    001    /*
    002     * Copyright (C) 2007 The Guava Authors
    003     *
    004     * Licensed under the Apache License, Version 2.0 (the "License");
    005     * you may not use this file except in compliance with the License.
    006     * You may obtain a copy of the License at
    007     *
    008     * http://www.apache.org/licenses/LICENSE-2.0
    009     *
    010     * Unless required by applicable law or agreed to in writing, software
    011     * distributed under the License is distributed on an "AS IS" BASIS,
    012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    013     * See the License for the specific language governing permissions and
    014     * limitations under the License.
    015     */
    016
    017    package com.google.common.io;
    018
    019    import com.google.common.annotations.Beta;
    020
    021    import java.io.FilterInputStream;
    022    import java.io.IOException;
    023    import java.io.InputStream;
    024
    025    /**
    026     * An {@link InputStream} that counts the number of bytes read.
    027     *
    028     * @author Chris Nokleberg
    029     * @since 1.0
    030     */
    031    @Beta
    032    public final class CountingInputStream extends FilterInputStream {
    033
    034      private long count;
    035      private long mark = -1;
    036
    037      /**
    038       * Wraps another input stream, counting the number of bytes read.
    039       *
    040       * @param in the input stream to be wrapped
    041       */
    042      public CountingInputStream(InputStream in) {
    043        super(in);
    044      }
    045
    046      /** Returns the number of bytes read. */
    047      public long getCount() {
    048        return count;
    049      }
    050
    051      @Override public int read() throws IOException {
    052        int result = in.read();
    053        if (result != -1) {
    054          count++;
    055        }
    056        return result;
    057      }
    058
    059      @Override public int read(byte[] b, int off, int len) throws IOException {
    060        int result = in.read(b, off, len);
    061        if (result != -1) {
    062          count += result;
    063        }
    064        return result;
    065      }
    066
    067      @Override public long skip(long n) throws IOException {
    068        long result = in.skip(n);
    069        count += result;
    070        return result;
    071      }
    072
    073      @Override public void mark(int readlimit) {
    074        in.mark(readlimit);
    075        mark = count;
    076        // it's okay to mark even if mark isn't supported, as reset won't work
    077      }
    078
    079      @Override public void reset() throws IOException {
    080        if (!in.markSupported()) {
    081          throw new IOException("Mark not supported");
    082        }
    083        if (mark == -1) {
    084          throw new IOException("Mark not set");
    085        }
    086
    087        in.reset();
    088        count = mark;
    089      }
    090    }