/*----------------------------------------------------------------------
  Copyright (c) 1999-2001, Digital Creations, Fredericksburg, VA, USA
  and Andrew Kuchling. All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:

    o Redistributions of source code must retain the above copyright
      notice, this list of conditions, and the disclaimer that follows.

    o Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions, and the following disclaimer in
      the documentation and/or other materials provided with the
      distribution.

    o Neither the name of Digital Creations nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS AND CONTRIBUTORS *AS
  IS* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DIGITAL
  CREATIONS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
  TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  DAMAGE.
------------------------------------------------------------------------*/


/*
 * Handwritten code to wrap version 3.x of the Berkeley DB library,
 * written to replace a SWIG-generated file.  It has since been updated
 * to compile with Berkeley DB versions 3.2 through 4.2.
 *
 * This module was started by Andrew Kuchling to remove the dependency
 * on SWIG in a package by Gregory P. Smith who based his work on a
 * similar package by Robin Dunn <robin@alldunn.com> which wrapped
 * Berkeley DB 2.7.x.
 *
 * Development of this module then returned full circle back to Robin Dunn
 * who worked on behalf of Digital Creations to complete the wrapping of
 * the DB 3.x API and to build a solid unit test suite.  Robin has
 * since gone onto other projects (wxPython).
 *
 * Gregory P. Smith <greg@krypto.org> was once again the maintainer.
 *
 * Since January 2008, new maintainer is Jesus Cea <jcea@jcea.es>.
 * Jesus Cea licenses this code to PSF under a Contributor Agreement.
 *
 * Use the pybsddb-users@lists.sf.net mailing list for all questions.
 * Things can change faster than the header of this file is updated.  This
 * file is shared with the PyBSDDB project at SourceForge:
 *
 * http://pybsddb.sf.net
 *
 * This file should remain backward compatible with Python 2.1, but see PEP
 * 291 for the most current backward compatibility requirements:
 *
 * http://www.python.org/peps/pep-0291.html
 *
 * This module contains 6 types:
 *
 * DB           (Database)
 * DBCursor     (Database Cursor)
 * DBEnv        (database environment)
 * DBTxn        (An explicit database transaction)
 * DBLock       (A lock handle)
 * DBSequence   (Sequence)
 *
 */

/* --------------------------------------------------------------------- */

/*
 * Portions of this module, associated unit tests and build scripts are the
 * result of a contract with The Written Word (http://thewrittenword.com/)
 * Many thanks go out to them for causing me to raise the bar on quality and
 * functionality, resulting in a better bsddb3 package for all of us to use.
 *
 * --Robin
 */

/* --------------------------------------------------------------------- */

#include <stddef.h>   /* for offsetof() */
#include <Python.h>

#define COMPILING_BSDDB_C
#include "bsddb.h"
#undef COMPILING_BSDDB_C

static char *rcs_id = "$Id: _bsddb.c 66568 2008-09-23 18:54:08Z jesus.cea $";

/* --------------------------------------------------------------------- */
/* Various macro definitions */

#if (PY_VERSION_HEX < 0x02050000)
typedef int Py_ssize_t;
#endif

#if (PY_VERSION_HEX < 0x02060000)  /* really: before python trunk r63675 */
/* This code now uses PyBytes* API function names instead of PyString*.
 * These #defines map to their equivalent on earlier python versions.    */
#define PyBytes_FromStringAndSize PyString_FromStringAndSize
#define PyBytes_FromString PyString_FromString
#define PyBytes_AsStringAndSize PyString_AsStringAndSize
#define PyBytes_Check PyString_Check
#define PyBytes_GET_SIZE PyString_GET_SIZE
#define PyBytes_AS_STRING PyString_AS_STRING
#endif

#if (PY_VERSION_HEX >= 0x03000000)
#define NUMBER_Check    PyLong_Check
#define NUMBER_AsLong   PyLong_AsLong
#define NUMBER_FromLong PyLong_FromLong
#else
#define NUMBER_Check    PyInt_Check
#define NUMBER_AsLong   PyInt_AsLong
#define NUMBER_FromLong PyInt_FromLong
#endif

#ifdef WITH_THREAD

/* These are for when calling Python --> C */
#define MYDB_BEGIN_ALLOW_THREADS Py_BEGIN_ALLOW_THREADS;
#define MYDB_END_ALLOW_THREADS Py_END_ALLOW_THREADS;

/* For 2.3, use the PyGILState_ calls */
#if (PY_VERSION_HEX >= 0x02030000)
#define MYDB_USE_GILSTATE
#endif

/* and these are for calling C --> Python */
#if defined(MYDB_USE_GILSTATE)
#define MYDB_BEGIN_BLOCK_THREADS \
		PyGILState_STATE __savestate = PyGILState_Ensure();
#define MYDB_END_BLOCK_THREADS \
		PyGILState_Release(__savestate);
#else /* MYDB_USE_GILSTATE */
/* Pre GILState API - do it the long old way */
static PyInterpreterState* _db_interpreterState = NULL;
#define MYDB_BEGIN_BLOCK_THREADS {                              \
        PyThreadState* prevState;                               \
        PyThreadState* newState;                                \
        PyEval_AcquireLock();                                   \
        newState  = PyThreadState_New(_db_interpreterState);    \
        prevState = PyThreadState_Swap(newState);

#define MYDB_END_BLOCK_THREADS                                  \
        newState = PyThreadState_Swap(prevState);               \
        PyThreadState_Clear(newState);                          \
        PyEval_ReleaseLock();                                   \
        PyThreadState_Delete(newState);                         \
        }
#endif /* MYDB_USE_GILSTATE */

#else
/* Compiled without threads - avoid all this cruft */
#define MYDB_BEGIN_ALLOW_THREADS
#define MYDB_END_ALLOW_THREADS
#define MYDB_BEGIN_BLOCK_THREADS
#define MYDB_END_BLOCK_THREADS

#endif

/* Should DB_INCOMPLETE be turned into a warning or an exception? */
#define INCOMPLETE_IS_WARNING 1

/* --------------------------------------------------------------------- */
/* Exceptions */

static PyObject* DBError;               /* Base class, all others derive from this */
static PyObject* DBCursorClosedError;   /* raised when trying to use a closed cursor object */
static PyObject* DBKeyEmptyError;       /* DB_KEYEMPTY: also derives from KeyError */
static PyObject* DBKeyExistError;       /* DB_KEYEXIST */
static PyObject* DBLockDeadlockError;   /* DB_LOCK_DEADLOCK */
static PyObject* DBLockNotGrantedError; /* DB_LOCK_NOTGRANTED */
static PyObject* DBNotFoundError;       /* DB_NOTFOUND: also derives from KeyError */
static PyObject* DBOldVersionError;     /* DB_OLD_VERSION */
static PyObject* DBRunRecoveryError;    /* DB_RUNRECOVERY */
static PyObject* DBVerifyBadError;      /* DB_VERIFY_BAD */
static PyObject* DBNoServerError;       /* DB_NOSERVER */
static PyObject* DBNoServerHomeError;   /* DB_NOSERVER_HOME */
static PyObject* DBNoServerIDError;     /* DB_NOSERVER_ID */
static PyObject* DBPageNotFoundError;   /* DB_PAGE_NOTFOUND */
static PyObject* DBSecondaryBadError;   /* DB_SECONDARY_BAD */

