[Ruby] Ruby & dbf

Nicolay A. Vasiliev n.vasiliev at apatit.com
Thu Feb 6 09:20:04 MSK 2003 

Dmitry Morozhnikov пишет:

>On Thu, 6 Feb 2003, Nicolay A. Vasiliev wrote:
>
>NAV> Очинно не хотелось бы завязываться исключительно на мелкомягкие
>NAV> технологии, так как впоследствии найденным решением хотелось бы
>NAV> поделиться с другими.
>
>ну не знаю. я бы за ради портабельности  слишком  себе  работу  не
>усложнял бы..
>  
>

Ну, может быть, Вы и правы, подумаю.

>ээ.. а БДЕ как в dbf ходит?
>
Своими низкоуровневыми функциями. Ну вот, например
DbiOpenTable   

C syntax

DBIResult DBIFN DbiOpenTable (hDb, pszTableName, [pszDriverType], 
pszIndexName, pszIndexTagName, iIndexId, eOpenMode, eShareMode, 
exltMode, [bUniDirectional], [pOptParams], phCursor);

Delphi syntax

function DbiOpenTable (hDb: hDBIDb; pszTableName: PChar; pszDriverType: 
PChar; pszIndexName: PChar; pszIndexTagName: PChar; iIndexId: Word; 
eOpenMode: DBIOpenMode; eShareMode: DBIShareMode; exltMode: XLTMode; 
bUniDirectional: Bool; pOptParams: Pointer; var hCursor: hDBICur): 
DBIResult stdcall;

Description

DbiOpenTable opens the given table for access and associates a cursor 
handle with the opened table.

Parameters

hDb     Type: hDBIDb     (Input)
Specifies the database handle associated with the database where the 
table exists.
pszTableName     Type: pCHAR     (Input)
Pointer to the table name. For Paradox, FoxPro, and dBASE, if 
pszTableName is a fully qualified name of a table, the pszDriverType 
parameter need not be specified. If the path is not included, the path 
name is taken from the current directory of the database associated with 
hDb.
For SQL databases, pszTableName can be a fully qualified name that 
includes the owner name, in the form <owner>.<tablename>.

If not specified, <owner> is supplied from the database handle. 
Extensions are not valid for SQL table names.
pszDriverType     Type: pCHAR     (Input)
Pointer to the driver type. Optional. pszDriverType can be one of the 
following values: szDBASE, szMSACCESS, szPARADOX, or szASCII (for 
importing or exporting data to/from text files; see the Usage section).
For Paradox, FoxPro, and dBASE tables, this parameter is required if 
pszTableName has no extension, or if the client application wants to 
overwrite the default file extension, including the situation where 
pszTableName is terminated with a period(.). If pszTableName does not 
supply the default extension, and pszDriverType is NULL, DbiOpenTable 
tries to open the table with the default file extension of all 
file-based drivers listed in the configuration file in the order that 
the drivers are listed.

This parameter is ignored if the database associated with hDb is a SQL 
or Access database.
pszIndexName     Type: pCHAR     (Input)
Pointer to the name of the index or pseudo-index to be used to order the 
records in the result set. Optional. For SQL tables, the index name does 
not have to be qualified with the owner for servers supporting naming 
conventions with owner qualification. The pszIndexName string is limited 
to 127 bytes in length.

pszIndexTagName     Type: pCHAR     (Input)
Pointer to the tag name of the index in a .MDX or .CDX file used to 
order the records in the result set. Optional; used for dBASE and FoxPro 
tables only. This parameter is ignored if the index given by 
pszIndexName is a .NDX index.
iIndexId     Type: UINT16     (Input)
Specifies the index identifier, which is the number of the index to be 
used to order the records in the result set. Optional; used for Paradox, 
Access, and SQL tables only.

Paradox: For Paradox tables, the range for the index identifier is 1 to 
511. This parameter is ignored if pszIndexName is specified.
SQL: For SQL tables, this field is used only to specify that the table 
should be opened with no default index. This is done by setting iIndexId 
to NODEFAULTINDEX and is useful when opening a table read-only to speed 
up record access time.
Access: For Access tables, the range for the index identifier is 1 to 
the number of valid indexes. This parameter is ignored if pszIndexName 
is specified.

eOpenMode     Type: DBIOpenMode     (Input)
Specifies the table open mode. If the mode is read-only, updates to the 
table are not permitted.
eShareMode     Type: DBIShareMode     (Input)
Specifies the table share mode, and determines whether other users or 
other cursors are able to open the table.
exltMode     Type: XLTMode     (Input)
Specifies the data translation mode.
bUniDirectional     Type: BOOL     (Input)
Specifies the scan mode of the cursor for SQL only.

pOptParams     Type: pBYTE     (Input)
Not currently used.
phCursor     Type: phDBICur     (Output)
Pointer to the cursor handle for the opened table.

Usage

Text: The DbiOpenTable call can be used to open a text file for 
import/export of data. The pszDriverType argument is used differently to 
indicate whether the fields in the text file are fixed length or 
delimited. The field separator and delimiter are passed through the 
pszDriverType argument.

dBASE: If no index is specified, the table is opened in physical order. 
If pszIndexTagName specifies an index tag, the table is opened with that 
tag active. The index name and the tag name are specified to open the index.

FoxPro: If no index is specified, the table is opened in physical order. 
If pszIndexTagName specifies an index tag, the table is opened with that 
tag active. The index name and the tag name are specified to open the 
index. To see if a cursor is referencing a FoxPro table, retrieve 
CURProps using DbiGetCursorProps.

Access: If a cursor is opened exclusively in the active session, no 
other cursors may be opened in that session.

Paradox: If all index parameters are NULL, the table is opened in 
primary key order, if a primary key exists. If a secondary key is 
specified, the table is opened in that key. Either pszIndexName or 
iIndexId can be used to specify a composite or non-composite secondary 
index. A single-field index that is case-insensitive is classified as a 
composite index. See also: szName

SQL: An index can be specified only in pszIndexName. The index name can 
be qualified or unqualified. SQL provides limited support for exclusive 
opens, depending on the level of server explicit lock support.

Pseudo-indexes: To describe a pseudo-index rather than an existing 
physical index, replace the pszIndexName parameter with a string 
composed of field names. The marker character @ denotes the use of a 
pseudo-index. For example, "@Customer Number at Order Number" describes a 
pseudo-index on a key formed by concatenating the Customer Number field 
with the Order Number field.

Each field identifier in the pseudo-index name must be preceded by the @ 
character. This character is illegal in "true" index names. No new index 
is generated at the server; the behavior of the pseudo-index is 
simulated entirely by use of the proper ORDER BY clauses on the query 
populating the local BDE record cache.

Fields can be identified by field numbers as well as by field names. For 
example,  the string "@2 at 3@11" describes a pseudo-index consisting of 
the second, third, and eleventh field of the table, concatenated to make 
up a single key.

Each of the component fields within a pszIndexName is assumed to be in 
ASCENDING order. Ordering is case-sensitive (unless case-sensitivity is 
not supported on the specific server). If the fields in the pszIndexName 
represent a real unique index on the server, the pseudo-index becomes 
unique; otherwise, it is non-unique.

Note:    Access does not support pseudo-indexes.

Referential integrity descriptions: By default, DbiOpenTable does not 
retrieve referential integrity information (primary keys, foreign keys, 
and so on) when opening a table. This improves performance. To retrieve 
referential integrity information, use DbiSetProp to set 
curGETEXTENDEDINFO to True, then call DbiGetCursorProps.

Prerequisites

If the database is opened read-only, the table cannot be opened read-write.

Completion state

After the table has been successfully opened, the cursor is opened and 
positioned on the crack at the beginning of the file. A valid cursor is 
returned.

DbiResult return values

DBIERR_NONE    The table was successfully opened.
DBIERR_INVALIDFILENAME    The specified file name is not valid.
DBIERR_NOSUCHFILE    The specified file could not be found.
DBIERR_TABLEREADONLY    This table cannot be opened for read-write access.
DBIERR_NOTSUFFTABLERIGHTS    The client application does not have 
sufficient rights to open this table.
DBIERR_INVALIDINDEXNAME    The specified index name is invalid.
DBIERR_INVALIDHNDL    The specified database handle is invalid or NULL.

DBIERR_INVALIDPARAM    The specified table name or the pointer to the 
table name is NULL, or phCursor is NULL.
DBIERR_UNKNOWNTBLTYPE    The specified table type is invalid.
DBIERR_NOSUCHTABLE    The specified table name is invalid.
DBIERR_NOSUCHINDEX    The specified index is not available.
DBIERR_LOCKED    The table is locked by another user.
DBIERR_DIRBUSY    Invalid attempt to open a table in private directory 
(Paradox only).
DBIERR_OPENTBLLIMIT    The maximum number of tables is already opened.

C Examples: DbiOpenTable

Open the specified table.

If the table is local (Paradox, FoxPro, Access, or dBASE), the table 
name must also have the extension. This function uses the following input:
    fDbiOpenTable(hDb, "CUSTOMER.DB", &hCur, &CurProps);



DBIResult fDbiOpenTable(hDBIDb hTmpDb, pCHAR pszTableName, phDBICur 
phTmpCur, pCURProps pCurProps)
{
   DBIResult      rslt;
   rslt = Chk(DbiOpenTable (hTmpDb, pszTableName, NULL, NULL, NULL, 0, 
dbiREADWRITE,
                   dbiOPENSHARED, xltFIELD, TRUE, NULL, phTmpCur));
   if (rslt != DBIERR_NONE)
      return rslt;
   if (pCurProps != NULL)
      rslt = Chk(DbiGetCursorProps(*phTmpCur, pCurProps));
   return rslt;

}


Delphi Examples: DbiOpenTable

Open a table: 

Delphi users should use the Open method associated with the TTable 
component rather than directly calling DbiOpenTable. This method is 
defined as:

  procedure Open;

The Open method opens the dataset, putting it in Browse state.

Table1.Open;

О как много всего!

>
>NAV> Короче, вроде отыскался порт библиотеки XBase для питона плюс
>NAV> указанный здесь swig. Может это и криво, но, может, попробую
>NAV> заделать xbase под Руби. Пожелайте мне удачи :).
>
>удачи! :-)
>  
>
Спасибо!


>  
>

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