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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.
*/
package org.apache.hadoop.hive.ql.udf;
import java.util.Arrays;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
/**
* UDFConv.
*
*/
@Description(name = "conv",
value = "_FUNC_(num, from_base, to_base) - convert num from from_base to"
+ " to_base",
extended = "If to_base is negative, treat num as a signed integer,"
+ "otherwise, treat it as an unsigned integer.\n"
+ "Example:\n"
+ " > SELECT _FUNC_('100', 2, 10) FROM src LIMIT 1;\n"
+ " '4'\n"
+ " > SELECT _FUNC_(-10, 16, -10) FROM src LIMIT 1;\n" + " '16'")
public class UDFConv extends UDF {
private final Text result = new Text();
private final byte[] value = new byte[64];
/**
* Divide x by m as if x is an unsigned 64-bit integer. Examples:
* unsignedLongDiv(-1, 2) == Long.MAX_VALUE unsignedLongDiv(6, 3) == 2
* unsignedLongDiv(0, 5) == 0
*
* @param x
* is treated as unsigned
* @param m
* is treated as signed
*/
private long unsignedLongDiv(long x, int m) {
if (x >= 0) {
return x / m;
}
// Let uval be the value of the unsigned long with the same bits as x
// Two's complement => x = uval - 2*MAX - 2
// => uval = x + 2*MAX + 2
// Now, use the fact: (a+b)/c = a/c + b/c + (a%c+b%c)/c
return x / m + 2 * (Long.MAX_VALUE / m) + 2 / m
+ (x % m + 2 * (Long.MAX_VALUE % m) + 2 % m) / m;
}
/**
* Decode val into value[].
*
* @param val
* is treated as an unsigned 64-bit integer
* @param radix
* must be between MIN_RADIX and MAX_RADIX
*/
private void decode(long val, int radix) {
Arrays.fill(value, (byte) 0);
for (int i = value.length - 1; val != 0; i--) {
long q = unsignedLongDiv(val, radix);
value[i] = (byte) (val - q * radix);
val = q;
}
}
/**
* Convert value[] into a long. On overflow, return -1 (as mySQL does). If a
* negative digit is found, ignore the suffix starting there.
*
* @param radix
* must be between MIN_RADIX and MAX_RADIX
* @param fromPos
* is the first element that should be conisdered
* @return the result should be treated as an unsigned 64-bit integer.
*/
private long encode(int radix, int fromPos) {
long val = 0;
long bound = unsignedLongDiv(-1 - radix, radix); // Possible overflow once
// val
// exceeds this value
for (int i = fromPos; i < value.length && value[i] >= 0; i++) {
if (val >= bound) {
// Check for overflow
if (unsignedLongDiv(-1 - value[i], radix) < val) {
return -1;
}
}
val = val * radix + value[i];
}
return val;
}
/**
* Convert the bytes in value[] to the corresponding chars.
*
* @param radix
* must be between MIN_RADIX and MAX_RADIX
* @param fromPos
* is the first nonzero element
*/
private void byte2char(int radix, int fromPos) {
for (int i = fromPos; i < value.length; i++) {
value[i] = (byte) Character.toUpperCase(Character.forDigit(value[i],
radix));
}
}
/**
* Convert the chars in value[] to the corresponding integers. Convert invalid
* characters to -1.
*
* @param radix
* must be between MIN_RADIX and MAX_RADIX
* @param fromPos
* is the first nonzero element
*/
private void char2byte(int radix, int fromPos) {
for (int i = fromPos; i < value.length; i++) {
value[i] = (byte) Character.digit(value[i], radix);
}
}
/**
* Convert numbers between different number bases. If toBase>0 the result is
* unsigned, otherwise it is signed.
*
*/
public Text evaluate(Text n, IntWritable fromBase, IntWritable toBase) {
if (n == null || fromBase == null || toBase == null) {
return null;
}
int fromBs = fromBase.get();
int toBs = toBase.get();
if (fromBs < Character.MIN_RADIX || fromBs > Character.MAX_RADIX
|| Math.abs(toBs) < Character.MIN_RADIX
|| Math.abs(toBs) > Character.MAX_RADIX) {
return null;
}
byte[] num = n.getBytes();
boolean negative = (num[0] == '-');
int first = 0;
if (negative) {
first = 1;
}
// Copy the digits in the right side of the array
for (int i = 1; i <= n.getLength() - first; i++) {
value[value.length - i] = num[n.getLength() - i];
}
char2byte(fromBs, value.length - n.getLength() + first);
// Do the conversion by going through a 64 bit integer
long val = encode(fromBs, value.length - n.getLength() + first);
if (negative && toBs > 0) {
if (val < 0) {
val = -1;
} else {
val = -val;
}
}
if (toBs < 0 && val < 0) {
val = -val;
negative = true;
}
decode(val, Math.abs(toBs));
// Find the first non-zero digit or the last digits if all are zero.
for (first = 0; first < value.length - 1 && value[first] == 0; first++) {
;
}
byte2char(Math.abs(toBs), first);
if (negative && toBs < 0) {
value[--first] = '-';
}
result.set(value, first, value.length - first);
return result;
}
}
