8260337: Optimize ImageReader lookup, used by Class.getResource

Reviewed-by: jlaskey, sundar

Author: cl4es

src/java.base/share/classes/java/lang/Class.java

@@ -3048,15 +3048,19 @@ private static void checkPackageAccessForPermittedSubclasses(SecurityManager sm,
     }
 
     /**
-     * Add a package name prefix if the name is not absolute Remove leading "/"
+     * Add a package name prefix if the name is not absolute. Remove leading "/"
      * if name is absolute
      */
     private String resolveName(String name) {
         if (!name.startsWith("/")) {
-            Class<?> c = isArray() ? elementType() : this;
-            String baseName = c.getPackageName();
+            String baseName = getPackageName();
             if (baseName != null && !baseName.isEmpty()) {
-                name = baseName.replace('.', '/') + "/" + name;
+                int len = baseName.length() + 1 + name.length();
+                StringBuilder sb = new StringBuilder(len);
+                name = sb.append(baseName.replace('.', '/'))
+                    .append('/')
+                    .append(name)
+                    .toString();
             }
         } else {
             name = name.substring(1);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 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
@@ -249,57 +249,69 @@ public ImageStringsReader getStrings() {
         return stringsReader;
     }
 
-    public synchronized ImageLocation findLocation(String module, String name) {
-        Objects.requireNonNull(module);
-        Objects.requireNonNull(name);
-        // Details of the algorithm used here can be found in
-        // jdk.tools.jlink.internal.PerfectHashBuilder.
-        int count = header.getTableLength();
-        int index = redirect.get(ImageStringsReader.hashCode(module, name) % count);
-
+    public ImageLocation findLocation(String module, String name) {
+        int index = getLocationIndex(module, name);
         if (index < 0) {
-            // index is twos complement of location attributes index.
-            index = -index - 1;
-        } else if (index > 0) {
-            // index is hash seed needed to compute location attributes index.
-            index = ImageStringsReader.hashCode(module, name, index) % count;
-        } else {
-            // No entry.
             return null;
         }
-
         long[] attributes = getAttributes(offsets.get(index));
-
         if (!ImageLocation.verify(module, name, attributes, stringsReader)) {
             return null;
         }
         return new ImageLocation(attributes, stringsReader);
     }
 
-    public synchronized ImageLocation findLocation(String name) {
-        Objects.requireNonNull(name);
-        // Details of the algorithm used here can be found in
-        // jdk.tools.jlink.internal.PerfectHashBuilder.
+    public ImageLocation findLocation(String name) {
+        int index = getLocationIndex(name);
+        if (index < 0) {
+            return null;
+        }
+        long[] attributes = getAttributes(offsets.get(index));
+        if (!ImageLocation.verify(name, attributes, stringsReader)) {
+            return null;
+        }
+        return new ImageLocation(attributes, stringsReader);
+    }
+
+    public boolean verifyLocation(String module, String name) {
+        int index = getLocationIndex(module, name);
+        if (index < 0) {
+            return false;
+        }
+        int locationOffset = offsets.get(index);
+        return ImageLocation.verify(module, name, locations, locationOffset, stringsReader);
+    }
+
+    // Details of the algorithm used here can be found in
+    // jdk.tools.jlink.internal.PerfectHashBuilder.
+    public int getLocationIndex(String name) {
         int count = header.getTableLength();
         int index = redirect.get(ImageStringsReader.hashCode(name) % count);
-
         if (index < 0) {
             // index is twos complement of location attributes index.
-            index = -index - 1;
+            return -index - 1;
         } else if (index > 0) {
             // index is hash seed needed to compute location attributes index.
-            index = ImageStringsReader.hashCode(name, index) % count;
+            return ImageStringsReader.hashCode(name, index) % count;
         } else {
             // No entry.
-            return null;
+            return -1;
         }
+    }
 
-        long[] attributes = getAttributes(offsets.get(index));
-
-        if (!ImageLocation.verify(name, attributes, stringsReader)) {
-            return null;
+    private int getLocationIndex(String module, String name) {
+        int count = header.getTableLength();
+        int index = redirect.get(ImageStringsReader.hashCode(module, name) % count);
+        if (index < 0) {
+            // index is twos complement of location attributes index.
+            return -index - 1;
+        } else if (index > 0) {
+            // index is hash seed needed to compute location attributes index.
+            return ImageStringsReader.hashCode(module, name, index) % count;
+        } else {
+            // No entry.
+            return -1;
         }
-        return new ImageLocation(attributes, stringsReader);
     }
 
     public String[] getEntryNames() {
@@ -320,18 +332,21 @@ public long[] getAttributes(int offset) {
         if (offset < 0 || offset >= locations.limit()) {
             throw new IndexOutOfBoundsException("offset");
         }
-
-        ByteBuffer buffer = slice(locations, offset, locations.limit() - offset);
-        return ImageLocation.decompress(buffer);
+        return ImageLocation.decompress(locations, offset);
     }
 
     public String getString(int offset) {
         if (offset < 0 || offset >= strings.limit()) {
             throw new IndexOutOfBoundsException("offset");
         }
+        return ImageStringsReader.stringFromByteBuffer(strings, offset);
+    }
 
