HexDump.java解析

从包名我们可以看出该类并没有对应用开发者开放，也就是说在google开放的Android API文档中并没有该类的相关介绍；好在Android系统源码是开源的，因此我在解决framework中问题的时候发现了这个工具类，由于工作原因一直没有回头在细细的领会这个工具类的精髓，因此今天花点时间对这个类进行全面的分析一遍，以备不时之需。

首先分析之前，我们需要了解该类使用来进行16禁止转换的，我之前也写过相关的工具类，但是去了解Google的精神还是有必要的。

package com.android.internal.util;

public class HexDump

{

    private final static char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };//十六进制的组成元素

    

    public static String dumpHexString(byte[] array)

    {

        return dumpHexString(array, 0, array.length);

    }

    

    public static String dumpHexString(byte[] array, int offset, int length)

    {

        StringBuilder result = new StringBuilder();

        

        byte[] line = new byte[16];

        int lineIndex = 0;

        

        result.append("\n0x");

        result.append(toHexString(offset));

        

        for (int i = offset ; i < offset + length ; i++)

        {

            if (lineIndex == 16)

            {

                result.append(" ");

                

                for (int j = 0 ; j < 16 ; j++)

                {

                    if (line[j] > ' ' && line[j] < '~')

                    {

                        result.append(new String(line, j, 1));

                    }

                    else

                    {

                        result.append(".");

                    }

                }

                

                result.append("\n0x");

                result.append(toHexString(i));

                lineIndex = 0;

            }

            

            byte b = array[i];

            result.append(" ");

            result.append(HEX_DIGITS[(b >>> 4) & 0x0F]);

            result.append(HEX_DIGITS[b & 0x0F]);

            

            line[lineIndex++] = b;

        }

        

        if (lineIndex != 16)

        {

            int count = (16 - lineIndex) * 3;

            count++;

            for (int i = 0 ; i < count ; i++)

            {

                result.append(" ");

            }

            

            for (int i = 0 ; i < lineIndex ; i++)

            {

                if (line[i] > ' ' && line[i] < '~')

                {

                    result.append(new String(line, i, 1));

                }

                else

                {

                    result.append(".");

                }

            }

        }

        

        return result.toString();

    }

    

    public static String toHexString(byte b)

    {

        return toHexString(toByteArray(b));

    }



    public static String toHexString(byte[] array)

    {

        return toHexString(array, 0, array.length);

    }

    

    public static String toHexString(byte[] array, int offset, int length)

    {

        char[] buf = new char[length * 2];



        int bufIndex = 0;

        for (int i = offset ; i < offset + length; i++)

        {

            byte b = array[i];

            buf[bufIndex++] = HEX_DIGITS[(b >>> 4) & 0x0F];

            buf[bufIndex++] = HEX_DIGITS[b & 0x0F];

        }



        return new String(buf);        

    }

    

    public static String toHexString(int i)

    {

        return toHexString(toByteArray(i));

    }

    

    public static byte[] toByteArray(byte b)

    {

        byte[] array = new byte[1];

        array[0] = b;

        return array;

    }

    

    public static byte[] toByteArray(int i)

    {

        byte[] array = new byte[4];

        

        array[3] = (byte)(i & 0xFF);

        array[2] = (byte)((i >> 8) & 0xFF);

        array[1] = (byte)((i >> 16) & 0xFF);

        array[0] = (byte)((i >> 24) & 0xFF);

        

        return array;

    }

    

    private static int toByte(char c)

    {

        if (c >= '0' && c <= '9') return (c - '0');

        if (c >= 'A' && c <= 'F') return (c - 'A' + 10);

        if (c >= 'a' && c <= 'f') return (c - 'a' + 10);



        throw new RuntimeException ("Invalid hex char '" + c + "'");

    }

    

    public static byte[] hexStringToByteArray(String hexString)

    {

        int length = hexString.length();

        byte[] buffer = new byte[length / 2];



        for (int i = 0 ; i < length ; i += 2)

        {

            buffer[i / 2] = (byte)((toByte(hexString.charAt(i)) << 4) | toByte(hexString.charAt(i+1)));

        }

        

        return buffer;

    }    

}