FreeTDS API: Internals

# Internals
[The db-lib API]

Functions called within `db-lib` for self-help. More...

## Classes
struct | _dblib_error_message
## Defines
#define | DBSETLLABELED(x, y) dbsetlbool((x), (y), DBSETLABELED)
| Alternative way to set login packet fields.
#define | DBSETLVERSION(login, version) dbsetlversion((login), (version))
| maps to the Microsoft (lower-case) function.
## Typedefs
typedef struct _dblib_error_message | DBLIB_ERROR_MESSAGE
## Functions
int | _dblib_check_and_handle_interrupt (void *vdbproc)
| check interrupts for libtds.
RETCODE | dbcmdrow (DBPROCESS *dbproc)
| See if the current command can return rows.
int | dbcurcmd (DBPROCESS *dbproc)
| Get number of the row just returned.
DBINT | dbcurrow (DBPROCESS *dbproc)
| Get number of the row currently being read.
DBBOOL | dbdead (DBPROCESS *dbproc)
| Check if dbproc is an ex-parrot.
DBINT | dbfirstrow (DBPROCESS *dbproc)
| See if a server response has arrived.
int | dbiordesc (DBPROCESS *dbproc)
| Get file descriptor of the socket used by a `DBPROCESS` to read data coming from the server. (!).
int | dbiowdesc (DBPROCESS *dbproc)
| Get file descriptor of the socket used by a `DBPROCESS` to write data coming to the server. (!).
DBINT | dblastrow (DBPROCESS *dbproc)
| Get number of the last row in the row buffer.
int | dbperror (DBPROCESS *dbproc, DBINT msgno, long errnum,...)
| Call client-installed error handler.
RETCODE | dbrows (DBPROCESS *dbproc)
| Indicate whether a query returned rows.
STATUS | dbrowtype (DBPROCESS *dbproc)
| Get returned row's type.
void | dbsetavail (DBPROCESS *dbproc)
| Mark a `DBPROCESS` as "available".
RETCODE | dbsetlbool (LOGINREC *login, int value, int which)
| Set a boolean value in a `LOGINREC` structure.
RETCODE | dbsetllong (LOGINREC *login, long value, int which)
| Set an integer value in a `LOGINREC` structure.
RETCODE | dbsetlname (LOGINREC *login, const char *value, int which)
| Set the value of a string in a `LOGINREC` structure.
int | dbtds (DBPROCESS *dbproc)
| Get the TDS version in use for dbproc.
static int | default_err_handler (DBPROCESS *dbproc, int severity, int dberr, int oserr, char *dberrstr, char *oserrstr)
| default error handler for db-lib (handles library-generated errors)
DBPROCESS * | tdsdbopen (LOGINREC *login, const char *server, int msdblib)
| Form a connection with the server.

## Detailed Description

Functions called within `db-lib` for self-help.

These functions are of interest only to people hacking on the FreeTDS db-lib implementation.

## Define Documentation

DBSETLLABELED | ( | x,
|  | y |  | ) | dbsetlbool((x), (y), DBSETLABELED)

Alternative way to set login packet fields.

See also:
  dbsetllabeled()

DBSETLVERSION | ( | login,
|  | version |  | ) | dbsetlversion((login), (version))

maps to the Microsoft (lower-case) function.

See also:
  dbsetlversion()

## Typedef Documentation

typedef struct _dblib_error_message DBLIB_ERROR_MESSAGE

For internal use only.

Remarks:
  member msgno Vendor-defined message number
  member severity Is passed to the error handler
  member msgtext Text of message

## Function Documentation

int _dblib_check_and_handle_interrupt | ( | void * | vdbproc | ) |

check interrupts for libtds.

Parameters:

  | vdbproc | a DBPROCESS pointer, contains all information needed by db-lib to manage communications with the server.

See also:
  DBDEAD(), dbsetinterrupt().

RETCODE dbcmdrow | ( | DBPROCESS * | dbproc | ) |

See if the current command can return rows.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

Return values:

  | SUCCEED | Yes, it can.
  | FAIL | No, it can't.

Remarks:
  Use DBCMDROW() macro instead.

See also:
  DBCMDROW(), dbnextrow(), dbresults(), DBROWS(), DBROWTYPE().

int dbcurcmd | ( | DBPROCESS * | dbproc | ) |

Get number of the row just returned.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  DBCURROW().

Todo:
  Unimplemented.

