Add the CESU-8 encoding

Author: eregon

src/main/java/org/truffleruby/core/encoding/Encodings.java

@@ -12,7 +12,9 @@
  */
 package org.truffleruby.core.encoding;
 
+import com.oracle.truffle.api.CompilerDirectives;
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
+import com.oracle.truffle.api.strings.TruffleString;
 import org.jcodings.Encoding;
 import org.jcodings.EncodingDB;
 import org.jcodings.specific.ASCIIEncoding;
@@ -72,8 +74,11 @@ private static RubyEncoding[] initializeRubyEncodings() {
             if (encoding == USASCIIEncoding.INSTANCE) {
                 rubyEncoding = US_ASCII;
             } else {
-                final ImmutableRubyString name = FrozenStringLiterals.createStringAndCacheLater(
-                        TStringConstants.TSTRING_CONSTANTS.get(encoding.toString()), US_ASCII);
+                TruffleString tstring = TStringConstants.TSTRING_CONSTANTS.get(encoding.toString());
+                if (tstring == null) {
+                    throw CompilerDirectives.shouldNotReachHere("no TStringConstants for " + encoding);
+                }
+                final ImmutableRubyString name = FrozenStringLiterals.createStringAndCacheLater(tstring, US_ASCII);
                 rubyEncoding = new RubyEncoding(encoding, name, encoding.getIndex());
             }
             encodings[encoding.getIndex()] = rubyEncoding;

src/main/java/org/truffleruby/core/string/ImmutableRubyString.java

@@ -35,6 +35,8 @@
 import org.truffleruby.language.dispatch.DispatchNode;
 import org.truffleruby.language.library.RubyStringLibrary;
 
+import java.util.Objects;
+
 /** All ImmutableRubyString are interned and must be created through
  * {@link FrozenStringLiterals#getFrozenStringLiteral}. */
 @ExportLibrary(InteropLibrary.class)
@@ -47,8 +49,8 @@ public final class ImmutableRubyString extends ImmutableRubyObjectCopyable imple
     ImmutableRubyString(TruffleString tstring, RubyEncoding encoding) {
         assert tstring.isCompatibleToUncached(encoding.tencoding);
         assert tstring.isManaged();
-        this.tstring = tstring;
-        this.encoding = encoding;
+        this.tstring = Objects.requireNonNull(tstring);
+        this.encoding = Objects.requireNonNull(encoding);
     }
 
     /** should only be used for debugging */

src/main/java/org/truffleruby/core/string/TStringConstants.java

@@ -203,6 +203,8 @@ public class TStringConstants {
     public static final TruffleString STATELESS_ISO_2022_JP_KDDI = ascii("stateless-ISO-2022-JP-KDDI");
     public static final TruffleString UTF8_SOFTBANK = ascii("UTF8-SoftBank");
     public static final TruffleString SJIS_SOFTBANK = ascii("SJIS-SoftBank");
+    public static final TruffleString IBM720 = ascii("IBM720");
+    public static final TruffleString CESU_8 = ascii("CESU-8");
 
     private static TruffleString ascii(String string) {
         if (string.length() == 1) {