-        ByteBuffer buffer = slice(strings, offset, strings.limit() - offset);
-        return ImageStringsReader.stringFromByteBuffer(buffer);
+    public int match(int offset, String string, int stringOffset) {
+        if (offset < 0 || offset >= strings.limit()) {
+            throw new IndexOutOfBoundsException("offset");
+        }
+        return ImageStringsReader.stringFromByteBufferMatches(strings, offset, string, stringOffset);
     }
 
     private byte[] getBufferBytes(ByteBuffer buffer) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 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
@@ -59,41 +59,26 @@ ImageStrings getStrings() {
         return strings;
     }
 
-    static long[] decompress(ByteBuffer bytes) {
+    static long[] decompress(ByteBuffer bytes, int offset) {
         Objects.requireNonNull(bytes);
         long[] attributes = new long[ATTRIBUTE_COUNT];
 
-        if (bytes != null) {
-            while (bytes.hasRemaining()) {
-                int data = bytes.get() & 0xFF;
-                int kind = data >>> 3;
-
-                if (kind == ATTRIBUTE_END) {
-                    break;
-                }
-
-                if (kind < ATTRIBUTE_END || ATTRIBUTE_COUNT <= kind) {
-                    throw new InternalError(
-                        "Invalid jimage attribute kind: " + kind);
-                }
-
-                int length = (data & 0x7) + 1;
-                long value = 0;
-
-                for (int j = 0; j < length; j++) {
-                    value <<= 8;
-
-                    if (!bytes.hasRemaining()) {
-                        throw new InternalError("Missing jimage attribute data");
-                    }
-
-                    value |= bytes.get() & 0xFF;
-                }
-
-                 attributes[kind] = value;
+        int limit = bytes.limit();
+        while (offset < limit) {
+            int data = bytes.get(offset++) & 0xFF;
+            if (data <= 0x7) { // ATTRIBUTE_END
+                break;
+            }
+            int kind = data >>> 3;
+            if (ATTRIBUTE_COUNT <= kind) {
+                throw new InternalError(
+                    "Invalid jimage attribute kind: " + kind);
             }
-        }
 
+            int length = (data & 0x7) + 1;
+            attributes[kind] = readValue(length, bytes, offset, limit);
+            offset += length;
+        }
         return attributes;
     }
 
@@ -126,71 +111,125 @@ public boolean verify(String name) {
     /**
      * A simpler verification would be {@code name.equals(getFullName())}, but
      * by not creating the full name and enabling early returns we allocate
-     * fewer objects. Could possibly be made allocation free by extending
-     * ImageStrings to test if strings at an offset match the name region.
+     * fewer objects.
      */
     static boolean verify(String name, long[] attributes, ImageStrings strings) {
         Objects.requireNonNull(name);
         final int length = name.length();
         int index = 0;
         int moduleOffset = (int)attributes[ATTRIBUTE_MODULE];
-        if (moduleOffset != 0) {
-            String module = strings.get(moduleOffset);
-            final int moduleLen = module.length();
+        if (moduleOffset != 0 && length >= 1) {
+            int moduleLen = strings.match(moduleOffset, name, 1);
             index = moduleLen + 1;
-            if (length <= index
+            if (moduleLen < 0
+                    || length <= index
                     || name.charAt(0) != '/'
-                    || !name.regionMatches(1, module, 0, moduleLen)
                     || name.charAt(index++) != '/') {
                 return false;
             }
         }
+        return verifyName(null, name, index, length, 0,
+                (int) attributes[ATTRIBUTE_PARENT],
+                (int) attributes[ATTRIBUTE_BASE],
+                (int) attributes[ATTRIBUTE_EXTENSION],
+                strings);
+    }
 
