http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5. 
public class org.bouncycastle.crypto.generators.BaseKDFBytesGenerator implements org.bouncycastle.crypto.DerivationFunction
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.bouncycastle.crypto.generators.BaseKDFBytesGenerator
  super_class: java.lang.Object
{
  private int counterStart;
    descriptor: I
    flags: (0x0002) ACC_PRIVATE

  private org.bouncycastle.crypto.Digest digest;
    descriptor: Lorg/bouncycastle/crypto/Digest;
    flags: (0x0002) ACC_PRIVATE

  private byte[] shared;
    descriptor: [B
    flags: (0x0002) ACC_PRIVATE

  private byte[] iv;
    descriptor: [B
    flags: (0x0002) ACC_PRIVATE

  protected void <init>(int, org.bouncycastle.crypto.Digest);
    descriptor: (ILorg/bouncycastle/crypto/Digest;)V
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
        start local 1 // int counterStart
        start local 2 // org.bouncycastle.crypto.Digest digest
         0: .line 29
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 33
            aload 0 /* this */
            iload 1 /* counterStart */
            putfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.counterStart:I
         2: .line 34
            aload 0 /* this */
            aload 2 /* digest */
            putfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
         3: .line 35
            return
        end local 2 // org.bouncycastle.crypto.Digest digest
        end local 1 // int counterStart
        end local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
      LocalVariableTable:
        Start  End  Slot          Name  Signature
            0    4     0          this  Lorg/bouncycastle/crypto/generators/BaseKDFBytesGenerator;
            0    4     1  counterStart  I
            0    4     2        digest  Lorg/bouncycastle/crypto/Digest;
    MethodParameters:
              Name  Flags
      counterStart  
      digest        

  public void init(org.bouncycastle.crypto.DerivationParameters);
    descriptor: (Lorg/bouncycastle/crypto/DerivationParameters;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=3, args_size=2
        start local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
        start local 1 // org.bouncycastle.crypto.DerivationParameters param
         0: .line 40
            aload 1 /* param */
            instanceof org.bouncycastle.crypto.params.KDFParameters
            ifeq 5
         1: .line 42
            aload 1 /* param */
            checkcast org.bouncycastle.crypto.params.KDFParameters
            astore 2 /* p */
        start local 2 // org.bouncycastle.crypto.params.KDFParameters p
         2: .line 44
            aload 0 /* this */
            aload 2 /* p */
            invokevirtual org.bouncycastle.crypto.params.KDFParameters.getSharedSecret:()[B
            putfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.shared:[B
         3: .line 45
            aload 0 /* this */
            aload 2 /* p */
            invokevirtual org.bouncycastle.crypto.params.KDFParameters.getIV:()[B
            putfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.iv:[B
        end local 2 // org.bouncycastle.crypto.params.KDFParameters p
         4: .line 46
            goto 11
         5: .line 47
      StackMap locals:
      StackMap stack:
            aload 1 /* param */
            instanceof org.bouncycastle.crypto.params.ISO18033KDFParameters
            ifeq 10
         6: .line 49
            aload 1 /* param */
            checkcast org.bouncycastle.crypto.params.ISO18033KDFParameters
            astore 2 /* p */
        start local 2 // org.bouncycastle.crypto.params.ISO18033KDFParameters p
         7: .line 51
            aload 0 /* this */
            aload 2 /* p */
            invokevirtual org.bouncycastle.crypto.params.ISO18033KDFParameters.getSeed:()[B
            putfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.shared:[B
         8: .line 52
            aload 0 /* this */
            aconst_null
            putfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.iv:[B
        end local 2 // org.bouncycastle.crypto.params.ISO18033KDFParameters p
         9: .line 53
            goto 11
        10: .line 56
      StackMap locals:
      StackMap stack:
            new java.lang.IllegalArgumentException
            dup
            ldc "KDF parameters required for KDF2Generator"
            invokespecial java.lang.IllegalArgumentException.<init>:(Ljava/lang/String;)V
            athrow
        11: .line 58
      StackMap locals:
      StackMap stack:
            return
        end local 1 // org.bouncycastle.crypto.DerivationParameters param
        end local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0   12     0   this  Lorg/bouncycastle/crypto/generators/BaseKDFBytesGenerator;
            0   12     1  param  Lorg/bouncycastle/crypto/DerivationParameters;
            2    4     2      p  Lorg/bouncycastle/crypto/params/KDFParameters;
            7    9     2      p  Lorg/bouncycastle/crypto/params/ISO18033KDFParameters;
    MethodParameters:
       Name  Flags
      param  

  public org.bouncycastle.crypto.Digest getDigest();
    descriptor: ()Lorg/bouncycastle/crypto/Digest;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
         0: .line 65
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            areturn
        end local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/bouncycastle/crypto/generators/BaseKDFBytesGenerator;

