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JDBC Driver over YDB Java SDK

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/*
 * Copyright (C) 2007 The Guava Authors
 *
 * 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 tech.ydb.jdbc.common;

import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

final class LimitedReader extends FilterReader {

    // See LimitedInputStream in Guava implementation

    private long left;
    private long mark = -1;

    LimitedReader(Reader in, long limit) {
        super(in);
        checkNotNull(in);
        checkArgument(limit >= 0, "limit must be non-negative");
        left = limit;
    }

    // it's okay to mark even if mark isn't supported, as reset won't work
    @Override
    public synchronized void mark(int readLimit) throws IOException {
        in.mark(readLimit);
        mark = left;
    }

    @Override
    public int read() throws IOException {
        if (left == 0) {
            return -1;
        }

        int result = in.read();
        if (result != -1) {
            --left;
        }
        return result;
    }

    @Override
    public int read(char[] cbuf, int off, int len) throws IOException {
        if (left == 0) {
            return -1;
        }

        len = (int) Math.min(len, left);
        int result = in.read(cbuf, off, len);
        if (result != -1) {
            left -= result;
        }
        return result;
    }

    @Override
    public synchronized void reset() throws IOException {
        if (!in.markSupported()) {
            throw new IOException("Mark not supported");
        }
        if (mark == -1) {
            throw new IOException("Mark not set");
        }

        in.reset();
        left = mark;
    }

    @Override
    public long skip(long n) throws IOException {
        n = Math.min(n, left);
        long skipped = in.skip(n);
        left -= skipped;
        return skipped;
    }
}