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 * Copyright (c) 1999, 2020, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package com.sun.tools.javac.util;

import java.io.IOException;
import java.lang.ref.SoftReference;
import java.nio.CharBuffer;
import javax.tools.JavaFileObject;

import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.tree.EndPosTable;

import static com.sun.tools.javac.util.LayoutCharacters.*;

A simple abstraction of a source file, as needed for use in a diagnostic message.
Provides access to the line and position in a line for any given character offset.
 
This is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.
/**
 * A simple abstraction of a source file, as needed for use in a diagnostic message.
 * Provides access to the line and position in a line for any given character offset.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class DiagnosticSource {

    /* constant DiagnosticSource to be used when sourcefile is missing */
    public static final DiagnosticSource NO_SOURCE = new DiagnosticSource() {
        @Override
        protected boolean findLine(int pos) {
            return false;
        }
    };

    public DiagnosticSource(JavaFileObject fo, AbstractLog log) {
        this.fileObject = fo;
        this.log = log;
    }

    private DiagnosticSource() {}

    
Return the underlying file object handled by this
 DiagnosticSource object.
/** Return the underlying file object handled by this
     *  DiagnosticSource object.
     */
    public JavaFileObject getFile() {
        return fileObject;
    }

    
Return the one-based line number associated with a given pos
for the current source file.  Zero is returned if no line exists
for the given position.
/** Return the one-based line number associated with a given pos
     * for the current source file.  Zero is returned if no line exists
     * for the given position.
     */
    public int getLineNumber(int pos) {
        try {
            if (findLine(pos)) {
                return line;
            }
            return 0;
        } finally {
            buf = null;
        }
    }

    
Return the one-based column number associated with a given pos
for the current source file.  Zero is returned if no column exists
for the given position.
/** Return the one-based column number associated with a given pos
     * for the current source file.  Zero is returned if no column exists
     * for the given position.
     */
    public int getColumnNumber(int pos, boolean expandTabs) {
        try {
            if (findLine(pos)) {
                int column = 0;
                for (int bp = lineStart; bp < pos; bp++) {
                    if (bp >= bufLen) {
                        return 0;
                    }
                    if (buf[bp] == '\t' && expandTabs) {
                        column = tabulate(column);
                    } else {
                        column++;
                    }
                }
                return column + 1; // positions are one-based
            }
            return 0;
        } finally {
            buf = null;
        }
    }

    
Return the content of the line containing a given pos.
/** Return the content of the line containing a given pos.
     */
    public String getLine(int pos) {
        try {
            if (!findLine(pos))
                return null;

            int lineEnd = lineStart;
            while (lineEnd < bufLen && buf[lineEnd] != CR && buf[lineEnd] != LF)
                lineEnd++;
            if (lineEnd - lineStart == 0)
                return null;
            return new String(buf, lineStart, lineEnd - lineStart);
        } finally {
            buf = null;
        }
    }

    public EndPosTable getEndPosTable() {
        return endPosTable;
    }

    public void setEndPosTable(EndPosTable t) {
        if (endPosTable != null && endPosTable != t)
            throw new IllegalStateException("endPosTable already set");
        endPosTable = t;
    }

    
Find the line in the buffer that contains the current position
Params:
pos –      Character offset into the buffer/** Find the line in the buffer that contains the current position
     * @param pos      Character offset into the buffer
     */
    protected boolean findLine(int pos) {
        if (pos == Position.NOPOS)
            return false;

        try {
            // try and recover buffer from soft reference cache
            if (buf == null && refBuf != null)
                buf = refBuf.get();

            if (buf == null) {
                buf = initBuf(fileObject);
                lineStart = 0;
                line = 1;
            } else if (lineStart > pos) { // messages don't come in order
                lineStart = 0;
                line = 1;
            }

            int bp = lineStart;
            while (bp < bufLen && bp < pos) {
                switch (buf[bp++]) {
                case CR:
                    if (bp < bufLen && buf[bp] == LF) bp++;
                    line++;
                    lineStart = bp;
                    break;
                case LF:
                    line++;
                    lineStart = bp;
                    break;
                }
            }
            return bp <= bufLen;
        } catch (IOException e) {
            log.directError("source.unavailable");
            buf = new char[0];
            return false;
        }
    }

    protected char[] initBuf(JavaFileObject fileObject) throws IOException {
        char[] buf;
        CharSequence cs = fileObject.getCharContent(true);
        if (cs instanceof CharBuffer) {
            CharBuffer cb = (CharBuffer) cs;
            buf = JavacFileManager.toArray(cb);
            bufLen = cb.limit();
        } else {
            buf = cs.toString().toCharArray();
            bufLen = buf.length;
        }
        refBuf = new SoftReference<>(buf);
        return buf;
    }

    
The underlying file object. /** The underlying file object. */
    protected JavaFileObject fileObject;

    protected EndPosTable endPosTable;

    
A soft reference to the content of the file object. /** A soft reference to the content of the file object. */
    protected SoftReference<char[]> refBuf;

    
A temporary hard reference to the content of the file object. /** A temporary hard reference to the content of the file object. */
    protected char[] buf;

    
The length of the content. /** The length of the content. */
    protected int bufLen;

    
The start of a line found by findLine. /** The start of a line found by findLine. */
    protected int lineStart;

    
The line number of a line found by findLine. /** The line number of a line found by findLine. */
    protected int line;

    
A log for reporting errors, such as errors accessing the content. /** A log for reporting errors, such as errors accessing the content. */
    protected AbstractLog log;
}