--- a/src/java.base/share/classes/java/lang/StringConcatHelper.java Tue Apr 16 21:29:33 2019 +0000
+++ b/src/java.base/share/classes/java/lang/StringConcatHelper.java Wed Apr 17 00:06:38 2019 +0200
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2019, 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
@@ -25,6 +25,9 @@
package java.lang;
+import jdk.internal.misc.Unsafe;
+import jdk.internal.vm.annotation.ForceInline;
+
/**
* Helper for string concatenation. These methods are mostly looked up with private lookups
* from {@link java.lang.invoke.StringConcatFactory}, and used in {@link java.lang.invoke.MethodHandle}
@@ -38,8 +41,10 @@
/**
* Check for overflow, throw exception on overflow.
- * @param lengthCoder String length and coder
- * @return lengthCoder
+ *
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @return the given parameter value, if valid
*/
private static long checkOverflow(long lengthCoder) {
if ((int)lengthCoder >= 0) {
@@ -50,76 +55,83 @@
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, boolean value) {
- return checkOverflow(current + (value ? 4 : 5));
+ static long mix(long lengthCoder, boolean value) {
+ return checkOverflow(lengthCoder + (value ? 4 : 5));
}
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, byte value) {
- return mix(current, (int)value);
+ static long mix(long lengthCoder, byte value) {
+ return mix(lengthCoder, (int)value);
}
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, char value) {
- return checkOverflow(current + 1) | (StringLatin1.canEncode(value) ? 0 : UTF16);
+ static long mix(long lengthCoder, char value) {
+ return checkOverflow(lengthCoder + 1) | (StringLatin1.canEncode(value) ? 0 : UTF16);
}
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, short value) {
- return mix(current, (int)value);
+ static long mix(long lengthCoder, short value) {
+ return mix(lengthCoder, (int)value);
}
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, int value) {
- return checkOverflow(current + Integer.stringSize(value));
+ static long mix(long lengthCoder, int value) {
+ return checkOverflow(lengthCoder + Integer.stringSize(value));
}
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, long value) {
- return checkOverflow(current + Long.stringSize(value));
+ static long mix(long lengthCoder, long value) {
+ return checkOverflow(lengthCoder + Long.stringSize(value));
}
/**
* Mix value length and coder into current length and coder.
- * @param current current length
- * @param value value to mix in
- * @return new length and coder
+ * @param lengthCoder String length with coder packed into higher bits
+ * the upper word.
+ * @param value value to mix in
+ * @return new length and coder
*/
- static long mix(long current, String value) {
- current += value.length();
+ static long mix(long lengthCoder, String value) {
+ lengthCoder += value.length();
if (value.coder() == String.UTF16) {
- current |= UTF16;
+ lengthCoder |= UTF16;
}
- return checkOverflow(current);
+ return checkOverflow(lengthCoder);
}
/**
@@ -285,10 +297,62 @@
}
}
+ /**
+ * Perform a simple concatenation between two objects. Added for startup
+ * performance, but also demonstrates the code that would be emitted by
+ * {@code java.lang.invoke.StringConcatFactory$MethodHandleInlineCopyStrategy}
+ * for two Object arguments.
+ *
+ * @param first first argument
+ * @param second second argument
+ * @return String resulting string
+ */
+ @ForceInline
+ static String simpleConcat(Object first, Object second) {
+ String s1 = stringOf(first);
+ String s2 = stringOf(second);
+ // start "mixing" in length and coder or arguments, order is not
+ // important
+ long indexCoder = mix(initialCoder(), s2);
+ indexCoder = mix(indexCoder, s1);
+ byte[] buf = newArray(indexCoder);
+ // prepend each argument in reverse order, since we prepending
+ // from the end of the byte array
+ indexCoder = prepend(indexCoder, buf, s2);
+ indexCoder = prepend(indexCoder, buf, s1);
+ return newString(buf, indexCoder);
+ }
+
+ /**
+ * We need some additional conversion for Objects in general, because
+ * {@code String.valueOf(Object)} may return null. String conversion rules
+ * in Java state we need to produce "null" String in this case, so we
+ * provide a customized version that deals with this problematic corner case.
+ */
+ static String stringOf(Object value) {
+ String s;
+ return (value == null || (s = value.toString()) == null) ? "null" : s;
+ }
+
private static final long LATIN1 = (long)String.LATIN1 << 32;
private static final long UTF16 = (long)String.UTF16 << 32;
+ private static final Unsafe UNSAFE = Unsafe.getUnsafe();
+
+ /**
+ * Allocates an uninitialized byte array based on the length and coder information
+ * in indexCoder
+ * @param indexCoder
+ * @return the newly allocated byte array
+ */
+ @ForceInline
+ static byte[] newArray(long indexCoder) {
+ byte coder = (byte)(indexCoder >> 32);
+ int index = (int)indexCoder;
+ return (byte[]) UNSAFE.allocateUninitializedArray(byte.class, index << coder);
+ }
+
/**
* Provides the initial coder for the String.
* @return initial coder, adjusted into the upper half