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/*
 * Copyright 2016 Carlos Ballesteros Velasco
 *
 * Licensed 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 java.io;

public class BufferedInputStream extends FilterInputStream {
    protected volatile byte buf[];
    protected int count;
    protected int pos;
    protected int markpos = -1;
    protected int marklimit;

    private InputStream getInIfOpen() throws IOException {
        InputStream input = in;
        if (input == null) throw new IOException("Stream closed");
        return input;
    }

    private byte[] getBufIfOpen() throws IOException {
        byte[] buffer = buf;
        if (buffer == null) throw new IOException("Stream closed");
        return buffer;
    }

    public BufferedInputStream(InputStream in) {
        this(in, 8192);
    }

    public BufferedInputStream(InputStream in, int size) {
        super(in);
        if (size <= 0) throw new IllegalArgumentException("Buffer size <= 0");
        buf = new byte[size];
    }

    private void fill() throws IOException {
        byte[] buffer = getBufIfOpen();
        if (markpos < 0) pos = 0;
        else if (pos >= buffer.length) {
            if (markpos > 0) {
                int sz = pos - markpos;
                System.arraycopy(buffer, markpos, buffer, 0, sz);
                pos = sz;
                markpos = 0;
            } else if (buffer.length >= marklimit) {
                markpos = -1;
                pos = 0;
            } else {
                int nsz = pos * 2;
                if (nsz > marklimit) nsz = marklimit;
                byte nbuf[] = new byte[nsz];
                System.arraycopy(buffer, 0, nbuf, 0, pos);
                buffer = nbuf;
            }
        }
        count = pos;
        int n = getInIfOpen().read(buffer, pos, buffer.length - pos);
        if (n > 0) count = n + pos;
    }

    public synchronized int read() throws IOException {
        if (pos >= count) {
            fill();
            if (pos >= count) return -1;
        }
        return getBufIfOpen()[pos++] & 0xff;
    }

    private int read1(byte[] b, int off, int len) throws IOException {
        int avail = count - pos;
        if (avail <= 0) {
            if (len >= getBufIfOpen().length && markpos < 0) return getInIfOpen().read(b, off, len);
            fill();
            avail = count - pos;
            if (avail <= 0) return -1;
        }
        int cnt = (avail < len) ? avail : len;
        System.arraycopy(getBufIfOpen(), pos, b, off, cnt);
        pos += cnt;
        return cnt;
    }

    public synchronized int read(byte data[], int offset, int length) throws IOException {
        getBufIfOpen();
        if ((offset | length | (offset + length) | (data.length - (offset + length))) < 0) throw new IndexOutOfBoundsException();
        if (length == 0) return 0;

        int n = 0;
        for (; ; ) {
            int nread = read1(data, offset + n, length - n);
            if (nread <= 0) return (n == 0) ? nread : n;
            n += nread;
            if (n >= length) return n;
            InputStream input = in;
            if (input != null && input.available() <= 0) return n;
        }
    }

    public synchronized long skip(long n) throws IOException {
        getBufIfOpen();
        if (n <= 0) return 0;
        long avail = count - pos;

        if (avail <= 0) {
            if (markpos < 0) return getInIfOpen().skip(n);
            fill();
            avail = count - pos;
            if (avail <= 0) return 0;
        }

        long skipped = (avail < n) ? avail : n;
        pos += skipped;
        return skipped;
    }

    public synchronized int available() throws IOException {
        int n = count - pos;
        int avail = getInIfOpen().available();
        return n > (Integer.MAX_VALUE - avail) ? Integer.MAX_VALUE : n + avail;
    }

    public synchronized void mark(int readlimit) {
        marklimit = readlimit;
        markpos = pos;
    }

    public synchronized void reset() throws IOException {
        getBufIfOpen();
        if (markpos < 0) throw new IOException("Resetting to invalid mark");
        pos = markpos;
    }

    public boolean markSupported() {
        return true;
    }

    public void close() throws IOException {
        byte[] buffer;
        while ((buffer = buf) != null) {
            InputStream input = in;
            in = null;
            if (input != null) input.close();
            return;
        }
    }
}