connection.c

/* connection.c - the connection type
 *
 * Copyright (C) 2004-2010 Gerhard Häring <gh@ghaering.de>
 *
 * This file is part of pysqlite.
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

#include "cache.h"
#include "module.h"
#include "structmember.h"         // PyMemberDef
#include "connection.h"
#include "statement.h"
#include "cursor.h"
#include "prepare_protocol.h"
#include "util.h"

#define ACTION_FINALIZE 1
#define ACTION_RESET 2

#if SQLITE_VERSION_NUMBER >= 3003008
#ifndef SQLITE_OMIT_LOAD_EXTENSION
#define HAVE_LOAD_EXTENSION
#endif
#endif

#if SQLITE_VERSION_NUMBER >= 3006011
#define HAVE_BACKUP_API
#endif

_Py_IDENTIFIER(cursor);

static const char * const begin_statements[] = {
    "BEGIN ",
    "BEGIN DEFERRED",
    "BEGIN IMMEDIATE",
    "BEGIN EXCLUSIVE",
    NULL
};

static int pysqlite_connection_set_isolation_level(pysqlite_Connection* self, PyObject* isolation_level, void *Py_UNUSED(ignored));
static void _pysqlite_drop_unused_cursor_references(pysqlite_Connection* self);


static void _sqlite3_result_error(sqlite3_context* ctx, const char* errmsg, int len)
{
    /* in older SQLite versions, calling sqlite3_result_error in callbacks
     * triggers a bug in SQLite that leads either to irritating results or
     * segfaults, depending on the SQLite version */
#if SQLITE_VERSION_NUMBER >= 3003003
    sqlite3_result_error(ctx, errmsg, len);
#else
    PyErr_SetString(pysqlite_OperationalError, errmsg);
#endif
}

int pysqlite_connection_init(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    static char *kwlist[] = {
        "database", "timeout", "detect_types", "isolation_level",
        "check_same_thread", "factory", "cached_statements", "uri",
        NULL
    };

    const char* database;
    PyObject* database_obj;
    int detect_types = 0;
    PyObject* isolation_level = NULL;
    PyObject* factory = NULL;
    int check_same_thread = 1;
    int cached_statements = 100;
    int uri = 0;
    double timeout = 5.0;
    int rc;

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O&|diOiOip", kwlist,
                                     PyUnicode_FSConverter, &database_obj, &timeout, &detect_types,
                                     &isolation_level, &check_same_thread,
                                     &factory, &cached_statements, &uri))
    {
        return -1;
    }

    if (PySys_Audit("sqlite3.connect", "O", database_obj) < 0) {
        return -1;
    }

    database = PyBytes_AsString(database_obj);

    self->begin_statement = NULL;

    Py_CLEAR(self->statement_cache);
    Py_CLEAR(self->statements);
    Py_CLEAR(self->cursors);

    Py_INCREF(Py_None);
    Py_XSETREF(self->row_factory, Py_None);

    Py_INCREF(&PyUnicode_Type);
    Py_XSETREF(self->text_factory, (PyObject*)&PyUnicode_Type);

#ifdef SQLITE_OPEN_URI
    Py_BEGIN_ALLOW_THREADS
    rc = sqlite3_open_v2(database, &self->db,
                         SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
                         (uri ? SQLITE_OPEN_URI : 0), NULL);
#else
    if (uri) {
        PyErr_SetString(pysqlite_NotSupportedError, "URIs not supported");
        return -1;
    }
    Py_BEGIN_ALLOW_THREADS
    /* No need to use sqlite3_open_v2 as sqlite3_open(filename, db) is the
       same as sqlite3_open_v2(filename, db, SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE, NULL). */
    rc = sqlite3_open(database, &self->db);
#endif
    Py_END_ALLOW_THREADS

    Py_DECREF(database_obj);

    if (rc != SQLITE_OK) {
        _pysqlite_seterror(self->db, NULL);
        return -1;
    }

    if (!isolation_level) {
        isolation_level = PyUnicode_FromString("");
        if (!isolation_level) {
            return -1;
        }
    } else {
        Py_INCREF(isolation_level);
    }
    Py_CLEAR(self->isolation_level);
    if (pysqlite_connection_set_isolation_level(self, isolation_level, NULL) != 0) {
        Py_DECREF(isolation_level);
        return -1;
    }
    Py_DECREF(isolation_level);

    self->statement_cache = (pysqlite_Cache*)PyObject_CallFunction((PyObject*)&pysqlite_CacheType, "Oi", self, cached_statements);
    if (PyErr_Occurred()) {
        return -1;
    }

    self->created_statements = 0;
    self->created_cursors = 0;

    /* Create lists of weak references to statements/cursors */
    self->statements = PyList_New(0);
    self->cursors = PyList_New(0);
    if (!self->statements || !self->cursors) {
        return -1;
    }

    /* By default, the Cache class INCREFs the factory in its initializer, and
     * decrefs it in its deallocator method. Since this would create a circular
     * reference here, we're breaking it by decrementing self, and telling the
     * cache class to not decref the factory (self) in its deallocator.
     */
    self->statement_cache->decref_factory = 0;
    Py_DECREF(self);

    self->detect_types = detect_types;
    self->timeout = timeout;
    (void)sqlite3_busy_timeout(self->db, (int)(timeout*1000));
    self->thread_ident = PyThread_get_thread_ident();
    if (!check_same_thread && sqlite3_libversion_number() < 3003001) {
        PyErr_SetString(pysqlite_NotSupportedError, "shared connections not available");
        return -1;
    }
    self->check_same_thread = check_same_thread;

    self->function_pinboard_trace_callback = NULL;
    self->function_pinboard_progress_handler = NULL;
    self->function_pinboard_authorizer_cb = NULL;

    Py_XSETREF(self->collations, PyDict_New());
    if (!self->collations) {
        return -1;
    }

    self->Warning               = pysqlite_Warning;
    self->Error                 = pysqlite_Error;
    self->InterfaceError        = pysqlite_InterfaceError;
    self->DatabaseError         = pysqlite_DatabaseError;
    self->DataError             = pysqlite_DataError;
    self->OperationalError      = pysqlite_OperationalError;
    self->IntegrityError        = pysqlite_IntegrityError;
    self->InternalError         = pysqlite_InternalError;
    self->ProgrammingError      = pysqlite_ProgrammingError;
    self->NotSupportedError     = pysqlite_NotSupportedError;

    self->initialized = 1;

    return 0;
}

/* action in (ACTION_RESET, ACTION_FINALIZE) */
void pysqlite_do_all_statements(pysqlite_Connection* self, int action, int reset_cursors)
{
    int i;
    PyObject* weakref;
    PyObject* statement;
    pysqlite_Cursor* cursor;

    for (i = 0; i < PyList_Size(self->statements); i++) {
        weakref = PyList_GetItem(self->statements, i);
        statement = PyWeakref_GetObject(weakref);
        if (statement != Py_None) {
            Py_INCREF(statement);
            if (action == ACTION_RESET) {
                (void)pysqlite_statement_reset((pysqlite_Statement*)statement);
            } else {
                (void)pysqlite_statement_finalize((pysqlite_Statement*)statement);
            }
            Py_DECREF(statement);
        }
    }

    if (reset_cursors) {
        for (i = 0; i < PyList_Size(self->cursors); i++) {
            weakref = PyList_GetItem(self->cursors, i);
            cursor = (pysqlite_Cursor*)PyWeakref_GetObject(weakref);
            if ((PyObject*)cursor != Py_None) {
                cursor->reset = 1;
            }
        }
    }
}

void pysqlite_connection_dealloc(pysqlite_Connection* self)
{
    Py_XDECREF(self->statement_cache);

    /* Clean up if user has not called .close() explicitly. */
    if (self->db) {
        SQLITE3_CLOSE(self->db);
    }

    Py_XDECREF(self->isolation_level);
    Py_XDECREF(self->function_pinboard_trace_callback);
    Py_XDECREF(self->function_pinboard_progress_handler);
    Py_XDECREF(self->function_pinboard_authorizer_cb);
    Py_XDECREF(self->row_factory);
    Py_XDECREF(self->text_factory);
    Py_XDECREF(self->collations);
    Py_XDECREF(self->statements);
    Py_XDECREF(self->cursors);
    Py_TYPE(self)->tp_free((PyObject*)self);
}

/*
 * Registers a cursor with the connection.
 *
 * 0 => error; 1 => ok
 */
int pysqlite_connection_register_cursor(pysqlite_Connection* connection, PyObject* cursor)
{
    PyObject* weakref;

    weakref = PyWeakref_NewRef((PyObject*)cursor, NULL);
    if (!weakref) {
        goto error;
    }

    if (PyList_Append(connection->cursors, weakref) != 0) {
        Py_CLEAR(weakref);
        goto error;
    }

    Py_DECREF(weakref);

    return 1;
error:
    return 0;
}

PyObject* pysqlite_connection_cursor(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    static char *kwlist[] = {"factory", NULL};
    PyObject* factory = NULL;
    PyObject* cursor;

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", kwlist,
                                     &factory)) {
        return NULL;
    }

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (factory == NULL) {
        factory = (PyObject*)&pysqlite_CursorType;
    }

    cursor = PyObject_CallOneArg(factory, (PyObject *)self);
    if (cursor == NULL)
        return NULL;
    if (!PyObject_TypeCheck(cursor, &pysqlite_CursorType)) {
        PyErr_Format(PyExc_TypeError,
                     "factory must return a cursor, not %.100s",
                     Py_TYPE(cursor)->tp_name);
        Py_DECREF(cursor);
        return NULL;
    }

    _pysqlite_drop_unused_cursor_references(self);

    if (cursor && self->row_factory != Py_None) {
        Py_INCREF(self->row_factory);
        Py_XSETREF(((pysqlite_Cursor *)cursor)->row_factory, self->row_factory);
    }

    return cursor;
}

PyObject* pysqlite_connection_close(pysqlite_Connection* self, PyObject* args)
{
    int rc;

    if (!pysqlite_check_thread(self)) {
        return NULL;
    }

    if (!self->initialized) {
        PyErr_SetString(pysqlite_ProgrammingError,
                        "Base Connection.__init__ not called.");
        return NULL;
    }

    pysqlite_do_all_statements(self, ACTION_FINALIZE, 1);

    if (self->db) {
        rc = SQLITE3_CLOSE(self->db);

        if (rc != SQLITE_OK) {
            _pysqlite_seterror(self->db, NULL);
            return NULL;
        } else {
            self->db = NULL;
        }
    }

    Py_RETURN_NONE;
}

/*
 * Checks if a connection object is usable (i. e. not closed).
 *
 * 0 => error; 1 => ok
 */
int pysqlite_check_connection(pysqlite_Connection* con)
{
    if (!con->initialized) {
        PyErr_SetString(pysqlite_ProgrammingError, "Base Connection.__init__ not called.");
        return 0;
    }

    if (!con->db) {
        PyErr_SetString(pysqlite_ProgrammingError, "Cannot operate on a closed database.");
        return 0;
    } else {
        return 1;
    }
}

PyObject* _pysqlite_connection_begin(pysqlite_Connection* self)
{
    int rc;
    const char* tail;
    sqlite3_stmt* statement;

    Py_BEGIN_ALLOW_THREADS
    rc = sqlite3_prepare_v2(self->db, self->begin_statement, -1, &statement, &tail);
    Py_END_ALLOW_THREADS

    if (rc != SQLITE_OK) {
        _pysqlite_seterror(self->db, statement);
        goto error;
    }

    rc = pysqlite_step(statement, self);
    if (rc != SQLITE_DONE) {
        _pysqlite_seterror(self->db, statement);
    }

    Py_BEGIN_ALLOW_THREADS
    rc = sqlite3_finalize(statement);
    Py_END_ALLOW_THREADS

    if (rc != SQLITE_OK && !PyErr_Occurred()) {
        _pysqlite_seterror(self->db, NULL);
    }

error:
    if (PyErr_Occurred()) {
        return NULL;
    } else {
        Py_RETURN_NONE;
    }
}

PyObject* pysqlite_connection_commit(pysqlite_Connection* self, PyObject* args)
{
    int rc;
    const char* tail;
    sqlite3_stmt* statement;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!sqlite3_get_autocommit(self->db)) {

        Py_BEGIN_ALLOW_THREADS
        rc = sqlite3_prepare_v2(self->db, "COMMIT", -1, &statement, &tail);
        Py_END_ALLOW_THREADS
        if (rc != SQLITE_OK) {
            _pysqlite_seterror(self->db, NULL);
            goto error;
        }

        rc = pysqlite_step(statement, self);
        if (rc != SQLITE_DONE) {
            _pysqlite_seterror(self->db, statement);
        }

        Py_BEGIN_ALLOW_THREADS
        rc = sqlite3_finalize(statement);
        Py_END_ALLOW_THREADS
        if (rc != SQLITE_OK && !PyErr_Occurred()) {
            _pysqlite_seterror(self->db, NULL);
        }

    }

error:
    if (PyErr_Occurred()) {
        return NULL;
    } else {
        Py_RETURN_NONE;
    }
}

PyObject* pysqlite_connection_rollback(pysqlite_Connection* self, PyObject* args)
{
    int rc;
    const char* tail;
    sqlite3_stmt* statement;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!sqlite3_get_autocommit(self->db)) {
        pysqlite_do_all_statements(self, ACTION_RESET, 1);

        Py_BEGIN_ALLOW_THREADS
        rc = sqlite3_prepare_v2(self->db, "ROLLBACK", -1, &statement, &tail);
        Py_END_ALLOW_THREADS
        if (rc != SQLITE_OK) {
            _pysqlite_seterror(self->db, NULL);
            goto error;
        }

        rc = pysqlite_step(statement, self);
        if (rc != SQLITE_DONE) {
            _pysqlite_seterror(self->db, statement);
        }

        Py_BEGIN_ALLOW_THREADS
        rc = sqlite3_finalize(statement);
        Py_END_ALLOW_THREADS
        if (rc != SQLITE_OK && !PyErr_Occurred()) {
            _pysqlite_seterror(self->db, NULL);
        }