#if !INCOMPLETE_IS_WARNING
static PyObject* DBIncompleteError;     /* DB_INCOMPLETE */
#endif

static PyObject* DBInvalidArgError;     /* EINVAL */
static PyObject* DBAccessError;         /* EACCES */
static PyObject* DBNoSpaceError;        /* ENOSPC */
static PyObject* DBNoMemoryError;       /* DB_BUFFER_SMALL (ENOMEM when < 4.3) */
static PyObject* DBAgainError;          /* EAGAIN */
static PyObject* DBBusyError;           /* EBUSY  */
static PyObject* DBFileExistsError;     /* EEXIST */
static PyObject* DBNoSuchFileError;     /* ENOENT */
static PyObject* DBPermissionsError;    /* EPERM  */

#if (DBVER >= 42)
static PyObject* DBRepHandleDeadError;  /* DB_REP_HANDLE_DEAD */
#endif

static PyObject* DBRepUnavailError;     /* DB_REP_UNAVAIL */

#if (DBVER < 43)
#define	DB_BUFFER_SMALL		ENOMEM
#endif


/* --------------------------------------------------------------------- */
/* Structure definitions */

#if PYTHON_API_VERSION < 1010
#error "Python 2.1 or later required"
#endif


/* Defaults for moduleFlags in DBEnvObject and DBObject. */
#define DEFAULT_GET_RETURNS_NONE                1
#define DEFAULT_CURSOR_SET_RETURNS_NONE         1   /* 0 in pybsddb < 4.2, python < 2.4 */


/* See comment in Python 2.6 "object.h" */
#ifndef staticforward
#define staticforward static
#endif
#ifndef statichere
#define statichere static
#endif

staticforward PyTypeObject DB_Type, DBCursor_Type, DBEnv_Type, DBTxn_Type,
              DBLock_Type;
#if (DBVER >= 43)
staticforward PyTypeObject DBSequence_Type;
#endif

#ifndef Py_TYPE
/* for compatibility with Python 2.5 and earlier */
#define Py_TYPE(ob)              (((PyObject*)(ob))->ob_type)
#endif

#define DBObject_Check(v)           (Py_TYPE(v) == &DB_Type)
#define DBCursorObject_Check(v)     (Py_TYPE(v) == &DBCursor_Type)
#define DBEnvObject_Check(v)        (Py_TYPE(v) == &DBEnv_Type)
#define DBTxnObject_Check(v)        (Py_TYPE(v) == &DBTxn_Type)
#define DBLockObject_Check(v)       (Py_TYPE(v) == &DBLock_Type)
#if (DBVER >= 43)
#define DBSequenceObject_Check(v)   (Py_TYPE(v) == &DBSequence_Type)
#endif

#if (DBVER < 46)
  #define _DBC_close(dbc)           dbc->c_close(dbc)
  #define _DBC_count(dbc,a,b)       dbc->c_count(dbc,a,b)
  #define _DBC_del(dbc,a)           dbc->c_del(dbc,a)
  #define _DBC_dup(dbc,a,b)         dbc->c_dup(dbc,a,b)
  #define _DBC_get(dbc,a,b,c)       dbc->c_get(dbc,a,b,c)
  #define _DBC_pget(dbc,a,b,c,d)    dbc->c_pget(dbc,a,b,c,d)
  #define _DBC_put(dbc,a,b,c)       dbc->c_put(dbc,a,b,c)
#else
  #define _DBC_close(dbc)           dbc->close(dbc)
  #define _DBC_count(dbc,a,b)       dbc->count(dbc,a,b)
  #define _DBC_del(dbc,a)           dbc->del(dbc,a)
  #define _DBC_dup(dbc,a,b)         dbc->dup(dbc,a,b)
  #define _DBC_get(dbc,a,b,c)       dbc->get(dbc,a,b,c)
  #define _DBC_pget(dbc,a,b,c,d)    dbc->pget(dbc,a,b,c,d)
  #define _DBC_put(dbc,a,b,c)       dbc->put(dbc,a,b,c)
#endif


/* --------------------------------------------------------------------- */
/* Utility macros and functions */

#define INSERT_IN_DOUBLE_LINKED_LIST(backlink,object)                   \
    {                                                                   \
        object->sibling_next=backlink;                                  \
        object->sibling_prev_p=&(backlink);                             \
        backlink=object;                                                \
        if (object->sibling_next) {                                     \
          object->sibling_next->sibling_prev_p=&(object->sibling_next); \
        }                                                               \
    }

#define EXTRACT_FROM_DOUBLE_LINKED_LIST(object)                          \
    {                                                                    \
        if (object->sibling_next) {                                      \
            object->sibling_next->sibling_prev_p=object->sibling_prev_p; \
        }                                                                \
        *(object->sibling_prev_p)=object->sibling_next;                  \
    }

#define EXTRACT_FROM_DOUBLE_LINKED_LIST_MAYBE_NULL(object)               \
    {                                                                    \
        if (object->sibling_next) {                                      \
            object->sibling_next->sibling_prev_p=object->sibling_prev_p; \
        }                                                                \
        if (object->sibling_prev_p) {                                    \
            *(object->sibling_prev_p)=object->sibling_next;              \
        }                                                                \
    }

#define INSERT_IN_DOUBLE_LINKED_LIST_TXN(backlink,object)  \
    {                                                      \
        object->sibling_next_txn=backlink;                 \
        object->sibling_prev_p_txn=&(backlink);            \
        backlink=object;                                   \
        if (object->sibling_next_txn) {                    \
            object->sibling_next_txn->sibling_prev_p_txn=  \
                &(object->sibling_next_txn);               \
        }                                                  \
    }

#define EXTRACT_FROM_DOUBLE_LINKED_LIST_TXN(object)             \
    {                                                           \
        if (object->sibling_next_txn) {                         \
            object->sibling_next_txn->sibling_prev_p_txn=       \
                object->sibling_prev_p_txn;                     \
        }                                                       \
        *(object->sibling_prev_p_txn)=object->sibling_next_txn; \
    }


#define RETURN_IF_ERR()          \
    if (makeDBError(err)) {      \
        return NULL;             \
    }

#define RETURN_NONE()  Py_INCREF(Py_None); return Py_None;

