SQLite

** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.398 2008/09/10 13:09:24 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.

** this is important.
**
** There can only be a single busy handler defined for each
** [database connection].  Setting a new busy handler clears any
** previously set handler.  Note that calling [sqlite3_busy_timeout()]
** will also set or clear the busy handler.
**
** The busy callback should not take any actions which modify the
** database connection that invoked the busy handler.  Any such actions
** result in undefined behavior.
** 
** INVARIANTS:
**
** {H12311} The [sqlite3_busy_handler(D,C,A)] function shall replace
**          busy callback in the [database connection] D with a new
**          a new busy handler C and application data pointer A.
**
** {H12312} Newly created [database connections] shall have a busy

** in addition to using an authorizer.
**
** Only a single authorizer can be in place on a database connection
** at a time.  Each call to sqlite3_set_authorizer overrides the
** previous call.  Disable the authorizer by installing a NULL callback.
** The authorizer is disabled by default.
**
** The authorizer callback must not do anything that will modify
** the database connection that invoked the authorizer callback.
** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
** database connections for the meaning of "modify" in this paragraph.
**
** When [sqlite3_prepare_v2()] is used to prepare a statement, the
** statement might be reprepared during [sqlite3_step()] due to a 
** schema change.  Hence, the application should ensure that the
** correct authorizer callback remains in place during the [sqlite3_step()].
**
** Note that the authorizer callback is invoked only during
** [sqlite3_prepare()] or its variants.  Authorization is not

** progress callback - that is invoked periodically during long
** running calls to [sqlite3_exec()], [sqlite3_step()] and
** [sqlite3_get_table()].  An example use for this
** interface is to keep a GUI updated during a large query.
**
** If the progress callback returns non-zero, the operation is
** interrupted.  This feature can be used to implement a
** "Cancel" button on a GUI progress dialog box.
**
** The progress handler must not do anything that will modify
** the database connection that invoked the progress handler.
** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
** database connections for the meaning of "modify" in this paragraph.
**
** INVARIANTS:
**
** {H12911} The callback function registered by sqlite3_progress_handler()
**          is invoked periodically during long running calls to
**          [sqlite3_step()].
**

**
** The second parameter is the name of the SQL function to be created or
** redefined.  The length of the name is limited to 255 bytes, exclusive of
** the zero-terminator.  Note that the name length limit is in bytes, not
** characters.  Any attempt to create a function with a longer name
** will result in [SQLITE_ERROR] being returned.
**
** The third parameter (nArg)
** is the number of arguments that the SQL function or
** aggregate takes. If this parameter is negative, then the SQL function or
** aggregate may take any number of arguments.
**
** The fourth parameter, eTextRep, specifies what
** [SQLITE_UTF8 | text encoding] this SQL function prefers for
** its parameters.  Any SQL function implementation should be able to work
** work with UTF-8, UTF-16le, or UTF-16be.  But some implementations may be

** and xFinal and NULL should be passed for xFunc. To delete an existing
** SQL function or aggregate, pass NULL for all three function callbacks.
**
** It is permitted to register multiple implementations of the same
** functions with the same name but with either differing numbers of
** arguments or differing preferred text encodings.  SQLite will use
** the implementation most closely matches the way in which the
** SQL function is used.  A function implementation with a non-negative
** nArg parameter is a better match than a function implementation with
** a negative nArg.  A function where the preferred text encoding
** matches the database encoding is a better
** match than a function where the encoding is different.  
** A function where the encoding difference is between UTF16le and UTF16be
** is a closer match than a function where the encoding difference is
** between UTF8 and UTF16.
**
** Built-in functions may be overloaded by new application-defined functions.
** The first application-defined function with a given name overrides all
** built-in functions in the same [database connection] with the same name.
** Subsequent application-defined functions of the same name only override 
** prior application-defined functions that are an exact match for the
** number of parameters and preferred encoding.
**
** An application-defined function is permitted to call other
** SQLite interfaces.  However, such calls must not
** close the database connection nor finalize or reset the prepared
** statement in which the function is running.
**
** INVARIANTS:
**
** {H16103} The [sqlite3_create_function16(D,X,...)] interface shall behave
**          as [sqlite3_create_function(D,X,...)] in every way except that it
**          interprets the X argument as zero-terminated UTF-16
**          native byte order instead of as zero-terminated UTF-8.
**
** {H16106} A successful invocation of the
**          [sqlite3_create_function(D,X,N,E,...)] interface shall register
**          or replaces callback functions in the [database connection] D
**          used to implement the SQL function named X with N parameters
**          and having a preferred text encoding of E.
**
** {H16109} A successful call to [sqlite3_create_function(D,X,N,E,P,F,S,L)]
**          shall replace the P, F, S, and L values from any prior calls with
**          the same D, X, N, and E values.
**
** {H16112} The [sqlite3_create_function(D,X,...)] interface shall fail
**          if the SQL function name X is
**          longer than 255 bytes exclusive of the zero terminator.
**
** {H16118} The [sqlite3_create_function(D,X,N,E,P,F,S,L)] interface
**          shall fail unless either F is NULL and S and L are non-NULL or
***         F is non-NULL and S and L are NULL.

