diff options
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.java | 51 |
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)); + } +} |