#define _CHECK_OBJECT_NOT_CLOSED(nonNull, pyErrObj, name) \
    if ((nonNull) == NULL) {          \
        PyObject *errTuple = NULL;    \
        errTuple = Py_BuildValue("(is)", 0, #name " object has been closed"); \
        if (errTuple) { \
            PyErr_SetObject((pyErrObj), errTuple);  \
            Py_DECREF(errTuple);          \
        } \
        return NULL;                  \
    }

#define CHECK_DB_NOT_CLOSED(dbobj) \
        _CHECK_OBJECT_NOT_CLOSED(dbobj->db, DBError, DB)

#define CHECK_ENV_NOT_CLOSED(env) \
        _CHECK_OBJECT_NOT_CLOSED(env->db_env, DBError, DBEnv)

#define CHECK_CURSOR_NOT_CLOSED(curs) \
        _CHECK_OBJECT_NOT_CLOSED(curs->dbc, DBCursorClosedError, DBCursor)

#if (DBVER >= 43)
#define CHECK_SEQUENCE_NOT_CLOSED(curs) \
        _CHECK_OBJECT_NOT_CLOSED(curs->sequence, DBError, DBSequence)
#endif

#define CHECK_DBFLAG(mydb, flag)    (((mydb)->flags & (flag)) || \
                                     (((mydb)->myenvobj != NULL) && ((mydb)->myenvobj->flags & (flag))))

#define CLEAR_DBT(dbt)              (memset(&(dbt), 0, sizeof(dbt)))

#define FREE_DBT(dbt)               if ((dbt.flags & (DB_DBT_MALLOC|DB_DBT_REALLOC)) && \
                                         dbt.data != NULL) { free(dbt.data); dbt.data = NULL; }


static int makeDBError(int err);


/* Return the access method type of the DBObject */
static int _DB_get_type(DBObject* self)
{
    DBTYPE type;
    int err;

    err = self->db->get_type(self->db, &type);
    if (makeDBError(err)) {
        return -1;
    }
    return type;
}


/* Create a DBT structure (containing key and data values) from Python
   strings.  Returns 1 on success, 0 on an error. */
static int make_dbt(PyObject* obj, DBT* dbt)
{
    CLEAR_DBT(*dbt);
    if (obj == Py_None) {
        /* no need to do anything, the structure has already been zeroed */
    }
    else if (!PyArg_Parse(obj, "s#", &dbt->data, &dbt->size)) {
        PyErr_SetString(PyExc_TypeError,
#if (PY_VERSION_HEX < 0x03000000)
                        "Data values must be of type string or None.");
#else
                        "Data values must be of type bytes or None.");
#endif
        return 0;
    }
    return 1;
}


/* Recno and Queue DBs can have integer keys.  This function figures out
   what's been given, verifies that it's allowed, and then makes the DBT.

   Caller MUST call FREE_DBT(key) when done. */
static int
make_key_dbt(DBObject* self, PyObject* keyobj, DBT* key, int* pflags)
{
    db_recno_t recno;
    int type;

    CLEAR_DBT(*key);
    if (keyobj == Py_None) {
        type = _DB_get_type(self);
        if (type == -1)
            return 0;
        if (type == DB_RECNO || type == DB_QUEUE) {
            PyErr_SetString(
                PyExc_TypeError,
                "None keys not allowed for Recno and Queue DB's");
            return 0;
        }
        /* no need to do anything, the structure has already been zeroed */
    }

    else if (PyBytes_Check(keyobj)) {
        /* verify access method type */
        type = _DB_get_type(self);
        if (type == -1)
            return 0;
        if (type == DB_RECNO || type == DB_QUEUE) {
            PyErr_SetString(
                PyExc_TypeError,
#if (PY_VERSION_HEX < 0x03000000)
                "String keys not allowed for Recno and Queue DB's");
#else
                "Bytes keys not allowed for Recno and Queue DB's");
#endif
            return 0;
        }

        /*
         * NOTE(gps): I don't like doing a data copy here, it seems
         * wasteful.  But without a clean way to tell FREE_DBT if it
         * should free key->data or not we have to.  Other places in
         * the code check for DB_THREAD and forceably set DBT_MALLOC
         * when we otherwise would leave flags 0 to indicate that.
         */
        key->data = malloc(PyBytes_GET_SIZE(keyobj));
        if (key->data == NULL) {
            PyErr_SetString(PyExc_MemoryError, "Key memory allocation failed");
            return 0;
        }
        memcpy(key->data, PyBytes_AS_STRING(keyobj),
               PyBytes_GET_SIZE(keyobj));
        key->flags = DB_DBT_REALLOC;
        key->size = PyBytes_GET_SIZE(keyobj);
    }

    else if (NUMBER_Check(keyobj)) {
        /* verify access method type */
        type = _DB_get_type(self);
        if (type == -1)
            return 0;
        if (type == DB_BTREE && pflags != NULL) {
            /* if BTREE then an Integer key is allowed with the
             * DB_SET_RECNO flag */
            *pflags |= DB_SET_RECNO;
        }
        else if (type != DB_RECNO && type != DB_QUEUE) {
            PyErr_SetString(
                PyExc_TypeError,
                "Integer keys only allowed for Recno and Queue DB's");
            return 0;
        }

        /* Make a key out of the requested recno, use allocated space so DB
         * will be able to realloc room for the real key if needed. */
        recno = NUMBER_AsLong(keyobj);
        key->data = malloc(sizeof(db_recno_t));
        if (key->data == NULL) {
            PyErr_SetString(PyExc_MemoryError, "Key memory allocation failed");
            return 0;
        }
        key->ulen = key->size = sizeof(db_recno_t);
        memcpy(key->data, &recno, sizeof(db_recno_t));
        key->flags = DB_DBT_REALLOC;
    }
    else {
        PyErr_Format(PyExc_TypeError,
#if (PY_VERSION_HEX < 0x03000000)
                     "String or Integer object expected for key, %s found",
#else
                     "Bytes or Integer object expected for key, %s found",
#endif
                     Py_TYPE(keyobj)->tp_name);
        return 0;
    }

    return 1;
}


/* Add partial record access to an existing DBT data struct.
   If dlen and doff are set, then the DB_DBT_PARTIAL flag will be set
   and the data storage/retrieval will be done using dlen and doff. */
static int add_partial_dbt(DBT* d, int dlen, int doff) {
    /* if neither were set we do nothing (-1 is the default value) */
    if ((dlen == -1) && (doff == -1)) {
        return 1;
    }

    if ((dlen < 0) || (doff < 0)) {
        PyErr_SetString(PyExc_TypeError, "dlen and doff must both be >= 0");
        return 0;
    }

    d->flags = d->flags | DB_DBT_PARTIAL;
    d->dlen = (unsigned int) dlen;
    d->doff = (unsigned int) doff;
    return 1;
}

