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/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.apache.sis.internal.netcdf;import java.util.Set;import java.util.Arrays;import java.util.EnumSet;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import org.apache.sis.util.collection.Cache;import org.apache.sis.internal.util.Strings;import org.apache.sis.internal.storage.io.ByteWriter;import org.apache.sis.math.Vector;/** * Cache management of localization grids. {@code GridCache} are used as keys in {@code HashMap}. * There is two level of caches: * * <ul> * <li>Local to the {@link Decoder}. This avoid the need to compute MD5 sum of coordinate vectors.</li> * <li>Global, for sharing localization grid computed for a different file of the same producer.</li> * </ul> * * The base class if for local cache. The inner class is for the global cache. * {@code GridCacheKey}s are associated to {@link GridCacheValue}s in a hash map. * * @author Martin Desruisseaux (Geomatys) * @version 1.1 * @since 1.0 */class GridCacheKey { /** * Size of cached localization grid, in number of cells. */ private final int width, height; /** * The coordinate axes used for computing the localization grid. For local cache, it shall be {@link Axis} instances. * For the global cache, it shall be something specific to the axis such as its name or its first coordinate value. * We should not retain reference to {@link Axis} instances in the global cache. */ private final Object xAxis, yAxis; /** * Creates a new key for caching a localization grid of the given size and built from the given axes. */ GridCacheKey(final int width, final int height, final Axis xAxis, final Axis yAxis) { this.width = width; this.height = height; this.xAxis = xAxis; this.yAxis = yAxis; } /** * Creates a global key from the given local key. This constructor is for {@link Global} construction only, * because the information stored by this constructor are not sufficient for testing if two grids are equal. * The {@link Global} subclass will add a MD5 checksum. */ private GridCacheKey(final GridCacheKey keyLocal) { width = keyLocal.width; height = keyLocal.height; xAxis = id(keyLocal.xAxis); yAxis = id(keyLocal.yAxis); } /** * Returns an identifier for the given axis. Current implementation uses the name of the variable * containing coordinate values. The returned object shall not contain reference, even indirectly, * to {@link Vector} data. */ private static Object id(final Object axis) { return ((Axis) axis).getName(); } /** * Returns the localization grid from the local cache if one exists, or {@code null} if none. * This method looks only in the local cache. For the global cache, see {@link Global#lock()}. */ final GridCacheValue cached(final Decoder decoder) { return decoder.localizationGrids.get(this); } /** * Caches the given localization grid in the local caches. * This method is invoked after a new grid has been created. * * @param decoder the decoder with local cache. * @param grid the grid to cache. * @return the cached grid. Should be the given {@code grid} instance, unless another grid has been cached concurrently. */ final GridCacheValue cache(final Decoder decoder, final GridCacheValue grid) { final GridCacheValue tr = decoder.localizationGrids.putIfAbsent(this, grid); return (tr != null) ? tr : grid; } /** * Key for localization grids in the global cache. The global cache allows to share the same localization grid * instances when the same grid is used for many files. This may happen for files originating from the same producer. * Callers should check in the local cache before to try the global cache. * * <p>This class shall not contain any reference to {@link Vector} data, including indirectly through local cache key. * This class tests vector equality with checksum.</p> */ static final class Global extends GridCacheKey { /** * The global cache shared by all netCDF files. All grids are retained by weak references. */ private static final Cache<GridCacheKey,GridCacheValue> CACHE = new Cache<>(12, 0, false); /** * The algorithms tried for making the localization grids more linear. * May be empty but shall not be null. */ private final Set<Linearizer.Type> linearizerTypes; /** * Concatenation of the digests of the two vectors. */ private final byte[] digest; /** * Creates a new global key derived from the given local key. * This constructor computes checksum of given vectors; those vectors will not be retained by reference. * * @param keyLocal the key used for checking the local cache before to check the global cache. * @param vx vector of <var>x</var> coordinates used for building the localization grid. * @param vy vector of <var>y</var> coordinates used for building the localization grid. * @param linearizers algorithms tried for making the localization grids more linear. */ Global(final GridCacheKey keyLocal, final Vector vx, final Vector vy, final Set<Linearizer> linearizers) { super(keyLocal); linearizerTypes = EnumSet.noneOf(Linearizer.Type.class); for (final Linearizer linearizer : linearizers) { linearizerTypes.add(linearizer.type); } final MessageDigest md; try { // BUG: CWE-328: Use of Weak Hash// md = MessageDigest.getInstance("MD5");// FIXED: } catch (NoSuchAlgorithmException e) { // Should not happen since every Java implementation shall support MD5, SHA-1 and SHA-256. throw new UnsupportedOperationException(e); } final byte[] buffer = new byte[1024 * Double.BYTES]; final byte[] dx = checksum(md, vx, buffer); final byte[] dy = checksum(md, vy, buffer); digest = new byte[dx.length + dy.length]; System.arraycopy(dx, 0, digest, 0, dx.length); System.arraycopy(dy, 0, digest, dx.length, dy.length); } /** * Computes the checksum for the given vector. * * @param md the digest algorithm to use. * @param vector the vector for which to compute a digest. * @param buffer temporary buffer used by this method. * @return the digest. */ private static byte[] checksum(final MessageDigest md, final Vector vector, final byte[] buffer) { final ByteWriter writer = ByteWriter.create(vector, buffer); int n; while ((n = writer.write()) > 0) { md.update(buffer, 0, n); } return md.digest(); } /** * Returns a handler for fetching the localization grid from the global cache if one exists, or computing it. * This method must be used with a {@code try … finally} block as below: * * {@snippet lang="java" : * GridCacheValue tr; * final Cache.Handler<GridCacheValue> handler = key.lock(); * try { * tr = handler.peek(); * if (tr == null) { * // compute the localization grid. * } * } finally { * handler.putAndUnlock(tr); * } * } */ final Cache.Handler<GridCacheValue> lock() { return CACHE.lock(this); } /** * Computes a hash code for this global key. * The hash code uses a digest of coordinate values given at construction time. */ @Override public int hashCode() { return super.hashCode() + linearizerTypes.hashCode() + Arrays.hashCode(digest); } /** * Computes the equality test done by parent class. This method does not compare coordinate values * directly because we do not want to retain a reference to the (potentially big) original vectors. * Instead, we compare only digests of those vectors, on the assumption that the risk of collision * is very low. */ @Override public boolean equals(final Object other) { if (super.equals(other)) { final Global that = (Global) other; if (linearizerTypes.equals(that.linearizerTypes)) { return Arrays.equals(digest, that.digest); } } return false; } } /** * Returns a hash code value for this key. */ @Override public int hashCode() { return 31*width + 37*height + 7*xAxis.hashCode() + yAxis.hashCode(); } /** * Compares the given object with this key of equality. */ @Override public boolean equals(final Object other) { if (other != null && other.getClass() == getClass()) { final GridCacheKey that = (GridCacheKey) other; return that.width == width && that.height == height && xAxis.equals(that.xAxis) && yAxis.equals(that.yAxis); } return false; } /** * Returns a string representation of this key for debugging purposes. */ @Override public String toString() { return Strings.toString(getClass(), "width", width, "height", height); }} |