1 /*
   2  * Copyright (c) 2009, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 
  25 package org.graalvm.compiler.bytecode;
  26 
  27 /**
  28  * A collection of utility methods for dealing with bytes, particularly in byte arrays.
  29  */
  30 public class Bytes {
  31 
  32     /**
  33      * Gets a signed 1-byte value.
  34      *
  35      * @param data the array containing the data
  36      * @param bci the start index of the value to retrieve
  37      * @return the signed 1-byte value at index {@code bci} in array {@code data}
  38      */
  39     public static int beS1(byte[] data, int bci) {
  40         return data[bci];
  41     }
  42 
  43     /**
  44      * Gets a signed 2-byte big-endian value.
  45      *
  46      * @param data the array containing the data
  47      * @param bci the start index of the value to retrieve
  48      * @return the signed 2-byte, big-endian, value at index {@code bci} in array {@code data}
  49      */
  50     public static int beS2(byte[] data, int bci) {
  51         return (data[bci] << 8) | (data[bci + 1] & 0xff);
  52     }
  53 
  54     /**
  55      * Gets an unsigned 1-byte value.
  56      *
  57      * @param data the array containing the data
  58      * @param bci the start index of the value to retrieve
  59      * @return the unsigned 1-byte value at index {@code bci} in array {@code data}
  60      */
  61     public static int beU1(byte[] data, int bci) {
  62         return data[bci] & 0xff;
  63     }
  64 
  65     /**
  66      * Gets an unsigned 2-byte big-endian value.
  67      *
  68      * @param data the array containing the data
  69      * @param bci the start index of the value to retrieve
  70      * @return the unsigned 2-byte, big-endian, value at index {@code bci} in array {@code data}
  71      */
  72     public static int beU2(byte[] data, int bci) {
  73         return ((data[bci] & 0xff) << 8) | (data[bci + 1] & 0xff);
  74     }
  75 
  76     /**
  77      * Gets a signed 4-byte big-endian value.
  78      *
  79      * @param data the array containing the data
  80      * @param bci the start index of the value to retrieve
  81      * @return the signed 4-byte, big-endian, value at index {@code bci} in array {@code data}
  82      */
  83     public static int beS4(byte[] data, int bci) {
  84         return (data[bci] << 24) | ((data[bci + 1] & 0xff) << 16) | ((data[bci + 2] & 0xff) << 8) | (data[bci + 3] & 0xff);
  85     }
  86 
  87     /**
  88      * Gets either a signed 2-byte or a signed 4-byte big-endian value.
  89      *
  90      * @param data the array containing the data
  91      * @param bci the start index of the value to retrieve
  92      * @param fourByte if true, this method will return a 4-byte value
  93      * @return the signed 2 or 4-byte, big-endian, value at index {@code bci} in array {@code data}
  94      */
  95     public static int beSVar(byte[] data, int bci, boolean fourByte) {
  96         if (fourByte) {
  97             return beS4(data, bci);
  98         } else {
  99             return beS2(data, bci);
 100         }
 101     }
 102 }