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Library.java

/* This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p/>
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.  
 */
package com.sun.jna;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;

/** Derive from this interface for all native library definitions.
 *
 * Define an instance of your library like this:
 * <code><pre>
 * MyNativeLibrary INSTANCE = (MyNativeLibrary)
 *     Native.loadLibrary("mylib", MyNativeLibrary.class);
 * </pre></code>
 * <p>
 * By convention, method names are identical to the native names, although you
 * can map java names to different native names by providing a 
 * {@link FunctionMapper} as a value for key {@link #OPTION_FUNCTION_MAPPER}
 * in the options map passed to the
 * {@link Native#loadLibrary(String, Class, Map)} call.
 * <p>
 * Although the names for structures and structure fields may be chosen 
 * arbitrarily, they should correspond as closely as possible to the native 
 * definitions.  The same is true for parameter names.
 * <p>
 * This interface supports multiple, concurrent invocations of any library
 * methods on the Java side.  Check your library documentation for its
 * multi-threading requirements on the native side.  If a library is not safe
 * for simultaneous multi-threaded access, consider using 
 * {@link Native#synchronizedLibrary} to prevent simultaneous multi-threaded 
 * access to the native code.  
 * <p>
 * <b>Optional fields</b><br>
 * Interface options will be automatically propagated to structures defined
 * within the library provided a call to 
 * {@link Native#loadLibrary(String,Class,Map)} is made prior to instantiating
 * any of those structures.  One common way of ensuring this is to declare
 * an <b>INSTANCE</b> field in the interface which holds the 
 * <code>loadLibrary</code> result.
 * <p>
 * <b>OPTIONS</b> (an instance of {@link Map}),
 * <b>TYPE_MAPPER</b> (an instance of {@link TypeMapper}) and 
 * <b>STRUCTURE_ALIGNMENT</b> (one of the alignment types defined in 
 * {@link Structure}) may also be defined.  If no instance of the interface
 * has been instantiated, these fields will be used to determine customization
 * settings for structures and methods defined within the interface.
 * <p>
 * 
 * @author  Todd Fast, todd.fast@sun.com
 * @author  Timothy Wall, twalljava@dev.java.net
 */
00066 public interface Library {
    /** Option key for a {@link TypeMapper} for the library. */
00068     String OPTION_TYPE_MAPPER = "type-mapper";
    /** Option key for a {@link FunctionMapper} for the library. */
00070     String OPTION_FUNCTION_MAPPER = "function-mapper";
    /** Option key for an {@link InvocationMapper} for the library. */
00072     String OPTION_INVOCATION_MAPPER = "invocation-mapper";
    /** Option key for structure alignment type ({@link Integer}), which should
     * be one of the predefined alignment types in {@link Structure}. 
     */
00076     String OPTION_STRUCTURE_ALIGNMENT = "structure-alignment";
    static class Handler implements InvocationHandler {
        
        static final Method OBJECT_TOSTRING;
        static final Method OBJECT_HASHCODE;
        static final Method OBJECT_EQUALS;
        
        static {
            try {
                OBJECT_TOSTRING = Object.class.getMethod("toString", new Class[0]);
                OBJECT_HASHCODE= Object.class.getMethod("hashCode", new Class[0]);
                OBJECT_EQUALS = Object.class.getMethod("equals", new Class[] { Object.class });
            }
            catch (Exception e) {
                throw new Error("Error retrieving Object.toString() method");
            }
        }

        private static class FunctionNameMap implements FunctionMapper {
            private final Map map;
            public FunctionNameMap(Map map) {
                this.map = new HashMap(map);
            }
            public String getFunctionName(NativeLibrary library, Method method) {
                String name = method.getName();
                if (map.containsKey(name)) {
                    return (String)map.get(name);
                }
                return name;
            }
        }

        private final NativeLibrary nativeLibrary;
        private final Class interfaceClass;
        // Library invocation options
        private final Map options;
        private FunctionMapper functionMapper;
        private InvocationMapper invocationMapper;
        private final Map functions = new WeakHashMap();
        private int callingConvention;
        public Handler(String libname, Class interfaceClass, Map options) {

            if (libname == null || "".equals(libname.trim())) {
                throw new IllegalArgumentException("Invalid library name \""
                                                   + libname + "\"");
            }

            this.nativeLibrary = NativeLibrary.getInstance(libname);
            this.interfaceClass = interfaceClass;
            this.options = options;
            this.callingConvention = 
                AltCallingConvention.class.isAssignableFrom(interfaceClass)
                ? Function.ALT_CONVENTION : Function.C_CONVENTION;
            functionMapper = (FunctionMapper)options.get(OPTION_FUNCTION_MAPPER);
            if (functionMapper == null) {
                // backward compatibility; passed-in map is itself the name map
                functionMapper = new FunctionNameMap(options);
            }
            invocationMapper = (InvocationMapper)options.get(OPTION_INVOCATION_MAPPER);
        }

        public NativeLibrary getNativeLibrary() {
            return nativeLibrary;
        }
        
        public String getLibraryName() {
            return nativeLibrary.getName();
        }

        public Class getInterfaceClass() {
            return interfaceClass;
        }
        
        private static class FunctionInfo {
            InvocationHandler handler;
            Function function;
            boolean isVarArgs;
            Map options;
        }

        public Object invoke(Object proxy, Method method, Object[] inArgs)
            throws Throwable {

            // Intercept Object methods
            if (OBJECT_TOSTRING.equals(method)) {
                return "Proxy interface to " + nativeLibrary;
            }
            else if (OBJECT_HASHCODE.equals(method)) {
                return new Integer(hashCode());
            }
            else if (OBJECT_EQUALS.equals(method)) {
                Object o = inArgs[0];
                if (o != null && Proxy.isProxyClass(o.getClass())) {
                    return Function.valueOf(Proxy.getInvocationHandler(o) == this);
                }
                return Boolean.FALSE;
            }
            
            FunctionInfo f = null;
            synchronized(functions) {
                f = (FunctionInfo)functions.get(method);
                if (f == null) {
                    f = new FunctionInfo();
                    f.isVarArgs = Function.isVarArgs(method);
                    if (invocationMapper != null) {
                        f.handler = invocationMapper.getInvocationHandler(nativeLibrary, method);
                    }
                    if (f.handler == null) {
                        // Find the function to invoke
                        String methodName = 
                            functionMapper.getFunctionName(nativeLibrary, method);
                        if (methodName == null) {
                            // Just in case the function mapper screwed up
                            methodName = method.getName();
                        }
                        f.function = nativeLibrary.getFunction(methodName, callingConvention);
                        f.options = new HashMap(this.options);
                        f.options.put(Function.OPTION_INVOKING_METHOD, method);
                    }
                    functions.put(method, f);
                }
            }
            if (f.isVarArgs) {
                inArgs = Function.concatenateVarArgs(inArgs);
            }
            if (f.handler != null) {
                return f.handler.invoke(proxy, method, inArgs);
            }
            return f.function.invoke(method.getReturnType(), inArgs, f.options);
        }
    }
}

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