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/*
 * Copyright (C) 2009 Wayne Meissner
 *
 * This file is part of jffi.
 * 
 * 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.
 *
 * 
 * Alternatively, 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 3 of the License, or
 * (at your option) any later version.
 *
 * This code 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.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this work.  If not, see .
 */

package com.kenai.jffi;

import java.util.Arrays;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Native function call context
 *
 * This class holds all the information that JFFI needs to correctly call a
 * native function, or to implement a callback from native code to java.
 */
public final class CallContext {
    /** The native address of the context */
    final long contextAddress;

    /** The number of parameters this function takes */
    private final int parameterCount;

    /** The size of buffer required when packing parameters */
    private final int rawParameterSize;

    /** The return type of this function */
    final Type returnType;

    /** The parameter types of this function */
    final Type[] parameterTypes;
    
    final long[] parameterTypeHandles;
    
    final int flags;

    volatile int disposed;

    final AtomicIntegerFieldUpdater UPDATER = AtomicIntegerFieldUpdater.newUpdater(CallContext.class, "disposed");

    /** A handle to the foreign interface to keep it alive as long as this object is alive */
    @SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
    private final Foreign foreign = Foreign.getInstance();

    /**
     * Returns a {@link CallContext} instance.  This may return a previously cached instance that matches
     * the signature requested, and should be used in preference to instantiating new instances.
     *
     * @param returnType The return type of the native function.
     * @param parameterTypes The parameter types the function accepts.
     * @param convention The calling convention of the function.
     * @param saveErrno Indicates that the errno should be saved
     * @return An instance of CallContext
     */
    public static CallContext getCallContext(Type returnType, Type[] parameterTypes, CallingConvention convention, boolean saveErrno) {
        return CallContextCache.getInstance().getCallContext(returnType, parameterTypes, convention, saveErrno);
    }

    public static CallContext getCallContext(Type returnType, Type[] parameterTypes, CallingConvention convention,
                                             boolean saveErrno, boolean faultProtect) {
        return CallContextCache.getInstance().getCallContext(returnType, parameterTypes, convention, saveErrno, faultProtect);
    }

    /**
     * Creates a new instance of Function with default calling convention.
     *
     * @param returnType The return type of the native function.
     * @param parameterTypes The parameter types the function accepts.
     */
    public CallContext(Type returnType, Type... parameterTypes) {
        this(returnType, parameterTypes, CallingConvention.DEFAULT, true);
    }

    /**
     * Creates a new instance of Function.
     *
     * Function instances created with this constructor will save the
     * C errno contents after each call.
     *
     * @param returnType The return type of the native function.
     * @param parameterTypes The parameter types the function accepts.
     * @param convention The calling convention of the function.
     */
    public CallContext(Type returnType, Type[] parameterTypes, CallingConvention convention) {
        this(returnType, parameterTypes, convention, true);
    }

    public CallContext(Type returnType, Type[] parameterTypes, CallingConvention convention, boolean saveErrno) {
        this(returnType, parameterTypes, convention, saveErrno, false);
    }

    /**
     * Creates a new instance of Function.
     *
     * @param returnType The return type of the native function.
     * @param parameterTypes The parameter types the function accepts.
     * @param convention The calling convention of the function.
     * @param saveErrno Whether the errno should be saved or not
     */
    CallContext(Type returnType, Type[] parameterTypes, CallingConvention convention,
                       boolean saveErrno, boolean faultProtect) {

        final int flags = (!saveErrno ? Foreign.F_NOERRNO : 0)
                | (convention == CallingConvention.STDCALL ? Foreign.F_STDCALL : Foreign.F_DEFAULT)
                | (faultProtect ? Foreign.F_PROTECT : 0);

        final long h = foreign.newCallContext(returnType.handle(),
                Type.nativeHandles(parameterTypes), flags);
        if (h == 0) {
            throw new RuntimeException("Failed to create native function");
        }
        this.contextAddress = h;

        //
        // Keep references to the return and parameter types so they do not get
        // garbage collected
        //
        this.returnType = returnType;
        this.parameterTypes = parameterTypes.clone();

        this.parameterCount = parameterTypes.length;
        this.rawParameterSize = foreign.getCallContextRawParameterSize(h);
        this.parameterTypeHandles = Type.nativeHandles(parameterTypes);
        this.flags = flags;
    }

    /**
     * Gets the number of parameters the native function accepts.
     *
     * @return The number of parameters the native function accepts.
     */
    public final int getParameterCount() {
        return parameterCount;
    }

    /**
     * Gets the number of bytes required to pack all the parameters this function
     * accepts, into a region of memory.
     *
     * @return The number of bytes required to store all paraameters of this function.
     */
    public final int getRawParameterSize() {
        return rawParameterSize;
    }

    /**
     * Gets the address of the function context.
     *
     * @return The address of the native function context struct.
     */
    final long getAddress() {
        return contextAddress;
    }

    /**
     * Gets the native return type of this function.
     *
     * @return The native return type of this function.
     */
    public final Type getReturnType() {
        return returnType;
    }

    /**
     * Gets the type of a parameter.
     *
     * @param index The index of the parameter in the function signature
     * @return The Type of the parameter.
     */
    public final Type getParameterType(int index) {
        return parameterTypes[index];
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        CallContext that = (CallContext) o;

        if (flags != that.flags) return false;
        if (parameterCount != that.parameterCount) return false;
        if (rawParameterSize != that.rawParameterSize) return false;
        if (!Arrays.equals(parameterTypes, that.parameterTypes)) return false;
        if (!returnType.equals(that.returnType)) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = parameterCount;
        result = 31 * result + returnType.hashCode();
        result = 31 * result + Arrays.hashCode(parameterTypes);
        result = 31 * result + flags;
        return result;
    }

    @Deprecated
    public final void dispose() {}

    @Override
    protected void finalize() throws Throwable {
        try {
            int disposed = UPDATER.getAndSet(this, 1);
            if (disposed == 0 && contextAddress != 0) {
                foreign.freeCallContext(contextAddress);
            }
        } catch (Throwable t) {
            Logger.getLogger(getClass().getName()).log(Level.WARNING, 
                    "exception when freeing " + getClass() + ": %s", t.getLocalizedMessage());
        } finally {
            super.finalize();
        }
    }
}