DBINT dbcurrow | ( | DBPROCESS * | dbproc | ) |

Get number of the row currently being read.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

Returns:
  ostensibly the row number, or 0 if no rows have been read yet.

Return values:

  | 0 | Always.

See also:
  DBCURROW(), dbclrbuf(), DBFIRSTROW(), dbgetrow(), DBLASTROW(), dbnextrow(), dbsetopt(),.

Todo:
  Unimplemented.

DBBOOL dbdead | ( | DBPROCESS * | dbproc | ) |

Check if dbproc is an ex-parrot.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

Return values:

  | TRUE | process has been marked dead.
  | FALSE | process is OK.

Remarks:
  dbdead() does not communicate with the server. Unless a previously db-lib marked dbproc dead, dbdead() returns `FALSE`.

See also:
  dberrhandle().

DBINT dbfirstrow | ( | DBPROCESS * | dbproc | ) |

See if a server response has arrived.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.
  | milliseconds | how long to wait for the server before returning: `0` return immediately. `-1` do not return until the server responds or a system interrupt occurs.
  | ready_dbproc | output: DBPROCESS for which a response arrived, of `NULL`.
  | return_reason | output: `DBRESULT` server responded. `DBNOTIFICATION` registered procedure notification has arrived. dbpoll() the registered handler, if any, before it returns. `DBTIMEOUT` milliseconds elapsed before the server responded. `DBINTERRUPT` operating-system interrupt occurred before the server responded.

Return values:

  | SUCCEED | everything worked.
  | FAIL | a server connection died.

See also:
  DBIORDESC(), DBRBUF(), dbresults(), dbreghandle(), dbsqlok().

Todo:
  Unimplemented.

For internal use only.

Get number of the first row in the row buffer.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  DBFIRSTROW(), dbclrbuf(), DBCURROW(), dbgetrow(), DBLASTROW(), dbnextrow(), dbsetopt().

int dbiordesc | ( | DBPROCESS * | dbproc | ) |

Get file descriptor of the socket used by a `DBPROCESS` to read data coming from the server. (!).

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  dbcmd(), DBIORDESC(), DBIOWDESC(), dbnextrow(), dbpoll(), DBRBUF(), dbresults(), dbsqlok(), dbsqlsend().

int dbiowdesc | ( | DBPROCESS * | dbproc | ) |

Get file descriptor of the socket used by a `DBPROCESS` to write data coming to the server. (!).

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  dbcmd(), DBIORDESC(), DBIOWDESC(), dbnextrow(), dbpoll(), DBRBUF(), dbresults(), dbsqlok(), dbsqlsend().

DBINT dblastrow | ( | DBPROCESS * | dbproc | ) |

Get number of the last row in the row buffer.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  DBLASTROW(), dbclrbuf(), DBCURROW(), DBFIRSTROW(), dbgetrow(), dbnextrow(), dbsetopt().

int dbperror | ( | DBPROCESS * | dbproc,
|  | DBINT | msgno,
|  | long | errnum,
|  |  | ... |
| ) |  |  |

Call client-installed error handler.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.
  | msgno | identifies the error message to be passed to the client's handler.
  | errnum | identifies the OS error (errno), if any. Use 0 if not applicable.

Returns:
  the handler's return code, subject to correction and adjustment for vendor style:
  - INT_CANCEL The db-lib function that encountered the error will return FAIL.
  - INT_TIMEOUT The db-lib function will cancel the operation and return FAIL. dbproc remains useable.
  - INT_CONTINUE The db-lib function will retry the operation.

Remarks:
  The client-installed handler may also return INT_EXIT. If Sybase semantics are used, this function notifies the user and calls exit(3). If Microsoft semantics are used, this function returns INT_CANCEL.

If the client-installed handler returns something other than these four INT_* values, or returns timeout-related value for anything but SYBETIME, it's treated here as INT_EXIT (see above).

Instead of sprinkling error text all over db-lib, we consolidate it here, where it can be translated (one day), and where it can be mapped to the TDS error number. The libraries don't use consistent error numbers or messages, so when libtds has to emit an error message, it can't include the text. It can pass its error number to a client-library function, which will interpret it, add the text, call the application's installed handler (if any) and return the handler's return code back to the caller.

The call stack may look something like this:

1. application
2. db-lib function (encounters error)
3. dbperror
4. error handler (installed by application)

The error handling in this case is unambiguous: the caller invokes this function, the client's handler returns its instruction, which the caller receives. Quite often the caller will get INT_CANCEL, in which case it should put its house in order and return FAIL.

