8374308: ImageBufferCache has no effect and can be removed

Reviewed-by: alanb, rriggs

Author: david-beaumont

src/java.base/share/classes/jdk/internal/jimage/BasicImageReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 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
@@ -220,14 +220,6 @@ private IntBuffer intBuffer(ByteBuffer buffer, int offset, int size) {
         return slice(buffer, offset, size).order(byteOrder).asIntBuffer();
     }
 
-    public static void releaseByteBuffer(ByteBuffer buffer) {
-        Objects.requireNonNull(buffer);
-
-        if (!MAP_ALL) {
-            ImageBufferCache.releaseBuffer(buffer);
-        }
-    }
-
     public String getName() {
         return name;
     }
@@ -362,35 +354,34 @@ private ByteBuffer readBuffer(long offset, long size) {
         if (offset < 0 || Integer.MAX_VALUE <= offset) {
             throw new IndexOutOfBoundsException("Bad offset: " + offset);
         }
+        int checkedOffset = (int) offset;
 
         if (size < 0 || Integer.MAX_VALUE <= size) {
-            throw new IndexOutOfBoundsException("Bad size: " + size);
+            throw new IllegalArgumentException("Bad size: " + size);
         }
+        int checkedSize = (int) size;
 
         if (MAP_ALL) {
-            ByteBuffer buffer = slice(memoryMap, (int)offset, (int)size);
+            ByteBuffer buffer = slice(memoryMap, checkedOffset, checkedSize);
             buffer.order(ByteOrder.BIG_ENDIAN);
 
             return buffer;
         } else {
             if (channel == null) {
                 throw new InternalError("Image file channel not open");
             }
-
-            ByteBuffer buffer = ImageBufferCache.getBuffer(size);
+            ByteBuffer buffer = ByteBuffer.allocate(checkedSize);
             int read;
             try {
-                read = channel.read(buffer, offset);
+                read = channel.read(buffer, checkedOffset);
                 buffer.rewind();
             } catch (IOException ex) {
-                ImageBufferCache.releaseBuffer(buffer);
                 throw new RuntimeException(ex);
             }
 
-            if (read != size) {
-                ImageBufferCache.releaseBuffer(buffer);
+            if (read != checkedSize) {
                 throw new RuntimeException("Short read: " + read +
-                                           " instead of " + size + " bytes");
+                        " instead of " + checkedSize + " bytes");
             }
 
             return buffer;
@@ -406,17 +397,12 @@ public byte[] getResource(String name) {
 
     public byte[] getResource(ImageLocation loc) {
         ByteBuffer buffer = getResourceBuffer(loc);
-
-        if (buffer != null) {
-            byte[] bytes = getBufferBytes(buffer);
-            ImageBufferCache.releaseBuffer(buffer);
-
-            return bytes;
-        }
-
-        return null;
+        return buffer != null ? getBufferBytes(buffer) : null;
     }
 
+    /**
+     * Returns the content of jimage location in a newly allocated byte buffer.
+     */
     public ByteBuffer getResourceBuffer(ImageLocation loc) {
         Objects.requireNonNull(loc);
         long offset = loc.getContentOffset() + indexSize;
@@ -437,10 +423,8 @@ public ByteBuffer getResourceBuffer(ImageLocation loc) {
             return readBuffer(offset, uncompressedSize);
         } else {
             ByteBuffer buffer = readBuffer(offset, compressedSize);
-
             if (buffer != null) {
                 byte[] bytesIn = getBufferBytes(buffer);
-                ImageBufferCache.releaseBuffer(buffer);
                 byte[] bytesOut;
 
                 try {

src/java.base/share/classes/jdk/internal/jimage/ImageBufferCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 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
@@ -190,20 +190,7 @@ public byte[] getResource(Node node) throws IOException {
     }
 
     /**
-     * Releases a (possibly cached) {@link ByteBuffer} obtained via
-     * {@link #getResourceBuffer(Node)}.
-     *
-     * <p>Note that no testing is performed to check whether the buffer about
-     * to be released actually came from a call to {@code getResourceBuffer()}.
-     */
-    public static void releaseByteBuffer(ByteBuffer buffer) {
-        BasicImageReader.releaseByteBuffer(buffer);
-    }
-
-    /**
-     * Returns the content of a resource node in a possibly cached byte buffer.
-     * Callers of this method must call {@link #releaseByteBuffer(ByteBuffer)}
-     * when they are finished with it.
+     * Returns the content of a resource node in a newly allocated byte buffer.
      */
     public ByteBuffer getResourceBuffer(Node node) {
         requireOpen();

src/java.base/share/classes/jdk/internal/jimage/ImageReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 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
@@ -467,12 +467,6 @@ public Optional<ByteBuffer> read(String name) throws IOException {
                     .map(reader::getResourceBuffer);
         }
 
-        @Override
-        public void release(ByteBuffer bb) {
-            Objects.requireNonNull(bb);
-            ImageReader.releaseByteBuffer(bb);
-        }
-
         @Override
         public Stream<String> list() throws IOException {
             if (closed)