    }

error:
    if (PyErr_Occurred()) {
        return NULL;
    } else {
        Py_RETURN_NONE;
    }
}

static int
_pysqlite_set_result(sqlite3_context* context, PyObject* py_val)
{
    if (py_val == Py_None) {
        sqlite3_result_null(context);
    } else if (PyLong_Check(py_val)) {
        sqlite_int64 value = _pysqlite_long_as_int64(py_val);
        if (value == -1 && PyErr_Occurred())
            return -1;
        sqlite3_result_int64(context, value);
    } else if (PyFloat_Check(py_val)) {
        sqlite3_result_double(context, PyFloat_AsDouble(py_val));
    } else if (PyUnicode_Check(py_val)) {
        Py_ssize_t sz;
        const char *str = PyUnicode_AsUTF8AndSize(py_val, &sz);
        if (str == NULL) {
            return -1;
        }
        if (sz > INT_MAX) {
            PyErr_SetString(PyExc_OverflowError,
                            "string is longer than INT_MAX bytes");
            return -1;
        }
        sqlite3_result_text(context, str, (int)sz, SQLITE_TRANSIENT);
    } else if (PyObject_CheckBuffer(py_val)) {
        Py_buffer view;
        if (PyObject_GetBuffer(py_val, &view, PyBUF_SIMPLE) != 0) {
            PyErr_SetString(PyExc_ValueError,
                            "could not convert BLOB to buffer");
            return -1;
        }
        if (view.len > INT_MAX) {
            PyErr_SetString(PyExc_OverflowError,
                            "BLOB longer than INT_MAX bytes");
            PyBuffer_Release(&view);
            return -1;
        }
        sqlite3_result_blob(context, view.buf, (int)view.len, SQLITE_TRANSIENT);
        PyBuffer_Release(&view);
    } else {
        return -1;
    }
    return 0;
}

PyObject* _pysqlite_build_py_params(sqlite3_context *context, int argc, sqlite3_value** argv)
{
    PyObject* args;
    int i;
    sqlite3_value* cur_value;
    PyObject* cur_py_value;
    Py_ssize_t buflen;

    args = PyTuple_New(argc);
    if (!args) {
        return NULL;
    }

    for (i = 0; i < argc; i++) {
        cur_value = argv[i];
        switch (sqlite3_value_type(argv[i])) {
            case SQLITE_INTEGER:
                cur_py_value = PyLong_FromLongLong(sqlite3_value_int64(cur_value));
                break;
            case SQLITE_FLOAT:
                cur_py_value = PyFloat_FromDouble(sqlite3_value_double(cur_value));
                break;
            case SQLITE_TEXT: {
                sqlite3 *db = sqlite3_context_db_handle(context);
                const char *text = (const char *)sqlite3_value_text(cur_value);

                if (text == NULL && sqlite3_errcode(db) == SQLITE_NOMEM) {
                    PyErr_NoMemory();
                    goto error;
                }

                Py_ssize_t size = sqlite3_value_bytes(cur_value);
                cur_py_value = PyUnicode_FromStringAndSize(text, size);
                break;
            }
            case SQLITE_BLOB:
                buflen = sqlite3_value_bytes(cur_value);
                cur_py_value = PyBytes_FromStringAndSize(
                    sqlite3_value_blob(cur_value), buflen);
                break;
            case SQLITE_NULL:
            default:
                Py_INCREF(Py_None);
                cur_py_value = Py_None;
        }

        if (!cur_py_value) {
            goto error;
        }

        PyTuple_SetItem(args, i, cur_py_value);

    }

    return args;

error:
    Py_DECREF(args);
    return NULL;
}

void _pysqlite_func_callback(sqlite3_context* context, int argc, sqlite3_value** argv)
{
    PyObject* args;
    PyObject* py_func;
    PyObject* py_retval = NULL;
    int ok;

    PyGILState_STATE threadstate;

    threadstate = PyGILState_Ensure();

    py_func = (PyObject*)sqlite3_user_data(context);

    args = _pysqlite_build_py_params(context, argc, argv);
    if (args) {
        py_retval = PyObject_CallObject(py_func, args);
        Py_DECREF(args);
    }

    ok = 0;
    if (py_retval) {
        ok = _pysqlite_set_result(context, py_retval) == 0;
        Py_DECREF(py_retval);
    }
    if (!ok) {
        if (_pysqlite_enable_callback_tracebacks) {
            PyErr_Print();
        } else {
            PyErr_Clear();
        }
        _sqlite3_result_error(context, "user-defined function raised exception", -1);
    }

    PyGILState_Release(threadstate);
}

static void _pysqlite_step_callback(sqlite3_context *context, int argc, sqlite3_value** params)
{
    PyObject* args;
    PyObject* function_result = NULL;
    PyObject* aggregate_class;
    PyObject** aggregate_instance;
    PyObject* stepmethod = NULL;

    PyGILState_STATE threadstate;

    threadstate = PyGILState_Ensure();

    aggregate_class = (PyObject*)sqlite3_user_data(context);

    aggregate_instance = (PyObject**)sqlite3_aggregate_context(context, sizeof(PyObject*));

    if (*aggregate_instance == NULL) {
        *aggregate_instance = _PyObject_CallNoArg(aggregate_class);

        if (PyErr_Occurred()) {
            *aggregate_instance = 0;
            if (_pysqlite_enable_callback_tracebacks) {
                PyErr_Print();
            } else {
                PyErr_Clear();
            }
            _sqlite3_result_error(context, "user-defined aggregate's '__init__' method raised error", -1);
            goto error;
        }
    }

    stepmethod = PyObject_GetAttrString(*aggregate_instance, "step");
    if (!stepmethod) {
        goto error;
    }

    args = _pysqlite_build_py_params(context, argc, params);
    if (!args) {
        goto error;
    }

    function_result = PyObject_CallObject(stepmethod, args);
    Py_DECREF(args);

    if (!function_result) {
        if (_pysqlite_enable_callback_tracebacks) {
            PyErr_Print();
        } else {
            PyErr_Clear();
        }
        _sqlite3_result_error(context, "user-defined aggregate's 'step' method raised error", -1);
    }

error:
    Py_XDECREF(stepmethod);
    Py_XDECREF(function_result);

    PyGILState_Release(threadstate);
}

void _pysqlite_final_callback(sqlite3_context* context)
{
    PyObject* function_result;
    PyObject** aggregate_instance;
    _Py_IDENTIFIER(finalize);
    int ok;
    PyObject *exception, *value, *tb;
    int restore;

    PyGILState_STATE threadstate;

    threadstate = PyGILState_Ensure();

    aggregate_instance = (PyObject**)sqlite3_aggregate_context(context, sizeof(PyObject*));
    if (!*aggregate_instance) {
        /* this branch is executed if there was an exception in the aggregate's
         * __init__ */

        goto error;
    }

    /* Keep the exception (if any) of the last call to step() */
    PyErr_Fetch(&exception, &value, &tb);
    restore = 1;

    function_result = _PyObject_CallMethodIdNoArgs(*aggregate_instance, &PyId_finalize);

    Py_DECREF(*aggregate_instance);

    ok = 0;
    if (function_result) {
        ok = _pysqlite_set_result(context, function_result) == 0;
        Py_DECREF(function_result);
    }
    if (!ok) {
        if (_pysqlite_enable_callback_tracebacks) {
            PyErr_Print();
        } else {
            PyErr_Clear();
        }
        _sqlite3_result_error(context, "user-defined aggregate's 'finalize' method raised error", -1);
#if SQLITE_VERSION_NUMBER < 3003003
        /* with old SQLite versions, _sqlite3_result_error() sets a new Python
           exception, so don't restore the previous exception */
        restore = 0;
#endif
    }

    if (restore) {
        /* Restore the exception (if any) of the last call to step(),
           but clear also the current exception if finalize() failed */
        PyErr_Restore(exception, value, tb);
    }

error:
    PyGILState_Release(threadstate);
}

static void _pysqlite_drop_unused_statement_references(pysqlite_Connection* self)
{
    PyObject* new_list;
    PyObject* weakref;
    int i;

