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 package org.bouncycastle.crypto.paddings;
 
 
A padder that adds PKCS7/PKCS5 padding to a block.
 
public class PKCS7Padding
    implements BlockCipherPadding
{
    
Initialise the padder.

Parameters:
random - a SecureRandom if available.
    public void init(SecureRandom random)
        throws IllegalArgumentException
    {
        // nothing to do.
    }

    
Return the name of the algorithm the padder implements.

Returns:
the name of the algorithm the padder implements.
    public String getPaddingName()
    {
        return "PKCS7";
    }

    
add the pad bytes to the passed in block, returning the number of bytes added.
    public int addPadding(
        byte[]  in,
        int     inOff)
    {
        byte code = (byte)(in.length - inOff);
        while (inOff < in.length)
        {
            in[inOff] = code;
            inOff++;
        }
        return code;
    }

    
return the number of pad bytes present in the block.
    public int padCount(byte[] in)
        throws InvalidCipherTextException
    {
        int count = in[in.length - 1] & 0xff;
        byte countAsbyte = (byte)count;
        // constant time version
        boolean failed = (count > in.length | count == 0);
        for (int i = 0; i < in.lengthi++)
        {
            failed |= (in.length - i <= count) & (in[i] != countAsbyte);
        }
        if (failed)
        {
            throw new InvalidCipherTextException("pad block corrupted");
        }
        return count;
    }
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