8376226: CharsetEncoder.canEncode(CharSequence) is much slower than necessary

Reviewed-by: alanb, naoto

src/java.base/share/classes/java/nio/charset/Charset-X-Coder.java.template

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, 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
@@ -819,6 +819,12 @@ public abstract class Charset$Coder$ {
      */
     public final $Otype$Buffer $code$($Itype$Buffer in)
         throws CharacterCodingException
+    {
+        return $code$(in, true);
+    }
+
+    private $Otype$Buffer $code$($Itype$Buffer in, boolean throwOnError)
+        throws CharacterCodingException
     {
         int n = Math.min((int)(in.remaining() * average$ItypesPerOtype$()),
                     ArraysSupport.SOFT_MAX_ARRAY_LENGTH);
@@ -844,7 +850,11 @@ public abstract class Charset$Coder$ {
                 out = o;
                 continue;
             }
-            cr.throwException();
+            if (throwOnError) {
+                cr.throwException();
+            } else {
+                return null;
+            }
         }
         out.flip();
         return out;
@@ -938,7 +948,8 @@ public abstract class Charset$Coder$ {
         try {
             onMalformedInput(CodingErrorAction.REPORT);
             onUnmappableCharacter(CodingErrorAction.REPORT);
-            encode(cb);
+            ByteBuffer bb = encode(cb, false);
+            return bb != null;
         } catch (CharacterCodingException x) {
             return false;
         } finally {
@@ -946,7 +957,6 @@ public abstract class Charset$Coder$ {
             onUnmappableCharacter(ua);
             reset();
         }
-        return true;
     }
 
     /**

src/java.base/share/classes/sun/nio/cs/DoubleByte.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2026, 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
@@ -583,6 +583,16 @@ public class DoubleByte {
             return encodeChar(c) != UNMAPPABLE_ENCODING;
         }
 
+        public boolean canEncode(CharSequence cs) {
+            int length = cs.length();
+            for (int i = 0; i < length; i++) {
+                if (!canEncode(cs.charAt(i))) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
         protected Surrogate.Parser sgp() {
             if (sgp == null)
                 sgp = new Surrogate.Parser();

src/java.base/share/classes/sun/nio/cs/ISO_8859_1.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, 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
@@ -136,6 +136,16 @@ public class ISO_8859_1
             return c <= '\u00FF';
         }
 
+        public boolean canEncode(CharSequence cs) {
+            int length = cs.length();
+            for (int i = 0; i < length; i++) {
+                if (!canEncode(cs.charAt(i))) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
         public boolean isLegalReplacement(byte[] repl) {
             return true;  // we accept any byte value
         }

src/java.base/share/classes/sun/nio/cs/SingleByte.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2026, 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
@@ -201,6 +201,16 @@ public class SingleByte
             return encode(c) != UNMAPPABLE_ENCODING;
         }
 
+        public boolean canEncode(CharSequence cs) {
+            int length = cs.length();
+            for (int i = 0; i < length; i++) {
+                if (!canEncode(cs.charAt(i))) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
         public boolean isLegalReplacement(byte[] repl) {
             return ((repl.length == 1 && repl[0] == (byte)'?') ||
                     super.isLegalReplacement(repl));

src/java.base/share/classes/sun/nio/cs/US_ASCII.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, 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
@@ -139,6 +139,16 @@ public class US_ASCII
             return c < 0x80;
         }
 
+        public boolean canEncode(CharSequence cs) {
+            int length = cs.length();
+            for (int i = 0; i < length; i++) {
+                if (!canEncode(cs.charAt(i))) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
         public boolean isLegalReplacement(byte[] repl) {
             return (repl.length == 1 && repl[0] >= 0) ||
                    super.isLegalReplacement(repl);

