/* Integer.java -- object wrapper for int
   Copyright (C) 1998, 1999, 2001, 2002, 2004, 2005
   Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */

package java.lang;

/**
 * Instances of class <code>Integer</code> represent primitive
 * <code>int</code> values.
 *
 * Additionally, this class provides various helper functions and variables
 * related to ints.
 *
 * @author Paul Fisher
 * @author John Keiser
 * @author Warren Levy
 * @author Eric Blake (ebb9@email.byu.edu)
 * @author Tom Tromey (tromey@redhat.com)
 */
public final class Integer
{
    /**
     * The minimum value an <code>int</code> can represent is -2147483648 (or
     * -2<sup>31</sup>).
     */
    public static final int MIN_VALUE = 0x80000000;

    /**
     * The maximum value an <code>int</code> can represent is 2147483647 (or
     * 2<sup>31</sup> - 1).
     */
    public static final int MAX_VALUE = 0x7fffffff;

    /**
     * The immutable value of this Integer.
     *
     * @serial the wrapped int
     */
    private final int value;

    /**
     * Table for calculating digits, used in Character, Long, and Integer.
     */
    private static final char[] digits = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
        'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
        'u', 'v', 'w', 'x', 'y', 'z',
    };

    /**
     * Create an <code>Integer</code> object representing the value of the
     * <code>int</code> argument.
     *
     * @param value the value to use
     */
    public Integer(int value)
    {
        this.value = value;
    }

    /**
     * Converts the <code>int</code> to a <code>String</code> using
     * the specified radix (base). If the radix exceeds
     * <code>Character.MIN_RADIX</code> or <code>Character.MAX_RADIX</code>, 10
     * is used instead. If the result is negative, the leading character is
     * '-' ('\\u002D'). The remaining characters come from
     * <code>Character.forDigit(digit, radix)</code> ('0'-'9','a'-'z').
     *
     * @param num the <code>int</code> to convert to <code>String</code>
     * @param radix the radix (base) to use in the conversion
     * @return the <code>String</code> representation of the argument
     */
    public static String toString(int num, int radix)
    {
        if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
            radix = 10;

        // For negative numbers, print out the absolute value w/ a leading '-'.
        // Use an array large enough for a binary number.
        char[] buffer = new char[33];
        int i = 33;
        boolean isNeg = false;

        if (num < 0)
        {
            isNeg = true;
            num = -num;

            // When the value is MIN_VALUE, it overflows when made positive
            if (num < 0)
            {
                buffer[--i] = digits[(int) (-(num + radix) % radix)];
                num = -(num / radix);
            }
        }

        do
        {
            buffer[--i] = digits[num % radix];
            num /= radix;
        }
        while (num > 0);

        if (isNeg)
            buffer[--i] = '-';

        // Package constructor avoids an array copy.
        return new String(buffer, i, 33 - i, false);
    }

    /**
     * Converts the <code>int</code> to a <code>String</code> assuming it is
     * unsigned in base 16.
     *
     * @param i the <code>int</code> to convert to <code>String</code>
     * @return the <code>String</code> representation of the argument
     */
    public static String toHexString(int i)
    {
        return toUnsignedString(i, 4);
    }

    /**
     * Converts the <code>int</code> to a <code>String</code> assuming it is
     * unsigned in base 8.
     *
     * @param i the <code>int</code> to convert to <code>String</code>
     * @return the <code>String</code> representation of the argument
     */
    public static String toOctalString(int i)
    {
        return toUnsignedString(i, 3);
    }

    /**
     * Converts the <code>int</code> to a <code>String</code> assuming it is
     * unsigned in base 2.
     *
     * @param i the <code>int</code> to convert to <code>String</code>
     * @return the <code>String</code> representation of the argument
     */
    public static String toBinaryString(int i)
    {
        return toUnsignedString(i, 1);
    }

    /**
     * Converts the <code>int</code> to a <code>String</code> and assumes
     * a radix of 10.
     *
     * @param i the <code>int</code> to convert to <code>String</code>
     * @return the <code>String</code> representation of the argument
     * @see #toString(int, int)
     */
    public static String toString(int i)
    {
        // This is tricky: in libgcj, String.valueOf(int) is a fast native
        // implementation.  In Classpath it just calls back to
        // Integer.toString(int, int).
        return String.valueOf(i);
    }

    /**
     * Converts the specified <code>String</code> into an <code>int</code>
     * using the specified radix (base). The string must not be <code>null</code>
     * or empty. It may begin with an optional '-', which will negate the answer,
     * provided that there are also valid digits. Each digit is parsed as if by
     * <code>Character.digit(d, radix)</code>, and must be in the range
     * <code>0</code> to <code>radix - 1</code>. Finally, the result must be
     * within <code>MIN_VALUE</code> to <code>MAX_VALUE</code>, inclusive.
     * Unlike Double.parseDouble, you may not have a leading '+'.
     *
     * @param str the <code>String</code> to convert
     * @param radix the radix (base) to use in the conversion
     * @return the <code>String</code> argument converted to <code>int</code>
     * @throws NumberFormatException if <code>s</code> cannot be parsed as an
     *         <code>int</code>
     */
    public static int parseInt(String str, int radix)
        throws NumberFormatException
    {
        return parseIntInternal(str, radix);
    }

