![]() > WHEN state='DC' THEN 'District of Columbia' WHEN third conditional expression THEN column valueĬASE WHEN conditional expression THEN column value WHEN second conditional expression THEN column value Which can be used as, for example: for row in query('my.CASE WHEN first conditional expression THEN column value Libsqlite3.sqlite3_column_name(pp_stmt, i).decode()įor i in range(0, libsqlite3.sqlite3_column_count(pp_stmt))Įxtract(pp_stmt, i)įor i in range(0, len(row_constructor._fields)) Run_with_db(db, bind, pp_stmt, i + 1, param) Run_with_db(db, libsqlite3.sqlite3_finalize, pp_stmt) Run_with_db(db, libsqlite3.sqlite3_prepare_v3, db, sql.encode(), -1, 0, byref(pp_stmt), None) Run_with_db(db, libsqlite3.sqlite3_close, get_pp_stmt(db, sql): ![]() Run(libsqlite3.sqlite3_open_v2, db_file.encode(), byref(db), SQLITE_OPEN_READWRITE, None) Raise Exception(libsqlite3.sqlite3_errstr(res).decode()) Libsqlite3.sqlite3_column_bytes(pp_stmt, i), Libsqlite3.sqlite3_column_blob(pp_stmt, i), Type(None): lambda pp_stmt, i, _: libsqlite3.sqlite3_bind_null(pp_stmt, i), Type(b''): lambda pp_stmt, i, value: libsqlite3.sqlite3_bind_blob(pp_stmt, i, value, len(value), SQLITE_TRANSIENT), Type(''): lambda pp_stmt, i, value: libsqlite3.sqlite3_bind_text(pp_stmt, i, value.encode('utf-8'), len(value.encode('utf-8')), SQLITE_TRANSIENT), Type(0.0): libsqlite3.sqlite3_bind_double, Libsqlite3.sqlite3_column_bytes.restype = c_int64 Libsqlite3.sqlite3_column_blob.restype = c_void_p Libsqlite3.sqlite3_column_int64.restype = c_int64 Libsqlite3.sqlite3_column_double.restype = c_double Libsqlite3.sqlite3_column_name.restype = c_char_p Libsqlite3.sqlite3_errmsg.restype = c_char_p Libsqlite3.sqlite3_errstr.restype = c_char_p The below defines a (generator) function, query from contextlib import contextmanagerįrom ctypes import cdll, byref, string_at, c_char_p, c_int, c_double, c_int64, c_void_p But in the functions above, defaults get correct behavior so I've skipped this (otherwise important) step.īased on ead's answer, this is a more complete example of how to use libsqlite3 from Python, which is also at This is somewhat quick and dirty: usually one needs to set argument-types and return-value-type. Sqlite3_handle = None # make sure nobody accesses dangling pointer Print("close result", res)# check res = 0 Res = libsqlite3.sqlite3_close(sqlite3_handle) Print("pointer value:", sqlite3_handle) # address is set Print("open result", res) # check res = 0 Res = libsqlite3.sqlite3_open(b"mydb.db", ref(sqlite3_handle)) Sqlite3_handle = ctypes.c_void_p() # nullptr ![]() Libsqlite3 = ctypes.CDLL("libsqlite3.dylib") Any pointer can be replaced by void* as long as it points to a valid memory (i.e. The type-safety is something ensured by the compiler, once we have the machine code, the gloves are off and we can pass anything instead of sqlite3* to the function, but we have to ensure that it would work. Later, we only need the address of this structure to be able to use further functionality, i.e.: int sqlite3_close(sqlite3*) This function will create the structure and give its address to us - no need to know the exact layout of the the structur at all. the second parameter is a pointer to pointer. Sqlite3 **ppDb /* OUT: SQLite db handle */ The sqlite3-API uses an opaque pointer, so in the end there is no need to know its memory layout - one just could use a void-pointer.įor example, opening a sqlite3-database would create such a pointer: int sqlite3_open(Ĭonst char *filename, /* Database filename (UTF-8) */ ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |