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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.tools.javac.util;

import java.util.BitSet;

import com.sun.tools.javac.util.DefinedBy.Api;

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


A class that defines source code positions as simple character
 offsets from the beginning of the file. The first character
 is at position 0.
 Support is also provided for (line,column) coordinates, but tab
 expansion is optional and no Unicode excape translation is considered.
 The first character is at location (1,1).
 
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 class that defines source code positions as simple character
 *  offsets from the beginning of the file. The first character
 *  is at position 0.
 *
 *  Support is also provided for (line,column) coordinates, but tab
 *  expansion is optional and no Unicode excape translation is considered.
 *  The first character is at location (1,1).
 *
 *  <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 Position {
    public static final int NOPOS        = -1;

    public static final int FIRSTPOS     = 0;
    public static final int FIRSTLINE    = 1;
    public static final int FIRSTCOLUMN  = 1;

    public static final int LINESHIFT    = 10;
    public static final int MAXCOLUMN    = (1<<LINESHIFT) - 1;
    public static final int MAXLINE      = (1<<(Integer.SIZE-LINESHIFT)) - 1;

    public static final int MAXPOS       = Integer.MAX_VALUE;

    
This is class is not supposed to be instantiated.

/**
     * This is class is not supposed to be instantiated.
     */
    private Position() {}

    
A two-way map between line/column numbers and positions,
 derived from a scan done at creation time.  Tab expansion is
 optionally supported via a character map.  Text content
 is not retained.


 Notes:  The first character position FIRSTPOS is at
 (FIRSTLINE,FIRSTCOLUMN).  No account is taken of Unicode escapes.

Params:
  • src –         Source characters
  • max –         Number of characters to read
  • expandTabs –  If true, expand tabs when calculating columns
/** A two-way map between line/column numbers and positions,
     *  derived from a scan done at creation time.  Tab expansion is
     *  optionally supported via a character map.  Text content
     *  is not retained.
     *<p>
     *  Notes:  The first character position FIRSTPOS is at
     *  (FIRSTLINE,FIRSTCOLUMN).  No account is taken of Unicode escapes.
     *
     * @param   src         Source characters
     * @param   max         Number of characters to read
     * @param   expandTabs  If true, expand tabs when calculating columns
     */
    public static LineMap makeLineMap(char[] src, int max, boolean expandTabs) {
        LineMapImpl lineMap = expandTabs ?
            new LineTabMapImpl(max) : new LineMapImpl();
        lineMap.build(src, max);
        return lineMap;
    }

    
Encode line and column numbers in an integer as: line-number << LINESHIFT + column-number . NOPOS represents an undefined position. 
Params:
  • line –  number of line (first is 1)
  • col –   number of character on line (first is 1)
Throws:
Returns: an encoded position or NOPOS if the line or column number is too big to represent in the encoded format
/** Encode line and column numbers in an integer as:
     *  {@code line-number << LINESHIFT + column-number }.
     *  {@link Position#NOPOS} represents an undefined position.
     *
     * @param  line  number of line (first is 1)
     * @param  col   number of character on line (first is 1)
     * @return       an encoded position or {@link Position#NOPOS}
     *               if the line or column number is too big to
     *               represent in the encoded format
     * @throws IllegalArgumentException if line or col is less than 1
     */
    public static int encodePosition(int line, int col) {
        if (line < 1)
            throw new IllegalArgumentException("line must be greater than 0");
        if (col < 1)
            throw new IllegalArgumentException("column must be greater than 0");

        if (line > MAXLINE || col > MAXCOLUMN) {
            return NOPOS;
        }
        return (line << LINESHIFT) + col;
    }

    public static interface LineMap extends com.sun.source.tree.LineMap {
        
Find the start position of a line.

Params:
  • line – number of line (first is 1)
Throws:
Returns:    position of first character in line
/** Find the start position of a line.
         *
         * @param line number of line (first is 1)
         * @return     position of first character in line
         * @throws  ArrayIndexOutOfBoundsException
         *           if {@code lineNumber < 1}
         *           if {@code lineNumber > no. of lines}
         */
        int getStartPosition(int line);

        
Find the position corresponding to a (line,column).

Params:
  • line –    number of line (first is 1)
  • column –  number of character on line (first is 1)
Throws:
Returns: position of character
/** Find the position corresponding to a (line,column).
         *
         * @param   line    number of line (first is 1)
         * @param   column  number of character on line (first is 1)
         *
         * @return  position of character
         * @throws  ArrayIndexOutOfBoundsException
         *           if {@code line < 1}
         *           if {@code line > no. of lines}
         */
        int getPosition(int line, int column);

        
Find the line containing a position; a line termination
character is on the line it terminates.