**
** {H16121} The [sqlite3_create_function(D,...)] interface shall fails with an
**          error code of [SQLITE_BUSY] if there exist [prepared statements]
**          associated with the [database connection] D.
**
** {H16124} The [sqlite3_create_function(D,X,N,...)] interface shall fail with
**          an error code of [SQLITE_ERROR] if parameter N is less

**          than -1 or greater than 127.
**
** {H16127} When N is non-negative, the [sqlite3_create_function(D,X,N,...)]
**          interface shall register callbacks to be invoked for the
**          SQL function
**          named X when the number of arguments to the SQL function is
**          exactly N.
**
** {H16130} When N is -1, the [sqlite3_create_function(D,X,N,...)]
**          interface shall register callbacks to be invoked for the SQL
**          function named X with any number of arguments.
**
** {H16133} When calls to [sqlite3_create_function(D,X,N,...)]
**          specify multiple implementations of the same function X
**          and when one implementation has N>=0 and the other has N=(-1)
**          the implementation with a non-zero N shall be preferred.
**
** {H16136} When calls to [sqlite3_create_function(D,X,N,E,...)]
**          specify multiple implementations of the same function X with
**          the same number of arguments N but with different
**          encodings E, then the implementation where E matches the
**          database encoding shall preferred.
**
** {H16139} For an aggregate SQL function created using
**          [sqlite3_create_function(D,X,N,E,P,0,S,L)] the finalizer
**          function L shall always be invoked exactly once if the
**          step function S is called one or more times.
**
** {H16142} When SQLite invokes either the xFunc or xStep function of
**          an application-defined SQL function or aggregate created
**          by [sqlite3_create_function()] or [sqlite3_create_function16()],
**          then the array of [sqlite3_value] objects passed as the
**          third parameter shall be [protected sqlite3_value] objects.
*/
int sqlite3_create_function(
  sqlite3 *db,
  const char *zFunctionName,
  int nArg,
  int eTextRep,
  void *pApp,

** The pArg argument is passed through to the callback.
** If the callback on a commit hook function returns non-zero,
** then the commit is converted into a rollback.
**
** If another function was previously registered, its
** pArg value is returned.  Otherwise NULL is returned.
**
** The callback implementation must not do anything that will modify
** the database connection that invoked the callback.  Any actions
** to modify the database connection must be deferred until after the
** completion of the [sqlite3_step()] call that triggered the commit
** or rollback hook in the first place.
** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
** database connections for the meaning of "modify" in this paragraph.
**
** Registering a NULL function disables the callback.
**
** For the purposes of this API, a transaction is said to have been
** rolled back if an explicit "ROLLBACK" statement is executed, or
** an error or constraint causes an implicit rollback to occur.
** The rollback callback is not invoked if a transaction is
** automatically rolled back because the database connection is closed.

** The third and fourth arguments to the callback contain pointers to the
** database and table name containing the affected row.
** The final callback parameter is the rowid of the row. In the case of
** an update, this is the rowid after the update takes place.
**
** The update hook is not invoked when internal system tables are
** modified (i.e. sqlite_master and sqlite_sequence).
**
** The update hook implementation must not do anything that will modify
** the database connection that invoked the update hook.  Any actions
** to modify the database connection must be deferred until after the
** completion of the [sqlite3_step()] call that triggered the update hook.
** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
** database connections for the meaning of "modify" in this paragraph.
**
** If another function was previously registered, its pArg value
** is returned.  Otherwise NULL is returned.
**
** INVARIANTS:
**
** {H12971} The [sqlite3_update_hook(D,F,P)] interface causes the callback