AutoLFInputStream.java

/*
 * Copyright (C) 2010, 2013 Marc Strapetz <marc.strapetz@syntevo.com>
 * Copyright (C) 2015, 2020 Ivan Motsch <ivan.motsch@bsiag.com> 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.InputStream;
import java.util.Arrays;
import java.util.EnumSet;
import java.util.Set;

import org.eclipse.jgit.diff.RawText;

/**
 * An InputStream that normalizes CRLF to LF.
 * <p>
 * Existing single CR are not changed to LF but are retained as is.
 * </p>
 * <p>
 * Optionally, a binary check on the first 8kB is performed and in case of
 * binary files, canonicalization is turned off (for the complete file). If
 * binary checking determines that the input is CR/LF-delimited text and the
 * stream has been created for checkout, canonicalization is also turned off.
 * </p>
 *
 * @since 4.3
 */
public class AutoLFInputStream extends InputStream {

    // This is the former EolCanonicalizingInputStream with a new name in order
    // to have same naming for all LF / CRLF streams.

    /**
     * Flags for controlling auto-detection of binary vs. text content (for
     * text=auto).
     *
     * @since 5.9
     */
    public enum StreamFlag {
        /**
         * Check the first 8kB for binary content and switch off
         * canonicalization off for the whole file if so.
         */
        DETECT_BINARY,
        /**
         * If {@link #DETECT_BINARY} is set, throw an {@link IsBinaryException}
         * if binary content is detected.
         */
        ABORT_IF_BINARY,
        /**
         * If {@link #DETECT_BINARY} is set and content is found to be CR-LF
         * delimited text, switch off canonicalization.
         */
        FOR_CHECKOUT
    }

    private final byte[] single = new byte[1];

    private final byte[] buf = new byte[8 * 1024];

    private final InputStream in;

    private int cnt;

    private int ptr;

    /**
     * Set to {@code true} if no CR/LF processing is to be done: if the input is
     * binary data, or CR/LF-delimited text and {@link StreamFlag#FOR_CHECKOUT}
     * was given.
     */
    private boolean passAsIs;

    /**
     * Set to {@code true} if the input was detected to be binary data.
     */
    private boolean isBinary;

    private boolean detectBinary;

    private final boolean abortIfBinary;

    private final boolean forCheckout;

    /**
     * A special exception thrown when {@link AutoLFInputStream} is told to
     * throw an exception when attempting to read a binary file. The exception
     * may be thrown at any stage during reading.
     *
     * @since 3.3
     */
    public static class IsBinaryException extends IOException {
        private static final long serialVersionUID = 1L;

        IsBinaryException() {
            super();
        }
    }

    /**
     * Factory method for creating an {@link AutoLFInputStream} with the
     * specified {@link StreamFlag flags}.
     *
     * @param in
     *            raw input stream
     * @param flags
     *            {@link StreamFlag}s controlling the stream behavior
     * @return a new {@link AutoLFInputStream}
     * @since 5.9
     */
    public static AutoLFInputStream create(InputStream in,
            StreamFlag... flags) {
        if (flags == null) {
            return new AutoLFInputStream(in, null);
        }
        EnumSet<StreamFlag> set = EnumSet.noneOf(StreamFlag.class);
        set.addAll(Arrays.asList(flags));
        return new AutoLFInputStream(in, set);
    }

    /**
     * Creates a new InputStream, wrapping the specified stream.
     *
     * @param in
     *            raw input stream
     * @param flags
     *            {@link StreamFlag}s controlling the stream behavior;
     *            {@code null} is treated as an empty set
     * @since 5.9
     */
    public AutoLFInputStream(InputStream in, Set<StreamFlag> flags) {
        this.in = in;
        this.detectBinary = flags != null
                && flags.contains(StreamFlag.DETECT_BINARY);
        this.abortIfBinary = flags != null
                && flags.contains(StreamFlag.ABORT_IF_BINARY);
        this.forCheckout = flags != null
                && flags.contains(StreamFlag.FOR_CHECKOUT);
    }

    /**
     * Creates a new InputStream, wrapping the specified stream.
     *
     * @param in
     *            raw input stream
     * @param detectBinary
     *            whether binaries should be detected
     * @since 2.0
     * @deprecated since 5.9, use {@link #create(InputStream, StreamFlag...)}
     *             instead
     */
    @Deprecated
    public AutoLFInputStream(InputStream in, boolean detectBinary) {
        this(in, detectBinary, false);
    }

    /**
     * Creates a new InputStream, wrapping the specified stream.
     *
     * @param in
     *            raw input stream
     * @param detectBinary
     *            whether binaries should be detected
     * @param abortIfBinary
     *            throw an IOException if the file is binary
     * @since 3.3
     * @deprecated since 5.9, use {@link #create(InputStream, StreamFlag...)}
     *             instead
     */
    @Deprecated
    public AutoLFInputStream(InputStream in, boolean detectBinary,
            boolean abortIfBinary) {
        this.in = in;
        this.detectBinary = detectBinary;
        this.abortIfBinary = abortIfBinary;
        this.forCheckout = false;
    }

    /** {@inheritDoc} */
    @Override
    public int read() throws IOException {
        final int read = read(single, 0, 1);
        return read == 1 ? single[0] & 0xff : -1;
    }

    /** {@inheritDoc} */
    @Override
    public int read(byte[] bs, int off, int len)
            throws IOException {
        if (len == 0)
            return 0;

        if (cnt == -1)
            return -1;

        int i = off;
        final int end = off + len;

        while (i < end) {
            if (ptr == cnt && !fillBuffer()) {
                break;
            }

            byte b = buf[ptr++];
            if (passAsIs || b != '\r') {
                // Logic for binary files ends here
                bs[i++] = b;
                continue;
            }

            if (ptr == cnt && !fillBuffer()) {
                bs[i++] = '\r';
                break;
            }

            if (buf[ptr] == '\n') {
                bs[i++] = '\n';
                ptr++;
            } else
                bs[i++] = '\r';
        }

        return i == off ? -1 : i - off;
    }

    /**
     * Whether the stream has detected as a binary so far.
     *
     * @return true if the stream has detected as a binary so far.
     * @since 3.3
     */
    public boolean isBinary() {
        return isBinary;
    }

    /** {@inheritDoc} */
    @Override
    public void close() throws IOException {
        in.close();
    }

    private boolean fillBuffer() throws IOException {
        cnt = 0;
        while (cnt < buf.length) {
            int n = in.read(buf, cnt, buf.length - cnt);
            if (n < 0) {
                break;
            }
            cnt += n;
        }
        if (cnt < 1) {
            cnt = -1;
            return false;
        }
        if (detectBinary) {
            isBinary = RawText.isBinary(buf, cnt);
            passAsIs = isBinary;
            detectBinary = false;
            if (isBinary && abortIfBinary) {
                throw new IsBinaryException();
            }
            if (!passAsIs && forCheckout) {
                passAsIs = RawText.isCrLfText(buf, cnt);
            }
        }
        ptr = 0;
        return true;
    }
}