AutoLFOutputStream.java

/*
 * Copyright (C) 2015, Ivan Motsch <ivan.motsch@bsiag.com>
 * Copyright (C) 2020, Thomas Wolf <thomas.wolf@paranor.ch> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.util.io;

import java.io.IOException;
import java.io.OutputStream;

import org.eclipse.jgit.diff.RawText;

/**
 * An OutputStream that reduces CRLF to LF.
 * <p>
 * Existing single CR are not changed to LF, but retained as is.
 * </p>
 * <p>
 * A binary check on the first 8000 bytes is performed and in case of binary
 * files, canonicalization is turned off (for the complete file). If the binary
 * check determines that the input is not binary but text with CR/LF,
 * canonicalization is also turned off.
 * </p>
 *
 * @since 4.3
 */
public class AutoLFOutputStream extends OutputStream {

    static final int BUFFER_SIZE = 8000;

    private final OutputStream out;

    private int buf = -1;

    private byte[] binbuf = new byte[BUFFER_SIZE];

    private byte[] onebytebuf = new byte[1];

    private int binbufcnt = 0;

    private boolean detectBinary;

    private boolean isBinary;

    /**
     * Constructor for AutoLFOutputStream.
     *
     * @param out
     *            an {@link java.io.OutputStream} object.
     */
    public AutoLFOutputStream(OutputStream out) {
        this(out, true);
    }

    /**
     * Constructor for AutoLFOutputStream.
     *
     * @param out
     *            an {@link java.io.OutputStream} object.
     * @param detectBinary
     *            whether binaries should be detected
     */
    public AutoLFOutputStream(OutputStream out, boolean detectBinary) {
        this.out = out;
        this.detectBinary = detectBinary;
    }

    /** {@inheritDoc} */
    @Override
    public void write(int b) throws IOException {
        onebytebuf[0] = (byte) b;
        write(onebytebuf, 0, 1);
    }

    /** {@inheritDoc} */
    @Override
    public void write(byte[] b) throws IOException {
        int overflow = buffer(b, 0, b.length);
        if (overflow > 0) {
            write(b, b.length - overflow, overflow);
        }
    }

    /** {@inheritDoc} */
    @Override
    public void write(byte[] b, int startOff, int startLen)
            throws IOException {
        final int overflow = buffer(b, startOff, startLen);
        if (overflow <= 0) {
            return;
        }
        final int off = startOff + startLen - overflow;
        final int len = overflow;
        int lastw = off;
        if (isBinary) {
            out.write(b, off, len);
            return;
        }
        for (int i = off; i < off + len; ++i) {
            final byte c = b[i];
            switch (c) {
            case '\r':
                // skip write r but backlog r
                if (lastw < i) {
                    out.write(b, lastw, i - lastw);
                }
                lastw = i + 1;
                buf = '\r';
                break;
            case '\n':
                if (buf == '\r') {
                    out.write('\n');
                    lastw = i + 1;
                    buf = -1;
                } else {
                    if (lastw < i + 1) {
                        out.write(b, lastw, i + 1 - lastw);
                    }
                    lastw = i + 1;
                }
                break;
            default:
                if (buf == '\r') {
                    out.write('\r');
                    lastw = i;
                }
                buf = -1;
                break;
            }
        }
        if (lastw < off + len) {
            out.write(b, lastw, off + len - lastw);
        }
    }

    private int buffer(byte[] b, int off, int len) throws IOException {
        if (binbufcnt > binbuf.length) {
            return len;
        }
        int copy = Math.min(binbuf.length - binbufcnt, len);
        System.arraycopy(b, off, binbuf, binbufcnt, copy);
        binbufcnt += copy;
        int remaining = len - copy;
        if (remaining > 0) {
            decideMode();
        }
        return remaining;
    }

    private void decideMode() throws IOException {
        if (detectBinary) {
            isBinary = RawText.isBinary(binbuf, binbufcnt);
            if (!isBinary) {
                isBinary = RawText.isCrLfText(binbuf, binbufcnt);
            }
            detectBinary = false;
        }
        int cachedLen = binbufcnt;
        binbufcnt = binbuf.length + 1; // full!
        write(binbuf, 0, cachedLen);
    }

    /** {@inheritDoc} */
    @Override
    public void flush() throws IOException {
        if (binbufcnt <= binbuf.length) {
            decideMode();
        }
        out.flush();
    }

    /** {@inheritDoc} */
    @Override
    public void close() throws IOException {
        flush();
        if (buf == '\r') {
            out.write(buf);
            buf = -1;
        }
        out.close();
    }
}