    /* we only need to do this once in a while */
    if (self->created_statements++ < 200) {
        return;
    }

    self->created_statements = 0;

    new_list = PyList_New(0);
    if (!new_list) {
        return;
    }

    for (i = 0; i < PyList_Size(self->statements); i++) {
        weakref = PyList_GetItem(self->statements, i);
        if (PyWeakref_GetObject(weakref) != Py_None) {
            if (PyList_Append(new_list, weakref) != 0) {
                Py_DECREF(new_list);
                return;
            }
        }
    }

    Py_SETREF(self->statements, new_list);
}

static void _pysqlite_drop_unused_cursor_references(pysqlite_Connection* self)
{
    PyObject* new_list;
    PyObject* weakref;
    int i;

    /* we only need to do this once in a while */
    if (self->created_cursors++ < 200) {
        return;
    }

    self->created_cursors = 0;

    new_list = PyList_New(0);
    if (!new_list) {
        return;
    }

    for (i = 0; i < PyList_Size(self->cursors); i++) {
        weakref = PyList_GetItem(self->cursors, i);
        if (PyWeakref_GetObject(weakref) != Py_None) {
            if (PyList_Append(new_list, weakref) != 0) {
                Py_DECREF(new_list);
                return;
            }
        }
    }

    Py_SETREF(self->cursors, new_list);
}

static void _destructor(void* args)
{
    Py_DECREF((PyObject*)args);
}

PyObject* pysqlite_connection_create_function(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    static char *kwlist[] = {"name", "narg", "func", "deterministic", NULL};

    PyObject* func;
    char* name;
    int narg;
    int rc;
    int deterministic = 0;
    int flags = SQLITE_UTF8;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "siO|$p", kwlist,
                                     &name, &narg, &func, &deterministic))
    {
        return NULL;
    }

    if (deterministic) {
#if SQLITE_VERSION_NUMBER < 3008003
        PyErr_SetString(pysqlite_NotSupportedError,
                        "deterministic=True requires SQLite 3.8.3 or higher");
        return NULL;
#else
        if (sqlite3_libversion_number() < 3008003) {
            PyErr_SetString(pysqlite_NotSupportedError,
                            "deterministic=True requires SQLite 3.8.3 or higher");
            return NULL;
        }
        flags |= SQLITE_DETERMINISTIC;
#endif
    }
    Py_INCREF(func);
    rc = sqlite3_create_function_v2(self->db,
                                    name,
                                    narg,
                                    flags,
                                    (void*)func,
                                    _pysqlite_func_callback,
                                    NULL,
                                    NULL,
                                    &_destructor);  // will decref func

    if (rc != SQLITE_OK) {
        /* Workaround for SQLite bug: no error code or string is available here */
        PyErr_SetString(pysqlite_OperationalError, "Error creating function");
        return NULL;
    }
    Py_RETURN_NONE;
}

PyObject* pysqlite_connection_create_aggregate(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    PyObject* aggregate_class;

    int n_arg;
    char* name;
    static char *kwlist[] = { "name", "n_arg", "aggregate_class", NULL };
    int rc;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "siO:create_aggregate",
                                      kwlist, &name, &n_arg, &aggregate_class)) {
        return NULL;
    }
    Py_INCREF(aggregate_class);
    rc = sqlite3_create_function_v2(self->db,
                                    name,
                                    n_arg,
                                    SQLITE_UTF8,
                                    (void*)aggregate_class,
                                    0,
                                    &_pysqlite_step_callback,
                                    &_pysqlite_final_callback,
                                    &_destructor); // will decref func
    if (rc != SQLITE_OK) {
        /* Workaround for SQLite bug: no error code or string is available here */
        PyErr_SetString(pysqlite_OperationalError, "Error creating aggregate");
        return NULL;
    }
    Py_RETURN_NONE;
}

static int _authorizer_callback(void* user_arg, int action, const char* arg1, const char* arg2 , const char* dbname, const char* access_attempt_source)
{
    PyObject *ret;
    int rc;
    PyGILState_STATE gilstate;

    gilstate = PyGILState_Ensure();

    ret = PyObject_CallFunction((PyObject*)user_arg, "issss", action, arg1, arg2, dbname, access_attempt_source);

    if (ret == NULL) {
        if (_pysqlite_enable_callback_tracebacks)
            PyErr_Print();
        else
            PyErr_Clear();

        rc = SQLITE_DENY;
    }
    else {
        if (PyLong_Check(ret)) {
            rc = _PyLong_AsInt(ret);
            if (rc == -1 && PyErr_Occurred()) {
                if (_pysqlite_enable_callback_tracebacks)
                    PyErr_Print();
                else
                    PyErr_Clear();
                rc = SQLITE_DENY;
            }
        }
        else {
            rc = SQLITE_DENY;
        }
        Py_DECREF(ret);
    }

    PyGILState_Release(gilstate);
    return rc;
}

static int _progress_handler(void* user_arg)
{
    int rc;
    PyObject *ret;
    PyGILState_STATE gilstate;

    gilstate = PyGILState_Ensure();
    ret = _PyObject_CallNoArg((PyObject*)user_arg);

    if (!ret) {
        if (_pysqlite_enable_callback_tracebacks) {
            PyErr_Print();
        } else {
            PyErr_Clear();
        }

        /* abort query if error occurred */
        rc = 1;
    } else {
        rc = (int)PyObject_IsTrue(ret);
        Py_DECREF(ret);
    }

    PyGILState_Release(gilstate);
    return rc;
}

static void _trace_callback(void* user_arg, const char* statement_string)
{
    PyObject *py_statement = NULL;
    PyObject *ret = NULL;

    PyGILState_STATE gilstate;

    gilstate = PyGILState_Ensure();
    py_statement = PyUnicode_DecodeUTF8(statement_string,
            strlen(statement_string), "replace");
    if (py_statement) {
        ret = PyObject_CallOneArg((PyObject*)user_arg, py_statement);
        Py_DECREF(py_statement);
    }

    if (ret) {
        Py_DECREF(ret);
    } else {
        if (_pysqlite_enable_callback_tracebacks) {
            PyErr_Print();
        } else {
            PyErr_Clear();
        }
    }

    PyGILState_Release(gilstate);
}

static PyObject* pysqlite_connection_set_authorizer(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    PyObject* authorizer_cb;

    static char *kwlist[] = { "authorizer_callback", NULL };
    int rc;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O:set_authorizer",
                                      kwlist, &authorizer_cb)) {
        return NULL;
    }

    rc = sqlite3_set_authorizer(self->db, _authorizer_callback, (void*)authorizer_cb);
    if (rc != SQLITE_OK) {
        PyErr_SetString(pysqlite_OperationalError, "Error setting authorizer callback");
        Py_XSETREF(self->function_pinboard_authorizer_cb, NULL);
        return NULL;
    } else {
        Py_INCREF(authorizer_cb);
        Py_XSETREF(self->function_pinboard_authorizer_cb, authorizer_cb);
    }
    Py_RETURN_NONE;
}

static PyObject* pysqlite_connection_set_progress_handler(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    PyObject* progress_handler;
    int n;

    static char *kwlist[] = { "progress_handler", "n", NULL };

