jtie_tconv_object_impl.hpp

/*
 Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; version 2 of the License.

 This program 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 General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
*/
/*
 * jtie_tconv_object_impl.hpp
 */

#ifndef jtie_tconv_object_impl_hpp
#define jtie_tconv_object_impl_hpp

#include <assert.h> // not using namespaces yet
//#include <stdio.h> // not using namespaces yet
#include <jni.h>

#include "jtie_tconv_object.hpp"
#include "jtie_tconv_impl.hpp"
#include "jtie_tconv_idcache_impl.hpp"
#include "jtie_tconv_utils_impl.hpp"
#include "helpers.hpp"

// ---------------------------------------------------------------------------
// ObjectParam, Target, ObjectResult
// ---------------------------------------------------------------------------

// XXX cleanup, document

// Defines the field info type for Wrapper.cdelegate.
JTIE_DEFINE_FIELD_MEMBER_INFO(_Wrapper_cdelegate)

// Provides a (cached) access to field Id of Wrapper.cdelegate.
//typedef JniMemberId< NO_CACHING, _Wrapper_cdelegate > Wrapper_cdelegate;
typedef JniMemberId< WEAK_CACHING, _Wrapper_cdelegate > Wrapper_cdelegate;
//typedef JniMemberId< STRONG_CACHING, _Wrapper_cdelegate > Wrapper_cdelegate;

// XXX consider changing
//template< typename C > struct ObjectParam< _jtie_Object *, C * > {
// to
//template< typename J, typename C > struct ObjectParam< J *, C * > {
//
// same for Target, Result

// Implements the mapping of jtie_Objects parameters.
template< typename J, typename C >
struct ObjectParam;

// Implements the mapping of jtie_Object invocation targets.
template< typename J, typename C >
struct Target;

// Implements the mapping of jtie_Object results.
template< typename J, typename C >
struct ObjectResult;

// Implements the mapping of jtie_Objects parameters to pointers.
template< typename C >
struct ObjectParam< _jtie_Object *, C * > {
    static C *
    convert(cstatus & s, _jtie_Object * j, JNIEnv * env) {
        TRACE("C * ObjectParam.convert(cstatus &, _jtie_Object *, JNIEnv *)");        
        // init status to error
        s = -1;
        C * c = NULL;

        if (j == NULL) {
            // ok
            s = 0;
        } else {
            // get a (local or global) class object reference
            jclass cls = Wrapper_cdelegate::getClass(env);
            if (cls == NULL) {
                // exception pending
            } else {
                // get the field ID valid along with the class reference
                jfieldID fid = Wrapper_cdelegate::getId(env, cls);
                if (fid == NULL) {
                    // exception pending
                } else {
                    // get the field's value
                    jlong p = env->GetLongField(j, fid);
                    //printf("    c = %lx\n", (unsigned long)p);
                    if (p == 0L) {
                        const char * m
                            = ("JTie: Java wrapper object must have a"
                               " non-zero delegate when used as target or"
                               " argument in a method call"
                               " (file: " __FILE__ ")");
                        registerException(env, "java/lang/AssertionError", m);
                    } else {
                        // convert jlong to an address via intptr_t (C99)
                        intptr_t ip =  static_cast< intptr_t >(p);
                        assert(static_cast< jlong >(ip) == p);
                        c = reinterpret_cast< C * >(ip);
                        //printf("    c = %p\n", c);

                        // ok
                        s = 0;
                    }
                }
                // release reference (if needed)
                Wrapper_cdelegate::releaseRef(env, cls);
            }
        }
        return c;
    };

    static void
    release(C * c, _jtie_Object * j, JNIEnv * env) {
        TRACE("void ObjectParam.release(C *, _jtie_Object *, JNIEnv *)");
        //printf("    c = %lx\n", (unsigned long)c);
        (void)c; (void)j; (void)env;
    };
};

// Implements the mapping of jtie_Objects parameters to references.
template< typename C >
struct ObjectParam< _jtie_Object *, C & > {
    static C &
    convert(cstatus & s, _jtie_Object * j, JNIEnv * env) {
        TRACE("C & ObjectParam.convert(cstatus &, _jtie_Object *, JNIEnv *)");

