jtie_tconv_value_impl.hpp

/*
 Copyright 2010 Sun Microsystems, Inc.
 All rights reserved. Use is subject to license terms.

 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_value_impl.hpp
 */

#ifndef jtie_tconv_value_impl_hpp
#define jtie_tconv_value_impl_hpp

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

#include "jtie_tconv_value.hpp"
#include "jtie_tconv_impl.hpp"
#include "helpers.hpp"

// ---------------------------------------------------------------------------
// Java <-> C basic type conversions
// ---------------------------------------------------------------------------

// Implements primitive type parameter conversions.
template< typename J, typename C >
struct ParamBasicT {
    static C
    convert(cstatus & s, J j, JNIEnv * env) {
        TRACE("C ParamBasicT.convert(cstatus &, J, JNIEnv *)");
        (void)env;
        s = 0;
        // XXX assert(static_cast< J >(static_cast< C >(j)) == j);
        return static_cast< C >(j); // may convert to unsigned type
    }

    static void
    release(C c, J j, JNIEnv * env) {
        TRACE("void ParamBasicT.release(C, J, JNIEnv *)");
        (void)c; (void)j; (void)env;
    }

private:
    // prohibit instantiation
    ParamBasicT() {
        // prohibit unsupported template specializations
        is_valid_primitive_type_mapping< J, C >();
    }
};

// Implements primitive type result conversions.
template< typename J, typename C >
struct ResultBasicT {
    static J
    convert(C c, JNIEnv * env) {
        TRACE("J ResultBasicT.convert(C, JNIEnv *)");
        (void)env;
        // XXX assert(static_cast< C >(static_cast< J >(c)) == c);
        return static_cast< J >(c); // may convert to signed type
    }

private:
    // prohibit instantiation
    ResultBasicT() {
        // prohibit unsupported template specializations
        is_valid_primitive_type_mapping< J, C >();
    }
};

// ---------------------------------------------------------------------------
// Specializations for basic type conversions
// ---------------------------------------------------------------------------

// Avoid mapping types by broad, generic rules, which easily results in
// template instantiation ambiguities for non-primitive types.  Therefore,
// we enumerate all specicializations for primitive types.

// Lessons learned:
//
// Cannot extend Param/Result specializations for const types by a generic
// rule on the base class (no template match with this indirection)
//   template<> struct ParamBasicT< J, C const > : ParamBasicT< J, C > {};
//   template<> struct ResultBasicT< J, C const > : ResultBasicT< J, C > {};
// but have to specialize Param/Result directly
//   template<> struct Param< J, C const > : ParamBasicT< J, C > {};
//   template<> struct Result< J, C const > : ResultBasicT< J, C > {};
//
// Specializations must be defined over intrinsic types, not aliases
//
// Datatype     LP64    ILP64   LLP64   ILP32   LP32
// char         8       8       8       8       8
// short        16      16      16      16      16
// int          32      64      32      32      16
// long         64      64      32      32      32
// long long                    64
// pointer      64      64      64      32      32

// extend set of valid primitive type mappings for const value specializations
template < typename J, typename C >
struct is_valid_primitive_type_mapping< const J, C > {};
template < typename J, typename C >
struct is_valid_primitive_type_mapping< J, const C > {};
template < typename J, typename C >
struct is_valid_primitive_type_mapping< const J, const C > {};

// also provides specializations for 'const'
// template clutter can be reduced a bit: const value types do not need extra
// specializations of their implementation
//   ... : ParamBasicT< J, C const > {};
//   ... : ResultBasicT< J, C const > {};
// but can be derived from their non-const specializations
#define JTIE_SPECIALIZE_BASIC_TYPE_MAPPING( J, C )                      \
    template<> struct is_valid_primitive_type_mapping< J, C > {};       \
    template<> struct Param< J, C > : ParamBasicT< J, C > {};           \
    template<> struct Result< J, C > : ResultBasicT< J, C > {};         \
    template<> struct Param< J, C const > : ParamBasicT< J, C > {};     \
    template<> struct Result< J, C const > : ResultBasicT< J, C > {};

// ---------------------------------------------------------------------------
// Specializations for boolean conversions
// ---------------------------------------------------------------------------

// Implements boolean type parameter conversions.
template<>
struct ParamBasicT< jboolean, bool > {
    static bool
    convert(cstatus & s, jboolean j, JNIEnv * env) {
        TRACE("bool ParamBasicT.convert(cstatus &, jboolean, JNIEnv *)");
        (void)env;
        s = 0;
        // Java v C: jboolean is unsigned 8-bit, so, beware of truncation
        return (j == JNI_TRUE);
    }

    static void
    release(bool c, jboolean j, JNIEnv * env) {
        TRACE("void ParamBasicT.release(bool, jboolean, JNIEnv *)");
        (void)c; (void)j; (void)env;
    }
};

// Implements boolean type result conversions.
template<>
struct ResultBasicT< jboolean, bool > {
    static jboolean
    convert(bool c, JNIEnv * env) {
        TRACE("jboolean ResultBasicT.convert(bool, JNIEnv *)");
        (void)env;
        // Java v C: jboolean is unsigned 8-bit, so, beware of truncation
        // on some platforms, JNI_TRUE/FALSE seems top be defined as int
        return static_cast< jboolean >(c ? JNI_TRUE : JNI_FALSE);
    }
};

JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jboolean, bool)

// ---------------------------------------------------------------------------
// Specializations for exact-width number type conversions
// ---------------------------------------------------------------------------

JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jbyte, char)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jbyte, signed char)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jbyte, unsigned char)

JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jfloat, float)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jdouble, double)

// ---------------------------------------------------------------------------
// Specializations for variable-width number type conversions
// ---------------------------------------------------------------------------

// Datatype      LP32   ILP32   LP64    ILP64   LLP64
// char          8      8       8       8       8    
// short         16     16      16      16      16   
// int           16     32      32      64      32   
// long          32     32      64      64      32   
// long long                                    64
// pointer       32     32      64      64      64

// jshort in LP32, ILP32, LP64, ILP64, LLP64
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jshort, signed short)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jshort, unsigned short)

// jshort in LP32
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jshort, signed int)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jshort, unsigned int)

// jint in ILP32, LP64, LLP64
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jint, signed int)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jint, unsigned int)

// jint in LP32, ILP32, LLP64
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jint, signed long)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jint, unsigned long)

// jlong in ILP64
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jlong, signed int)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jlong, unsigned int)

// jlong in LP64, ILP64
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jlong, signed long)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jlong, unsigned long)

// jlong in LLP64
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jlong, signed long long)
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jlong, unsigned long long)

// jdouble
JTIE_SPECIALIZE_BASIC_TYPE_MAPPING(jdouble, long double)

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

#endif // jtie_tconv_value_impl_hpp