -662,7 +662,9 @@ LockedFile::Append(const jsval& aValue,
 }
 
 NS_IMETHODIMP
-LockedFile::Truncate(nsIDOMFileRequest** _retval)
+LockedFile::Truncate(PRUint64 aLocation,
+                     PRUint8 aOptionalArgCount,
+                     nsIDOMFileRequest** _retval)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
 
@@ -682,12 +684,18 @@ LockedFile::Truncate(nsIDOMFileRequest** _retval)
   nsRefPtr<FileRequest> fileRequest = GenerateFileRequest();
   NS_ENSURE_TRUE(fileRequest, NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR);
 
+  PRUint64 location = aOptionalArgCount ? aLocation : mLocation;
+
   nsRefPtr<TruncateHelper> helper =
-    new TruncateHelper(this, fileRequest, mLocation);
+    new TruncateHelper(this, fileRequest, location);
 
   nsresult rv = helper->Enqueue();
   NS_ENSURE_SUCCESS(rv, NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR);
 
+  if (aOptionalArgCount) {
+    mLocation = aLocation;
+  }
+
   fileRequest.forget(_retval);
   return NS_OK;
 }

dom/file/nsIDOMLockedFile.idl

@@ -16,7 +16,7 @@ dictionary DOMFileMetadataParameters
   boolean lastModified;
 };
 
-[scriptable, builtinclass, uuid(63055eeb-cc19-468b-bafa-7b7961796340)]
+[scriptable, builtinclass, uuid(e1f69cc5-c6ce-4850-bc09-c4211b1d4290)]
 interface nsIDOMLockedFile : nsISupports
 {
   readonly attribute nsIDOMFileHandle fileHandle;
@@ -49,8 +49,9 @@ interface nsIDOMLockedFile : nsISupports
   nsIDOMFileRequest
   append(in jsval value);
 
+  [optional_argc]
   nsIDOMFileRequest
-  truncate();
+  truncate([optional] in unsigned long long location);
 
   nsIDOMFileRequest
   flush();

dom/file/test/test_truncate.html

@@ -31,7 +31,7 @@
       is(lockedFile.location, 100000, "Correct location");
 
       for (let i = 0; i < 10; i++) {
-        let location = lockedFile.location - 10000
+        let location = lockedFile.location - 10000;
         lockedFile.location = location;
 
         request = lockedFile.truncate();
@@ -46,6 +46,27 @@
 
         is(event.target.result.size, location, "Correct size");
       }
+
+      request = lockedFile.write(testBuffer);
+      request.onsuccess = grabEventAndContinueHandler;
+      event = yield;
+
+      let location = lockedFile.location;
+      for (let i = 0; i < 10; i++) {
+        location -= 10000;
+
+        request = lockedFile.truncate(location);
+        request.onsuccess = grabEventAndContinueHandler;
+        event = yield;
+
+        is(lockedFile.location, location, "Correct location");
+
+        request = lockedFile.getMetadata({ size: true });
+        request.onsuccess = grabEventAndContinueHandler;
+        event = yield;
+
+        is(event.target.result.size, location, "Correct size");
+      }
     }
 
     finishTest();