arangodb/lib/Basics/memory-map-posix.cpp

////////////////////////////////////////////////////////////////////////////////
/// @brief memory mapped files in posix
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2014 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// 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.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Dr. Oreste Costa-Panaia
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2012-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#include "memory-map.h"

#ifdef TRI_HAVE_POSIX_MMAP

#include "Basics/logging.h"
#include "Basics/tri-strings.h"

#include <sys/mman.h>

////////////////////////////////////////////////////////////////////////////////
// @brief flush memory mapped file to disk
////////////////////////////////////////////////////////////////////////////////

int TRI_FlushMMFile (int fileDescriptor,
                     void** mmHandle,
                     void* startingAddress,
                     size_t numOfBytesToFlush,
                     int flags) {

  // ...........................................................................
  // Possible flags to send are (based upon the Ubuntu Linux ASM include files:
  // #define MS_ASYNC        1             /* sync memory asynchronously */
  // #define MS_INVALIDATE   2               /* invalidate the caches */
  // #define MS_SYNC         4               /* synchronous memory sync */
  // Note: under windows all flushes are achieved synchronously
  //
  // *mmHandle should always be NULL
  // ...........................................................................

  int res;

  TRI_ASSERT(*mmHandle == NULL);

  res = msync(startingAddress, numOfBytesToFlush, flags);

#ifdef __APPLE__
  if (res == 0) {
    res = fcntl(fileDescriptor, F_FULLFSYNC, 0);
  }
#endif

  if (res == 0) {
    // msync was successful
    return TRI_ERROR_NO_ERROR;
  }

  if (errno == ENOMEM) {
    // we have synced a region that was not mapped

    // set a special error. ENOMEM (out of memory) is not appropriate
    LOG_ERROR("msync failed for range %p - %p", startingAddress, (void*) (((char*) startingAddress) + numOfBytesToFlush));

    return TRI_ERROR_ARANGO_MSYNC_FAILED;
  }

  return TRI_ERROR_SYS_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
// @brief memory map a file
////////////////////////////////////////////////////////////////////////////////

int TRI_MMFile (void* memoryAddress,
                size_t numOfBytesToInitialise,
                int memoryProtection,
                int flags,
                int fileDescriptor,
                void** mmHandle,
                int64_t offset,
                void** result) {

  off_t offsetRetyped = (off_t)(offset);

  *mmHandle = NULL; // only useful for windows

  *result = mmap(memoryAddress, numOfBytesToInitialise, memoryProtection, flags, fileDescriptor, offsetRetyped);

  if (*result != MAP_FAILED) {
    return TRI_ERROR_NO_ERROR;
  }

  if (errno == ENOMEM) {
    return TRI_ERROR_OUT_OF_MEMORY_MMAP;
  }

  return TRI_ERROR_SYS_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
// @brief unmap a memory-mapped file
////////////////////////////////////////////////////////////////////////////////

int TRI_UNMMFile (void* memoryAddress,
                  size_t numOfBytesToUnMap,
                  int fileDescriptor,
                  void** mmHandle) {
  int result;

  TRI_ASSERT(*mmHandle == NULL);

  result = munmap(memoryAddress, numOfBytesToUnMap);

  if (result == 0) {
    return TRI_ERROR_NO_ERROR;
  }

  if (errno == ENOSPC) {
    return TRI_ERROR_ARANGO_FILESYSTEM_FULL;
  }

  return TRI_ERROR_SYS_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
// @brief protect a region in a memory-mapped file
////////////////////////////////////////////////////////////////////////////////

int TRI_ProtectMMFile (void* memoryAddress,
                       size_t numOfBytesToProtect,
                       int flags,
                       int fileDescriptor,
                       void** mmHandle) {
  int result;

  TRI_ASSERT(*mmHandle == NULL);

  result = mprotect(memoryAddress, numOfBytesToProtect, flags);

  if (result == 0) {
    return TRI_ERROR_NO_ERROR;
  }

  return TRI_ERROR_SYS_ERROR;
}

#endif

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