/**
 * fast data-reading from a byte-array
 *
 * @author ab
 */
package btools.util;


public class ByteDataReader
{
  protected byte[] ab;
  protected int aboffset;
  protected int aboffsetEnd;

  public ByteDataReader( byte[] byteArray )
  {
	 ab = byteArray;
	 aboffsetEnd = ab == null ? 0 : ab.length;
  }

  public ByteDataReader( byte[] byteArray, int offset )
  {
	 ab = byteArray;
	 aboffset = offset;
	 aboffsetEnd = ab == null ? 0 : ab.length;
  }

  public final int readInt()
  {
      int i3 = ab[aboffset++]& 0xff;
      int i2 = ab[aboffset++]& 0xff;
      int i1 = ab[aboffset++]& 0xff;
      int i0 = ab[aboffset++]& 0xff;
      return (i3 << 24) + (i2 << 16) + (i1 << 8) + i0;
  }

  public final long readLong()
  {
      long i7 = ab[aboffset++]& 0xff;
      long i6 = ab[aboffset++]& 0xff;
      long i5 = ab[aboffset++]& 0xff;
      long i4 = ab[aboffset++]& 0xff;
      long i3 = ab[aboffset++]& 0xff;
      long i2 = ab[aboffset++]& 0xff;
      long i1 = ab[aboffset++]& 0xff;
      long i0 = ab[aboffset++]& 0xff;
      return (i7 << 56) + (i6 << 48) + (i5 << 40) + (i4 << 32) + (i3 << 24) + (i2 << 16) + (i1 << 8) + i0;
  }

  public final boolean readBoolean()
  {
      int i0 = ab[aboffset++]& 0xff;
      return i0 != 0;
  }

  public final byte readByte()
  {
      int i0 = ab[aboffset++] & 0xff;
      return (byte)(i0);
  }

  public final short readShort()
  {
      int i1 = ab[aboffset++] & 0xff;
      int i0 = ab[aboffset++] & 0xff;
      return (short)( (i1 << 8) | i0);
  }

  /**
   * Read a size value and return a pointer to the end of a data section of that size
   *
   * @return the pointer to the first byte after that section
   */
  public int getEndPointer()
  {
    int size = readVarLengthUnsigned();
    return aboffset + size;
  }

  public byte[] readDataUntil( int endPointer )
  {
    int size = endPointer - aboffset;
    if ( size == 0 )
    {
      return null;
    }
    byte[] data = new byte[size];
    readFully( data );
    return data;
  }

  public byte[] readVarBytes()
  {
    int len = readVarLengthUnsigned();
    if ( len == 0 )
    {
      return null;
    }
    byte[] bytes = new byte[len];
    readFully( bytes );
    return bytes;
  }

  public final int readVarLengthSigned()
  {
	  int v = readVarLengthUnsigned();
	  return ( v & 1 ) == 0 ? v >> 1 : -(v >> 1 );
  }

  public final int readVarLengthUnsigned()
  {
    byte b;
    int v = (b=ab[aboffset++]) & 0x7f;
    if ( b >= 0 ) return v;
    v |= ( (b=ab[aboffset++]) & 0x7f ) <<  7;
    if ( b >= 0 ) return v;
    v |= ( (b=ab[aboffset++]) & 0x7f ) << 14;
    if ( b >= 0 ) return v;
    v |= ( (b=ab[aboffset++]) & 0x7f ) << 21;
    if ( b >= 0 ) return v;
    v |= ( (b=ab[aboffset++]) &  0xf ) << 28;
    return v;
  }

  public final void readFully( byte[] ta )
  {
	  System.arraycopy( ab, aboffset, ta, 0, ta.length );
	  aboffset += ta.length;
  }

  public boolean hasMoreData()
  {
    return aboffset < aboffsetEnd;
  }

  @Override
  public String toString()
  {
	  StringBuilder sb = new StringBuilder( "[" );
	  for( int i=0; i<ab.length; i++ ) sb.append( i == 0 ? " " : ", " ).append( Integer.toString( ab[i] ) );
      sb.append( " ]" );
      return sb.toString();
  }

}