/* a safe strcpy() without the zeroing behaviour and semantics of strncpy. */
/* TODO: make this use the native libc strlcpy() when available (BSD)      */
unsigned int our_strlcpy(char* dest, const char* src, unsigned int n)
{
    unsigned int srclen, copylen;

    srclen = strlen(src);
    if (n <= 0)
	return srclen;
    copylen = (srclen > n-1) ? n-1 : srclen;
    /* populate dest[0] thru dest[copylen-1] */
    memcpy(dest, src, copylen);
    /* guarantee null termination */
    dest[copylen] = 0;

    return srclen;
}

/* Callback used to save away more information about errors from the DB
 * library. */
static char _db_errmsg[1024];
#if (DBVER <= 42)
static void _db_errorCallback(const char* prefix, char* msg)
#else
static void _db_errorCallback(const DB_ENV *db_env,
	const char* prefix, const char* msg)
#endif
{
    our_strlcpy(_db_errmsg, msg, sizeof(_db_errmsg));
}


/*
** We need these functions because some results
** are undefined if pointer is NULL. Some other
** give None instead of "".
**
** This functions are static and will be
** -I hope- inlined.
*/
static const char *DummyString = "This string is a simple placeholder";
static PyObject *Build_PyString(const char *p,int s)
{
  if (!p) {
    p=DummyString;
    assert(s==0);
  }
  return PyBytes_FromStringAndSize(p,s);
}

static PyObject *BuildValue_S(const void *p,int s)
{
  if (!p) {
    p=DummyString;
    assert(s==0);
  }
  return PyBytes_FromStringAndSize(p, s);
}

static PyObject *BuildValue_SS(const void *p1,int s1,const void *p2,int s2)
{
PyObject *a, *b, *r;

  if (!p1) {
    p1=DummyString;
    assert(s1==0);
  }
  if (!p2) {
    p2=DummyString;
    assert(s2==0);
  }

  if (!(a = PyBytes_FromStringAndSize(p1, s1))) {
      return NULL;
  }
  if (!(b = PyBytes_FromStringAndSize(p2, s2))) {
      Py_DECREF(a);
      return NULL;
  }

#if (PY_VERSION_HEX >= 0x02040000)
  r = PyTuple_Pack(2, a, b) ;
#else
  r = Py_BuildValue("OO", a, b);
#endif
  Py_DECREF(a);
  Py_DECREF(b);
  return r;
}

static PyObject *BuildValue_IS(int i,const void *p,int s)
{
  PyObject *a, *r;

  if (!p) {
    p=DummyString;
    assert(s==0);
  }

  if (!(a = PyBytes_FromStringAndSize(p, s))) {
      return NULL;
  }

  r = Py_BuildValue("iO", i, a);
  Py_DECREF(a);
  return r;
}

static PyObject *BuildValue_LS(long l,const void *p,int s)
{
  PyObject *a, *r;

  if (!p) {
    p=DummyString;
    assert(s==0);
  }

  if (!(a = PyBytes_FromStringAndSize(p, s))) {
      return NULL;
  }

  r = Py_BuildValue("lO", l, a);
  Py_DECREF(a);
  return r;
}



/* make a nice exception object to raise for errors. */
static int makeDBError(int err)
{
    char errTxt[2048];  /* really big, just in case... */
    PyObject *errObj = NULL;
    PyObject *errTuple = NULL;
    int exceptionRaised = 0;
    unsigned int bytes_left;

    switch (err) {
        case 0:                     /* successful, no error */      break;

#if (DBVER < 41)
        case DB_INCOMPLETE:
#if INCOMPLETE_IS_WARNING
            bytes_left = our_strlcpy(errTxt, db_strerror(err), sizeof(errTxt));
            /* Ensure that bytes_left never goes negative */
            if (_db_errmsg[0] && bytes_left < (sizeof(errTxt) - 4)) {
                bytes_left = sizeof(errTxt) - bytes_left - 4 - 1;
		assert(bytes_left >= 0);
                strcat(errTxt, " -- ");
                strncat(errTxt, _db_errmsg, bytes_left);
            }
            _db_errmsg[0] = 0;
            exceptionRaised = PyErr_Warn(PyExc_RuntimeWarning, errTxt);

#else  /* do an exception instead */
        errObj = DBIncompleteError;
#endif
        break;
#endif /* DBVER < 41 */

        case DB_KEYEMPTY:           errObj = DBKeyEmptyError;       break;
        case DB_KEYEXIST:           errObj = DBKeyExistError;       break;
        case DB_LOCK_DEADLOCK:      errObj = DBLockDeadlockError;   break;
        case DB_LOCK_NOTGRANTED:    errObj = DBLockNotGrantedError; break;
        case DB_NOTFOUND:           errObj = DBNotFoundError;       break;
        case DB_OLD_VERSION:        errObj = DBOldVersionError;     break;
        case DB_RUNRECOVERY:        errObj = DBRunRecoveryError;    break;
        case DB_VERIFY_BAD:         errObj = DBVerifyBadError;      break;
        case DB_NOSERVER:           errObj = DBNoServerError;       break;
        case DB_NOSERVER_HOME:      errObj = DBNoServerHomeError;   break;
        case DB_NOSERVER_ID:        errObj = DBNoServerIDError;     break;
        case DB_PAGE_NOTFOUND:      errObj = DBPageNotFoundError;   break;
        case DB_SECONDARY_BAD:      errObj = DBSecondaryBadError;   break;
        case DB_BUFFER_SMALL:       errObj = DBNoMemoryError;       break;

#if (DBVER >= 43)
	/* ENOMEM and DB_BUFFER_SMALL were one and the same until 4.3 */
	case ENOMEM:  errObj = PyExc_MemoryError;   break;
#endif
        case EINVAL:  errObj = DBInvalidArgError;   break;
        case EACCES:  errObj = DBAccessError;       break;
        case ENOSPC:  errObj = DBNoSpaceError;      break;
        case EAGAIN:  errObj = DBAgainError;        break;
        case EBUSY :  errObj = DBBusyError;         break;
        case EEXIST:  errObj = DBFileExistsError;   break;
        case ENOENT:  errObj = DBNoSuchFileError;   break;
        case EPERM :  errObj = DBPermissionsError;  break;

