On Thu, 31 Aug 2023 11:39:57 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> 温绍锦 has updated the pull request incrementally with one additional commit
>> since the last revision:
>>
>> add method CharacterDataLatin1#isLowerCaseEx
>
> src/java.base/share/classes/java/lang/CharacterDataLatin1.java.template line
> 94:
>
>> 92:
>> 93: boolean isLowerCaseEx(int ch) {
>> 94: return ch >= 'a' && (ch <= 'z' || ch == 181 || (ch >= 223 && ch
>> != 247));
>
> What is the contract for this? Specifically there are two special
> superscripte codepoints (170 and 186) which are lower-case
> (`Character.isLowerCase(170) => true`) but doesn't have an upper-case
> (`Character.toUpperCase(170) => 170`). It seems reasonable to exclude them if
> only used for operations like toUpper/toLower (since they won't change), but
> it should be spelled out to avoid surprises.
>
> For consistency I think we should use hex literals in this file, e.g. `0xDF`
> instead of `223`
The current implementation of the isLowerCaseEx method and the previous
implementation "cp != CharacterDataLatin1.instance.toUpperCaseEx(cp)"
The result is exactly the same.
The code below compares all numbers in [-128, 128]
import sun.misc.Unsafe;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Field;
import java.nio.charset.StandardCharsets;
import static com.alibaba.fastjson2.util.JDKUtils.UNSAFE;
public class CharacterDataLatin1Test {
public static void main(String[] args) throws Throwable {
for (int i = Byte.MIN_VALUE; i <= Byte.MAX_VALUE; ++i) {
byte b = (byte) i;
int cp = b & 0xff;
boolean r0 = cp != toUpperCaseEx(cp);
boolean r1 = isLowerCaseEx(cp);
if (r0) {
System.out.println(cp + "\t0x" + Integer.toHexString(cp)
+ "\t" + new String(new byte[] {b},
StandardCharsets.ISO_8859_1));
}
if (r0 != r1) {
System.out.println("error " + i);
}
}
}
static boolean isLowerCaseEx(int ch) {
return ch >= 'a' && (ch <= 'z' || ch == 0xb5 || (ch >= 0xdf && ch !=
0xf7));
}
static int toUpperCaseEx(int cp) throws Throwable {
Field theUnsafeField = Unsafe.class.getDeclaredField("theUnsafe");
theUnsafeField.setAccessible(true);
Unsafe unsafe = (Unsafe) theUnsafeField.get(null);
Class<?> charbinClass = Class.forName("java.lang.CharacterDataLatin1");
Field field = charbinClass.getDeclaredField("instance");
long fieldOffset = unsafe.staticFieldOffset(field);
Object instance = unsafe.getObject(charbinClass, fieldOffset);
Class lookupClass = MethodHandles.Lookup.class;
Field implLookup = lookupClass.getDeclaredField("IMPL_LOOKUP");
MethodHandles.Lookup trustedLookup = (MethodHandles.Lookup)
unsafe.getObject(lookupClass,
UNSAFE.staticFieldOffset(implLookup));
MethodHandles.lookup();
MethodHandle toLowerCase = trustedLookup
.findVirtual(charbinClass, "toUpperCaseEx",
MethodType.methodType(int.class, int.class));
return (Integer) toLowerCase.invoke(instance, cp);
}
}
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14751#discussion_r1313453795
