4926314: Optimize Reader.read(CharBuffer)

Reviewed-by: alanb, bpb

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

@@ -25,6 +25,7 @@
 
 package java.io;
 
+import java.nio.CharBuffer;
 import java.util.Objects;
 
 /**
@@ -152,6 +153,23 @@ public class CharArrayReader extends Reader {
         }
     }
 
+    @Override
+    public int read(CharBuffer target) throws IOException {
+        synchronized (lock) {
+            ensureOpen();
+
+            if (pos >= count) {
+                return -1;
+            }
+
+            int avail = count - pos;
+            int len = Math.min(avail, target.remaining());
+            target.put(buf, pos, len);
+            pos += len;
+            return len;
+        }
+    }
+
     /**
      * Skips characters. If the stream is already at its end before this method
      * is invoked, then no characters are skipped and zero is returned.