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A library for invoking native functions from java
There is a newer version: 2.2.17
/*
 * Copyright (C) 2008-2010 Wayne Meissner
 *
 * This file is part of the JNR project.
 *
 * Licensed 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 jnr.ffi.provider.jffi;

import jnr.ffi.Platform;

import java.io.File;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;

public class NativeLibrary {

    private final String[] libraryNames;
    
    private volatile List nativeLibraries = Collections.EMPTY_LIST;
    
    NativeLibrary(String name) {
        this.libraryNames = new String[] { name };
    }

    NativeLibrary(String... names) {
        this.libraryNames = (String[]) names.clone();
    }

    public static String locateLibrary(String libraryName) {
        if (new File(libraryName).isAbsolute()) {
            return libraryName;
        }
        List searchPath = new LinkedList();

        //
        // Prepend any custom search paths specifically for this library
        //
        searchPath.addAll(0, jnr.ffi.Library.getLibraryPath(libraryName));
        searchPath.addAll(StaticDataHolder.userLibraryPath);
        String path = Platform.getNativePlatform().locateLibrary(libraryName, searchPath);
        return path != null ? path : null;
    }

    private static final List getPropertyPaths(String propName) {
        String value = System.getProperty(propName);
        if (value != null) {
            String[] paths = value.split(File.pathSeparator);
            return new ArrayList(Arrays.asList(paths));
        }
        return Collections.emptyList();
    }

    long getSymbolAddress(String name) {
        for (com.kenai.jffi.Library l : getNativeLibraries()) {
            long address = l.getSymbolAddress(name);
            if (address != 0) {
                return address;
            }
        }
        return 0;
    }

    long findSymbolAddress(String name) {
        long address = getSymbolAddress(name);
        if (address == 0) {
            throw new SymbolNotFoundError(com.kenai.jffi.Library.getLastError());
        }
        return address;
    }

    private synchronized List getNativeLibraries() {
        if (!this.nativeLibraries.isEmpty()) {
            return nativeLibraries;
        }
        return nativeLibraries = loadNativeLibraries();
    }

    private synchronized List loadNativeLibraries() {
        List libs = new ArrayList();
        
        for (String libraryName : libraryNames) {
            com.kenai.jffi.Library lib;
            
            lib = com.kenai.jffi.Library.getCachedInstance(libraryName, com.kenai.jffi.Library.LAZY | com.kenai.jffi.Library.GLOBAL);
            if (lib == null) {
                String path;
                if (libraryName != null && (path = locateLibrary(libraryName)) != null && !libraryName.equals(path)) {
                    lib = com.kenai.jffi.Library.getCachedInstance(path, com.kenai.jffi.Library.LAZY | com.kenai.jffi.Library.GLOBAL);
                }
            }
            if (lib == null) {
                throw new UnsatisfiedLinkError(com.kenai.jffi.Library.getLastError());
            }
            libs.add(lib);
        }

        return Collections.unmodifiableList(libs);
    }

    private static final class StaticDataHolder {
        private static final List userLibraryPath = new CopyOnWriteArrayList();
        static {
            userLibraryPath.addAll(getPropertyPaths("jnr.ffi.library.path"));
            userLibraryPath.addAll(getPropertyPaths("jaffl.library.path"));
            // Add JNA paths for compatibility
            userLibraryPath.addAll(getPropertyPaths("jna.library.path"));
        }
    }
}