Backed out changeset 4370dbfde05c (bug 1361443)

dom/file/FileReader.cpp

@@ -280,8 +280,6 @@ FileReader::DoReadData(uint64_t aCount)
 {
   MOZ_ASSERT(mAsyncStream);
 
-  uint32_t bytesRead = 0;
-
   if (mDataFormat == FILE_AS_BINARY) {
     //Continuously update our binary string as data comes in
     uint32_t oldLen = mResult.Length();
@@ -303,13 +301,14 @@ FileReader::DoReadData(uint64_t aCount)
       NS_ENSURE_SUCCESS(rv, rv);
     }
 
+    uint32_t bytesRead = 0;
     rv = mBufferedStream->ReadSegments(ReadFuncBinaryString, buf + oldLen,
                                        aCount, &bytesRead);
     if (NS_WARN_IF(NS_FAILED(rv))) {
       return rv;
     }
 
-    mResult.Truncate(oldLen + bytesRead);
+    MOZ_ASSERT(bytesRead == aCount, "failed to read data");
   }
   else {
     CheckedInt<uint64_t> size = mDataLen;
@@ -323,16 +322,22 @@ FileReader::DoReadData(uint64_t aCount)
       return NS_ERROR_OUT_OF_MEMORY;
     }
 
-    MOZ_DIAGNOSTIC_ASSERT(mFileData);
-    MOZ_RELEASE_ASSERT((mDataLen + aCount) <= mTotal);
+    if (mDataFormat != FILE_AS_ARRAYBUFFER) {
+      mFileData = (char *) realloc(mFileData, mDataLen + aCount);
+      NS_ENSURE_TRUE(mFileData, NS_ERROR_OUT_OF_MEMORY);
+    }
 
+    uint32_t bytesRead = 0;
+    MOZ_DIAGNOSTIC_ASSERT(mFileData);
     nsresult rv = mAsyncStream->Read(mFileData + mDataLen, aCount, &bytesRead);
     if (NS_WARN_IF(NS_FAILED(rv))) {
       return rv;
     }
+
+    MOZ_ASSERT(bytesRead == aCount, "failed to read data");
   }
 
-  mDataLen += bytesRead;
+  mDataLen += aCount;
   return NS_OK;
 }
 
@@ -411,15 +416,8 @@ FileReader::ReadFileContent(Blob& aBlob,
     return;
   }
 
-  // Binary Format doesn't need a post-processing of the data. Everything is
-  // written directly into mResult.
-  if (mDataFormat != FILE_AS_BINARY) {
-    if (mDataFormat == FILE_AS_ARRAYBUFFER) {
-      mFileData = js_pod_malloc<char>(mTotal);
-    } else {
-      mFileData = (char *) malloc(mTotal);
-    }
-
+  if (mDataFormat == FILE_AS_ARRAYBUFFER) {
+    mFileData = js_pod_malloc<char>(mTotal);
     if (!mFileData) {
       NS_WARNING("Preallocation failed for ReadFileData");
       aRv.Throw(NS_ERROR_OUT_OF_MEMORY);