        // init return value and status to error
        s = -1;
        C * c = NULL;

        if (j == NULL) {
            const char * msg
                = ("JTie: Java argument must not be null when mapped"
                   " to a C reference (file: " __FILE__ ")");
            registerException(env, "java/lang/IllegalArgumentException", msg);
        } else {
            c = ObjectParam< _jtie_Object *, C * >::convert(s, j, env);
            assert(s != 0 || c != NULL);
        }

        // never actually dereferenced if status indicates an error
        return *c;
    };

    static void
    release(C & c, _jtie_Object * j, JNIEnv * env) {
        TRACE("void ObjectParam.release(C &, _jtie_Object *, JNIEnv *)");
        ObjectParam< _jtie_Object *, C * >::release(&c, j, env);
    };
};

// Implements the mapping of jtie_Object invocation targets.
template< typename C >
struct Target< _jtie_Object *, C > {
    static C &
    convert(cstatus & s, _jtie_Object * j, JNIEnv * env) {
        TRACE("C & Target.convert(cstatus &, _jtie_Object *, JNIEnv *)");

        // init return value and status to error
        s = -1;
        C * c = NULL;

        if (j == NULL) {
            const char * msg = ("JTie: Java target object of a method call"
                                " must not be null (file: " __FILE__ ")");
            registerException(env, "java/lang/NullPointerException", msg);
        } else {
            // to avoid template instantiation clutter and ambiguities
            // specialize/delegate to either ObjectParam< _jtie_Object *, C * >
            // (preferred for smaller type space) or Param< J *, C * > 
            c = ObjectParam< _jtie_Object *, C * >::convert(s, j, env);
            assert(s != 0 || c != NULL);
        }

        // never actually dereferenced if status indicates an error
        return *c;
    };

    static void
    release(C & c, _jtie_Object * j, JNIEnv * env) {
        TRACE("void Target.release(C &, _jtie_Object *, JNIEnv *)");
        // match delegation in convert()
        ObjectParam< _jtie_Object *, C * >::release(&c, j, env);
    };
};

// Implements the mapping of jtie_Object results to pointers.
template< typename J, typename C >
struct ObjectResult< J *, C * > {
    // Provides a (cached) access to the method Id of the constructor of J.
    //typedef JniMemberId< NO_CACHING, J > J_ctor;
    typedef JniMemberId< WEAK_CACHING, J > J_ctor;
    //typedef JniMemberId< STRONG_CACHING, J > J_ctor;
    
    static J *
    convert(C * c, JNIEnv * env) {
        TRACE("J * ObjectResult.convert(JNIEnv *, C *)");
        J * j = NULL;

        if (c == NULL) {
            // ok
        } else {
            // get a (local or global) class object reference
            jclass cls = J_ctor::getClass(env);
            if (cls == NULL) {
                // exception pending
            } else {
                // get the method ID valid along with the class reference
                jmethodID cid = J_ctor::getId(env, cls);
                if (cid == NULL) {
                    // exception pending
                } else {
                    J * jo = wrapAsJavaObject(cls, cid, c, env);
                    if (jo == NULL) {
                        // exception pending
                    } else {
                        // ok
                        j = jo;
                    }
                }
                // release reference (if needed)
                J_ctor::releaseRef(env, cls);
            }
        }
        return j;
    }

private:
    // Constructs a Wrapper object of user-defined type.
    static J *
    wrapAsJavaObject(jclass cls, jmethodID cid, C * c, JNIEnv * env);
};

// Implements the mapping of jtie_Object results to references.
template< typename J , typename C >
struct ObjectResult< J *, C & > {
    static J *
    convert(C & c, JNIEnv * env) {
        TRACE("J * ObjectResult.convert(JNIEnv *, C &)");        
        J * j = NULL; // init to error
        C * p = &c;

        if (p == NULL) {
            const char * msg
                = ("JTie: returned C reference must not be null"
                   " (e.g., check if memory allocation has failed without"
                   " raising an exception, as can happen with older C++"
                   " compilers?) (file: " __FILE__ ")");
            registerException(env, "java/lang/AssertionError", msg);
        } else {
            // ok
            j = ObjectResult< J *, C * >::convert(p, env);
        }
        return j;
    }
};

// ---------------------------------------------------------------------------
// Helper functions
// ---------------------------------------------------------------------------

