aboutsummaryrefslogtreecommitdiff
path: root/src/main/java/org/apache/commons/compress/utils/SkipShieldingInputStream.java
diff options
context:
space:
mode:
Diffstat (limited to 'src/main/java/org/apache/commons/compress/utils/SkipShieldingInputStream.java')
-rw-r--r--src/main/java/org/apache/commons/compress/utils/SkipShieldingInputStream.java51
1 files changed, 51 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/compress/utils/SkipShieldingInputStream.java b/src/main/java/org/apache/commons/compress/utils/SkipShieldingInputStream.java
new file mode 100644
index 000000000..e1cbcbc66
--- /dev/null
+++ b/src/main/java/org/apache/commons/compress/utils/SkipShieldingInputStream.java
@@ -0,0 +1,51 @@
+/*
+ * 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.commons.compress.utils;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * A wrapper that overwrites {@link #skip} and delegates to {@link #read} instead.
+ *
+ * <p>Some implementations of {@link InputStream} implement {@link
+ * InputStream#skip} in a way that throws an exception if the stream
+ * is not seekable - {@link System#in System.in} is known to behave
+ * that way. For such a stream it is impossible to invoke skip at all
+ * and you have to read from the stream (and discard the data read)
+ * instead. Skipping is potentially much faster than reading so we do
+ * want to invoke {@code skip} when possible. We provide this class so
+ * you can wrap your own {@link InputStream} in it if you encounter
+ * problems with {@code skip} throwing an excpetion.</p>
+ *
+ * @since 1.17
+ */
+public class SkipShieldingInputStream extends FilterInputStream {
+ private static final int SKIP_BUFFER_SIZE = 8192;
+ // we can use a shared buffer as the content is discarded anyway
+ private static final byte[] SKIP_BUFFER = new byte[SKIP_BUFFER_SIZE];
+ public SkipShieldingInputStream(InputStream in) {
+ super(in);
+ }
+
+ @Override
+ public long skip(long n) throws IOException {
+ return n < 0 ? 0 : read(SKIP_BUFFER, 0, (int) Math.min(n, SKIP_BUFFER_SIZE));
+ }
+}