The call stack may otherwise look something like this:

1. application
2. db-lib function
3. libtds function (encounters error)
4. _dblib_handle_err_message
5. dbperror
6. error handler (installed by application)

Because different client libraries specify their handler semantics differently, and because libtds doesn't know which client library is in charge of any given connection, it cannot interpret the raw return code from a db-lib error handler. For these reasons, libtds calls _dblib_handle_err_message, which translates between libtds and db-lib semantics.

See also:
  dberrhandle(), _dblib_handle_err_message().

RETCODE dbrows | ( | DBPROCESS * | dbproc | ) |

Indicate whether a query returned rows.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  DBROWS(), DBCMDROW(), dbnextrow(), dbresults(), DBROWTYPE().

STATUS dbrowtype | ( | DBPROCESS * | dbproc | ) |

Get returned row's type.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

See also:
  DBROWTYPE().

void dbsetavail | ( | DBPROCESS * | dbproc | ) |

Mark a `DBPROCESS` as "available".

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

Remarks:
  Basically bogus. `FreeTDS` behaves the way Sybase's implementation does, but so what? Many `db-lib` functions set the `DBPROCESS` to "not available", but only dbsetavail() resets it to "available".

See also:
  DBISAVAIL(). DBSETAVAIL().

RETCODE dbsetlbool | ( | LOGINREC * | login,
|  | int | value,
|  | int | which |
| ) |  |  |

Set a boolean value in a `LOGINREC` structure.

For internal use only.

Called by various macros to populate login.

Parameters:

  | login | the `LOGINREC*` to modify.
  | value | the value to set it to.
  | which | the field to set.

Remarks:
  Only DBSETBCP is implemented.

Return values:

  | SUCCEED | the value was set.
  | FAIL | invalid value passed for which.

Todo:
  DBSETNOSHORT, DBSETENCRYPT, DBSETLABELED

RETCODE dbsetllong | ( | LOGINREC * | login,
|  | long | value,
|  | int | which |
| ) |  |  |

Set an integer value in a `LOGINREC` structure.

For internal use only.

Called by various macros to populate login.

Parameters:

  | login | the `LOGINREC*` to modify.
  | value | the value to set it to.
  | which | the field to set.

Return values:

  | SUCCEED | the value was set.
  | FAIL | anything other than `DBSETPACKET` was passed for which.

RETCODE dbsetlname | ( | LOGINREC * | login,
|  | const char * | value,
|  | int | which |
| ) |  |  |

Set the value of a string in a `LOGINREC` structure.

For internal use only.

Called by various macros to populate login.

Parameters:

  | login | the `LOGINREC*` to modify.
  | value | the value to set it to.
  | which | the field to set.

Return values:

  | SUCCEED | the value was set.
  | FAIL | `DBSETHID` or other invalid which was tried.

int dbtds | ( | DBPROCESS * | dbproc | ) |

Get the TDS version in use for dbproc.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.

Returns:
  a `DBTDS*` token.

Remarks:
  The integer values of the constants are counterintuitive.

See also:
  DBTDS().

static int default_err_handler | ( | DBPROCESS * | dbproc,
|  | int | severity,
|  | int | dberr,
|  | int | oserr,
|  | char * | dberrstr,
|  | char * | oserrstr |
| ) |  |  | `[static]`

default error handler for db-lib (handles library-generated errors)

For internal use only.

The default error handler doesn't print anything. If you want to see your messages printed, install an error handler. If you think that should be an optional compile- or run-time default, submit a patch. It could be done.

See also:
  DBDEAD(), dberrhandle().

DBPROCESS* tdsdbopen | ( | LOGINREC * | login,
|  | const char * | server,
|  | int | msdblib |
| ) |  |  |

Form a connection with the server.

For internal use only.

Called by the `dbopen()` macro, normally. If FreeTDS was configured with `--enable-msdblib`, this function is called by (exported) `dbopen()` function. `tdsdbopen` is so-named to avoid namespace conflicts with other database libraries that use the same function name.

Parameters:

  | login | `LOGINREC*` carrying the account information.
  | server | name of the dataserver to connect to.

Returns:
  valid pointer on successful login.

Return values:

  | NULL | insufficient memory, unable to connect for any reason.

See also:
  dbopen()

Todo:

  use `asprintf()` to avoid buffer overflow.

  separate error messages for no-such-server and no-such-user.

All Classes Files Functions Variables Typedefs Enumerations Enumerator Defines