package org.bouncycastle.asn1;

import java.io.ByteArrayOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;

import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.io.Streams;

Base class for BIT STRING objects
/**
 * Base class for BIT STRING objects
 */
public abstract class ASN1BitString
    extends ASN1Primitive
    implements ASN1String
{
    private static final char[]  table = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    protected final byte[]      data;
    protected final int         padBits;

    
Params:
bitString – an int containing the BIT STRING
Returns:
the correct number of pad bits for a bit string defined in
a 32 bit constant/**
     * @param bitString an int containing the BIT STRING
     * @return the correct number of pad bits for a bit string defined in
     * a 32 bit constant
     */
    static protected int getPadBits(
        int bitString)
    {
        int val = 0;
        for (int i = 3; i >= 0; i--)
        {
            //
            // this may look a little odd, but if it isn't done like this pre jdk1.2
            // JVM's break!
            //
            if (i != 0)
            {
                if ((bitString >> (i * 8)) != 0)
                {
                    val = (bitString >> (i * 8)) & 0xFF;
                    break;
                }
            }
            else
            {
                if (bitString != 0)
                {
                    val = bitString & 0xFF;
                    break;
                }
            }
        }

        if (val == 0)
        {
            return 0;
        }


        int bits = 1;

        while (((val <<= 1) & 0xFF) != 0)
        {
            bits++;
        }

        return 8 - bits;
    }

    
Params:
bitString – an int containing the BIT STRING
Returns:
the correct number of bytes for a bit string defined in
a 32 bit constant/**
     * @param bitString an int containing the BIT STRING
     * @return the correct number of bytes for a bit string defined in
     * a 32 bit constant
     */
    static protected byte[] getBytes(int bitString)
    {
        if (bitString == 0)
        {
            return new byte[0];
        }

        int bytes = 4;
        for (int i = 3; i >= 1; i--)
        {
            if ((bitString & (0xFF << (i * 8))) != 0)
            {
                break;
            }
            bytes--;
        }

        byte[] result = new byte[bytes];
        for (int i = 0; i < bytes; i++)
        {
            result[i] = (byte) ((bitString >> (i * 8)) & 0xFF);
        }

        return result;
    }

    
Base constructor.
Params:
data – the octets making up the bit string.
padBits – the number of extra bits at the end of the string./**
     * Base constructor.
     *
     * @param data the octets making up the bit string.
     * @param padBits the number of extra bits at the end of the string.
     */
    public ASN1BitString(
        byte[]  data,
        int     padBits)
    {
        if (data == null)
        {
            throw new NullPointerException("data cannot be null");
        }
        if (data.length == 0 && padBits != 0)
        {
            throw new IllegalArgumentException("zero length data with non-zero pad bits");
        }
        if (padBits > 7 || padBits < 0)
        {
            throw new IllegalArgumentException("pad bits cannot be greater than 7 or less than 0");
        }

        this.data = Arrays.clone(data);
        this.padBits = padBits;
    }

    
Return a String representation of this BIT STRING
Returns:
a String representation./**
     * Return a String representation of this BIT STRING
     *
     * @return a String representation.
     */
    public String getString()
    {
        StringBuffer          buf = new StringBuffer("#");
        ByteArrayOutputStream bOut = new ByteArrayOutputStream();
        ASN1OutputStream aOut = new ASN1OutputStream(bOut);

        try
        {
            aOut.writeObject(this);
        }
        catch (IOException e)
        {
            throw new ASN1ParsingException("Internal error encoding BitString: " + e.getMessage(), e);
        }

        byte[]    string = bOut.toByteArray();

        for (int i = 0; i != string.length; i++)
        {
            buf.append(table[(string[i] >>> 4) & 0xf]);
            buf.append(table[string[i] & 0xf]);
        }

        return buf.toString();
    }

    
Returns:
the value of the bit string as an int (truncating if necessary)/**
     * @return the value of the bit string as an int (truncating if necessary)
     */
    public int intValue()
    {
        int value = 0;
        byte[] string = data;

        if (padBits > 0 && data.length <= 4)
        {
            string = derForm(data, padBits);
        }

        for (int i = 0; i != string.length && i != 4; i++)
        {
            value |= (string[i] & 0xff) << (8 * i);
        }

        return value;
    }

    
Return the octets contained in this BIT STRING, checking that this BIT STRING really
does represent an octet aligned string. Only use this method when the standard you are
following dictates that the BIT STRING will be octet aligned.
Returns:
a copy of the octet aligned data./**
     * Return the octets contained in this BIT STRING, checking that this BIT STRING really
     * does represent an octet aligned string. Only use this method when the standard you are
     * following dictates that the BIT STRING will be octet aligned.
     *
     * @return a copy of the octet aligned data.
     */
    public byte[] getOctets()
    {
        if (padBits != 0)
        {
            throw new IllegalStateException("attempt to get non-octet aligned data from BIT STRING");
        }

        return Arrays.clone(data);
    }

    public byte[] getBytes()
    {
        return derForm(data, padBits);
    }

    public int getPadBits()
    {
        return padBits;
    }

    public String toString()
    {
        return getString();
    }

    public int hashCode()
    {
        return padBits ^ Arrays.hashCode(this.getBytes());
    }

    protected boolean asn1Equals(
        ASN1Primitive o)
    {
        if (!(o instanceof ASN1BitString))
        {
            return false;
        }

        ASN1BitString other = (ASN1BitString)o;

        return this.padBits == other.padBits
            && Arrays.areEqual(this.getBytes(), other.getBytes());
    }

    protected static byte[] derForm(byte[] data, int padBits)
    {
        byte[] rv = Arrays.clone(data);
        // DER requires pad bits be zero
        if (padBits > 0)
        {
            rv[data.length - 1] &= 0xff << padBits;
        }

        return rv;
    }

    static ASN1BitString fromInputStream(int length, InputStream stream)
        throws IOException
    {
        if (length < 1)
        {
            throw new IllegalArgumentException("truncated BIT STRING detected");
        }

        int padBits = stream.read();
        byte[] data = new byte[length - 1];

        if (data.length != 0)
        {
            if (Streams.readFully(stream, data) != data.length)
            {
                throw new EOFException("EOF encountered in middle of BIT STRING");
            }

            if (padBits > 0 && padBits < 8)
            {
                if (data[data.length - 1] != (byte)(data[data.length - 1] & (0xff << padBits)))
                {
                    return new DLBitString(data, padBits);
                }
            }
        }

        return new DERBitString(data, padBits);
    }

    public ASN1Primitive getLoadedObject()
    {
        return this.toASN1Primitive();
    }

    ASN1Primitive toDERObject()
    {
        return new DERBitString(data, padBits);
    }

    ASN1Primitive toDLObject()
    {
        return new DLBitString(data, padBits);
    }

    abstract void encode(ASN1OutputStream out)
        throws IOException;
}