-        return verifyName(name, index, length, attributes, strings);
+    static boolean verify(String module, String name, ByteBuffer locations,
+                          int locationOffset, ImageStrings strings) {
+        int moduleOffset = 0;
+        int parentOffset = 0;
+        int baseOffset = 0;
+        int extOffset = 0;
+
+        int limit = locations.limit();
+        while (locationOffset < limit) {
+            int data = locations.get(locationOffset++) & 0xFF;
+            if (data <= 0x7) { // ATTRIBUTE_END
+                break;
+            }
+            int kind = data >>> 3;
+            if (ATTRIBUTE_COUNT <= kind) {
+                throw new InternalError(
+                        "Invalid jimage attribute kind: " + kind);
+            }
+
+            int length = (data & 0x7) + 1;
+            switch (kind) {
+                case ATTRIBUTE_MODULE:
+                    moduleOffset = (int) readValue(length, locations, locationOffset, limit);
+                    break;
+                case ATTRIBUTE_BASE:
+                    baseOffset = (int) readValue(length, locations, locationOffset, limit);
+                    break;
+                case ATTRIBUTE_PARENT:
+                    parentOffset = (int) readValue(length, locations, locationOffset, limit);
+                    break;
+                case ATTRIBUTE_EXTENSION:
+                    extOffset = (int) readValue(length, locations, locationOffset, limit);
+                    break;
+            }
+            locationOffset += length;
+        }
+        return verifyName(module, name, 0, name.length(),
+                moduleOffset, parentOffset, baseOffset, extOffset, strings);
+    }
+
+    private static long readValue(int length, ByteBuffer buffer, int offset, int limit) {
+        long value = 0;
+        for (int j = 0; j < length; j++) {
+            value <<= 8;
+            if (offset >= limit) {
+                throw new InternalError("Missing jimage attribute data");
+            }
+            value |= buffer.get(offset++) & 0xFF;
+        }
+        return value;
     }
 
     static boolean verify(String module, String name, long[] attributes,
             ImageStrings strings) {
         Objects.requireNonNull(module);
         Objects.requireNonNull(name);
-        int moduleOffset = (int)attributes[ATTRIBUTE_MODULE];
+        return verifyName(module, name, 0, name.length(),
+                (int) attributes[ATTRIBUTE_MODULE],
+                (int) attributes[ATTRIBUTE_PARENT],
+                (int) attributes[ATTRIBUTE_BASE],
+                (int) attributes[ATTRIBUTE_EXTENSION],
+                strings);
+    }
+
+    private static boolean verifyName(String module, String name, int index, int length,
+            int moduleOffset, int parentOffset, int baseOffset, int extOffset, ImageStrings strings) {
+
         if (moduleOffset != 0) {
-            if (!module.equals(strings.get(moduleOffset))) {
+            if (strings.match(moduleOffset, module, 0) != module.length()) {
                 return false;
             }
         }
-
-        return verifyName(name, 0, name.length(), attributes, strings);
-    }
-
-    private static boolean verifyName(String name, int index, int length,
-            long[] attributes, ImageStrings strings) {
-
-        int parentOffset = (int) attributes[ATTRIBUTE_PARENT];
         if (parentOffset != 0) {
-            String parent = strings.get(parentOffset);
-            final int parentLen = parent.length();
-            if (!name.regionMatches(index, parent, 0, parentLen)) {
+            int parentLen = strings.match(parentOffset, name, index);
+            if (parentLen < 0) {
                 return false;
             }
             index += parentLen;
             if (length <= index || name.charAt(index++) != '/') {
                 return false;
             }
         }
-        String base = strings.get((int) attributes[ATTRIBUTE_BASE]);
-        final int baseLen = base.length();
-        if (!name.regionMatches(index, base, 0, baseLen)) {
+        int baseLen = strings.match(baseOffset, name, index);
+        if (baseLen < 0) {
             return false;
         }
         index += baseLen;
-        int extOffset = (int) attributes[ATTRIBUTE_EXTENSION];
         if (extOffset != 0) {
-            String extension = strings.get(extOffset);
-            int extLen = extension.length();
             if (length <= index
-                    || name.charAt(index++) != '.'
-                    || !name.regionMatches(index, extension, 0, extLen)) {
+                    || name.charAt(index++) != '.') {
+                return false;
+            }
+
+            int extLen = strings.match(extOffset, name, index);
+            if (extLen < 0) {
                 return false;
             }
             index += extLen;
@@ -203,7 +242,6 @@ long getAttribute(int kind) {
             throw new InternalError(
                 "Invalid jimage attribute kind: " + kind);
         }
-
         return attributes[kind];
     }
 
@@ -212,7 +250,6 @@ String getAttributeString(int kind) {
             throw new InternalError(
                 "Invalid jimage attribute kind: " + kind);
         }
-
         return getStrings().get((int)attributes[kind]);
     }