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "Oi:set_progress_handler",
                                      kwlist, &progress_handler, &n)) {
        return NULL;
    }

    if (progress_handler == Py_None) {
        /* None clears the progress handler previously set */
        sqlite3_progress_handler(self->db, 0, 0, (void*)0);
        Py_XSETREF(self->function_pinboard_progress_handler, NULL);
    } else {
        sqlite3_progress_handler(self->db, n, _progress_handler, progress_handler);
        Py_INCREF(progress_handler);
        Py_XSETREF(self->function_pinboard_progress_handler, progress_handler);
    }
    Py_RETURN_NONE;
}

static PyObject* pysqlite_connection_set_trace_callback(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    PyObject* trace_callback;

    static char *kwlist[] = { "trace_callback", NULL };

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O:set_trace_callback",
                                      kwlist, &trace_callback)) {
        return NULL;
    }

    if (trace_callback == Py_None) {
        /* None clears the trace callback previously set */
        sqlite3_trace(self->db, 0, (void*)0);
        Py_XSETREF(self->function_pinboard_trace_callback, NULL);
    } else {
        sqlite3_trace(self->db, _trace_callback, trace_callback);
        Py_INCREF(trace_callback);
        Py_XSETREF(self->function_pinboard_trace_callback, trace_callback);
    }

    Py_RETURN_NONE;
}

#ifdef HAVE_LOAD_EXTENSION
static PyObject* pysqlite_enable_load_extension(pysqlite_Connection* self, PyObject* args)
{
    int rc;
    int onoff;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTuple(args, "i", &onoff)) {
        return NULL;
    }

    rc = sqlite3_enable_load_extension(self->db, onoff);

    if (rc != SQLITE_OK) {
        PyErr_SetString(pysqlite_OperationalError, "Error enabling load extension");
        return NULL;
    } else {
        Py_RETURN_NONE;
    }
}

static PyObject* pysqlite_load_extension(pysqlite_Connection* self, PyObject* args)
{
    int rc;
    char* extension_name;
    char* errmsg;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!PyArg_ParseTuple(args, "s", &extension_name)) {
        return NULL;
    }

    rc = sqlite3_load_extension(self->db, extension_name, 0, &errmsg);
    if (rc != 0) {
        PyErr_SetString(pysqlite_OperationalError, errmsg);
        return NULL;
    } else {
        Py_RETURN_NONE;
    }
}
#endif

int pysqlite_check_thread(pysqlite_Connection* self)
{
    if (self->check_same_thread) {
        if (PyThread_get_thread_ident() != self->thread_ident) {
            PyErr_Format(pysqlite_ProgrammingError,
                        "SQLite objects created in a thread can only be used in that same thread. "
                        "The object was created in thread id %lu and this is thread id %lu.",
                        self->thread_ident, PyThread_get_thread_ident());
            return 0;
        }

    }
    return 1;
}

static PyObject* pysqlite_connection_get_isolation_level(pysqlite_Connection* self, void* unused)
{
    if (!pysqlite_check_connection(self)) {
        return NULL;
    }
    Py_INCREF(self->isolation_level);
    return self->isolation_level;
}

static PyObject* pysqlite_connection_get_total_changes(pysqlite_Connection* self, void* unused)
{
    if (!pysqlite_check_connection(self)) {
        return NULL;
    } else {
        return Py_BuildValue("i", sqlite3_total_changes(self->db));
    }
}

static PyObject* pysqlite_connection_get_in_transaction(pysqlite_Connection* self, void* unused)
{
    if (!pysqlite_check_connection(self)) {
        return NULL;
    }
    if (!sqlite3_get_autocommit(self->db)) {
        Py_RETURN_TRUE;
    }
    Py_RETURN_FALSE;
}

static int
pysqlite_connection_set_isolation_level(pysqlite_Connection* self, PyObject* isolation_level, void *Py_UNUSED(ignored))
{
    if (isolation_level == NULL) {
        PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
        return -1;
    }
    if (isolation_level == Py_None) {
        /* We might get called during connection init, so we cannot use
         * pysqlite_connection_commit() here. */
        if (self->db && !sqlite3_get_autocommit(self->db)) {
            int rc;
            Py_BEGIN_ALLOW_THREADS
            rc = sqlite3_exec(self->db, "COMMIT", NULL, NULL, NULL);
            Py_END_ALLOW_THREADS
            if (rc != SQLITE_OK) {
                return _pysqlite_seterror(self->db, NULL);
            }
        }

        self->begin_statement = NULL;
    } else {
        const char * const *candidate;
        PyObject *uppercase_level;
        _Py_IDENTIFIER(upper);

        if (!PyUnicode_Check(isolation_level)) {
            PyErr_Format(PyExc_TypeError,
                         "isolation_level must be a string or None, not %.100s",
                         Py_TYPE(isolation_level)->tp_name);
            return -1;
        }

        uppercase_level = _PyObject_CallMethodIdOneArg(
                        (PyObject *)&PyUnicode_Type, &PyId_upper,
                        isolation_level);
        if (!uppercase_level) {
            return -1;
        }
        for (candidate = begin_statements; *candidate; candidate++) {
            if (_PyUnicode_EqualToASCIIString(uppercase_level, *candidate + 6))
                break;
        }
        Py_DECREF(uppercase_level);
        if (!*candidate) {
            PyErr_SetString(PyExc_ValueError,
                            "invalid value for isolation_level");
            return -1;
        }
        self->begin_statement = *candidate;
    }

    Py_INCREF(isolation_level);
    Py_XSETREF(self->isolation_level, isolation_level);
    return 0;
}

PyObject* pysqlite_connection_call(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
{
    PyObject* sql;
    pysqlite_Statement* statement;
    PyObject* weakref;
    int rc;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!_PyArg_NoKeywords(MODULE_NAME ".Connection", kwargs))
        return NULL;

    if (!PyArg_ParseTuple(args, "U", &sql))
        return NULL;

    _pysqlite_drop_unused_statement_references(self);

    statement = PyObject_New(pysqlite_Statement, &pysqlite_StatementType);
    if (!statement) {
        return NULL;
    }

    statement->db = NULL;
    statement->st = NULL;
    statement->sql = NULL;
    statement->in_use = 0;
    statement->in_weakreflist = NULL;

    rc = pysqlite_statement_create(statement, self, sql);
    if (rc != SQLITE_OK) {
        if (rc == PYSQLITE_TOO_MUCH_SQL) {
            PyErr_SetString(pysqlite_Warning, "You can only execute one statement at a time.");
        } else if (rc == PYSQLITE_SQL_WRONG_TYPE) {
            if (PyErr_ExceptionMatches(PyExc_TypeError))
                PyErr_SetString(pysqlite_Warning, "SQL is of wrong type. Must be string.");
        } else {
            (void)pysqlite_statement_reset(statement);
            _pysqlite_seterror(self->db, NULL);
        }
        goto error;
    }

    weakref = PyWeakref_NewRef((PyObject*)statement, NULL);
    if (weakref == NULL)
        goto error;
    if (PyList_Append(self->statements, weakref) != 0) {
        Py_DECREF(weakref);
        goto error;
    }
    Py_DECREF(weakref);

    return (PyObject*)statement;

error:
    Py_DECREF(statement);
    return NULL;
}

PyObject* pysqlite_connection_execute(pysqlite_Connection* self, PyObject* args)
{
    PyObject* cursor = 0;
    PyObject* result = 0;
    PyObject* method = 0;

    cursor = _PyObject_CallMethodIdNoArgs((PyObject*)self, &PyId_cursor);
    if (!cursor) {
        goto error;
    }

    method = PyObject_GetAttrString(cursor, "execute");
    if (!method) {
        Py_CLEAR(cursor);
        goto error;
    }

    result = PyObject_CallObject(method, args);
    if (!result) {
        Py_CLEAR(cursor);
    }

error:
    Py_XDECREF(result);
    Py_XDECREF(method);

    return cursor;
}

PyObject* pysqlite_connection_executemany(pysqlite_Connection* self, PyObject* args)
{
    PyObject* cursor = 0;
    PyObject* result = 0;
    PyObject* method = 0;

    cursor = _PyObject_CallMethodIdNoArgs((PyObject*)self, &PyId_cursor);
    if (!cursor) {
        goto error;
    }

    method = PyObject_GetAttrString(cursor, "executemany");
    if (!method) {
        Py_CLEAR(cursor);
        goto error;
    }

    result = PyObject_CallObject(method, args);
    if (!result) {
        Py_CLEAR(cursor);
    }

error:
    Py_XDECREF(result);
    Py_XDECREF(method);

    return cursor;
}

PyObject* pysqlite_connection_executescript(pysqlite_Connection* self, PyObject* args)
{
    PyObject* cursor = 0;
    PyObject* result = 0;
    PyObject* method = 0;

    cursor = _PyObject_CallMethodIdNoArgs((PyObject*)self, &PyId_cursor);
    if (!cursor) {
        goto error;
    }

    method = PyObject_GetAttrString(cursor, "executescript");
    if (!method) {
        Py_CLEAR(cursor);
        goto error;
    }

    result = PyObject_CallObject(method, args);
    if (!result) {
        Py_CLEAR(cursor);
    }

error:
    Py_XDECREF(result);
    Py_XDECREF(method);

    return cursor;
}

/* ------------------------- COLLATION CODE ------------------------ */

static int
pysqlite_collation_callback(
        void* context,
        int text1_length, const void* text1_data,
        int text2_length, const void* text2_data)
{
    PyObject* callback = (PyObject*)context;
    PyObject* string1 = 0;
    PyObject* string2 = 0;
    PyGILState_STATE gilstate;
    PyObject* retval = NULL;
    long longval;
    int result = 0;
    gilstate = PyGILState_Ensure();

    if (PyErr_Occurred()) {
        goto finally;
    }

    string1 = PyUnicode_FromStringAndSize((const char*)text1_data, text1_length);
    string2 = PyUnicode_FromStringAndSize((const char*)text2_data, text2_length);

    if (!string1 || !string2) {
        goto finally; /* failed to allocate strings */
    }

    retval = PyObject_CallFunctionObjArgs(callback, string1, string2, NULL);

    if (!retval) {
        /* execution failed */
        goto finally;
    }

    longval = PyLong_AsLongAndOverflow(retval, &result);
    if (longval == -1 && PyErr_Occurred()) {
        PyErr_Clear();
        result = 0;
    }
    else if (!result) {
        if (longval > 0)
            result = 1;
        else if (longval < 0)
            result = -1;
    }

finally:
    Py_XDECREF(string1);
    Py_XDECREF(string2);
    Py_XDECREF(retval);
    PyGILState_Release(gilstate);
    return result;
}

static PyObject *
pysqlite_connection_interrupt(pysqlite_Connection* self, PyObject* args)
{
    PyObject* retval = NULL;

    if (!pysqlite_check_connection(self)) {
        goto finally;
    }

    sqlite3_interrupt(self->db);

    Py_INCREF(Py_None);
    retval = Py_None;

finally:
    return retval;
}

/* Function author: Paul Kippes <kippesp@gmail.com>
 * Class method of Connection to call the Python function _iterdump
 * of the sqlite3 module.
 */
static PyObject *
pysqlite_connection_iterdump(pysqlite_Connection* self, PyObject* args)
{
    _Py_IDENTIFIER(_iterdump);
    PyObject* retval = NULL;
    PyObject* module = NULL;
    PyObject* module_dict;
    PyObject* pyfn_iterdump;

    if (!pysqlite_check_connection(self)) {
        goto finally;
    }

    module = PyImport_ImportModule(MODULE_NAME ".dump");
    if (!module) {
        goto finally;
    }

    module_dict = PyModule_GetDict(module);
    if (!module_dict) {
        goto finally;
    }

    pyfn_iterdump = _PyDict_GetItemIdWithError(module_dict, &PyId__iterdump);
    if (!pyfn_iterdump) {
        if (!PyErr_Occurred()) {
            PyErr_SetString(pysqlite_OperationalError,
                            "Failed to obtain _iterdump() reference");
        }
        goto finally;
    }

    retval = PyObject_CallOneArg(pyfn_iterdump, (PyObject *)self);

finally:
    Py_XDECREF(module);
    return retval;
}

#ifdef HAVE_BACKUP_API
static PyObject *
pysqlite_connection_backup(pysqlite_Connection *self, PyObject *args, PyObject *kwds)
{
    PyObject *target = NULL;
    int pages = -1;
    PyObject *progress = Py_None;
    const char *name = "main";
    int rc;
    int callback_error = 0;
    PyObject *sleep_obj = NULL;
    int sleep_ms = 250;
    sqlite3 *bck_conn;
    sqlite3_backup *bck_handle;
    static char *keywords[] = {"target", "pages", "progress", "name", "sleep", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O!|$iOsO:backup", keywords,
                                     &pysqlite_ConnectionType, &target,
                                     &pages, &progress, &name, &sleep_obj)) {
        return NULL;
    }

    if (sleep_obj != NULL) {
        _PyTime_t sleep_secs;
        if (_PyTime_FromSecondsObject(&sleep_secs, sleep_obj,
                                      _PyTime_ROUND_TIMEOUT)) {
            return NULL;
        }
        _PyTime_t ms = _PyTime_AsMilliseconds(sleep_secs,
                                              _PyTime_ROUND_TIMEOUT);
        if (ms < INT_MIN || ms > INT_MAX) {
            PyErr_SetString(PyExc_OverflowError, "sleep is too large");
            return NULL;
        }
        sleep_ms = (int)ms;
    }

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        return NULL;
    }

    if (!pysqlite_check_connection((pysqlite_Connection *)target)) {
        return NULL;
    }

    if ((pysqlite_Connection *)target == self) {
        PyErr_SetString(PyExc_ValueError, "target cannot be the same connection instance");
        return NULL;
    }

#if SQLITE_VERSION_NUMBER < 3008008
    /* Since 3.8.8 this is already done, per commit
       https://www.sqlite.org/src/info/169b5505498c0a7e */
    if (!sqlite3_get_autocommit(((pysqlite_Connection *)target)->db)) {
        PyErr_SetString(pysqlite_OperationalError, "target is in transaction");
        return NULL;
    }
#endif

    if (progress != Py_None && !PyCallable_Check(progress)) {
        PyErr_SetString(PyExc_TypeError, "progress argument must be a callable");
        return NULL;
    }

    if (pages == 0) {
        pages = -1;
    }

    bck_conn = ((pysqlite_Connection *)target)->db;

    Py_BEGIN_ALLOW_THREADS
    bck_handle = sqlite3_backup_init(bck_conn, "main", self->db, name);
    Py_END_ALLOW_THREADS

    if (bck_handle) {
        do {
            Py_BEGIN_ALLOW_THREADS
            rc = sqlite3_backup_step(bck_handle, pages);
            Py_END_ALLOW_THREADS

            if (progress != Py_None) {
                PyObject *res;

                res = PyObject_CallFunction(progress, "iii", rc,
                                            sqlite3_backup_remaining(bck_handle),
                                            sqlite3_backup_pagecount(bck_handle));
                if (res == NULL) {
                    /* User's callback raised an error: interrupt the loop and
                       propagate it. */
                    callback_error = 1;
                    rc = -1;
                } else {
                    Py_DECREF(res);
                }
            }

            /* Sleep for a while if there are still further pages to copy and
               the engine could not make any progress */
            if (rc == SQLITE_BUSY || rc == SQLITE_LOCKED) {
                Py_BEGIN_ALLOW_THREADS
                sqlite3_sleep(sleep_ms);
                Py_END_ALLOW_THREADS
            }
        } while (rc == SQLITE_OK || rc == SQLITE_BUSY || rc == SQLITE_LOCKED);

        Py_BEGIN_ALLOW_THREADS
        rc = sqlite3_backup_finish(bck_handle);
        Py_END_ALLOW_THREADS
    } else {
        rc = _pysqlite_seterror(bck_conn, NULL);
    }

    if (!callback_error && rc != SQLITE_OK) {
        /* We cannot use _pysqlite_seterror() here because the backup APIs do
           not set the error status on the connection object, but rather on
           the backup handle. */
        if (rc == SQLITE_NOMEM) {
            (void)PyErr_NoMemory();
        } else {
#if SQLITE_VERSION_NUMBER > 3007015
            PyErr_SetString(pysqlite_OperationalError, sqlite3_errstr(rc));
#else
            switch (rc) {
                case SQLITE_ERROR:
                    /* Description of SQLITE_ERROR in SQLite 3.7.14 and older
                       releases. */
                    PyErr_SetString(pysqlite_OperationalError,
                                    "SQL logic error or missing database");
                    break;
                case SQLITE_READONLY:
                    PyErr_SetString(pysqlite_OperationalError,
                                    "attempt to write a readonly database");
                    break;
                case SQLITE_BUSY:
                    PyErr_SetString(pysqlite_OperationalError, "database is locked");
                    break;
                case SQLITE_LOCKED:
                    PyErr_SetString(pysqlite_OperationalError,
                                    "database table is locked");
                    break;
                default:
                    PyErr_Format(pysqlite_OperationalError,
                                 "unrecognized error code: %d", rc);
                    break;
            }
#endif
        }
    }

    if (!callback_error && rc == SQLITE_OK) {
        Py_RETURN_NONE;
    } else {
        return NULL;
    }
}
#endif

static PyObject *
pysqlite_connection_create_collation(pysqlite_Connection* self, PyObject* args)
{
    PyObject* callable;
    PyObject* uppercase_name = 0;
    PyObject* name;
    PyObject* retval;
    Py_ssize_t i, len;
    _Py_IDENTIFIER(upper);
    const char *uppercase_name_str;
    int rc;
    unsigned int kind;
    const void *data;

    if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
        goto finally;
    }

    if (!PyArg_ParseTuple(args, "UO:create_collation(name, callback)",
                          &name, &callable)) {
        goto finally;
    }

    uppercase_name = _PyObject_CallMethodIdOneArg((PyObject *)&PyUnicode_Type,
                                                  &PyId_upper, name);
    if (!uppercase_name) {
        goto finally;
    }

    if (PyUnicode_READY(uppercase_name))
        goto finally;
    len = PyUnicode_GET_LENGTH(uppercase_name);
    kind = PyUnicode_KIND(uppercase_name);
    data = PyUnicode_DATA(uppercase_name);
    for (i=0; i<len; i++) {
        Py_UCS4 ch = PyUnicode_READ(kind, data, i);
        if ((ch >= '0' && ch <= '9')
         || (ch >= 'A' && ch <= 'Z')
         || (ch == '_'))
        {
            continue;
        } else {
            PyErr_SetString(pysqlite_ProgrammingError, "invalid character in collation name");
            goto finally;
        }
    }

    uppercase_name_str = PyUnicode_AsUTF8(uppercase_name);
    if (!uppercase_name_str)
        goto finally;

    if (callable != Py_None && !PyCallable_Check(callable)) {
        PyErr_SetString(PyExc_TypeError, "parameter must be callable");
        goto finally;
    }

    if (callable != Py_None) {
        if (PyDict_SetItem(self->collations, uppercase_name, callable) == -1)
            goto finally;
    } else {
        if (PyDict_DelItem(self->collations, uppercase_name) == -1)
            goto finally;
    }

    rc = sqlite3_create_collation(self->db,
                                  uppercase_name_str,
                                  SQLITE_UTF8,
                                  (callable != Py_None) ? callable : NULL,
                                  (callable != Py_None) ? pysqlite_collation_callback : NULL);
    if (rc != SQLITE_OK) {
        if (callable != Py_None) {
            if (PyDict_DelItem(self->collations, uppercase_name) < 0) {
                PyErr_Clear();
            }
        }
        _pysqlite_seterror(self->db, NULL);
        goto finally;
    }

finally:
    Py_XDECREF(uppercase_name);

    if (PyErr_Occurred()) {
        retval = NULL;
    } else {
        Py_INCREF(Py_None);
        retval = Py_None;
    }

    return retval;
}

/* Called when the connection is used as a context manager. Returns itself as a
 * convenience to the caller. */
static PyObject *
pysqlite_connection_enter(pysqlite_Connection* self, PyObject* args)
{
    Py_INCREF(self);
    return (PyObject*)self;
}

/** Called when the connection is used as a context manager. If there was any
 * exception, a rollback takes place; otherwise we commit. */
static PyObject *
pysqlite_connection_exit(pysqlite_Connection* self, PyObject* args)
{
    PyObject *exc_type, *exc_value, *exc_tb;
    if (!PyArg_ParseTuple(args, "OOO", &exc_type, &exc_value, &exc_tb)) {
        return NULL;
    }

    int commit = 0;
    PyObject *result;
    if (exc_type == Py_None && exc_value == Py_None && exc_tb == Py_None) {
        commit = 1;
        result = pysqlite_connection_commit(self, NULL);
    }
    else {
        result = pysqlite_connection_rollback(self, NULL);
    }

    if (result == NULL) {
        if (commit) {
            /* Commit failed; try to rollback in order to unlock the database.
             * If rollback also fails, chain the exceptions. */
            PyObject *exc, *val, *tb;
            PyErr_Fetch(&exc, &val, &tb);
            result = pysqlite_connection_rollback(self, NULL);
            if (result == NULL) {
                _PyErr_ChainExceptions(exc, val, tb);
            }
            else {
                Py_DECREF(result);
                PyErr_Restore(exc, val, tb);
            }
        }
        return NULL;
    }
    Py_DECREF(result);

    Py_RETURN_FALSE;
}

static const char connection_doc[] =
PyDoc_STR("SQLite database connection object.");

static PyGetSetDef connection_getset[] = {
    {"isolation_level",  (getter)pysqlite_connection_get_isolation_level, (setter)pysqlite_connection_set_isolation_level},
    {"total_changes",  (getter)pysqlite_connection_get_total_changes, (setter)0},
    {"in_transaction",  (getter)pysqlite_connection_get_in_transaction, (setter)0},
    {NULL}
};

static PyMethodDef connection_methods[] = {
    {"cursor", (PyCFunction)(void(*)(void))pysqlite_connection_cursor, METH_VARARGS|METH_KEYWORDS,
        PyDoc_STR("Return a cursor for the connection.")},
    {"close", (PyCFunction)pysqlite_connection_close, METH_NOARGS,
        PyDoc_STR("Closes the connection.")},
    {"commit", (PyCFunction)pysqlite_connection_commit, METH_NOARGS,
        PyDoc_STR("Commit the current transaction.")},
    {"rollback", (PyCFunction)pysqlite_connection_rollback, METH_NOARGS,
        PyDoc_STR("Roll back the current transaction.")},
    {"create_function", (PyCFunction)(void(*)(void))pysqlite_connection_create_function, METH_VARARGS|METH_KEYWORDS,
        PyDoc_STR("Creates a new function. Non-standard.")},
    {"create_aggregate", (PyCFunction)(void(*)(void))pysqlite_connection_create_aggregate, METH_VARARGS|METH_KEYWORDS,
        PyDoc_STR("Creates a new aggregate. Non-standard.")},
    {"set_authorizer", (PyCFunction)(void(*)(void))pysqlite_connection_set_authorizer, METH_VARARGS|METH_KEYWORDS,
        PyDoc_STR("Sets authorizer callback. Non-standard.")},
    #ifdef HAVE_LOAD_EXTENSION
    {"enable_load_extension", (PyCFunction)pysqlite_enable_load_extension, METH_VARARGS,
        PyDoc_STR("Enable dynamic loading of SQLite extension modules. Non-standard.")},
    {"load_extension", (PyCFunction)pysqlite_load_extension, METH_VARARGS,
        PyDoc_STR("Load SQLite extension module. Non-standard.")},
    #endif
    {"set_progress_handler", (PyCFunction)(void(*)(void))pysqlite_connection_set_progress_handler, METH_VARARGS|METH_KEYWORDS,
        PyDoc_STR("Sets progress handler callback. Non-standard.")},
    {"set_trace_callback", (PyCFunction)(void(*)(void))pysqlite_connection_set_trace_callback, METH_VARARGS|METH_KEYWORDS,
        PyDoc_STR("Sets a trace callback called for each SQL statement (passed as unicode). Non-standard.")},
    {"execute", (PyCFunction)pysqlite_connection_execute, METH_VARARGS,
        PyDoc_STR("Executes a SQL statement. Non-standard.")},
    {"executemany", (PyCFunction)pysqlite_connection_executemany, METH_VARARGS,
        PyDoc_STR("Repeatedly executes a SQL statement. Non-standard.")},
    {"executescript", (PyCFunction)pysqlite_connection_executescript, METH_VARARGS,
        PyDoc_STR("Executes a multiple SQL statements at once. Non-standard.")},
    {"create_collation", (PyCFunction)pysqlite_connection_create_collation, METH_VARARGS,
        PyDoc_STR("Creates a collation function. Non-standard.")},
    {"interrupt", (PyCFunction)pysqlite_connection_interrupt, METH_NOARGS,
        PyDoc_STR("Abort any pending database operation. Non-standard.")},
    {"iterdump", (PyCFunction)pysqlite_connection_iterdump, METH_NOARGS,
        PyDoc_STR("Returns iterator to the dump of the database in an SQL text format. Non-standard.")},
    #ifdef HAVE_BACKUP_API
    {"backup", (PyCFunction)(void(*)(void))pysqlite_connection_backup, METH_VARARGS | METH_KEYWORDS,
        PyDoc_STR("Makes a backup of the database. Non-standard.")},
    #endif
    {"__enter__", (PyCFunction)pysqlite_connection_enter, METH_NOARGS,
        PyDoc_STR("For context manager. Non-standard.")},
    {"__exit__", (PyCFunction)pysqlite_connection_exit, METH_VARARGS,
        PyDoc_STR("For context manager. Non-standard.")},
    {NULL, NULL}
};

static struct PyMemberDef connection_members[] =
{
    {"Warning", T_OBJECT, offsetof(pysqlite_Connection, Warning), READONLY},
    {"Error", T_OBJECT, offsetof(pysqlite_Connection, Error), READONLY},
    {"InterfaceError", T_OBJECT, offsetof(pysqlite_Connection, InterfaceError), READONLY},
    {"DatabaseError", T_OBJECT, offsetof(pysqlite_Connection, DatabaseError), READONLY},
    {"DataError", T_OBJECT, offsetof(pysqlite_Connection, DataError), READONLY},
    {"OperationalError", T_OBJECT, offsetof(pysqlite_Connection, OperationalError), READONLY},
    {"IntegrityError", T_OBJECT, offsetof(pysqlite_Connection, IntegrityError), READONLY},
    {"InternalError", T_OBJECT, offsetof(pysqlite_Connection, InternalError), READONLY},
    {"ProgrammingError", T_OBJECT, offsetof(pysqlite_Connection, ProgrammingError), READONLY},
    {"NotSupportedError", T_OBJECT, offsetof(pysqlite_Connection, NotSupportedError), READONLY},
    {"row_factory", T_OBJECT, offsetof(pysqlite_Connection, row_factory)},
    {"text_factory", T_OBJECT, offsetof(pysqlite_Connection, text_factory)},
    {NULL}
};

PyTypeObject pysqlite_ConnectionType = {
        PyVarObject_HEAD_INIT(NULL, 0)
        MODULE_NAME ".Connection",                      /* tp_name */
        sizeof(pysqlite_Connection),                    /* tp_basicsize */
        0,                                              /* tp_itemsize */
        (destructor)pysqlite_connection_dealloc,        /* tp_dealloc */
        0,                                              /* tp_vectorcall_offset */
        0,                                              /* tp_getattr */
        0,                                              /* tp_setattr */
        0,                                              /* tp_as_async */
        0,                                              /* tp_repr */
        0,                                              /* tp_as_number */
        0,                                              /* tp_as_sequence */
        0,                                              /* tp_as_mapping */
        0,                                              /* tp_hash */
        (ternaryfunc)pysqlite_connection_call,          /* tp_call */
        0,                                              /* tp_str */
        0,                                              /* tp_getattro */
        0,                                              /* tp_setattro */
        0,                                              /* tp_as_buffer */
        Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE,         /* tp_flags */
        connection_doc,                                 /* tp_doc */
        0,                                              /* tp_traverse */
        0,                                              /* tp_clear */
        0,                                              /* tp_richcompare */
        0,                                              /* tp_weaklistoffset */
        0,                                              /* tp_iter */
        0,                                              /* tp_iternext */
        connection_methods,                             /* tp_methods */
        connection_members,                             /* tp_members */
        connection_getset,                              /* tp_getset */
        0,                                              /* tp_base */
        0,                                              /* tp_dict */
        0,                                              /* tp_descr_get */
        0,                                              /* tp_descr_set */
        0,                                              /* tp_dictoffset */
        (initproc)pysqlite_connection_init,             /* tp_init */
        0,                                              /* tp_alloc */
        0,                                              /* tp_new */
        0                                               /* tp_free */
};

extern int pysqlite_connection_setup_types(void)
{
    pysqlite_ConnectionType.tp_new = PyType_GenericNew;
    return PyType_Ready(&pysqlite_ConnectionType);
}