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8299576: Reimplement java.io.Bits using VarHandle access

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Reviewed-by: uschindler, alanb
This commit is contained in:
Per Minborg 2023-01-17 07:44:26 +00:00
parent f829a67935
commit 3462438ae1
3 changed files with 443 additions and 39 deletions
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75
src/java.base/share/classes/java/io/Bits.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2001, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -25,11 +25,20 @@
package java.io;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.nio.ByteOrder;
/**
* Utility methods for packing/unpacking primitive values in/out of byte arrays
* using big-endian byte ordering.
* using big-endian byte ordering (i.e. "Network Order").
*/
class Bits {
final class Bits {
private Bits() {}
private static final VarHandle SHORT = create(short[].class);
private static final VarHandle INT = create(int[].class);
private static final VarHandle LONG = create(long[].class);
/*
* Methods for unpacking primitive values from byte arrays starting at
@ -41,39 +50,31 @@ class Bits {
}
static char getChar(byte[] b, int off) {
return (char) ((b[off + 1] & 0xFF) +
(b[off] << 8));
return (char) (short) SHORT.get(b, off);
}
static short getShort(byte[] b, int off) {
return (short) ((b[off + 1] & 0xFF) +
(b[off] << 8));
return (short) SHORT.get(b, off);
}
static int getInt(byte[] b, int off) {
return ((b[off + 3] & 0xFF) ) +
((b[off + 2] & 0xFF) << 8) +
((b[off + 1] & 0xFF) << 16) +
((b[off ] ) << 24);
return (int) INT.get(b, off);
}
static float getFloat(byte[] b, int off) {
return Float.intBitsToFloat(getInt(b, off));
// Using Float.intBitsToFloat collapses NaN values to a single
// "canonical" NaN value
return Float.intBitsToFloat((int) INT.get(b, off));
}
static long getLong(byte[] b, int off) {
return ((b[off + 7] & 0xFFL) ) +
((b[off + 6] & 0xFFL) << 8) +
((b[off + 5] & 0xFFL) << 16) +
((b[off + 4] & 0xFFL) << 24) +
((b[off + 3] & 0xFFL) << 32) +
((b[off + 2] & 0xFFL) << 40) +
((b[off + 1] & 0xFFL) << 48) +
(((long) b[off]) << 56);
return (long) LONG.get(b, off);
}
static double getDouble(byte[] b, int off) {
return Double.longBitsToDouble(getLong(b, off));
// Using Double.longBitsToDouble collapses NaN values to a single
// "canonical" NaN value
return Double.longBitsToDouble((long) LONG.get(b, off));
}
/*
@ -86,38 +87,34 @@ class Bits {
}
static void putChar(byte[] b, int off, char val) {
b[off + 1] = (byte) (val );
b[off ] = (byte) (val >>> 8);
SHORT.set(b, off, (short) val);
}
static void putShort(byte[] b, int off, short val) {
b[off + 1] = (byte) (val );
b[off ] = (byte) (val >>> 8);
SHORT.set(b, off, val);
}
static void putInt(byte[] b, int off, int val) {
b[off + 3] = (byte) (val );
b[off + 2] = (byte) (val >>> 8);
b[off + 1] = (byte) (val >>> 16);
b[off ] = (byte) (val >>> 24);
INT.set(b, off, val);
}
static void putFloat(byte[] b, int off, float val) {
putInt(b, off, Float.floatToIntBits(val));
// Using Float.floatToIntBits collapses NaN values to a single
// "canonical" NaN value
INT.set(b, off, Float.floatToIntBits(val));
}
static void putLong(byte[] b, int off, long val) {
b[off + 7] = (byte) (val );
b[off + 6] = (byte) (val >>> 8);
b[off + 5] = (byte) (val >>> 16);
b[off + 4] = (byte) (val >>> 24);
b[off + 3] = (byte) (val >>> 32);
b[off + 2] = (byte) (val >>> 40);
b[off + 1] = (byte) (val >>> 48);
b[off ] = (byte) (val >>> 56);
LONG.set(b, off, val);
}
static void putDouble(byte[] b, int off, double val) {
putLong(b, off, Double.doubleToLongBits(val));
// Using Double.doubleToLongBits collapses NaN values to a single
// "canonical" NaN value
LONG.set(b, off, Double.doubleToLongBits(val));
}
private static VarHandle create(Class<?> viewArrayClass) {
return MethodHandles.byteArrayViewVarHandle(viewArrayClass, ByteOrder.BIG_ENDIAN);
}
}