com.github.fge.grappa.buffers.CharSequenceInputBuffer Maven / Gradle / Ivy

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Write parsers in pure Java
There is a newer version: 2.1.0-beta.3
/*
 * Copyright (C) 2014 Francis Galiegue 
 *
 * 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 com.github.fge.grappa.buffers;

import com.github.fge.grappa.support.Chars;
import com.github.fge.grappa.support.IndexRange;
import com.github.fge.grappa.support.Position;
import com.google.common.base.Preconditions;
import com.google.common.collect.Range;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ThreadFactoryBuilder;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.util.Objects;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * An {@link InputBuffer} over a {@link CharSequence}
 *
 * A {@link CharSequence} is the most basic character interface in the JDK.
 * It is implemented by a lot of character related classes, including {@link
 * String}, and is also the argument type used by a {@link Pattern}'s {@link
 * Matcher}.
 *
 * Among other things, this means you can use this package on very large
 * files using largetext, which
 * implements {@link CharSequence} over multi-gigabyte files.
 */
@Immutable
public final class CharSequenceInputBuffer
    implements InputBuffer
{
    private static final ExecutorService EXECUTOR_SERVICE;

    static {
        final ThreadFactory factory = new ThreadFactoryBuilder()
            .setDaemon(true).setNameFormat("linecounter-thread-%d").build();
        EXECUTOR_SERVICE = Executors.newCachedThreadPool(factory);
    }

    private final CharSequence charSequence;
    private final Future lineCounter;

    public CharSequenceInputBuffer(@Nonnull final CharSequence charSequence)
    {
        this.charSequence = Objects.requireNonNull(charSequence);
        lineCounter = EXECUTOR_SERVICE.submit(new Callable()
        {
            @Override
            public LineCounter call()
                throws Exception
            {
                return new LineCounter(charSequence);
            }
        });
    }

    @Override
    public char charAt(final int index)
    {
        if (index < 0)
            throw new IllegalArgumentException("index is negative");

        return index < charSequence.length() ? charSequence.charAt(index)
            : Chars.EOI;
    }

    @SuppressWarnings("ImplicitNumericConversion")
    @Override
    public int codePointAt(final int index)
    {
        final int length = charSequence.length();
        if (index >= length)
            return -1;
        if (index < 0)
            throw new IllegalArgumentException("index is negative");

        final char c = charSequence.charAt(index);
        if (!Character.isHighSurrogate(c))
            return c;
        if (index == length - 1)
            return c;
        final char c2 = charSequence.charAt(index + 1);
        return Character.isLowSurrogate(c2) ? Character.toCodePoint(c, c2) : c;
    }

    @Override
    public String extract(final int start, final int end)
    {
        final int realStart = Math.max(start, 0);
        final int realEnd = Math.min(end, charSequence.length());
        return charSequence.subSequence(realStart, realEnd).toString();
    }

    @Override
    public String extract(final IndexRange range)
    {
        return extract(range.start, range.end);
    }

    @Override
    public Position getPosition(final int index)
    {
        return Futures.getUnchecked(lineCounter).toPosition(index);
    }

    @Override
    public String extractLine(final int lineNumber)
    {
        Preconditions.checkArgument(lineNumber > 0, "line number is negative");
        final LineCounter counter = Futures.getUnchecked(lineCounter);
        final Range range = counter.getLineRange(lineNumber);
        final int start = range.lowerEndpoint();
        int end = range.upperEndpoint();
        if (charAt(end - 1) == '\n')
            end--;
        if (charAt(end - 1) == '\r')
            end--;
        return extract(start, end);
    }

    @SuppressWarnings("AutoUnboxing")
    @Override
    public IndexRange getLineRange(final int lineNumber)
    {
        final Range range
            = Futures.getUnchecked(lineCounter).getLineRange(lineNumber);
        return new IndexRange(range.lowerEndpoint(), range.upperEndpoint());
    }

    @Override
    public int getLineCount()
    {
        return Futures.getUnchecked(lineCounter).getNrLines();
    }

    @Override
    public int length()
    {
        return charSequence.length();
    }
}