Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/2321#discussion_r17260471
--- Diff:
core/src/main/scala/org/apache/spark/util/io/LengthBoundedInputStream.scala ---
@@ -0,0 +1,69 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.util.io
+
+import java.io.InputStream
+
+
+/**
+ * An InputStream that decorator that limits the number of bytes returned
from the underlying
+ * InputStream. If the underlying InputStream returns end of stream (-1
value in read) before
+ * the limit is reached, then the end of stream is properly returned to
the caller as well.
+ *
+ * One use case is to read a segment of a file (FileInputStream always
reads until the end of a
+ * file, whereas caller can use this one to limit it to stop before the
end of the file).
+ *
+ * @param underlying Underlying InputStream to read from
+ * @param limit number of bytes to read before returning EOF
+ */
+final class LengthBoundedInputStream(underlying: InputStream, limit: Long)
extends InputStream {
+
+ private[this] var pos: Long = 0L
+
+ override def close(): Unit = underlying.close()
+
+ override def read(): Int = {
--- End diff --
Although you only have to override the version of `read()` that reads a
byte at a time to make this works, it will be very inefficient. Obviously most
`InputStream` override versions of `read()` that read a large chunk of bytes.
This won't delegate those method calls though. I think you'd have to delegate
more of the API to make this work reasonably.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