#if (DBVER >= 42)
        case DB_REP_HANDLE_DEAD : errObj = DBRepHandleDeadError; break;
#endif

        case DB_REP_UNAVAIL : errObj = DBRepUnavailError; break;

        default:      errObj = DBError;             break;
    }

    if (errObj != NULL) {
        bytes_left = our_strlcpy(errTxt, db_strerror(err), sizeof(errTxt));
        /* Ensure that bytes_left never goes negative */
        if (_db_errmsg[0] && bytes_left < (sizeof(errTxt) - 4)) {
            bytes_left = sizeof(errTxt) - bytes_left - 4 - 1;
            assert(bytes_left >= 0);
            strcat(errTxt, " -- ");
            strncat(errTxt, _db_errmsg, bytes_left);
        }
        _db_errmsg[0] = 0;

        errTuple = Py_BuildValue("(is)", err, errTxt);
        if (errTuple == NULL) {
            Py_DECREF(errObj);
            return !0;
        }
        PyErr_SetObject(errObj, errTuple);
        Py_DECREF(errTuple);
    }

    return ((errObj != NULL) || exceptionRaised);
}



/* set a type exception */
static void makeTypeError(char* expected, PyObject* found)
{
    PyErr_Format(PyExc_TypeError, "Expected %s argument, %s found.",
                 expected, Py_TYPE(found)->tp_name);
}


/* verify that an obj is either None or a DBTxn, and set the txn pointer */
static int checkTxnObj(PyObject* txnobj, DB_TXN** txn)
{
    if (txnobj == Py_None || txnobj == NULL) {
        *txn = NULL;
        return 1;
    }
    if (DBTxnObject_Check(txnobj)) {
        *txn = ((DBTxnObject*)txnobj)->txn;
        return 1;
    }
    else
        makeTypeError("DBTxn", txnobj);
    return 0;
}


/* Delete a key from a database
  Returns 0 on success, -1 on an error.  */
static int _DB_delete(DBObject* self, DB_TXN *txn, DBT *key, int flags)
{
    int err;

    MYDB_BEGIN_ALLOW_THREADS;
    err = self->db->del(self->db, txn, key, 0);
    MYDB_END_ALLOW_THREADS;
    if (makeDBError(err)) {
        return -1;
    }
    self->haveStat = 0;
    return 0;
}


/* Store a key into a database
   Returns 0 on success, -1 on an error.  */
static int _DB_put(DBObject* self, DB_TXN *txn, DBT *key, DBT *data, int flags)
{
    int err;

    MYDB_BEGIN_ALLOW_THREADS;
    err = self->db->put(self->db, txn, key, data, flags);
    MYDB_END_ALLOW_THREADS;
    if (makeDBError(err)) {
        return -1;
    }
    self->haveStat = 0;
    return 0;
}

/* Get a key/data pair from a cursor */
static PyObject* _DBCursor_get(DBCursorObject* self, int extra_flags,
			       PyObject *args, PyObject *kwargs, char *format)
{
    int err;
    PyObject* retval = NULL;
    DBT key, data;
    int dlen = -1;
    int doff = -1;
    int flags = 0;
    static char* kwnames[] = { "flags", "dlen", "doff", NULL };

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, format, kwnames,
				     &flags, &dlen, &doff)) 
      return NULL;

    CHECK_CURSOR_NOT_CLOSED(self);

    flags |= extra_flags;
    CLEAR_DBT(key);
    CLEAR_DBT(data);
    if (!add_partial_dbt(&data, dlen, doff))
        return NULL;

    MYDB_BEGIN_ALLOW_THREADS;
    err = _DBC_get(self->dbc, &key, &data, flags);
    MYDB_END_ALLOW_THREADS;

    if ((err == DB_NOTFOUND || err == DB_KEYEMPTY)
	    && self->mydb->moduleFlags.getReturnsNone) {
        Py_INCREF(Py_None);
        retval = Py_None;
    }
    else if (makeDBError(err)) {
        retval = NULL;
    }
    else {  /* otherwise, success! */

        /* if Recno or Queue, return the key as an Int */
        switch (_DB_get_type(self->mydb)) {
        case -1:
            retval = NULL;
            break;

        case DB_RECNO:
        case DB_QUEUE:
            retval = BuildValue_IS(*((db_recno_t*)key.data), data.data, data.size);
            break;
        case DB_HASH:
        case DB_BTREE:
        default:
            retval = BuildValue_SS(key.data, key.size, data.data, data.size);
            break;
        }
    }
    return retval;
}


/* add an integer to a dictionary using the given name as a key */
static void _addIntToDict(PyObject* dict, char *name, int value)
{
    PyObject* v = NUMBER_FromLong((long) value);
    if (!v || PyDict_SetItemString(dict, name, v))
        PyErr_Clear();

    Py_XDECREF(v);
}

/* The same, when the value is a time_t */
static void _addTimeTToDict(PyObject* dict, char *name, time_t value)
{
    PyObject* v;
	/* if the value fits in regular int, use that. */
#ifdef PY_LONG_LONG
	if (sizeof(time_t) > sizeof(long))
		v = PyLong_FromLongLong((PY_LONG_LONG) value);
	else
#endif
		v = NUMBER_FromLong((long) value);
    if (!v || PyDict_SetItemString(dict, name, v))
        PyErr_Clear();

    Py_XDECREF(v);
}

#if (DBVER >= 43)
/* add an db_seq_t to a dictionary using the given name as a key */
static void _addDb_seq_tToDict(PyObject* dict, char *name, db_seq_t value)
{
    PyObject* v = PyLong_FromLongLong(value);
    if (!v || PyDict_SetItemString(dict, name, v))
        PyErr_Clear();

    Py_XDECREF(v);
}
#endif

static void _addDB_lsnToDict(PyObject* dict, char *name, DB_LSN value)
{
    PyObject *v = Py_BuildValue("(ll)",value.file,value.offset);
    if (!v || PyDict_SetItemString(dict, name, v))
        PyErr_Clear();

    Py_XDECREF(v);
}

/* --------------------------------------------------------------------- */
/* Allocators and deallocators */

static DBObject*
newDBObject(DBEnvObject* arg, int flags)
{
    DBObject* self;
    DB_ENV* db_env = NULL;
    int err;

    self = PyObject_New(DBObject, &DB_Type);
    if (self == NULL)
        return NULL;

    self->haveStat = 0;
    self->flags = 0;
    self->setflags = 0;
    self->myenvobj = NULL;
    self->db = NULL;
    self->children_cursors = NULL;
#if (DBVER >=43)
    self->children_sequences = NULL;
#endif
    self->associateCallback = NULL;
    self->btCompareCallback = NULL;
    self->primaryDBType = 0;
    Py_INCREF(Py_None);
    self->private_obj = Py_None;
    self->in_weakreflist = NULL;

    /* keep a reference to our python DBEnv object */
    if (arg) {
        Py_INCREF(arg);
        self->myenvobj = arg;
        db_env = arg->db_env;
        INSERT_IN_DOUBLE_LINKED_LIST(self->myenvobj->children_dbs,self);
    } else {
      self->sibling_prev_p=NULL;
      self->sibling_next=NULL;
    }
    self->txn=NULL;
    self->sibling_prev_p_txn=NULL;
    self->sibling_next_txn=NULL;

    if (self->myenvobj)
        self->moduleFlags = self->myenvobj->moduleFlags;
    else
        self->moduleFlags.getReturnsNone = DEFAULT_GET_RETURNS_NONE;
        self->moduleFlags.cursorSetReturnsNone = DEFAULT_CURSOR_SET_RETURNS_NONE;

