org.metafacture.biblio.iso2709.DirectoryEntry Maven / Gradle / Ivy

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Modules for processing bibliographic data
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/*
 * Copyright 2016 Christoph Böhme
 *
 * 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 org.metafacture.biblio.iso2709;

import static org.metafacture.biblio.iso2709.Iso2709Constants.MAX_BASE_ADDRESS;
import static org.metafacture.biblio.iso2709.Iso2709Constants.MIN_BASE_ADDRESS;
import static org.metafacture.biblio.iso2709.Iso2709Constants.RECORD_LABEL_LENGTH;
import static org.metafacture.biblio.iso2709.Iso2709Constants.TAG_LENGTH;

/**
 * Provides access to a directory entry. A {@code DirectoryEntry} works like
 * an iterator or cursor. Use {@link #gotoNext()} to advance to the next
 * directory entry. Use {@link #rewind()} to go back to the first directory
 * entry.
 *
 * @author Christoph Böhme
 */
class DirectoryEntry {

    private final Iso646ByteBuffer buffer;

    private final int directoryEnd;
    private final int fieldLengthLength;
    private final int fieldStartLength;
    private final int implDefinedPartLength;
    private final int entryLength;

    private int currentPosition;

    DirectoryEntry(final Iso646ByteBuffer buffer, final RecordFormat recordFormat,
            final int baseAddress) {
        assert buffer != null;
        assert baseAddress >= MIN_BASE_ADDRESS;
        assert baseAddress <= MAX_BASE_ADDRESS;

        this.buffer = buffer;
        directoryEnd = baseAddress - Byte.BYTES;
        fieldLengthLength = recordFormat.getFieldLengthLength();
        fieldStartLength = recordFormat.getFieldStartLength();
        implDefinedPartLength = recordFormat.getImplDefinedPartLength();
        entryLength = TAG_LENGTH + fieldLengthLength + fieldStartLength +
                implDefinedPartLength;
        rewind();
    }

    void rewind() {
        currentPosition = RECORD_LABEL_LENGTH;
    }

    void gotoNext() {
        assert currentPosition < directoryEnd;
        currentPosition += entryLength;
    }

    boolean endOfDirectoryReached() {
        return currentPosition >= directoryEnd;
    }

    char[] getTag() {
        assert currentPosition < directoryEnd;
        return buffer.charsAt(currentPosition, TAG_LENGTH);
    }

    int getFieldLength() {
        assert currentPosition < directoryEnd;
        final int fieldLengthStart = currentPosition + TAG_LENGTH;
        return buffer.parseIntAt(fieldLengthStart, fieldLengthLength);
    }

    int getFieldStart() {
        assert currentPosition < directoryEnd;
        final int fieldStartStart = currentPosition + TAG_LENGTH +
                fieldLengthLength;
        return buffer.parseIntAt(fieldStartStart, fieldStartLength);
    }

    char[] getImplDefinedPart() {
        assert currentPosition < directoryEnd;
        final int implDefinedPartStart = currentPosition + TAG_LENGTH +
                fieldLengthLength + fieldStartLength;
        return buffer.charsAt(implDefinedPartStart, implDefinedPartLength);
    }

    boolean isRecordIdField() {
        final char[] tag = getTag();
        return tag[0] == '0' && tag[1] == '0' && tag[2] == '1';
    }

    boolean isReferenceField() {
        final char[] tag = getTag();
        return tag[0] == '0' && tag[1] == '0';
    }

    boolean isContinuedField() {
        return getFieldLength() == 0;
    }

    @Override
    public String toString() {
        if (endOfDirectoryReached()) {
            return "@END-OF-DIRECTORY";
        }
        return String.valueOf(getTag()) + String.valueOf(getFieldLength()) +
                String.valueOf(getFieldStart()) + String.valueOf(getImplDefinedPart());
    }

}