    /**
     * Converts the specified <code>String</code> into an <code>int</code>.
     * This function assumes a radix of 10.
     *
     * @param s the <code>String</code> to convert
     * @return the <code>int</code> value of <code>s</code>
     * @throws NumberFormatException if <code>s</code> cannot be parsed as an
     *         <code>int</code>
     * @see #parseInt(String, int)
     */
    public static int parseInt(String s) throws NumberFormatException
    {
        return parseIntInternal(s, 10);
    }

    /**
     * Creates a new <code>Integer</code> object using the <code>String</code>
     * and specified radix (base).
     *
     * @param s the <code>String</code> to convert
     * @param radix the radix (base) to convert with
     * @return the new <code>Integer</code>
     * @throws NumberFormatException if <code>s</code> cannot be parsed as an
     *         <code>int</code>
     * @see #parseInt(String, int)
     */
    public static Integer valueOf(String s, int radix)
    {
        return new Integer(parseIntInternal(s, radix));
    }

    /**
     * Creates a new <code>Integer</code> object using the <code>String</code>,
     * assuming a radix of 10.
     *
     * @param s the <code>String</code> to convert
     * @return the new <code>Integer</code>
     * @throws NumberFormatException if <code>s</code> cannot be parsed as an
     *         <code>int</code>
     */
    public static Integer valueOf(String s)
    {
        return new Integer(parseIntInternal(s, 10));
    }

    /**
     * Return the value of this <code>Integer</code> as a <code>byte</code>.
     *
     * @return the byte value
     */
    public byte byteValue()
    {
        return (byte) value;
    }

    /**
     * Return the value of this <code>Integer</code> as a <code>short</code>.
     *
     * @return the short value
     */
    public short shortValue()
    {
        return (short) value;
    }

    /**
     * Return the value of this <code>Integer</code>.
     * @return the int value
     */
    public int intValue()
    {
        return value;
    }

    /**
     * Return the value of this <code>Integer</code> as a <code>long</code>.
     *
     * @return the long value
     */
    public long longValue()
    {
        return value;
    }

    /**
     * Return the value of this <code>Integer</code> as a <code>float</code>.
     *
     * @return the float value
     */
    public float floatValue()
    {
        return value;
    }

    /**
     * Return the value of this <code>Integer</code> as a <code>double</code>.
     *
     * @return the double value
     */
    public double doubleValue()
    {
        return value;
    }

    /**
     * Converts the <code>Integer</code> value to a <code>String</code> and
     * assumes a radix of 10.
     *
     * @return the <code>String</code> representation
     */
    public String toString()
    {
        return String.valueOf(value);
    }

    /**
     * Return a hashcode representing this Object. <code>Integer</code>'s hash
     * code is simply its value.
     *
     * @return this Object's hash code
     */
    public int hashCode()
    {
        return value;
    }

    /**
     * Returns <code>true</code> if <code>obj</code> is an instance of
     * <code>Integer</code> and represents the same int value.
     *
     * @param obj the object to compare
     * @return whether these Objects are semantically equal
     */
    public boolean equals(Object obj)
    {
        return obj instanceof Integer && value == ((Integer) obj).value;
    }

    /**
     * Helper for converting unsigned numbers to String.
     *
     * @param num the number
     * @param exp log2(digit) (ie. 1, 3, or 4 for binary, oct, hex)
     */
    // Package visible for use by Long.
    static String toUnsignedString(int num, int exp)
    {
        // Use an array large enough for a binary number.
        int mask = (1 << exp) - 1;
        char[] buffer = new char[32];
        int i = 32;
        
        do
        {
            buffer[--i] = digits[num & mask];
            num >>>= exp;
        } while (num != 0);

        // Package constructor avoids an array copy.
        return new String(buffer, i, 32 - i, true);
    }

    /**
     * Helper for parsing ints, used by Integer, Short, and Byte.
     *
     * @param str the string to parse
     * @param radix the radix to use
     * @return the parsed int value
     * @throws NumberFormatException if there is an error
     * @see #parseInt(String, int)
     * @see Byte#parseByte(String, int)
     * @see Short#parseShort(String, int)
     */
    static int parseIntInternal(String str, int radix)
    {
        int index = 0;
        int len = str.length();
        boolean isNeg = false;
    
        if (len == 0)
            throw new NumberFormatException("string length is null");
    
        int ch = str.charAt(index);
        
        if (ch == '-')
        {
            if (len == 1)
                throw new NumberFormatException("pure '-'");
            
            isNeg = true;
            ch = str.charAt(++index);
        }
    
        if (index == len)
            throw new NumberFormatException("non terminated number: " + str);

        int max = MAX_VALUE / radix;
        // We can't directly write `max = (MAX_VALUE + 1) / radix'.
        // So instead we fake it.
        if (isNeg && MAX_VALUE % radix == radix - 1)
            ++max;

        int val = 0;
    
        while (index < len)
        {
	       if (val < 0 || val > max)
	           throw new NumberFormatException(
	               "number overflow (pos=" + index + ") : " + str
	               );

            ch = Character.digit(str.charAt(index++), radix);
            val = val * radix + ch;
            
            if (ch < 0 || (val < 0 && (! isNeg || val != MIN_VALUE)))
                throw new NumberFormatException(
                    "invalid character at position " + index + " in " + str
                    );
        }
        
        return isNeg ? -val : val;
    }
}