Mega Code Archive
Operations on bit-mapped fields
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Operations on bit-mapped fields.
*
* @author Apache Jakarta POI
* @author Scott Sanders (sanders at apache dot org)
* @author Marc Johnson (mjohnson at apache dot org)
* @author Andrew C. Oliver (acoliver at apache dot org)
* @author Stephen Colebourne
* @author Pete Gieser
* @author Gary Gregory
* @since 2.0
* @version $Id: BitField.java 437554 2006-08-28 06:21:41Z bayard $
*/
public class BitField {
private final int _mask;
private final int _shift_count;
/**
* Creates a BitField instance.
*
* @param mask the mask specifying which bits apply to this
* BitField. Bits that are set in this mask are the bits
* that this BitField operates on
*/
public BitField(int mask) {
_mask = mask;
int count = 0;
int bit_pattern = mask;
if (bit_pattern != 0) {
while ((bit_pattern & 1) == 0) {
count++;
bit_pattern >>= 1;
}
}
_shift_count = count;
}
/**
* Obtains the value for the specified BitField, appropriately
* shifted right.
*
* Many users of a BitField will want to treat the specified
* bits as an int value, and will not want to be aware that the
* value is stored as a BitField (and so shifted left so many
* bits).
*
* @see #setValue(int,int)
* @param holder the int data containing the bits we're interested
* in
* @return the selected bits, shifted right appropriately
*/
public int getValue(int holder) {
return getRawValue(holder) >> _shift_count;
}
/**
* Obtains the value for the specified BitField, appropriately
* shifted right, as a short.
*
* Many users of a BitField will want to treat the specified
* bits as an int value, and will not want to be aware that the
* value is stored as a BitField (and so shifted left so many
* bits).
*
* @see #setShortValue(short,short)
* @param holder the short data containing the bits we're
* interested in
* @return the selected bits, shifted right appropriately
*/
public short getShortValue(short holder) {
return (short) getValue(holder);
}
/**
* Obtains the value for the specified BitField, unshifted.
*
* @param holder the int data containing the bits we're
* interested in
* @return the selected bits
*/
public int getRawValue(int holder) {
return holder & _mask;
}
/**
* Obtains the value for the specified BitField, unshifted.
*
* @param holder the short data containing the bits we're
* interested in
* @return the selected bits
*/
public short getShortRawValue(short holder) {
return (short) getRawValue(holder);
}
/**
* Returns whether the field is set or not.
*
* This is most commonly used for a single-bit field, which is
* often used to represent a boolean value; the results of using
* it for a multi-bit field is to determine whether *any* of its
* bits are set.
*
* @param holder the int data containing the bits we're interested
* in
* @return <code>true</code> if any of the bits are set,
* else <code>false</code>
*/
public boolean isSet(int holder) {
return (holder & _mask) != 0;
}
/**
* Returns whether all of the bits are set or not.
*
* This is a stricter test than {@link #isSet(int)},
* in that all of the bits in a multi-bit set must be set
* for this method to return <code>true</code>.
*
* @param holder the int data containing the bits we're
* interested in
* @return <code>true</code> if all of the bits are set,
* else <code>false</code>
*/
public boolean isAllSet(int holder) {
return (holder & _mask) == _mask;
}
/**
* Replaces the bits with new values.
*
* @see #getValue(int)
* @param holder the int data containing the bits we're
* interested in
* @param value the new value for the specified bits
* @return the value of holder with the bits from the value
* parameter replacing the old bits
*/
public int setValue(int holder, int value) {
return (holder & ~_mask) | ((value << _shift_count) & _mask);
}
/**
* Replaces the bits with new values.
*
* @see #getShortValue(short)
* @param holder the short data containing the bits we're
* interested in
* @param value the new value for the specified bits
* @return the value of holder with the bits from the value
* parameter replacing the old bits
*/
public short setShortValue(short holder, short value) {
return (short) setValue(holder, value);
}
/**
* Clears the bits.
*
* @param holder the int data containing the bits we're
* interested in
* @return the value of holder with the specified bits cleared
* (set to <code>0</code>)
*/
public int clear(int holder) {
return holder & ~_mask;
}
/**
* Clears the bits.
*
* @param holder the short data containing the bits we're
* interested in
* @return the value of holder with the specified bits cleared
* (set to <code>0</code>)
*/
public short clearShort(short holder) {
return (short) clear(holder);
}
/**
* Clears the bits.
*
* @param holder the byte data containing the bits we're
* interested in
*
* @return the value of holder with the specified bits cleared
* (set to <code>0</code>)
*/
public byte clearByte(byte holder) {
return (byte) clear(holder);
}
/**
* Sets the bits.
*
* @param holder the int data containing the bits we're
* interested in
* @return the value of holder with the specified bits set
* to <code>1</code>
*/
public int set(int holder) {
return holder | _mask;
}
/**
* Sets the bits.
*
* @param holder the short data containing the bits we're
* interested in
* @return the value of holder with the specified bits set
* to <code>1</code>
*/
public short setShort(short holder) {
return (short) set(holder);
}
/**
* Sets the bits.
*
* @param holder the byte data containing the bits we're
* interested in
*
* @return the value of holder with the specified bits set
* to <code>1</code>
*/
public byte setByte(byte holder) {
return (byte) set(holder);
}
/**
* Sets a boolean BitField.
*
* @param holder the int data containing the bits we're
* interested in
* @param flag indicating whether to set or clear the bits
* @return the value of holder with the specified bits set or
* cleared
*/
public int setBoolean(int holder, boolean flag) {
return flag ? set(holder) : clear(holder);
}
/**
* Sets a boolean BitField.
*
* @param holder the short data containing the bits we're
* interested in
* @param flag indicating whether to set or clear the bits
* @return the value of holder with the specified bits set or
* cleared
*/
public short setShortBoolean(short holder, boolean flag) {
return flag ? setShort(holder) : clearShort(holder);
}
/**
* Sets a boolean BitField.
*
* @param holder the byte data containing the bits we're
* interested in
* @param flag indicating whether to set or clear the bits
* @return the value of holder with the specified bits set or
* cleared
*/
public byte setByteBoolean(byte holder, boolean flag) {
return flag ? setByte(holder) : clearByte(holder);
}
}
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