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 import static org.graalvm.compiler.core.common.util.TypeConversion.asS1; 26 import static org.graalvm.compiler.core.common.util.TypeConversion.asS2; 27 import static org.graalvm.compiler.core.common.util.TypeConversion.asS4; 28 import static org.graalvm.compiler.core.common.util.TypeConversion.asU1; 29 import static org.graalvm.compiler.core.common.util.TypeConversion.asU2; 30 import static org.graalvm.compiler.core.common.util.TypeConversion.asU4; 31 import sun.misc.Unsafe; 32 33 /** 34 * Provides low-level sequential write access to a byte[] array for signed and unsigned values of 35 * size 1, 2, 4, and 8 bytes. To avoid copying an array when the buffer size is no longer 36 * sufficient, the buffer is split into chunks of a fixed size. 37 * 38 * The flag {@code supportsUnalignedMemoryAccess} must be set according to the capabilities of the 39 * hardware architecture: the value {@code true} allows more efficient memory access on 40 * architectures that support unaligned memory accesses; the value {@code false} is the safe 41 * fallback that works on every hardware. 42 */ 43 public abstract class UnsafeArrayTypeWriter implements TypeWriter { 44 45 private static final int MIN_CHUNK_LENGTH = 200; 46 private static final int MAX_CHUNK_LENGTH = 16000; 47 48 static class Chunk { 49 protected final byte[] data; 50 protected int size; 51 protected Chunk next; 52 53 protected Chunk(int arrayLength) { 54 data = new byte[arrayLength]; 55 } 56 } 57 58 protected final Chunk firstChunk; 59 protected Chunk writeChunk; 60 protected int totalSize; 61 62 public static UnsafeArrayTypeWriter create(boolean supportsUnalignedMemoryAccess) { 63 if (supportsUnalignedMemoryAccess) { 64 return new UnalignedUnsafeArrayTypeWriter(); 65 } else { 66 return new AlignedUnsafeArrayTypeWriter(); 67 } 68 } 69 70 protected UnsafeArrayTypeWriter() { 71 firstChunk = new Chunk(MIN_CHUNK_LENGTH); 72 writeChunk = firstChunk; 73 } 74 75 @Override 76 public final long getBytesWritten() { 77 return totalSize; 78 } 79 80 /** 81 * Copies the buffer into the provided byte[] array of length {@link #getBytesWritten()}. 82 */ 83 public final byte[] toArray(byte[] result) { 84 assert result.length == totalSize; 85 int resultIdx = 0; 86 for (Chunk cur = firstChunk; cur != null; cur = cur.next) { 87 System.arraycopy(cur.data, 0, result, resultIdx, cur.size); 88 resultIdx += cur.size; 89 } 90 assert resultIdx == totalSize; 91 return result; 92 } 93 94 @Override 95 public final void putS1(long value) { 96 long offset = writeOffset(Byte.BYTES); 97 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset, asS1(value)); 98 } 99 100 @Override 101 public final void putU1(long value) { 102 long offset = writeOffset(Byte.BYTES); 103 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset, asU1(value)); 104 } 105 106 @Override 107 public final void putU2(long value) { 108 putS2(asU2(value)); 109 } 110 111 @Override 112 public final void putU4(long value) { 113 putS4(asU4(value)); 114 } 115 116 protected long writeOffset(int writeBytes) { 117 if (writeChunk.size + writeBytes >= writeChunk.data.length) { 118 Chunk newChunk = new Chunk(Math.min(writeChunk.data.length * 2, MAX_CHUNK_LENGTH)); 119 writeChunk.next = newChunk; 120 writeChunk = newChunk; 121 } 122 123 assert Unsafe.ARRAY_BYTE_INDEX_SCALE == 1; 124 long result = writeChunk.size + Unsafe.ARRAY_BYTE_BASE_OFFSET; 125 126 totalSize += writeBytes; 127 writeChunk.size += writeBytes; 128 assert writeChunk.size <= writeChunk.data.length; 129 130 return result; 131 } 132 } 133 134 final class UnalignedUnsafeArrayTypeWriter extends UnsafeArrayTypeWriter { 135 @Override 136 public void putS2(long value) { 137 long offset = writeOffset(Short.BYTES); 138 UnsafeAccess.UNSAFE.putShort(writeChunk.data, offset, asS2(value)); 139 } 140 141 @Override 142 public void putS4(long value) { 143 long offset = writeOffset(Integer.BYTES); 144 UnsafeAccess.UNSAFE.putInt(writeChunk.data, offset, asS4(value)); 145 } 146 147 @Override 148 public void putS8(long value) { 149 long offset = writeOffset(Long.BYTES); 150 UnsafeAccess.UNSAFE.putLong(writeChunk.data, offset, value); 151 } 152 } 153 154 final class AlignedUnsafeArrayTypeWriter extends UnsafeArrayTypeWriter { 155 @Override 156 public void putS2(long value) { 157 long offset = writeOffset(Short.BYTES); 158 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 0, (byte) (value >> 0)); 159 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 1, (byte) (value >> 8)); 160 } 161 162 @Override 163 public void putS4(long value) { 164 long offset = writeOffset(Integer.BYTES); 165 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 0, (byte) (value >> 0)); 166 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 1, (byte) (value >> 8)); 167 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 2, (byte) (value >> 16)); 168 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 3, (byte) (value >> 24)); 169 } 170 171 @Override 172 public void putS8(long value) { 173 long offset = writeOffset(Long.BYTES); 174 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 0, (byte) (value >> 0)); 175 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 1, (byte) (value >> 8)); 176 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 2, (byte) (value >> 16)); 177 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 3, (byte) (value >> 24)); 178 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 4, (byte) (value >> 32)); 179 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 5, (byte) (value >> 40)); 180 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 6, (byte) (value >> 48)); 181 UnsafeAccess.UNSAFE.putByte(writeChunk.data, offset + 7, (byte) (value >> 56)); 182 } 183 }