    MYDB_BEGIN_ALLOW_THREADS;
    err = db_create(&self->db, db_env, flags);
    if (self->db != NULL) {
        self->db->set_errcall(self->db, _db_errorCallback);
        self->db->app_private = (void*)self;
    }
    MYDB_END_ALLOW_THREADS;
    /* TODO add a weakref(self) to the self->myenvobj->open_child_weakrefs
     * list so that a DBEnv can refuse to close without aborting any open
     * DBTxns and closing any open DBs first. */
    if (makeDBError(err)) {
        if (self->myenvobj) {
            Py_DECREF(self->myenvobj);
            self->myenvobj = NULL;
        }
        Py_DECREF(self);
        self = NULL;
    }
    return self;
}


/* Forward declaration */
static PyObject *DB_close_internal(DBObject* self, int flags, int do_not_close);

static void
DB_dealloc(DBObject* self)
{
  PyObject *dummy;

    if (self->db != NULL) {
        dummy=DB_close_internal(self, 0, 0);
        /*
        ** Raising exceptions while doing
        ** garbage collection is a fatal error.
        */
        if (dummy)
            Py_DECREF(dummy);
        else
            PyErr_Clear();
    }
    if (self->in_weakreflist != NULL) {
        PyObject_ClearWeakRefs((PyObject *) self);
    }
    if (self->myenvobj) {
        Py_DECREF(self->myenvobj);
        self->myenvobj = NULL;
    }
    if (self->associateCallback != NULL) {
        Py_DECREF(self->associateCallback);
        self->associateCallback = NULL;
    }
    if (self->btCompareCallback != NULL) {
        Py_DECREF(self->btCompareCallback);
        self->btCompareCallback = NULL;
    }
    Py_DECREF(self->private_obj);
    PyObject_Del(self);
}

static DBCursorObject*
newDBCursorObject(DBC* dbc, DBTxnObject *txn, DBObject* db)
{
    DBCursorObject* self = PyObject_New(DBCursorObject, &DBCursor_Type);
    if (self == NULL)
        return NULL;

    self->dbc = dbc;
    self->mydb = db;

    INSERT_IN_DOUBLE_LINKED_LIST(self->mydb->children_cursors,self);
    if (txn && ((PyObject *)txn!=Py_None)) {
	    INSERT_IN_DOUBLE_LINKED_LIST_TXN(txn->children_cursors,self);
	    self->txn=txn;
    } else {
	    self->txn=NULL;
    }

    self->in_weakreflist = NULL;
    Py_INCREF(self->mydb);
    return self;
}


/* Forward declaration */
static PyObject *DBC_close_internal(DBCursorObject* self);

static void
DBCursor_dealloc(DBCursorObject* self)
{
    PyObject *dummy;

    if (self->dbc != NULL) {
        dummy=DBC_close_internal(self);
        /*
        ** Raising exceptions while doing
        ** garbage collection is a fatal error.
        */
        if (dummy)
            Py_DECREF(dummy);
        else
            PyErr_Clear();
    }
    if (self->in_weakreflist != NULL) {
        PyObject_ClearWeakRefs((PyObject *) self);
    }
    Py_DECREF(self->mydb);
    PyObject_Del(self);
}


static DBEnvObject*
newDBEnvObject(int flags)
{
    int err;
    DBEnvObject* self = PyObject_New(DBEnvObject, &DBEnv_Type);
    if (self == NULL)
        return NULL;

    self->db_env = NULL;
    self->closed = 1;
    self->flags = flags;
    self->moduleFlags.getReturnsNone = DEFAULT_GET_RETURNS_NONE;
    self->moduleFlags.cursorSetReturnsNone = DEFAULT_CURSOR_SET_RETURNS_NONE;
    self->children_dbs = NULL;
    self->children_txns = NULL;
    Py_INCREF(Py_None);
    self->private_obj = Py_None;
    Py_INCREF(Py_None);
    self->rep_transport = Py_None;
    self->in_weakreflist = NULL;
    self->event_notifyCallback = NULL;

    MYDB_BEGIN_ALLOW_THREADS;
    err = db_env_create(&self->db_env, flags);
    MYDB_END_ALLOW_THREADS;
    if (makeDBError(err)) {
        Py_DECREF(self);
        self = NULL;
    }
    else {
        self->db_env->set_errcall(self->db_env, _db_errorCallback);
        self->db_env->app_private = self;
    }
    return self;
}

/* Forward declaration */
static PyObject *DBEnv_close_internal(DBEnvObject* self, int flags);

static void
DBEnv_dealloc(DBEnvObject* self)
{
  PyObject *dummy;

    if (self->db_env) {
        dummy=DBEnv_close_internal(self, 0);
        /*
        ** Raising exceptions while doing
        ** garbage collection is a fatal error.
        */
        if (dummy)
            Py_DECREF(dummy);
        else
            PyErr_Clear();
    }

    Py_XDECREF(self->event_notifyCallback);
    self->event_notifyCallback = NULL;

    if (self->in_weakreflist != NULL) {
        PyObject_ClearWeakRefs((PyObject *) self);
    }
    Py_DECREF(self->private_obj);
    Py_DECREF(self->rep_transport);
    PyObject_Del(self);
}


static DBTxnObject*
newDBTxnObject(DBEnvObject* myenv, DBTxnObject *parent, DB_TXN *txn, int flags)
{
    int err;
    DB_TXN *parent_txn = NULL;

    DBTxnObject* self = PyObject_New(DBTxnObject, &DBTxn_Type);
    if (self == NULL)
        return NULL;

    self->in_weakreflist = NULL;
    self->children_txns = NULL;
    self->children_dbs = NULL;
    self->children_cursors = NULL;
    self->children_sequences = NULL;
    self->flag_prepare = 0;
    self->parent_txn = NULL;
    self->env = NULL;

    if (parent && ((PyObject *)parent!=Py_None)) {
        parent_txn = parent->txn;
    }

    if (txn) {
        self->txn = txn;
    } else {
        MYDB_BEGIN_ALLOW_THREADS;
        err = myenv->db_env->txn_begin(myenv->db_env, parent_txn, &(self->txn), flags);
        MYDB_END_ALLOW_THREADS;

        if (makeDBError(err)) {
            Py_DECREF(self);
            return NULL;
        }
    }