Params:
  • pos –  character offset of the position
Returns:the line number on which pos occurs (first line is 1)
/** Find the line containing a position; a line termination
         * character is on the line it terminates.
         *
         * @param   pos  character offset of the position
         * @return the line number on which pos occurs (first line is 1)
         */
        int getLineNumber(int pos);

        
Find the column for a character position.
 Note:  this method does not handle tab expansion.
 If tab expansion is needed, use a LineTabMap instead.

Params:
  • pos –   character offset of the position
Returns:      the column number at which pos occurs
/** Find the column for a character position.
         *  Note:  this method does not handle tab expansion.
         *  If tab expansion is needed, use a LineTabMap instead.
         *
         * @param  pos   character offset of the position
         * @return       the column number at which pos occurs
         */
        int getColumnNumber(int pos);
    }

    static class LineMapImpl implements LineMap {
        protected int[] startPosition; // start position of each line

        protected LineMapImpl() {}

        protected void build(char[] src, int max) {
            int c = 0;
            int i = 0;
            int[] linebuf = new int[max];
            while (i < max) {
                linebuf[c++] = i;
                do {
                    char ch = src[i];
                    if (ch == '\r' || ch == '\n') {
                        if (ch == '\r' && (i+1) < max && src[i+1] == '\n')
                            i += 2;
                        else
                            ++i;
                        break;
                    }
                    else if (ch == '\t')
                        setTabPosition(i);
                } while (++i < max);
            }
            this.startPosition = new int[c];
            System.arraycopy(linebuf, 0, startPosition, 0, c);
        }

        public int getStartPosition(int line) {
            return startPosition[line - FIRSTLINE];
        }

        @DefinedBy(Api.COMPILER_TREE)
        public long getStartPosition(long line) {
            return getStartPosition(longToInt(line));
        }

        public int getPosition(int line, int column) {
            return startPosition[line - FIRSTLINE] + column - FIRSTCOLUMN;
        }

        @DefinedBy(Api.COMPILER_TREE)
        public long getPosition(long line, long column) {
            return getPosition(longToInt(line), longToInt(column));
        }

        // Cache of last line number lookup
        private int lastPosition = Position.FIRSTPOS;
        private int lastLine = Position.FIRSTLINE;

        public int getLineNumber(int pos) {
            if (pos == lastPosition) {
                return lastLine;
            }
            lastPosition = pos;

            int low = 0;
            int high = startPosition.length-1;
            while (low <= high) {
                int mid = (low + high) >> 1;
                int midVal = startPosition[mid];

                if (midVal < pos)
                    low = mid + 1;
                else if (midVal > pos)
                    high = mid - 1;
                else {
                    lastLine = mid + 1; // pos is at beginning of this line
                    return lastLine;
                }
            }
            lastLine = low;
            return lastLine;  // pos is on this line
        }

        @DefinedBy(Api.COMPILER_TREE)
        public long getLineNumber(long pos) {
            return getLineNumber(longToInt(pos));
        }

        public int getColumnNumber(int pos) {
            return pos - startPosition[getLineNumber(pos) - FIRSTLINE] + FIRSTCOLUMN;
        }

        @DefinedBy(Api.COMPILER_TREE)
        public long getColumnNumber(long pos) {
            return getColumnNumber(longToInt(pos));
        }

        private static int longToInt(long longValue) {
            int intValue = (int)longValue;
            if (intValue != longValue)
                throw new IndexOutOfBoundsException();
            return intValue;
        }

        protected void setTabPosition(int offset) {}
    }

    
A LineMap that handles tab expansion correctly.  The cost is
an additional bit per character in the source array.

/**
     * A LineMap that handles tab expansion correctly.  The cost is
     * an additional bit per character in the source array.
     */
    public static class LineTabMapImpl extends LineMapImpl {
        private BitSet tabMap;       // bits set for tab positions.

        public LineTabMapImpl(int max) {
            super();
            tabMap = new BitSet(max);
        }

        protected void setTabPosition(int offset) {
            tabMap.set(offset);
        }

        public int getColumnNumber(int pos) {
            int lineStart = startPosition[getLineNumber(pos) - FIRSTLINE];
            int column = 0;
            for (int bp = lineStart; bp < pos; bp++) {
                if (tabMap.get(bp))
                    column = (column / TabInc * TabInc) + TabInc;
                else
                    column++;
            }
            return column + FIRSTCOLUMN;
        }

        public int getPosition(int line, int column) {
            int pos = startPosition[line - FIRSTLINE];
            column -= FIRSTCOLUMN;
            int col = 0;
            while (col < column) {
                pos++;
                if (tabMap.get(pos))
                    col = (col / TabInc * TabInc) + TabInc;
                else
                    col++;
            }
            return pos;
        }
    }
}