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PlatformDependent String char[] optimization

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Motivation:
PlatformDependent0 has an optimization which grabs the char[] from a String. Since this code was introduced http://openjdk.java.net/jeps/254 has been gaining momentum in JDK 9. This JEP changes the internal storage from char[] to byte[], and thus the existing char[] only based optimizations will not work.

Modifications:
- The ASCII encoding char[] String optimizations should also work for byte[].

Result:
ASCII encoding char[] String optimizations don't break if the underlying storage in String is byte[].
This commit is contained in:
Scott Mitchell 2016-01-19 15:47:50 -08:00
parent d4a1665941
commit ca305d86fb
2 changed files with 51 additions and 11 deletions
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10
common/src/main/java/io/netty/util/internal/PlatformDependent.java
View File

@ -541,12 +541,14 @@ public final class PlatformDependent {
* The resulting hash code will be case insensitive.
*/
public static int hashCodeAscii(CharSequence bytes) {
char[] array;
if (!hasUnsafe() || !PlatformDependent0.unalignedAccess() ||
(array = PlatformDependent0.array(bytes)) == null) {
if (!hasUnsafe() || !PlatformDependent0.unalignedAccess()) {
return hashCodeAsciiSafe(bytes);
} else if (PlatformDependent0.hasCharArray(bytes)) {
return PlatformDependent0.hashCodeAscii(PlatformDependent0.charArray(bytes));
} else if (PlatformDependent0.hasByteArray(bytes)) {
return PlatformDependent0.hashCodeAscii(PlatformDependent0.byteArray(bytes));
}
return PlatformDependent0.hashCodeAscii(array);
return hashCodeAsciiSafe(bytes);
}
/**

52
common/src/main/java/io/netty/util/internal/PlatformDependent0.java
View File

@ -42,7 +42,8 @@ final class PlatformDependent0 {
private static final long BYTE_ARRAY_BASE_OFFSET;
private static final long CHAR_ARRAY_BASE_OFFSET;
private static final long CHAR_ARRAY_INDEX_SCALE;
private static final long STRING_VALUE_FIELD_OFFSET;
private static final long STRING_CHAR_VALUE_FIELD_OFFSET;
private static final long STRING_BYTE_VALUE_FIELD_OFFSET;
static final int HASH_CODE_ASCII_SEED = 0xc2b2ae35; // constant borrowed from murmur3
/**
@ -114,7 +115,7 @@ final class PlatformDependent0 {
ADDRESS_FIELD_OFFSET = -1;
BYTE_ARRAY_BASE_OFFSET = CHAR_ARRAY_BASE_OFFSET = CHAR_ARRAY_INDEX_SCALE = -1;
UNALIGNED = false;
STRING_VALUE_FIELD_OFFSET = -1;
STRING_CHAR_VALUE_FIELD_OFFSET = STRING_BYTE_VALUE_FIELD_OFFSET = -1;
} else {
ADDRESS_FIELD_OFFSET = objectFieldOffset(addressField);
BYTE_ARRAY_BASE_OFFSET = UNSAFE.arrayBaseOffset(byte[].class);
@ -159,8 +160,24 @@ final class PlatformDependent0 {
logger.debug("AccessController.doPrivileged failed to get String value array." +
"String hash code optimizations are disabled.", t);
}
STRING_VALUE_FIELD_OFFSET = stringValueField == null ?
-1 : UNSAFE.objectFieldOffset(stringValueField);
if (stringValueField == null) {
STRING_CHAR_VALUE_FIELD_OFFSET = STRING_BYTE_VALUE_FIELD_OFFSET = -1;
} else {
long stringValueFieldOffset = UNSAFE.objectFieldOffset(stringValueField);
Object o = UNSAFE.getObject("", stringValueFieldOffset);
if (char[].class.isInstance(o)) {
STRING_CHAR_VALUE_FIELD_OFFSET = stringValueFieldOffset;
STRING_BYTE_VALUE_FIELD_OFFSET = -1;
} else if (byte[].class.isInstance(o)) {
STRING_CHAR_VALUE_FIELD_OFFSET = -1;
STRING_BYTE_VALUE_FIELD_OFFSET = stringValueFieldOffset;
} else {
STRING_CHAR_VALUE_FIELD_OFFSET = STRING_BYTE_VALUE_FIELD_OFFSET = -1;
logger.info("Unexpected type [" + o.getClass() + "] for String value array." +
"String hash code optimizations are disabled.");
}
}
}
}
@ -343,6 +360,10 @@ final class PlatformDependent0 {
}
}
static int hashCodeAscii(byte[] bytes) {
return hashCodeAscii(bytes, 0, bytes.length);
}
/**
* This must remain consistent with {@link #hashCodeAscii(char[])}.
*/
@ -433,9 +454,26 @@ final class PlatformDependent0 {
}
}
static char[] array(CharSequence data) {
return (STRING_VALUE_FIELD_OFFSET != -1 && data.getClass() == String.class) ?
(char[]) UNSAFE.getObject(data, STRING_VALUE_FIELD_OFFSET) : null;
static boolean hasCharArray(CharSequence data) {
return STRING_CHAR_VALUE_FIELD_OFFSET != -1 && data.getClass() == String.class;
}
static boolean hasByteArray(CharSequence data) {
return STRING_BYTE_VALUE_FIELD_OFFSET != -1 && data.getClass() == String.class;
}
/**
* Callers are expected to call {@link #hasCharArray(CharSequence)} before calling this method.
*/
static char[] charArray(CharSequence data) {
return (char[]) UNSAFE.getObject(data, STRING_CHAR_VALUE_FIELD_OFFSET);
}
/**
* Callers are expected to call {@link #hasByteArray(CharSequence)} before calling this method.
*/
static byte[] byteArray(CharSequence data) {
return (byte[]) UNSAFE.getObject(data, STRING_BYTE_VALUE_FIELD_OFFSET);
}
static int hashCodeAsciiCompute(long value, int hash) {