    /* Can't use 'parent' because could be 'parent==Py_None' */
    if (parent_txn) {
        self->parent_txn = parent;
        Py_INCREF(parent);
        self->env = NULL;
        INSERT_IN_DOUBLE_LINKED_LIST(parent->children_txns, self);
    } else {
        self->parent_txn = NULL;
        Py_INCREF(myenv);
        self->env = myenv;
        INSERT_IN_DOUBLE_LINKED_LIST(myenv->children_txns, self);
    }

    return self;
}

/* Forward declaration */
static PyObject *
DBTxn_abort_discard_internal(DBTxnObject* self, int discard);

static void
DBTxn_dealloc(DBTxnObject* self)
{
  PyObject *dummy;

    if (self->txn) {
        int flag_prepare = self->flag_prepare;

        dummy=DBTxn_abort_discard_internal(self,0);
        /*
        ** Raising exceptions while doing
        ** garbage collection is a fatal error.
        */
        if (dummy)
            Py_DECREF(dummy);
        else
            PyErr_Clear();

        if (!flag_prepare) {
            PyErr_Warn(PyExc_RuntimeWarning,
              "DBTxn aborted in destructor.  No prior commit() or abort().");
        }
    }

    if (self->in_weakreflist != NULL) {
        PyObject_ClearWeakRefs((PyObject *) self);
    }

    if (self->env) {
        Py_DECREF(self->env);
    } else {
        Py_DECREF(self->parent_txn);
    }
    PyObject_Del(self);
}


static DBLockObject*
newDBLockObject(DBEnvObject* myenv, u_int32_t locker, DBT* obj,
                db_lockmode_t lock_mode, int flags)
{
    int err;
    DBLockObject* self = PyObject_New(DBLockObject, &DBLock_Type);
    if (self == NULL)
        return NULL;
    self->in_weakreflist = NULL;

    MYDB_BEGIN_ALLOW_THREADS;
    err = myenv->db_env->lock_get(myenv->db_env, locker, flags, obj, lock_mode,
                                  &self->lock);
    MYDB_END_ALLOW_THREADS;
    if (makeDBError(err)) {
        Py_DECREF(self);
        self = NULL;
    }

    return self;
}


static void
DBLock_dealloc(DBLockObject* self)
{
    if (self->in_weakreflist != NULL) {
        PyObject_ClearWeakRefs((PyObject *) self);
    }
    /* TODO: is this lock held? should we release it? */

    PyObject_Del(self);
}


#if (DBVER >= 43)
static DBSequenceObject*
newDBSequenceObject(DBObject* mydb,  int flags)
{
    int err;
    DBSequenceObject* self = PyObject_New(DBSequenceObject, &DBSequence_Type);
    if (self == NULL)
        return NULL;
    Py_INCREF(mydb);
    self->mydb = mydb;

    INSERT_IN_DOUBLE_LINKED_LIST(self->mydb->children_sequences,self);
    self->txn = NULL;

    self->in_weakreflist = NULL;

    MYDB_BEGIN_ALLOW_THREADS;
    err = db_sequence_create(&self->sequence, self->mydb->db, flags);
    MYDB_END_ALLOW_THREADS;
    if (makeDBError(err)) {
        Py_DECREF(self);
        self = NULL;
    }

    return self;
}

/* Forward declaration */
static PyObject
*DBSequence_close_internal(DBSequenceObject* self, int flags, int do_not_close);

static void
DBSequence_dealloc(DBSequenceObject* self)
{
    PyObject *dummy;

    if (self->sequence != NULL) {
        dummy=DBSequence_close_internal(self,0,0);
        /*
        ** Raising exceptions while doing
        ** garbage collection is a fatal error.
        */
        if (dummy)
            Py_DECREF(dummy);
        else
            PyErr_Clear();
    }

    if (self->in_weakreflist != NULL) {
        PyObject_ClearWeakRefs((PyObject *) self);
    }

    Py_DECREF(self->mydb);
    PyObject_Del(self);
}
#endif

/* --------------------------------------------------------------------- */
/* DB methods */

static PyObject*
DB_append(DBObject* self, PyObject* args, PyObject* kwargs)
{
    PyObject* txnobj = NULL;
    PyObject* dataobj;
    db_recno_t recno;
    DBT key, data;
    DB_TXN *txn = NULL;
    static char* kwnames[] = { "data", "txn", NULL };

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|O:append", kwnames,
                                     &dataobj, &txnobj))
        return NULL;

    CHECK_DB_NOT_CLOSED(self);

    /* make a dummy key out of a recno */
    recno = 0;
    CLEAR_DBT(key);
    key.data = &recno;
    key.size = sizeof(recno);
    key.ulen = key.size;
    key.flags = DB_DBT_USERMEM;

    if (!make_dbt(dataobj, &data)) return NULL;
    if (!checkTxnObj(txnobj, &txn)) return NULL;

    if (-1 == _DB_put(self, txn, &key, &data, DB_APPEND))
        return NULL;

    return NUMBER_FromLong(recno);
}


static int
_db_associateCallback(DB* db, const DBT* priKey, const DBT* priData,
                      DBT* secKey)
{
    int       retval = DB_DONOTINDEX;
    DBObject* secondaryDB = (DBObject*)db->app_private;
    PyObject* callback = secondaryDB->associateCallback;
    int       type = secondaryDB->primaryDBType;
    PyObject* args;
    PyObject* result = NULL;


    if (callback != NULL) {
        MYDB_BEGIN_BLOCK_THREADS;

        if (type == DB_RECNO || type == DB_QUEUE)
            args = BuildValue_LS(*((db_recno_t*)priKey->data), priData->data, priData->size);
        else
            args = BuildValue_SS(priKey->data, priKey->size, priData->data, priData->size);
        if (args != NULL) {
                result = PyEval_CallObject(callback, args);
        }
        if (args == NULL || result == NULL) {
            PyErr_Print();
        }
        else if (result == Py_None) {
            retval = DB_DONOTINDEX;
        }
        else if (NUMBER_Check(result)) {
            retval = NUMBER_AsLong(result);
        }
        else if (PyBytes_Check(result)) {
            char* data;
            Py_ssize_t size;

            CLEAR_DBT(*secKey);
            PyBytes_AsStringAndSize(result, &data, &size);
            secKey->flags = DB_DBT_APPMALLOC;   /* DB will free */
            secKey->data = malloc(size);        /* TODO, check this */
	    if (secKey->data) {
		memcpy(secKey->data, data, size);
		secKey->size = size;
		retval = 0;
	    }
	    else {
		PyErr_SetString(PyExc_MemoryError,
                                "malloc failed in _db_associateCallback");
		PyErr_Print();
	    }
        }
        else {
            PyErr_SetString(
               PyExc_TypeError,
               "DB associate callback should return DB_DONOTINDEX or string.");
            PyErr_Print();
        }

        Py_XDECREF(args);
        Py_XDECREF(result);