// Nullifies a Wrapper object's stored address of the native delegate.
inline void
detachWrapper(_jtie_Object * jo, JNIEnv * env) {
    // get a (local or global) class object reference
    // as a precaution, do not use env->GetObjectClass(jobject), for we
    // never want to access a field from a subclass that hides the delegate
    // field in Wrapper
    jclass cls = Wrapper_cdelegate::getClass(env);
    if (cls == NULL) {
        // exception pending
    } else {
        // get the field ID valid along with the class reference
        jfieldID fid = Wrapper_cdelegate::getId(env, cls);
        if (fid == NULL) {
            // exception pending
        } else {
            // convert address to a jlong via intptr_t (C99)
            //printf("    p = %p\n", c);
            intptr_t ip = 0; //reinterpret_cast< intptr_t >((void*)NULL);
            jlong p = static_cast< jlong >(ip);
            assert(static_cast< intptr_t >(p) == ip);

            // set the field's value
            env->SetLongField(jo, fid, p);
        }
        // release reference (if needed)
        Wrapper_cdelegate::releaseRef(env, cls);
    }
}

// Constructs a Wrapper object of user-defined type.
template< typename J, typename C >
inline J *
ObjectResult< J *, C * >::
wrapAsJavaObject(jclass cls, jmethodID cid, C * c, JNIEnv * env) {
    J * j = NULL;

    // get a (local or global) class object reference
    // as a precaution, do not use parameter cls, for we never want to access
    // a field from a subclass that hides the delegate field in Wrapper
    jclass cls0 = Wrapper_cdelegate::getClass(env);
    if (cls0 == NULL) {
        // exception pending
    } else {
        // get the field ID valid along with the class reference
        jfieldID fid = Wrapper_cdelegate::getId(env, cls0);
        if (fid == NULL) {
            // exception pending
        } else {
            // construct a Wrapper object
            jobject jo = env->NewObject(cls, cid);
            if (jo == NULL) {
                // exception pending
            } else {
                // convert address to a jlong via intptr_t (C99)
                //printf("    p = %p\n", c);
                intptr_t ip = reinterpret_cast< intptr_t >(c);
                jlong p = static_cast< jlong >(ip);
                assert(static_cast< intptr_t >(p) == ip);

                // set the field's value
                env->SetLongField(jo, fid, p);

                // ok
                j = static_cast< J * >(jo);
            }
        }
        // release reference (if needed)
        Wrapper_cdelegate::releaseRef(env, cls0);
    }
    return j;
}

// ---------------------------------------------------------------------------
// Specializations for Object type conversions
// ---------------------------------------------------------------------------

// extend jtie_Object specializations to const pointers
template< typename J, typename C >
struct Param< _jtie_ObjectMapper< J > *, C * const >
    : Param< _jtie_ObjectMapper< J > *, C * > {};
template< typename J, typename C >
struct Result< _jtie_ObjectMapper< J > *, C * const >
    :  Result< _jtie_ObjectMapper< J > *, C * > {};

// Sufficient to specialize Param<> and Target<> over jtie_Object.

// specialize Target (note usage of C, which is a direct type)
template< typename J, typename C >
struct Target< _jtie_ObjectMapper< J > *, C >
    : Target< _jtie_Object *, C > {};

// specialize Param for pointers (note usage of C)
template< typename J, typename C >
struct Param< _jtie_ObjectMapper< J > *, C * >
    : ObjectParam< _jtie_Object *, C * > {};

// specialize Param for references (note usage of C)
template< typename J, typename C >
struct Param< _jtie_ObjectMapper< J > *, C & >
    : ObjectParam< _jtie_Object *, C & > {};

// Result<> needs to be specialized over ObjectMapper, which carries
// additional information needed for instantiating Java wrapper objects.

// specialize Result for pointers (note usage of C)
template< typename J, typename C >
struct Result< _jtie_ObjectMapper< J > *, C * >
    : ObjectResult< _jtie_ObjectMapper< J > *, C * > {};

// specialize Result for references (note usage of C)
template< typename J, typename C >
struct Result< _jtie_ObjectMapper< J > *, C & >
    : ObjectResult< _jtie_ObjectMapper< J > *, C & > {};

// ---------------------------------------------------------------------------

#endif // jtie_tconv_object_impl_hpp