duke@435: /*
coleenp@4037:  * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #ifndef SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP
stefank@2314: #define SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP
stefank@2314: 
duke@435: class jfieldIDWorkaround: AllStatic {
duke@435:   // This workaround is because JVMTI doesn't have distinct entry points
duke@435:   // for methods that use static jfieldIDs and instance jfieldIDs.
duke@435:   // The workaround is to steal a low-order bit:
duke@435:   //   a 1 means the jfieldID is an instance jfieldID,
duke@435:   //             and the rest of the word is the offset of the field.
duke@435:   //   a 0 means the jfieldID is a static jfieldID,
duke@435:   //             and the rest of the word is the JNIid*.
duke@435:   //
duke@435:   // Another low-order bit is used to mark if an instance field
duke@435:   // is accompanied by an indication of which class it applies to.
duke@435:   //
duke@435:   // Bit-format of a jfieldID (most significant first):
duke@435:   //  address:30        instance=0:1 checked=0:1
duke@435:   //  offset:30         instance=1:1 checked=0:1
duke@435:   //  klass:23 offset:7 instance=1:1 checked=1:1
duke@435:   //
duke@435:   // If the offset does not fit in 7 bits, or if the fieldID is
duke@435:   // not checked, then the checked bit is zero and the rest of
duke@435:   // the word (30 bits) contains only the offset.
duke@435:   //
duke@435:  private:
duke@435:   enum {
duke@435:     checked_bits           = 1,
duke@435:     instance_bits          = 1,
duke@435:     address_bits           = BitsPerWord - checked_bits - instance_bits,
duke@435: 
duke@435:     large_offset_bits      = address_bits,  // unioned with address
duke@435:     small_offset_bits      = 7,
duke@435:     klass_bits             = address_bits - small_offset_bits,
duke@435: 
duke@435:     checked_shift          = 0,
duke@435:     instance_shift         = checked_shift  + checked_bits,
duke@435:     address_shift          = instance_shift + instance_bits,
duke@435: 
duke@435:     offset_shift           = address_shift,  // unioned with address
duke@435:     klass_shift            = offset_shift + small_offset_bits,
duke@435: 
duke@435:     checked_mask_in_place  = right_n_bits(checked_bits)  << checked_shift,
duke@435:     instance_mask_in_place = right_n_bits(instance_bits) << instance_shift,
duke@435: #ifndef _WIN64
duke@435:     large_offset_mask      = right_n_bits(large_offset_bits),
duke@435:     small_offset_mask      = right_n_bits(small_offset_bits),
duke@435:     klass_mask             = right_n_bits(klass_bits)
duke@435: #endif
duke@435:     };
duke@435: 
duke@435: #ifdef _WIN64
duke@435:     // These values are too big for Win64
duke@435:     const static uintptr_t large_offset_mask = right_n_bits(large_offset_bits);
duke@435:     const static uintptr_t small_offset_mask = right_n_bits(small_offset_bits);
duke@435:     const static uintptr_t klass_mask        = right_n_bits(klass_bits);
duke@435: #endif
duke@435: 
duke@435:   // helper routines:
duke@435:   static bool is_checked_jfieldID(jfieldID id) {
duke@435:     uintptr_t as_uint = (uintptr_t) id;
duke@435:     return ((as_uint & checked_mask_in_place) != 0);
duke@435:   }
duke@435:   static intptr_t raw_instance_offset(jfieldID id) {
duke@435:     uintptr_t result = (uintptr_t) id >> address_shift;
duke@435:     if (VerifyJNIFields && is_checked_jfieldID(id)) {
duke@435:       result &= small_offset_mask;  // cut off the hash bits
duke@435:     }
duke@435:     return (intptr_t)result;
duke@435:   }
coleenp@4037:   static intptr_t encode_klass_hash(Klass* k, intptr_t offset);
coleenp@4037:   static bool             klass_hash_ok(Klass* k, jfieldID id);
coleenp@4037:   static void  verify_instance_jfieldID(Klass* k, jfieldID id);
duke@435: 
duke@435:  public:
coleenp@4037:   static bool is_valid_jfieldID(Klass* k, jfieldID id);
duke@435: 
coleenp@4037:   static bool is_instance_jfieldID(Klass* k, jfieldID id) {
duke@435:     uintptr_t as_uint = (uintptr_t) id;
duke@435:     return ((as_uint & instance_mask_in_place) != 0);
duke@435:   }
duke@435:   static bool is_static_jfieldID(jfieldID id) {
duke@435:     uintptr_t as_uint = (uintptr_t) id;
duke@435:     return ((as_uint & instance_mask_in_place) == 0);
duke@435:   }
duke@435: 
coleenp@4037:   static jfieldID to_instance_jfieldID(Klass* k, int offset) {
duke@435:     intptr_t as_uint = ((offset & large_offset_mask) << offset_shift) | instance_mask_in_place;
duke@435:     if (VerifyJNIFields) {
duke@435:       as_uint |= encode_klass_hash(k, offset);
duke@435:     }
duke@435:     jfieldID result = (jfieldID) as_uint;
duke@435: #ifndef ASSERT
duke@435:     // always verify in debug mode; switchable in anything else
duke@435:     if (VerifyJNIFields)
duke@435: #endif // ASSERT
duke@435:     {
duke@435:       verify_instance_jfieldID(k, result);
duke@435:     }
duke@435:     assert(raw_instance_offset(result) == (offset & large_offset_mask), "extract right offset");
duke@435:     return result;
duke@435:   }
duke@435: 
coleenp@4037:   static intptr_t from_instance_jfieldID(Klass* k, jfieldID id) {
duke@435: #ifndef ASSERT
duke@435:     // always verify in debug mode; switchable in anything else
duke@435:     if (VerifyJNIFields)
duke@435: #endif // ASSERT
duke@435:     {
duke@435:       verify_instance_jfieldID(k, id);
duke@435:     }
duke@435:     return raw_instance_offset(id);
duke@435:   }
duke@435: 
duke@435:   static jfieldID to_static_jfieldID(JNIid* id) {
duke@435:     assert(id->is_static_field_id(), "from_JNIid, but not static field id");
duke@435:     jfieldID result = (jfieldID) id;
duke@435:     assert(from_static_jfieldID(result) == id, "must produce the same static id");
duke@435:     return result;
duke@435:   }
duke@435: 
duke@435:   static JNIid* from_static_jfieldID(jfieldID id) {
duke@435:     assert(jfieldIDWorkaround::is_static_jfieldID(id),
duke@435:            "to_JNIid, but not static jfieldID");
duke@435:     JNIid* result = (JNIid*) id;
duke@435:     assert(result->is_static_field_id(), "to_JNIid, but not static field id");
duke@435:     return result;
duke@435:   }
duke@435: 
duke@435:   static jfieldID to_jfieldID(instanceKlassHandle k, int offset, bool is_static) {
duke@435:     if (is_static) {
duke@435:       JNIid *id = k->jni_id_for(offset);
duke@435:       debug_only(id->set_is_static_field_id());
duke@435:       return jfieldIDWorkaround::to_static_jfieldID(id);
duke@435:     } else {
duke@435:       return jfieldIDWorkaround::to_instance_jfieldID(k(), offset);
duke@435:     }
duke@435:   }
duke@435: };
stefank@2314: 
stefank@2314: #endif // SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP