Quelle ReadOnlyNoLockVFS.cpp Sprache: C

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
* This VFS is built on top of the (unix|win32)-none, but it additionally
* sets any opened file as immutable, that allows to also open in read-only
* mode databases using WAL, or other journals that need auxiliary files, when
* such files cannot be created.
* This is useful when trying to read from third-party databases, avoiding any
* risk of creating auxiliary files (e.g. journals).
* It can only be used on read-only connections, because being a no-lock VFS
* it would be trivial to corrupt the data.
*/

#include "nsDebug.h"
#include "sqlite3.h"

#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))

#if defined(XP_WIN)
#  define BASE_VFS "win32-none"
#else
#  define BASE_VFS "unix-none"
#endif

#define VFS_NAME "readonly-immutable-nolock"

namespace {

static int vfsOpen(sqlite3_vfs* vfs, const char* zName, sqlite3_file* pFile,
                   int flags, int* pOutFlags) {
  if ((flags & SQLITE_OPEN_READONLY) == 0) {
    // This is not done to be used in readwrite connections.
    return SQLITE_CANTOPEN;
  }

  sqlite3_vfs* pOrigVfs = ORIGVFS(vfs);
  int rc = pOrigVfs->xOpen(pOrigVfs, zName, pFile, flags, pOutFlags);
  if (rc != SQLITE_OK) {
    return rc;
  }

  const sqlite3_io_methods* pOrigMethods = pFile->pMethods;

  // If the IO version is higher than the last known one, you should update
  // this IO adding appropriate methods for any methods added in the version
  // change.
  MOZ_ASSERT(pOrigMethods->iVersion <= 3);

  static const sqlite3_io_methods vfs_io_methods = {
      pOrigMethods->iVersion,           /* iVersion */
      pOrigMethods->xClose,             /* xClose */
      pOrigMethods->xRead,              /* xRead */
      pOrigMethods->xWrite,             /* xWrite */
      pOrigMethods->xTruncate,          /* xTruncate */
      pOrigMethods->xSync,              /* xSync */
      pOrigMethods->xFileSize,          /* xFileSize */
      pOrigMethods->xLock,              /* xLock */
      pOrigMethods->xUnlock,            /* xUnlock */
      pOrigMethods->xCheckReservedLock, /* xCheckReservedLock */
      pOrigMethods->xFileControl,       /* xFileControl */
      pOrigMethods->xSectorSize,        /* xSectorSize */
      [](sqlite3_file*) {
        return SQLITE_IOCAP_IMMUTABLE;
      },                         /* xDeviceCharacteristics */
      pOrigMethods->xShmMap,     /* xShmMap */
      pOrigMethods->xShmLock,    /* xShmLock */
      pOrigMethods->xShmBarrier, /* xShmBarrier */
      pOrigMethods->xShmUnmap,   /* xShmUnmap */
      pOrigMethods->xFetch,      /* xFetch */
      pOrigMethods->xUnfetch     /* xUnfetch */
  };
  pFile->pMethods = &vfs_io_methods;
  if (pOutFlags) {
    *pOutFlags = flags;
  }

  return SQLITE_OK;
}

}  // namespace

namespace mozilla::storage {

UniquePtr<sqlite3_vfs> ConstructReadOnlyNoLockVFS() {
  if (sqlite3_vfs_find(VFS_NAME) != nullptr) {
    return nullptr;
  }
  sqlite3_vfs* pOrigVfs = sqlite3_vfs_find(BASE_VFS);
  if (!pOrigVfs) {
    return nullptr;
  }

  // If the VFS version is higher than the last known one, you should update
  // this VFS adding appropriate methods for any methods added in the version
  // change.
  MOZ_ASSERT(pOrigVfs->iVersion <= 3);

  static const sqlite3_vfs vfs = {
      pOrigVfs->iVersion,          /* iVersion  */
      pOrigVfs->szOsFile,          /* szOsFile */
      pOrigVfs->mxPathname,        /* mxPathname */
      nullptr,                     /* pNext */
      VFS_NAME,                    /* zName */
      pOrigVfs,                    /* pAppData */
      vfsOpen,                     /* xOpen */
      pOrigVfs->xDelete,           /* xDelete */
      pOrigVfs->xAccess,           /* xAccess */
      pOrigVfs->xFullPathname,     /* xFullPathname */
      pOrigVfs->xDlOpen,           /* xDlOpen */
      pOrigVfs->xDlError,          /* xDlError */
      pOrigVfs->xDlSym,            /* xDlSym */
      pOrigVfs->xDlClose,          /* xDlClose */
      pOrigVfs->xRandomness,       /* xRandomness */
      pOrigVfs->xSleep,            /* xSleep */
      pOrigVfs->xCurrentTime,      /* xCurrentTime */
      pOrigVfs->xGetLastError,     /* xGetLastError */
      pOrigVfs->xCurrentTimeInt64, /* xCurrentTimeInt64 */
      pOrigVfs->xSetSystemCall,    /* xSetSystemCall */
      pOrigVfs->xGetSystemCall,    /* xGetSystemCall */
      pOrigVfs->xNextSystemCall    /* xNextSystemCall */
  };

  return MakeUnique<sqlite3_vfs>(vfs);
}

}  // namespace mozilla::storage

quality100%

¤ Dauer der Verarbeitung: 0.13 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.