4926314: Optimize Reader.read(CharBuffer)

src/java.base/share/classes/java/io/InputStreamReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2021, 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 +25,7 @@
 
 package java.io;
 
+import java.nio.CharBuffer;
 import java.nio.charset.Charset;
 import java.nio.charset.CharsetDecoder;
 import sun.nio.cs.StreamDecoder;
@@ -149,6 +150,10 @@ public String getEncoding() {
         return sd.getEncoding();
     }
 
+    public int read(CharBuffer target) throws IOException {
+        return sd.read(target);
+    }
+
     /**
      * Reads a single character.
      *

src/java.base/share/classes/java/io/Reader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2021, 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
@@ -184,12 +184,33 @@ protected Reader(Object lock) {
      * @since 1.5
      */
     public int read(CharBuffer target) throws IOException {
-        int len = target.remaining();
-        char[] cbuf = new char[len];
-        int n = read(cbuf, 0, len);
-        if (n > 0)
-            target.put(cbuf, 0, n);
-        return n;
+        int nread;
+        if (target.hasArray()) {
+            char cbuf[] = target.array();
+            int off = target.arrayOffset() + target.position();
+            int len = target.remaining();
+            nread = this.read(cbuf, off, len);
+            if (nread > 0)
+                target.position(target.position() + nread);
+        } else {
+            int remaining = target.remaining();
+            char cbuf[] = new char[Math.min(remaining, TRANSFER_BUFFER_SIZE)];
+            nread = 0;
+            synchronized (lock) {
+                int n;
+                do {
+                    // read to EOF which may read more or less than buffer size
+                    if ((n = read(cbuf, 0, Math.min(remaining, cbuf.length))) > 0) {
+                        target.put(cbuf, 0, n);
+                        nread += n;
+                        remaining -= n;
+                    }
+                    // if the last call to read returned -1 or the number of bytes
+                    // requested have been read then break
+                } while (n >= 0 && remaining > 0);
+            }
+        }
+        return nread;
     }
 
     /**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2021, 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
@@ -189,6 +189,30 @@ public int read(char cbuf[], int offset, int length) throws IOException {
         }
     }
 
+    public int read(CharBuffer target) throws IOException {
+        int len = target.remaining();
+        synchronized (lock) {
+            ensureOpen();
+            if (len == 0)
+                return 0;
+
+            int n = 0;
+
+            if (haveLeftoverChar) {
+                // Copy the leftover char into the buffer
+                target.put(leftoverChar);
+                len--;
+                haveLeftoverChar = false;
+                n = 1;
+                if ((len == 0) || !implReady())
+                    // Return now if this is all we can produce w/o blocking
+                    return n;
+            }
+
+            return n + implRead(target);
+        }
+    }
+
     public boolean ready() throws IOException {
         synchronized (lock) {
             ensureOpen();
@@ -322,47 +346,57 @@ int implRead(char[] cbuf, int off, int end) throws IOException {
         assert (end - off > 1);
 
         CharBuffer cb = CharBuffer.wrap(cbuf, off, end - off);
-        if (cb.position() != 0)
-        // Ensure that cb[0] == cbuf[off]
-        cb = cb.slice();
+
+        return implRead(cb);
+    }
+
+    int implRead(CharBuffer cb) throws IOException {
+
+        // In order to handle surrogate pairs, this method requires that
+        // the invoker attempt to read at least two characters.  Saving the
+        // extra character, if any, at a higher level is easier than trying
+        // to deal with it here.
 
         boolean eof = false;
+        int initialPosition = cb.position();
+        int nread;
         for (;;) {
-        CoderResult cr = decoder.decode(bb, cb, eof);
-        if (cr.isUnderflow()) {
-            if (eof)
-                break;
-            if (!cb.hasRemaining())
-                break;
-            if ((cb.position() > 0) && !inReady())
-                break;          // Block at most once
-            int n = readBytes();
-            if (n < 0) {
-                eof = true;
-                if ((cb.position() == 0) && (!bb.hasRemaining()))
+            CoderResult cr = decoder.decode(bb, cb, eof);
+            nread = cb.position() - initialPosition;
+            if (cr.isUnderflow()) {
+                if (eof)
+                    break;
+                if (!cb.hasRemaining())
                     break;
-                decoder.reset();
+                if ((nread > 0) && !inReady())
+                    break;          // Block at most once
+                int n = readBytes();
+                if (n < 0) {
+                    eof = true;
+                    if ((nread == 0) && (!bb.hasRemaining()))
+                        break;
+                    decoder.reset();
+                }
+                continue;
             }
-            continue;
-        }
-        if (cr.isOverflow()) {
-            assert cb.position() > 0;
-            break;
-        }
-        cr.throwException();
+            if (cr.isOverflow()) {
+                assert nread > 0;
+                break;
+            }
+            cr.throwException();
         }
 
         if (eof) {
-        // ## Need to flush decoder
-        decoder.reset();
+            // ## Need to flush decoder
+            decoder.reset();
         }
 
-        if (cb.position() == 0) {
+        if (nread == 0) {
             if (eof)
                 return -1;
             assert false;
         }
-        return cb.position();
+        return nread;
     }
 
     String encodingName() {

test/jdk/java/io/InputStreamReader/ReadCharBuffer.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2021, 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.
+ */
+
+/*
+ * @test
+ * @bug 4926314
+ * @summary Test for InputStreamReader#read(CharBuffer).
+ * @run testng ReadCharBuffer
+ */
+
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+import java.io.*;
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.util.Arrays;
+
+import static java.nio.charset.StandardCharsets.US_ASCII;
+import static org.testng.Assert.assertEquals;
+
+public class ReadCharBuffer {
+
+    private static final int BUFFER_SIZE = 24;
+
+    @DataProvider(name = "buffers")
+    public Object[][] createBuffers() {
+        // test both on-heap and off-heap buffers has they make use different code paths
+        return new Object[][]{
+                new Object[]{CharBuffer.allocate(BUFFER_SIZE)},
+                new Object[]{ByteBuffer.allocateDirect(BUFFER_SIZE * 2).asCharBuffer()}
+        };
+    }
+
+    @Test(dataProvider = "buffers")
+    public void read(CharBuffer buffer) throws IOException {
+        fillBuffer(buffer);
+
+        try (Reader reader = new InputStreamReader(new ByteArrayInputStream("ABCDEFGHIJKLMNOPQRTUVWXYZ".getBytes(US_ASCII)), US_ASCII)) {
+            buffer.limit(7);
+            buffer.position(1);
+            assertEquals(reader.read(buffer), 6);
+            assertEquals(buffer.position(), 7);
+            assertEquals(buffer.limit(), 7);
+
+            buffer.limit(16);
+            buffer.position(8);
+            assertEquals(reader.read(buffer), 8);
+            assertEquals(buffer.position(), 16);
+            assertEquals(buffer.limit(), 16);
+        }
+
+        buffer.clear();
+        assertEquals(buffer.toString(), "xABCDEFxGHIJKLMNxxxxxxxx");
+    }
+
+    private void fillBuffer(CharBuffer buffer) {
+        char[] filler = new char[BUFFER_SIZE];
+        Arrays.fill(filler, 'x');
+        buffer.put(filler);
+        buffer.clear();
+    }
+
+}