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 *
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 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
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 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
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package org.hsqldb.types;

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

import org.hsqldb.SessionInterface;
import org.hsqldb.error.Error;
import org.hsqldb.error.ErrorCode;
import org.hsqldb.lib.java.JavaSystem;

This class is used as an InputStream to retrieve data from a Clob.
mark() and reset() are not supported.
Author:
Fred Toussi (fredt@users dot sourceforge.net)
Version:
2.3.4
Since:
1.9.0/**
 * This class is used as an InputStream to retrieve data from a Clob.
 * mark() and reset() are not supported.
 *
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 2.3.4
 * @since 1.9.0
 */
public final class ClobInputStream extends Reader {

    final ClobData                clob;
    final long                    availableLength;
    long                          bufferOffset;
    long                          currentPosition;
    char[]                        buffer;
    boolean                       isClosed;
    int                           streamBlockSize;
    public final SessionInterface session;

    public ClobInputStream(SessionInterface session, ClobData clob,
                           long offset, long length) {

        final long clobLength = clob.length(session);

        this.session         = session;
        this.clob            = clob;
        this.availableLength = offset + Math.min(length, clobLength - offset);
        this.currentPosition = offset;
        this.streamBlockSize = session.getStreamBlockSize();
    }

    public int read() throws IOException {

        checkClosed();

        if (currentPosition >= availableLength) {
            return -1;
        }

        if (buffer == null
                || currentPosition >= bufferOffset + buffer.length) {
            try {
                checkClosed();
                readIntoBuffer();
            } catch (Exception e) {
                throw JavaSystem.toIOException(e);
            }
        }

        int val = buffer[(int) (currentPosition - bufferOffset)];

        currentPosition++;

        return val;
    }

    public int read(char[] cbuf, int off, int len) throws IOException {

        checkClosed();

        if (currentPosition >= availableLength) {
            return -1;
        }

        if (currentPosition + len > availableLength) {
            len = (int) (availableLength - currentPosition);
        }

        for (int i = off; i < off + len && i < cbuf.length; i++) {
            cbuf[i] = (char) read();
        }

        return len;
    }

    public long skip(long n) throws IOException {

        checkClosed();

        if (n <= 0) {
            return 0;
        }

        if (currentPosition + n > availableLength) {
            n = availableLength - currentPosition;
        }

        currentPosition += n;

        return n;
    }

    public int available() {

        long avail = availableLength - currentPosition;

        if (avail > Integer.MAX_VALUE) {
            return Integer.MAX_VALUE;
        }

        return (int) avail;
    }

    public void close() throws IOException {
        isClosed = true;
    }

    private void checkClosed() throws IOException {

        if (isClosed) {
            throw new IOException(Error.getMessage(ErrorCode.X_0F503));
        }
    }

    private void readIntoBuffer() {

        long readLength = availableLength - currentPosition;

        if (readLength <= 0) {
            return;
        }

        if (readLength > streamBlockSize) {
            readLength = streamBlockSize;
        }

        buffer = clob.getChars(session, currentPosition, (int) readLength);
        bufferOffset = currentPosition;
    }

    static boolean isInLimits(long fullLength, long pos, long len) {
        return pos >= 0 && len >= 0 && pos + len <= fullLength;
    }
}