  public int generateBytes(byte[], int, int);
    descriptor: ([BII)I
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=5, locals=11, args_size=4
        start local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
        start local 1 // byte[] out
        start local 2 // int outOff
        start local 3 // int len
         0: .line 81
            aload 1 /* out */
            arraylength
            iload 3 /* len */
            isub
            iload 2 /* outOff */
            if_icmpge 2
         1: .line 83
            new org.bouncycastle.crypto.DataLengthException
            dup
            ldc "output buffer too small"
            invokespecial org.bouncycastle.crypto.DataLengthException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 86
      StackMap locals:
      StackMap stack:
            iload 3 /* len */
            i2l
            lstore 4 /* oBytes */
        start local 4 // long oBytes
         3: .line 87
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            invokeinterface org.bouncycastle.crypto.Digest.getDigestSize:()I
            istore 6 /* outLen */
        start local 6 // int outLen
         4: .line 95
            lload 4 /* oBytes */
            ldc 8589934591
            lcmp
            ifle 6
         5: .line 97
            new java.lang.IllegalArgumentException
            dup
            ldc "Output length too large"
            invokespecial java.lang.IllegalArgumentException.<init>:(Ljava/lang/String;)V
            athrow
         6: .line 100
      StackMap locals: long int
      StackMap stack:
            lload 4 /* oBytes */
            iload 6 /* outLen */
            i2l
            ladd
            lconst_1
            lsub
            iload 6 /* outLen */
            i2l
            ldiv
            l2i
            istore 7 /* cThreshold */
        start local 7 // int cThreshold
         7: .line 102
            aconst_null
            astore 8 /* dig */
        start local 8 // byte[] dig
         8: .line 104
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            invokeinterface org.bouncycastle.crypto.Digest.getDigestSize:()I
            newarray 8
            astore 8 /* dig */
         9: .line 106
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.counterStart:I
            istore 9 /* counter */
        start local 9 // int counter
        10: .line 108
            iconst_0
            istore 10 /* i */
        start local 10 // int i
        11: goto 28
        12: .line 110
      StackMap locals: org.bouncycastle.crypto.generators.BaseKDFBytesGenerator byte[] int int long int int byte[] int int
      StackMap stack:
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.shared:[B
            iconst_0
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.shared:[B
            arraylength
            invokeinterface org.bouncycastle.crypto.Digest.update:([BII)V
        13: .line 112
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            iload 9 /* counter */
            bipush 24
            ishr
            i2b
            invokeinterface org.bouncycastle.crypto.Digest.update:(B)V
        14: .line 113
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            iload 9 /* counter */
            bipush 16
            ishr
            i2b
            invokeinterface org.bouncycastle.crypto.Digest.update:(B)V
        15: .line 114
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            iload 9 /* counter */
            bipush 8
            ishr
            i2b
            invokeinterface org.bouncycastle.crypto.Digest.update:(B)V
        16: .line 115
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            iload 9 /* counter */
            i2b
            invokeinterface org.bouncycastle.crypto.Digest.update:(B)V
        17: .line 117
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.iv:[B
            ifnull 19
        18: .line 119
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.iv:[B
            iconst_0
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.iv:[B
            arraylength
            invokeinterface org.bouncycastle.crypto.Digest.update:([BII)V
        19: .line 122
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            aload 8 /* dig */
            iconst_0
            invokeinterface org.bouncycastle.crypto.Digest.doFinal:([BI)I
            pop
        20: .line 124
            iload 3 /* len */
            iload 6 /* outLen */
            if_icmple 25
        21: .line 126
            aload 8 /* dig */
            iconst_0
            aload 1 /* out */
            iload 2 /* outOff */
            iload 6 /* outLen */
            invokestatic java.lang.System.arraycopy:(Ljava/lang/Object;ILjava/lang/Object;II)V
        22: .line 127
            iload 2 /* outOff */
            iload 6 /* outLen */
            iadd
            istore 2 /* outOff */
        23: .line 128
            iload 3 /* len */
            iload 6 /* outLen */
            isub
            istore 3 /* len */
        24: .line 129
            goto 26
        25: .line 132
      StackMap locals:
      StackMap stack:
            aload 8 /* dig */
            iconst_0
            aload 1 /* out */
            iload 2 /* outOff */
            iload 3 /* len */
            invokestatic java.lang.System.arraycopy:(Ljava/lang/Object;ILjava/lang/Object;II)V
        26: .line 135
      StackMap locals:
      StackMap stack:
            iinc 9 /* counter */ 1
        27: .line 108
            iinc 10 /* i */ 1
      StackMap locals:
      StackMap stack:
        28: iload 10 /* i */
            iload 7 /* cThreshold */
            if_icmplt 12
        end local 10 // int i
        29: .line 138
            aload 0 /* this */
            getfield org.bouncycastle.crypto.generators.BaseKDFBytesGenerator.digest:Lorg/bouncycastle/crypto/Digest;
            invokeinterface org.bouncycastle.crypto.Digest.reset:()V
        30: .line 140
            iload 3 /* len */
            ireturn
        end local 9 // int counter
        end local 8 // byte[] dig
        end local 7 // int cThreshold
        end local 6 // int outLen
        end local 4 // long oBytes
        end local 3 // int len
        end local 2 // int outOff
        end local 1 // byte[] out
        end local 0 // org.bouncycastle.crypto.generators.BaseKDFBytesGenerator this
      LocalVariableTable:
        Start  End  Slot        Name  Signature
            0   31     0        this  Lorg/bouncycastle/crypto/generators/BaseKDFBytesGenerator;
            0   31     1         out  [B
            0   31     2      outOff  I
            0   31     3         len  I
            3   31     4      oBytes  J
            4   31     6      outLen  I
            7   31     7  cThreshold  I
            8   31     8         dig  [B
           10   31     9     counter  I
           11   29    10           i  I
    Exceptions:
      throws org.bouncycastle.crypto.DataLengthException, java.lang.IllegalArgumentException
    MethodParameters:
        Name  Flags
      out     
      outOff  
      len     
}
SourceFile: "BaseKDFBytesGenerator.java"