# Internals
[The db-lib API]

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

## 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.

## Functions

int | _dblib_client_msg (DBPROCESS *dbproc, int dberr, int severity, const char *dberrstr)
| Pass a server-generated error message to the client's installed handler.
RETCODE | dbcmdrow (DBPROCESS *dbproc)
| See if the current command can return rows.
DBINT | dbcount (DBPROCESS *dbproc)
| Get count of rows processed.
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)
| Get number of the first row in the row buffer.
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, int 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".
int | dbtds (DBPROCESS *dbproc)
| Get the TDS version in use for dbproc.
DBPROCESS * | tdsdbopen (LOGINREC *login, 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()

## Function Documentation

int _dblib_client_msg | ( | DBPROCESS * | dbproc,
|  | int | dberr,
|  | int | severity,
|  | const char * | dberrstr
| ) |

Pass a server-generated error message to the client's installed handler.

For internal use only.

Parameters:

  | dbproc | contains all information needed by db-lib to manage communications with the server.
  | dberr | error number
  | severity | severity level
  | dberrstr | null-terminated ASCII string, the error message.

Returns:
  Propogates return code of tds_client_msg().

See also:
  tds_client_msg().

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().

DBINT dbcount | ( | DBPROCESS * | dbproc | ) |

Get count of rows processed.

For internal use only.

Parameters:

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

Returns:
  - for insert/update/delete, count of rows affected.
  - for select, count of rows returned, after all rows have been fetched.

See also:
  DBCOUNT(), dbnextrow(), dbresults().

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 | ) |

Get number of the first 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:
  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,
|  | int | 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)

Here libtds invokes the client's handler. 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. Similarly, the libtds error message number will not be in the db-lib msgno list. For these reasons, libtds calls _dblib_handle_err_message which translates between libtds and db-lib semantics.

See also:
  dberrhandle(), _dblib_handle_err_message(), tds_client_msg().

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().

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().

DBPROCESS* tdsdbopen | ( | LOGINREC * | login,
|  | 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.

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