        MYDB_END_BLOCK_THREADS;
    }
    return retval;
}


static PyObject*
DB_associate(DBObject* self, PyObject* args, PyObject* kwargs)
{
    int err, flags=0;
    DBObject* secondaryDB;
    PyObject* callback;
#if (DBVER >= 41)
    PyObject *txnobj = NULL;
    DB_TXN *txn = NULL;
    static char* kwnames[] = {"secondaryDB", "callback", "flags", "txn",
                                    NULL};
#else
    static char* kwnames[] = {"secondaryDB", "callback", "flags", NULL};
#endif

#if (DBVER >= 41)
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "OO|iO:associate", kwnames,
                                     &secondaryDB, &callback, &flags,
                                     &txnobj)) {
#else
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "OO|i:associate", kwnames,
                                     &secondaryDB, &callback, &flags)) {
#endif
        return NULL;
    }

#if (DBVER >= 41)
    if (!checkTxnObj(txnobj, &txn)) return NULL;
#endif

    CHECK_DB_NOT_CLOSED(self);
    if (!DBObject_Check(secondaryDB)) {
        makeTypeError("DB", (PyObject*)secondaryDB);
        return NULL;
    }
    CHECK_DB_NOT_CLOSED(secondaryDB);
    if (callback == Py_None) {
        callback = NULL;
    }
    else if (!PyCallable_Check(callback)) {
        makeTypeError("Callable", callback);
        return NULL;
    }

    /* Save a reference to the callback in the secondary DB. */
    Py_XDECREF(secondaryDB->associateCallback);
    Py_XINCREF(callback);
    secondaryDB->associateCallback = callback;
    secondaryDB->primaryDBType = _DB_get_type(self);

    /* PyEval_InitThreads is called here due to a quirk in python 1.5
     * - 2.2.1 (at least) according to Russell Williamson <merel@wt.net>:
     * The global interepreter lock is not initialized until the first
     * thread is created using thread.start_new_thread() or fork() is
     * called.  that would cause the ALLOW_THREADS here to segfault due
     * to a null pointer reference if no threads or child processes
     * have been created.  This works around that and is a no-op if
     * threads have already been initialized.
     *  (see pybsddb-users mailing list post on 2002-08-07)
     */
#ifdef WITH_THREAD
    PyEval_InitThreads();
#endif
    MYDB_BEGIN_ALLOW_THREADS;
#if (DBVER >= 41)
    err = self->db->associate(self->db,
	                      txn,
                              secondaryDB->db,
                              _db_associateCallback,
                              flags);
#else
    err = self->db->associate(self->db,
                              secondaryDB->db,
                              _db_associateCallback,
                              flags);
#endif
    MYDB_END_ALLOW_THREADS;

    if (err) {
        Py_XDECREF(secondaryDB->associateCallback);
        secondaryDB->associateCallback = NULL;
        secondaryDB->primaryDBType = 0;
    }

    RETURN_IF_ERR();
    RETURN_NONE();
}


static PyObject*
DB_close_internal(DBObject* self, int flags, int do_not_close)
{
    PyObject *dummy;
    int err = 0;

    if (self->db != NULL) {
        /* Can be NULL if db is not in an environment */
        EXTRACT_FROM_DOUBLE_LINKED_LIST_MAYBE_NULL(self);

        if (self->txn) {
            EXTRACT_FROM_DOUBLE_LINKED_LIST_TXN(self);
            self->txn=NULL;
        }

        while(self->children_cursors) {
          dummy=DBC_close_internal(self->children_cursors);
          Py_XDECREF(dummy);
        }

#if (DBVER >= 43)
        while(self->children_sequences) {
            dummy=DBSequence_close_internal(self->children_sequences,0,0);
            Py_XDECREF(dummy);
        }
#endif

        /*
        ** "do_not_close" is used to dispose all related objects in the
        ** tree, without actually releasing the "root" object.
        ** This is done, for example, because function calls like
        ** "DB.verify()" implicitly close the underlying handle. So
        ** the handle doesn't need to be closed, but related objects
        ** must be cleaned up.
        */
        if (!do_not_close) {
            MYDB_BEGIN_ALLOW_THREADS;
            err = self->db->close(self->db, flags);
            MYDB_END_ALLOW_THREADS;
            self->db = NULL;
        }
        RETURN_IF_ERR();
    }
    RETURN_NONE();
}

static PyObject*
DB_close(DBObject* self, PyObject* args)
{
    int flags=0;
    if (!PyArg_ParseTuple(args,"|i:close", &flags))
        return NULL;
    return DB_close_internal(self, flags, 0);
}


static PyObject*
_DB_consume(DBObject* self, PyObject* args, PyObject* kwargs, int consume_flag)
{
    int err, flags=0, type;
    PyObject* txnobj = NULL;
    PyObject* retval = NULL;
    DBT key, data;
    DB_TXN *txn = NULL;
    static char* kwnames[] = { "txn", "flags", NULL };

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|Oi:consume", kwnames,
                                     &txnobj, &flags))
        return NULL;

    CHECK_DB_NOT_CLOSED(self);
    type = _DB_get_type(self);
    if (type == -1)
        return NULL;
    if (type != DB_QUEUE) {
        PyErr_SetString(PyExc_TypeError,
                        "Consume methods only allowed for Queue DB's");
        return NULL;
    }
    if (!checkTxnObj(txnobj, &txn))
        return NULL;

    CLEAR_DBT(key);
    CLEAR_DBT(data);
    if (CHECK_DBFLAG(self, DB_THREAD)) {
        /* Tell Berkeley DB to malloc the return value (thread safe) */
        data.flags = DB_DBT_MALLOC;
        key.flags = DB_DBT_MALLOC;
    }

    MYDB_BEGIN_ALLOW_THREADS;
    err = self->db->get(self->db, txn, &key, &data, flags|consume_flag);
    MYDB_END_ALLOW_THREADS;

    if ((err == DB_NOTFOUND || err == DB_KEYEMPTY)
	    && self->moduleFlags.getReturnsNone) {
        err = 0;
        Py_INCREF(Py_None);
        retval = Py_None;
    }
    else if (!err) {
        retval = BuildValue_SS(key.data, key.size, data.data, data.size);
        FREE_DBT(key);
        FREE_DBT(data);
    }

    RETURN_IF_ERR();
    return retval;
}

static PyObject*
DB_consume(DBObject* self, PyObject* args, PyObject* kwargs, int consume_flag)
{
    return _DB_consume(self, args, kwargs, DB_CONSUME);
}

static PyObject*
DB_consume_wait(DBObject* self, PyObject* args, PyObject* kwargs,
                int consume_flag)
{
    return _DB_consume(self, args, kwargs, DB_CONSUME_WAIT);
}


static PyObject*
DB_cursor(DBObject* self, PyObject* args, PyObject* kwargs)
{
    int err, flags=0;
    DBC* dbc;
    PyObject* txnobj = NULL;
    DB_TXN *txn = NULL;
    static char* kwnames[] = { "txn", "flags", NULL };

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|Oi:cursor", kwnames,…