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/*
* Copyright 2000,2002,2004 The Apache Software Foundation
*
* Licensed 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.
*
*/
/*
* This package is based on the work done by Timothy Gerard Endres
* (time@ice.com) to whom the Ant project is very grateful for his great code.
*/
package org.apache.tools.tar;
/**
* This class provides static utility methods to work with byte streams.
*
* @author Timothy Gerard Endres <a href="mailto:time@ice.com">time@ice.com</a>
* @author Stefano Mazzocchi <a href="mailto:stefano@apache.org">stefano@apache.org</a>
*/
public class TarUtils {
/**
* 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(byte[] header, int offset, 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;
}
/**
* 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(byte[] header, int offset, 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;
}
/**
* Determine the number of bytes in an entry name.
*
* @param name The header name 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 number of bytes in a header's entry name.
*/
public static int getNameBytes(StringBuffer name, byte[] buf, int offset, int length) {
int i;
for (i = 0; i < length && i < name.length(); ++i) {
buf[offset + i] = (byte) name.charAt(i);
}
for (; i < length; ++i) {
buf[offset + i] = 0;
}
return offset + length;
}
/**
* Parse an octal integer from a header buffer.
*
* @param value The header value
* @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(long value, byte[] buf, int offset, int length) {
int idx = length - 1;
buf[offset + idx] = 0;
--idx;
buf[offset + idx] = (byte) ' ';
--idx;
if (value == 0) {
buf[offset + idx] = (byte) '0';
--idx;
} else {
for (long val = value; idx >= 0 && val > 0; --idx) {
buf[offset + idx] = (byte) ((byte) '0' + (byte) (val & 7));
val = val >> 3;
}
}
for (; idx >= 0; --idx) {
buf[offset + idx] = (byte) ' ';
}
return offset + length;
}
/**
* Parse an octal long integer from a header buffer.
*
* @param value The header value
* @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 bytes.
*/
public static int getLongOctalBytes(long value, byte[] buf, int offset, int length) {
byte[] temp = new byte[length + 1];
getOctalBytes(value, temp, 0, length + 1);
System.arraycopy(temp, 0, buf, offset, length);
return offset + length;
}
/**
* Parse the checksum octal integer from a header buffer.
*
* @param value The header value
* @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 entry's checksum.
*/
public static int getCheckSumOctalBytes(long value, byte[] buf, int offset, int length) {
getOctalBytes(value, buf, offset, length);
buf[offset + length - 1] = (byte) ' ';
buf[offset + length - 2] = 0;
return offset + length;
}
/**
* Compute the checksum of a tar entry header.
*
* @param buf The tar entry's header buffer.
* @return The computed checksum.
*/
public static long computeCheckSum(byte[] buf) {
long sum = 0;
for (int i = 0; i < buf.length; ++i) {
sum += 255 & buf[i];
}
return sum;
}
}
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