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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.
*/
/*
* $Id: SuballocatedByteVector.java 468655 2006-10-28 07:12:06Z minchau $
*/
package org.apache.xml.utils;
/**
* A very simple table that stores a list of byte. Very similar API to our
* IntVector class (same API); different internal storage.
*
* This version uses an array-of-arrays solution. Read/write access is thus
* a bit slower than the simple IntVector, and basic storage is a trifle
* higher due to the top-level array -- but appending is O(1) fast rather
* than O(N**2) slow, which will swamp those costs in situations where
* long vectors are being built up.
*
* Known issues:
*
* Some methods are private because they haven't yet been tested properly.
*
* If an element has not been set (because we skipped it), its value will
* initially be 0. Shortening the vector does not clear old storage; if you
* then skip values and setElementAt a higher index again, you may see old data
* reappear in the truncated-and-restored section. Doing anything else would
* have performance costs.
* @xsl.usage internal
*/
public class SuballocatedByteVector
{
/** Size of blocks to allocate */
protected int m_blocksize;
/** Number of blocks to (over)allocate by */
protected int m_numblocks=32;
/** Array of arrays of bytes */
protected byte m_map[][];
/** Number of bytes in array */
protected int m_firstFree = 0;
/** "Shortcut" handle to m_map[0] */
protected byte m_map0[];
/**
* Default constructor. Note that the default
* block size is very small, for small lists.
*/
public SuballocatedByteVector()
{
this(2048);
}
/**
* Construct a ByteVector, using the given block size.
*
* @param blocksize Size of block to allocate
*/
public SuballocatedByteVector(int blocksize)
{
m_blocksize = blocksize;
m_map0=new byte[blocksize];
m_map = new byte[m_numblocks][];
m_map[0]=m_map0;
}
/**
* Construct a ByteVector, using the given block size.
*
* @param blocksize Size of block to allocate
*/
public SuballocatedByteVector(int blocksize, int increaseSize)
{
// increaseSize not currently used.
this(blocksize);
}
/**
* Get the length of the list.
*
* @return length of the list
*/
public int size()
{
return m_firstFree;
}
/**
* Set the length of the list.
*
* @return length of the list
*/
private void setSize(int sz)
{
if(m_firstFree=m_map.length)
{
int newsize=index+m_numblocks;
byte[][] newMap=new byte[newsize][];
System.arraycopy(m_map, 0, newMap, 0, m_map.length);
m_map=newMap;
}
byte[] block=m_map[index];
if(null==block)
block=m_map[index]=new byte[m_blocksize];
block[offset]=value;
}
}
/**
* Append several byte values onto the vector.
*
* @param value Byte to add to the list
*/
private void addElements(byte value, int numberOfElements)
{
if(m_firstFree+numberOfElements0)
{
if(index>=m_map.length)
{
int newsize=index+m_numblocks;
byte[][] newMap=new byte[newsize][];
System.arraycopy(m_map, 0, newMap, 0, m_map.length);
m_map=newMap;
}
byte[] block=m_map[index];
if(null==block)
block=m_map[index]=new byte[m_blocksize];
int copied=(m_blocksize-offset < numberOfElements)
? m_blocksize-offset : numberOfElements;
numberOfElements-=copied;
while(copied-- > 0)
block[offset++]=value;
++index;offset=0;
}
}
}
/**
* Append several slots onto the vector, but do not set the values.
* Note: "Not Set" means the value is unspecified.
*
* @param numberOfElements
*/
private void addElements(int numberOfElements)
{
int newlen=m_firstFree+numberOfElements;
if(newlen>m_blocksize)
{
int index=m_firstFree%m_blocksize;
int newindex=(m_firstFree+numberOfElements)%m_blocksize;
for(int i=index+1;i<=newindex;++i)
m_map[i]=new byte[m_blocksize];
}
m_firstFree=newlen;
}
/**
* Inserts the specified node in this vector at the specified index.
* Each component in this vector with an index greater or equal to
* the specified index is shifted upward to have an index one greater
* than the value it had previously.
*
* Insertion may be an EXPENSIVE operation!
