/*
* 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.
*/
package org.apache.commons.vfs.provider.tar;
/**
* This class provides static utility methods to work with byte streams.
*
* @author <a href="mailto:time@ice.com">Timothy Gerard Endres</a>
* @author <a href="mailto:stefano@apache.org">Stefano Mazzocchi</a>
* @version $Revision: 480428 $ $Date: 2006-11-29 07:15:24 +0100 (Mi, 29 Nov 2006) $
*/
class TarUtils
{
/**
* Parse the checksum octal integer from a header buffer.
*
* @param offset The offset into the buffer from which to parse.
* @param length The number of header bytes to parse.
* @param value Description of Parameter
* @param buf Description of Parameter
* @return The integer value of the entry's checksum.
*/
public static int getCheckSumOctalBytes( final long value,
final byte[] buf,
final int offset,
final int length )
{
getOctalBytes( value, buf, offset, length );
buf[ offset + length - 1 ] = (byte)' ';
buf[ offset + length - 2 ] = 0;
return offset + length;
}
/**
* Parse an octal long integer from a header buffer.
*
* @param offset The offset into the buffer from which to parse.
* @param length The number of header bytes to parse.
* @param value Description of Parameter
* @param buf Description of Parameter
* @return The long value of the octal bytes.
*/
public static int getLongOctalBytes( final long value,
final byte[] buf,
final int offset,
final int length )
{
byte[] temp = new byte[ length + 1 ];
getOctalBytes( value, temp, 0, length + 1 );
System.arraycopy( temp, 0, buf, offset, length );
return offset + length;
}
/**
* Determine the number of bytes in an entry name.
*
* @param offset The offset into the buffer from which to parse.
* @param length The number of header bytes to parse.
* @param name Description of Parameter
* @param buffer Description of Parameter
* @return The number of bytes in a header's entry name.
*/
public static int getNameBytes( final StringBuffer name,
final byte[] buffer,
final int offset,
final int length )
{
int i;
for( i = 0; i < length && i < name.length(); ++i )
{
buffer[ offset + i ] = (byte)name.charAt( i );
}
for( ; i < length; ++i )
{
buffer[ offset + i ] = 0;
}
return offset + length;
}
/**
* Parse an octal integer from a header buffer.
*
* @param offset The offset into the buffer from which to parse.
* @param length The number of header bytes to parse.
* @return The integer value of the octal bytes.
*/
public static int getOctalBytes( final long value,
final byte[] buffer,
final int offset,
final int length )
{
int idx = length - 1;
buffer[ offset + idx ] = 0;
--idx;
buffer[ offset + idx ] = (byte)' ';
--idx;
if( value == 0 )
{
buffer[ offset + idx ] = (byte)'0';
--idx;
}
else
{
long val = value;
while( idx >= 0 && val > 0 )
{
buffer[ offset + idx ] = (byte)( (byte)'0' + (byte)( val & 7 ) );
val = val >> 3;
idx--;
}
}
while( idx >= 0 )
{
buffer[ offset + idx ] = (byte)' ';
idx--;
}
return offset + length;
}
/**
* Compute the checksum of a tar entry header.
*
* @param buffer The tar entry's header buffer.
* @return The computed checksum.
*/
public static long computeCheckSum( final byte[] buffer )
{
long sum = 0;
for( int i = 0; i < buffer.length; ++i )
{
sum += 255 & buffer[ i ];
}
return sum;
}
/**
* Parse an entry name from a header buffer.
*
* @param header The header buffer from which to parse.
* @param offset The offset into the buffer from which to parse.
* @param length The number of header bytes to parse.
* @return The header's entry name.
*/
public static StringBuffer parseName( final byte[] header,
final int offset,
final int length )
{
StringBuffer result = new StringBuffer( length );
int end = offset + length;
for( int i = offset; i < end; ++i )
{
if( header[ i ] == 0 )
{
break;
}
result.append( (char)header[ i ] );
}
return result;
}
/**
* Parse an octal string from a header buffer. This is used for the file
* permission mode value.
*
* @param header The header buffer from which to parse.
* @param offset The offset into the buffer from which to parse.
* @param length The number of header bytes to parse.
* @return The long value of the octal string.
*/
public static long parseOctal( final byte[] header,
final int offset,
final int length )
{
long result = 0;
boolean stillPadding = true;
int end = offset + length;
for( int i = offset; i < end; ++i )
{
if( header[ i ] == 0 )
{
break;
}
if( header[ i ] == (byte)' ' || header[ i ] == '0' )
{
if( stillPadding )
{
continue;
}
if( header[ i ] == (byte)' ' )
{
break;
}
}
stillPadding = false;
result = ( result << 3 ) + ( header[ i ] - '0' );
}
return result;
}
}
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