8277501: Revisit PathFileObject.getCharContent and friends

Reviewed-by: vromero, jjg

src/jdk.compiler/share/classes/com/sun/tools/javac/file/BaseFileManager.java

@@ -75,10 +75,12 @@ import com.sun.tools.javac.util.Options;
  * java.io.File or java.nio.file.Path.
  */
 public abstract class BaseFileManager implements JavaFileManager {
+
+    private static final byte[] EMPTY_ARRAY = new byte[0];
+
     @SuppressWarnings("this-escape")
     protected BaseFileManager(Charset charset) {
         this.charset = charset;
-        byteBufferCache = new ByteBufferCache();
         locations = createLocations();
     }
 
@@ -403,56 +405,33 @@ public abstract class BaseFileManager implements JavaFileManager {
 
     // <editor-fold defaultstate="collapsed" desc="ByteBuffers">
     /**
-     * Make a byte buffer from an input stream.
+     * Make a {@link ByteBuffer} from an input stream.
      * @param in the stream
      * @return a byte buffer containing the contents of the stream
      * @throws IOException if an error occurred while reading the stream
      */
-    public ByteBuffer makeByteBuffer(InputStream in)
+    public ByteBuffer makeByteBuffer(InputStream in) throws IOException {
-        throws IOException {
+        byte[] array;
-        int limit = in.available();
+        synchronized (this) {
-        if (limit < 1024) limit = 1024;
+            if ((array = byteArrayCache) != null)
-        ByteBuffer result = byteBufferCache.get(limit);
+                byteArrayCache = null;
-        int position = 0;
+            else
-        while (in.available() != 0) {
+                array = EMPTY_ARRAY;
-            if (position >= limit)
-                // expand buffer
-                result = ByteBuffer.
-                    allocate(limit <<= 1).
-                    put(result.flip());
-            int count = in.read(result.array(),
-                position,
-                limit - position);
-            if (count < 0) break;
-            result.position(position += count);
         }
-        return result.flip();
+        com.sun.tools.javac.util.ByteBuffer buf = new com.sun.tools.javac.util.ByteBuffer(array);
+        buf.appendStream(in);
+        return buf.asByteBuffer();
     }
 
-    public void recycleByteBuffer(ByteBuffer bb) {
+    public void recycleByteBuffer(ByteBuffer buf) {
-        byteBufferCache.put(bb);
+        if (buf.hasArray()) {
+            synchronized (this) {
+                byteArrayCache = buf.array();
             }
-
-    /**
-     * A single-element cache of direct byte buffers.
-     */
-    private static class ByteBufferCache {
-        private ByteBuffer cached;
-        ByteBuffer get(int capacity) {
-            if (capacity < 20480) capacity = 20480;
-            ByteBuffer result =
-                (cached != null && cached.capacity() >= capacity)
-                ? cached.clear()
-                : ByteBuffer.allocate(capacity);
-            cached = null;
-            return result;
-        }
-        void put(ByteBuffer x) {
-            cached = x;
         }
     }
 
-    private final ByteBufferCache byteBufferCache;
+    private byte[] byteArrayCache;
     // </editor-fold>
 
     // <editor-fold defaultstate="collapsed" desc="Content cache">

src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassReader.java

@@ -2741,7 +2741,9 @@ public class ClassReader {
         try {
             bp = 0;
             buf.reset();
-            buf.appendStream(c.classfile.openInputStream());
+            try (InputStream input = c.classfile.openInputStream()) {
+                buf.appendStream(input);
+            }
             readClassBuffer(c);
             if (!missingTypeVariables.isEmpty() && !foundTypeVariables.isEmpty()) {
                 List<Type> missing = missingTypeVariables;

src/jdk.compiler/share/classes/com/sun/tools/javac/util/ByteBuffer.java

@@ -56,8 +56,13 @@ public class ByteBuffer {
      *  of given size.
      */
     public ByteBuffer(int initialSize) {
-        elems = new byte[initialSize];
+        this(new byte[initialSize]);
-        length = 0;
+    }
+
+    /** Create a new byte buffer using the given array for storage.
+     */
+    public ByteBuffer(byte[] elems) {
+        this.elems = elems;
     }
 
     /** Append byte to this buffer.
@@ -147,10 +152,9 @@ public class ByteBuffer {
         appendBytes(name.getByteArray(), name.getByteOffset(), name.getByteLength());
     }
 
-     /** Append the content of a given input stream, and then close the stream.
+     /** Append the content of the given input stream.
      */
-    public void appendStream(InputStream is) throws IOException {
+    public void appendStream(InputStream input) throws IOException {
-        try (InputStream input = is) {
         while (true) {
 
             // Read another chunk of data, using size hint from available().
@@ -173,7 +177,6 @@ public class ByteBuffer {
             }
         }
     }
-    }
 
     /** Extract an integer at position bp from elems.
      *
@@ -292,6 +295,15 @@ public class ByteBuffer {
             throw new UnderflowException(length);
     }
 
+    /** Create a {@link java.nio.ByteBuffer} view of this instance.
+     *
+     *  <p>
+     *  If this instance is modified, the returned buffer may no longer reflect it.
+     */
+    public java.nio.ByteBuffer asByteBuffer() {
+        return java.nio.ByteBuffer.wrap(elems, 0, length);
+    }
+
 // UnderflowException
 
     /** Thrown when trying to read past the end of the buffer.