1 /*
   2  * Copyright (c) 2015, 2015, 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 package org.graalvm.compiler.core.common.util;
  24 
  25 /**
  26  * Provides low-level read access for signed and unsigned values of size 1, 2, 4, and 8 bytes.
  27  */
  28 public interface TypeReader {
  29 
  30     /** Returns the next byte index to be read. */
  31     long getByteIndex();
  32 
  33     /** Sets the next byte index to be read. */
  34     void setByteIndex(long byteIndex);
  35 
  36     /** Reads a signed 1 byte value. */
  37     int getS1();
  38 
  39     /** Reads an unsigned 1 byte value. */
  40     int getU1();
  41 
  42     /** Reads a signed 2 byte value. */
  43     int getS2();
  44 
  45     /** Reads an unsigned 2 byte value. */
  46     int getU2();
  47 
  48     /** Reads a signed 4 byte value. */
  49     int getS4();
  50 
  51     /** Reads an unsigned 4 byte value. */
  52     long getU4();
  53 
  54     /** Reads a signed 4 byte value. */
  55     long getS8();
  56 
  57     /**
  58      * Reads a signed value that has been written using {@link TypeWriter#putSV variable byte size
  59      * encoding}.
  60      */
  61     default long getSV() {
  62         long result = 0;
  63         int shift = 0;
  64         long b;
  65         do {
  66             b = getU1();
  67             result |= (b & 0x7f) << shift;
  68             shift += 7;
  69         } while ((b & 0x80) != 0);
  70 
  71         if ((b & 0x40) != 0 && shift < 64) {
  72             result |= -1L << shift;
  73         }
  74         return result;
  75     }
  76 
  77     /**
  78      * Reads a signed variable byte size encoded value that is known to fit into the range of int.
  79      */
  80     default int getSVInt() {
  81         return TypeConversion.asS4(getSV());
  82     }
  83 
  84     /**
  85      * Reads an unsigned value that has been written using {@link TypeWriter#putSV variable byte
  86      * size encoding}.
  87      */
  88     default long getUV() {
  89         long result = 0;
  90         int shift = 0;
  91         long b;
  92         do {
  93             b = getU1();
  94             result |= (b & 0x7f) << shift;
  95             shift += 7;
  96         } while ((b & 0x80) != 0);
  97 
  98         return result;
  99     }
 100 
 101     /**
 102      * Reads an unsigned variable byte size encoded value that is known to fit into the range of
 103      * int.
 104      */
 105     default int getUVInt() {
 106         return TypeConversion.asS4(getUV());
 107     }
 108 }