*
* @param value Byte to insert
* @param at Index of where to insert
*/
private void insertElementAt(byte value, int at)
{
if(at==m_firstFree)
addElement(value);
else if (at>m_firstFree)
{
int index=at/m_blocksize;
if(index>=m_map.length)
{
int newsize=index+m_numblocks;
byte[][] newMap=new byte[newsize][];
System.arraycopy(m_map, 0, newMap, 0, m_map.length);
m_map=newMap;
}
byte[] block=m_map[index];
if(null==block)
block=m_map[index]=new byte[m_blocksize];
int offset=at%m_blocksize;
block[offset]=value;
m_firstFree=offset+1;
}
else
{
int index=at/m_blocksize;
int maxindex=m_firstFree+1/m_blocksize;
++m_firstFree;
int offset=at%m_blocksize;
byte push;
// ***** Easier to work down from top?
while(index<=maxindex)
{
int copylen=m_blocksize-offset-1;
byte[] block=m_map[index];
if(null==block)
{
push=0;
block=m_map[index]=new byte[m_blocksize];
}
else
{
push=block[m_blocksize-1];
System.arraycopy(block, offset , block, offset+1, copylen);
}
block[offset]=value;
value=push;
offset=0;
++index;
}
}
}
/**
* Wipe it out.
*/
public void removeAllElements()
{
m_firstFree = 0;
}
/**
* Removes the first occurrence of the argument from this vector.
* If the object is found in this vector, each component in the vector
* with an index greater or equal to the object's index is shifted
* downward to have an index one smaller than the value it had
* previously.
*
* @param s Byte to remove from array
*
* @return True if the byte was removed, false if it was not found
*/
private boolean removeElement(byte s)
{
int at=indexOf(s,0);
if(at<0)
return false;
removeElementAt(at);
return true;
}
/**
* Deletes the component at the specified index. Each component in
* this vector with an index greater or equal to the specified
* index is shifted downward to have an index one smaller than
* the value it had previously.
*
* @param at index of where to remove a byte
*/
private void removeElementAt(int at)
{
// No point in removing elements that "don't exist"...
if(at=m_map.length)
{
int newsize=index+m_numblocks;
byte[][] newMap=new byte[newsize][];
System.arraycopy(m_map, 0, newMap, 0, m_map.length);
m_map=newMap;
}
byte[] block=m_map[index];
if(null==block)
block=m_map[index]=new byte[m_blocksize];
block[offset]=value;
if(at>=m_firstFree)
m_firstFree=at+1;
}
/**
* Get the nth element. This is often at the innermost loop of an
* application, so performance is critical.
*
* @param i index of value to get
*
* @return value at given index. If that value wasn't previously set,
* the result is undefined for performance reasons. It may throw an
* exception (see below), may return zero, or (if setSize has previously
* been used) may return stale data.
*
* @throws ArrayIndexOutOfBoundsException if the index was _clearly_
* unreasonable (negative, or past the highest block).
*
* @throws NullPointerException if the index points to a block that could
* have existed (based on the highest index used) but has never had anything
* set into it.
* %REVIEW% Could add a catch to create the block in that case, or return 0.
* Try/Catch is _supposed_ to be nearly free when not thrown to. Do we
* believe that? Should we have a separate safeElementAt?
*/
public byte elementAt(int i)
{
// %OPT% Does this really buy us anything? Test versus division for small,
// test _plus_ division for big docs.
if(i= 0);
}
/**
* Searches for the first occurence of the given argument,
* beginning the search at index, and testing for equality
* using the equals method.
*
* @param elem object to look for
* @param index Index of where to begin search
* @return the index of the first occurrence of the object
* argument in this vector at position index or later in the
* vector; returns -1 if the object is not found.
*/
public int indexOf(byte elem, int index)
{
if(index>=m_firstFree)
return -1;
int bindex=index/m_blocksize;
int boffset=index%m_blocksize;
int maxindex=m_firstFree/m_blocksize;
byte[] block;
for(;bindex=0;
--index)
{
byte[] block=m_map[index];
if(block!=null)
for(int offset=boffset; offset>=0; --offset)
if(block[offset]==elem)
return offset+index*m_blocksize;
boffset=0; // after first
}
return -1;
}
}
