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      1 /*
      2  *  Licensed to the Apache Software Foundation (ASF) under one or more
      3  *  contributor license agreements.  See the NOTICE file distributed with
      4  *  this work for additional information regarding copyright ownership.
      5  *  The ASF licenses this file to You under the Apache License, Version 2.0
      6  *  (the "License"); you may not use this file except in compliance with
      7  *  the License.  You may obtain a copy of the License at
      8  *
      9  *     http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  *  Unless required by applicable law or agreed to in writing, software
     12  *  distributed under the License is distributed on an "AS IS" BASIS,
     13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  *  See the License for the specific language governing permissions and
     15  *  limitations under the License.
     16  */
     17 
     18 package com.google.common.primitives;
     19 
     20 import static com.google.common.base.Preconditions.checkArgument;
     21 import static com.google.common.base.Preconditions.checkNotNull;
     22 
     23 import javax.annotation.CheckForNull;
     24 
     25 /**
     26  * Static utility methods derived from Android's {@code Integer.java}.
     27  */
     28 final class AndroidInteger {
     29   /**
     30    * See {@link Ints#tryParse(String)} for the public interface.
     31    */
     32   @CheckForNull
     33   static Integer tryParse(String string) {
     34     return tryParse(string, 10);
     35   }
     36 
     37   /**
     38    * See {@link Ints#tryParse(String, int)} for the public interface.
     39    */
     40   @CheckForNull
     41   static Integer tryParse(String string, int radix) {
     42     checkNotNull(string);
     43     checkArgument(radix >= Character.MIN_RADIX,
     44         "Invalid radix %s, min radix is %s", radix, Character.MIN_RADIX);
     45     checkArgument(radix <= Character.MAX_RADIX,
     46         "Invalid radix %s, max radix is %s", radix, Character.MAX_RADIX);
     47     int length = string.length(), i = 0;
     48     if (length == 0) {
     49       return null;
     50     }
     51     boolean negative = string.charAt(i) == '-';
     52     if (negative && ++i == length) {
     53       return null;
     54     }
     55     return tryParse(string, i, radix, negative);
     56   }
     57 
     58   @CheckForNull
     59   private static Integer tryParse(String string, int offset, int radix,
     60       boolean negative) {
     61     int max = Integer.MIN_VALUE / radix;
     62     int result = 0, length = string.length();
     63     while (offset < length) {
     64       int digit = Character.digit(string.charAt(offset++), radix);
     65       if (digit == -1) {
     66         return null;
     67       }
     68       if (max > result) {
     69         return null;
     70       }
     71       int next = result * radix - digit;
     72       if (next > result) {
     73         return null;
     74       }
     75       result = next;
     76     }
     77     if (!negative) {
     78       result = -result;
     79       if (result < 0) {
     80         return null;
     81       }
     82     }
     83     // For GWT where ints do not overflow
     84     if (result > Integer.MAX_VALUE || result < Integer.MIN_VALUE) {
     85       return null;
     86     }
     87     return result;
     88   }
     89 
     90   private AndroidInteger() {}
     91 }
     92