test/micro/org/openjdk/bench/java/nio/CharsetCanEncode.java

@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2026, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package org.openjdk.bench.java.nio;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetEncoder;
+import java.util.concurrent.TimeUnit;
+
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
+@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Thread)
+@Fork(3)
+public class CharsetCanEncode {
+
+    private static final char ALEF_CHAR = '\u05d0';
+    private static final String ALEF_STRING = "\u05d0";
+
+    // sun.nio.cs.US_ASCII
+    private CharsetEncoder ascii = Charset.forName("US-ASCII").newEncoder();
+
+    // sun.nio.cs.ISO_8859_1
+    private CharsetEncoder iso88591 = Charset.forName("ISO-8859-1").newEncoder();
+
+    // sun.nio.cs.SingleByte
+    private CharsetEncoder iso88592 = Charset.forName("ISO-8859-2").newEncoder();
+
+    // sun.nio.cs.DoubleByte
+    private CharsetEncoder shiftjis = Charset.forName("Shift_JIS").newEncoder();
+
+    // sun.nio.cs.UTF_8
+    private CharsetEncoder utf8 = Charset.forName("UTF-8").newEncoder();
+
+    // sun.nio.cs.UTF_16LE
+    private CharsetEncoder utf16le = Charset.forName("UTF-16LE").newEncoder();
+
+    @Benchmark
+    public boolean asciiCanEncodeCharYes() {
+        return ascii.canEncode('D');
+    }
+
+    @Benchmark
+    public boolean asciiCanEncodeStringYes() {
+        return ascii.canEncode("D");
+    }
+
+    @Benchmark
+    public boolean asciiCanEncodeCharNo() {
+        return ascii.canEncode(ALEF_CHAR);
+    }
+
+    @Benchmark
+    public boolean asciiCanEncodeStringNo() {
+        return ascii.canEncode(ALEF_STRING);
+    }
+
+    @Benchmark
+    public boolean iso88591CanEncodeCharYes() {
+        return iso88591.canEncode('D');
+    }
+
+    @Benchmark
+    public boolean iso88591CanEncodeStringYes() {
+        return iso88591.canEncode("D");
+    }
+
+    @Benchmark
+    public boolean iso88591CanEncodeCharNo() {
+        return iso88591.canEncode(ALEF_CHAR);
+    }
+
+    @Benchmark
+    public boolean iso88591CanEncodeStringNo() {
+        return iso88591.canEncode(ALEF_STRING);
+    }
+
+    @Benchmark
+    public boolean iso88592CanEncodeCharYes() {
+        return iso88592.canEncode('D');
+    }
+
+    @Benchmark
+    public boolean iso88592CanEncodeStringYes() {
+        return iso88592.canEncode("D");
+    }
+
+    @Benchmark
+    public boolean iso88592CanEncodeCharNo() {
+        return iso88592.canEncode(ALEF_CHAR);
+    }
+
+    @Benchmark
+    public boolean iso88592CanEncodeStringNo() {
+        return iso88592.canEncode(ALEF_STRING);
+    }
+
+    @Benchmark
+    public boolean shiftjisCanEncodeCharYes() {
+        return shiftjis.canEncode('D');
+    }
+
+    @Benchmark
+    public boolean shiftjisCanEncodeStringYes() {
+        return shiftjis.canEncode("D");
+    }
+
+    @Benchmark
+    public boolean shiftjisCanEncodeCharNo() {
+        return shiftjis.canEncode(ALEF_CHAR);
+    }
+
+    @Benchmark
+    public boolean shiftjisCanEncodeStringNo() {
+        return shiftjis.canEncode(ALEF_STRING);
+    }
+
+    @Benchmark
+    public boolean utf8CanEncodeCharYes() {
+        return utf8.canEncode('D');
+    }
+
+    @Benchmark
+    public boolean utf8CanEncodeStringYes() {
+        return utf8.canEncode("D");
+    }
+
+    @Benchmark
+    public boolean utf8CanEncodeCharNo() {
+        return utf8.canEncode(Character.MIN_SURROGATE);
+    }
+
+    @Benchmark
+    public boolean utf8CanEncodeStringNo() {
+        return utf8.canEncode(String.valueOf(Character.MIN_SURROGATE));
+    }
+
+    @Benchmark
+    public boolean utf16leCanEncodeCharYes() {
+        return utf16le.canEncode('D');
+    }
+
+    @Benchmark
+    public boolean utf16leCanEncodeStringYes() {
+        return utf16le.canEncode("D");
+    }
+
+    @Benchmark
+    public boolean utf16leCanEncodeCharNo() {
+        return utf16le.canEncode(Character.MIN_SURROGATE);
+    }
+
+    @Benchmark
+    public boolean utf16leCanEncodeStringNo() {
+        return utf16le.canEncode(String.valueOf(Character.MIN_SURROGATE));
+    }
+}