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/**
* ByteArray
* Copyright 2007 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
* First published 30.03.2007 on http://yacy.net
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program in the file lgpl21.txt
* If not, see <http://www.gnu.org/licenses/>.
*/
package net.yacy.cora.util;
import java.util.HashMap;
import net.yacy.cora.document.encoding.UTF8;
/**
* this class is a experimental replacement of byte[].
* It can be used if a byte[] shall be stored within a HashMap or HashSet
* which is faster than TreeMap but is generally not possible because storing
* a byte[] in a Hashtable does not work because the hash computation does not
* work for byte[]. This class extends byte[] with a cached hashing function,
* so it can be used in hashtables.
* //FIXME: so does storing byte[] in HashMap help? as I'm moving use of Hashtable to
* //FIXME: HashMap, if so, please remove this class- or notify me
*/
public class ByteArray {
private final byte[] buffer;
public ByteArray(final byte[] bb) {
this.buffer = bb;
}
public long usedMemory() {
return this.buffer.length;
}
public byte[] asBytes() {
return this.buffer;
}
public static boolean startsWith(final byte[] buffer, final byte[] pattern) {
// compares two byte arrays: true, if pattern appears completely at offset position
if (buffer == null && pattern == null) return true;
if (buffer == null || pattern == null) return false;
if (buffer.length < pattern.length) return false;
for (int i = 0; i < pattern.length; i++) if (buffer[i] != pattern[i]) return false;
return true;
}
private int hashCache = Integer.MIN_VALUE; // if this is used in a compare method many times, a cache is useful
@Override
public int hashCode() {
if (this.hashCache == Integer.MIN_VALUE) {
this.hashCache = ByteArray.hashCode(this.buffer);
}
return this.hashCache;
}
/**
* compute a hash code that is equal to the hash computation of String()
* @param b
* @return a hash number
*/
public static int hashCode(byte[] b) {
int h = 0;
for (byte c: b) h = 31 * h + (c & 0xFF);
return h;
}
@Override
public boolean equals(Object other) {
ByteArray b = (ByteArray) other;
if (this.buffer == null && b == null) return true;
if (this.buffer == null || b == null) return false;
if (this.buffer.length != b.buffer.length) return false;
int l = this.buffer.length;
while (--l >= 0) if (this.buffer[l] != b.buffer[l]) return false;
return true;
}
public static long parseDecimal(final byte[] s) throws NumberFormatException {
if (s == null) throw new NumberFormatException("null");
long result = 0;
boolean negative = false;
int i = 0, max = s.length;
long limit;
long multmin;
long digit;
if (max <= 0) throw new NumberFormatException(UTF8.String(s));
if (s[0] == '-') {
negative = true;
limit = Long.MIN_VALUE;
i++;
} else {
limit = -Long.MAX_VALUE;
}
multmin = limit / 10;
if (i < max) {
digit = s[i++] - 48;
if (digit < 0) throw new NumberFormatException(UTF8.String(s));
result = -digit;
}
while (i < max) {
// Accumulating negatively avoids surprises near MAX_VALUE
digit = s[i++] - 48;
if (digit < 0) throw new NumberFormatException(UTF8.String(s));
if (result < multmin) throw new NumberFormatException(UTF8.String(s));
result *= 10;
if (result < limit + digit) throw new NumberFormatException(UTF8.String(s));
result -= digit;
}
if (negative) {
if (i > 1) return result;
throw new NumberFormatException(UTF8.String(s));
}
return -result;
}
public static void main(String[] args) {
ByteArray a0 = new ByteArray("abc".getBytes());
ByteArray a1 = new ByteArray("abc".getBytes());
ByteArray b = new ByteArray("bbb".getBytes());
System.out.println("a0 " + ((a0.equals(a1)) ? "=" : "!=") + " a1");
System.out.println("a0 " + ((a0.equals(b)) ? "=" : "!=") + " b");
HashMap<ByteArray, Integer> map = new HashMap<ByteArray, Integer>();
map.put(a0, 1);
//map.put(a1, 1);
map.put(b, 2);
System.out.println("map.size() = " + map.size());
System.out.println("hashCode(a0) = " + a0.hashCode());
System.out.println("UTF8.String(a0).hashCode = " + (UTF8.String(a0.asBytes())).hashCode());
System.out.println("hashCode(a1) = " + a1.hashCode());
System.out.println("UTF8.String(a1).hashCode = " + (UTF8.String(a1.asBytes())).hashCode());
System.out.println("hashCode(b) = " + b.hashCode());
System.out.println("a0 " + ((map.containsKey(a0)) ? "in" : "not in") + " map");
System.out.println("a1 " + ((map.containsKey(a1)) ? "in" : "not in") + " map");
System.out.println("b " + ((map.containsKey(b)) ? "in" : "not in") + " map");
System.out.println("parseIntDecimal " + parseDecimal("6543".getBytes()));
}
}
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