Quelle aobjects.h Sprache: C

/****************************************************************************
**
**  This file is part of GAP, a system for computational discrete algebra.
**
**  Copyright of GAP belongs to its developers, whose names are too numerous
**  to list here. Please refer to the COPYRIGHT file for details.
**
**  SPDX-License-Identifier: GPL-2.0-or-later
*/

#ifndef GAP_AOBJECTS_H
#define GAP_AOBJECTS_H

#include "../objects.h"
#include "atomic.h"

#ifndef HPCGAP
#error This header is only meant to be used with HPC-GAP
#endif

StructInitInfo *InitInfoAObjects(void);
Obj NewAtomicRecord(UInt capacity);
Obj SetARecordField(Obj record, UInt field, Obj obj);
Obj GetARecordField(Obj record, UInt field);
Obj ElmARecord(Obj record, UInt rnam);
BOOL IsbARecord(Obj record, UInt rnam);
void AssARecord(Obj record, UInt rnam, Obj value);
void UnbARecord(Obj record, UInt rnam);

void AssTLRecord(Obj record, UInt field, Obj obj);
Obj GetTLRecordField(Obj record, UInt field);
Obj FromAtomicRecord(Obj record);
void SetTLDefault(Obj record, UInt rnam, Obj value);
void SetTLConstructor(Obj record, UInt rnam, Obj func);

Obj NewAtomicList(UInt tnum, UInt capacity);
Obj FromAtomicList(Obj list);
UInt AddAList(Obj list, Obj obj);
void AssAList(Obj list, Int pos, Obj obj);
Obj ElmAList(Obj list, Int pos);
Obj Elm0AList(Obj list, Int pos);
Obj LengthAList(Obj list);

/*****************************************************************************
**
*F  CompareAndSwapObj(<addr>, <old>, <new_>)
**
**  Atomically compare *<addr> with <old> and exchange for <new_>.
**
**  The function implements the usual compare-and-swap semantics for
**  objects. It atomically does the following:
**
**    (1) Compare *<addr> with <old>.
**    (2) Exchange *<addr> with <new_> if the comparison succeeded.
**
**  It returns a non-zero value if the comparison in (1) succeeded, zero
**  otherwise.
**  markuspf: renamed new to new_ for compatibility with C++ packages.
*/

EXPORT_INLINE int CompareAndSwapObj(Obj *addr, Obj old, Obj new_) {
#ifndef WARD_ENABLED
  return COMPARE_AND_SWAP((AtomicUInt *) addr,
    (AtomicUInt) old, (AtomicUInt) new_);
#endif
}

/*****************************************************************************
**
*F  ATOMIC_SET_ELM_PLIST(<list>, <index>, <value>)
*F  ATOMIC_SET_ELM_PLIST_ONCE(<list>, <index>, <value>)
*F  ATOMIC_ELM_PLIST(<list>, <index>)
**
**  Set or access plain lists atomically. The plain lists must be of fixed
**  size and not be resized concurrently with such operations. The functions
**  assume that <index> is in the range 1..LEN_PLIST(<list>).
**
**  <value> must be an atomic or immutable object or access to it must be
**  properly regulated by locks.
**
**  'ATOMIC_ELM_PLIST' and 'ATOMIC_SET_ELM_PLIST' read and write plain lists,
**  annotated with memory barriers that ensure that concurrent threads do
**  not read objects that have not been fully initialized.
**
**  'ATOMIC_SET_ELM_PLIST_ONCE' assigns a value similar to 'SET_PLIST',
**  but only if <list>[<index>] is currently unbound. If that value has
**  been bound already, it will return the existing value; otherwise it
**  assigns <value> and returns it.
**
**  Canonical usage to read or initialize the field of a plist is as
**  follows:
**
**    obj = ATOMIC_ELM_PLIST(list, index);
**    if (!obj) {
**       obj = ...;
**       obj = ATOMIC_SET_ELM_PLIST(list, index, obj);
**    }
**
**  This construction ensures that while <obj> may be calculated more
**  than once, all threads will share the same value; furthermore,
**  reading an alreadu initialized value is generally very cheap,
**  incurring the cost of a read, a read barrier, and a branch (which,
**  after initialization, will generally predicted correctly by branch
**  prediction logic).
*/

EXPORT_INLINE void ATOMIC_SET_ELM_PLIST(Obj list, UInt index, Obj value) {
#ifndef WARD_ENABLED
  Obj *contents = ADDR_OBJ(list);
  MEMBAR_WRITE(); /* ensure that contents[index] becomes visible to
                   * other threads only after value has become visible,
                   * too.
                   */
  contents[index] = value;
#endif
}

EXPORT_INLINE Obj ATOMIC_SET_ELM_PLIST_ONCE(Obj list, UInt index, Obj value) {
#ifndef WARD_ENABLED
  Obj *contents = ADDR_OBJ(list);
  Obj result;
  for (;;) {
    result = contents[index];
    if (result) {
      MEMBAR_READ(); // matching memory barrier.
      return result;
    }
    if (COMPARE_AND_SWAP((AtomicUInt *)(contents+index),
      (AtomicUInt) 0, (AtomicUInt) value)) {
      /* no extra memory barrier needed, a full barrier is implicit in the
       * COMPARE_AND_SWAP() call.
       */
      return value;
    }
  }
#endif
}

EXPORT_INLINE Obj ATOMIC_ELM_PLIST(Obj list, UInt index) {
#ifndef WARD_ENABLED
  const Obj *contents = CONST_ADDR_OBJ(list);
  Obj result;
  result = contents[index];
  MEMBAR_READ(); // matching memory barrier.
  return result;
#endif
}

#endif // GAP_AOBJECTS_H

quality93%

¤ Dauer der Verarbeitung: 0.26 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.