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 1.325 2008/06/12 00:07:29 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++.

#define SQLITE_ACCESS_EXISTS    0
#define SQLITE_ACCESS_READWRITE 1
#define SQLITE_ACCESS_READ      2

/*
** CAPI3REF: Initialize The SQLite Library {F10130}
**
** The sqlite3_initialize() routine initializes the
** SQLite library prior to use.  The sqlite3_shutdown() routine
** deallocates any resources that were allocated by sqlite3_initialize().




**
** A call to sqlite3_initialize() is an "effective" call if it is
** the first time sqlite3_initialize() is invoked during the lifetime of
** the process, or if it is the first time sqlite3_initialize() is invoked
** following a call to sqlite3_shutdown().  Only an effective call
** of sqlite3_initialize() does any initialization.  All other calls
** are harmless no-ops.  In other words,
** the sqlite3_initialize() routine may be called multiple times
** without consequence.  Second and subsequent evaluations of
** sqlite3_initialize() are no-ops.  The sqlite3_initialize() routine
** only works the first time it is called for a process, or the first
** time it is called after sqlite3_shutdown().  In all other cases,
** sqlite3_initialize() returns SQLITE_OK without doing any real work.
**
** Among other things, sqlite3_initialize() shall invoke
** [sqlite3_mutex_init()] and sqlite3_os_init().  Similarly, sqlite3_shutdown()
** shall invoke [sqlite3_mutex_end()] and sqlite3_os_end().
**
** The sqlite3_initialize() routine returns SQLITE_OK on success.
** If for some reason, sqlite3_initialize() is unable to initialize
** the library (perhaps it is unable to allocate a needed resource such
** as a mutex) it returns an [error code] other than SQLITE_OK.
**
** The sqlite3_initialize() routine is called internally by many other
** SQLite interfaces so that an application usually does not need to
** invoke sqlite3_initialize() directly.  For example, [sqlite3_open()]
** calls sqlite3_initialize() so the SQLite library will be automatically
** initialized when [sqlite3_open()] is called if it has not be initialized
** already.  However, if SQLite is compiled with the SQLITE_OMIT_AUTOINIT
** compile-time option, then the automatic calls to sqlite3_initialize()
** are omitted and the application must call sqlite3_initialize() directly
** prior to using any other SQLite interface.  For maximum portability,
** it is recommended that applications always invoke sqlite3_initialize()
** directly prior to using any other SQLite interface.  Future releases
** of SQLite may require this.  In other words, the behavior exhibited
** when SQLite is compiled with SQLITE_OMIT_AUTOINIT might become the


** default behavior in some future release of SQLite.
**
** The sqlite3_os_init() routine does operating-system specific
** initialization of the SQLite library.  The sqlite3_os_end()

** routine undoes the effect of sqlite3_os_init().  Typical tasks

** performed by these routines include allocation or deallocation
** of static resources, initialization of global variables,
** setting up a default [sqlite3_vfs] module, or setting up

** a default configuration using [sqlite3_config()].  
**
** The application should never invoke either sqlite3_os_init()
** or sqlite3_os_end() directly.  The application should only invoke
** sqlite3_initialize() and sqlite3_shutdown().  The sqlite3_os_init()
** interface is called automatically by sqlite3_initialize() and 
** sqlite3_os_end() is called by sqlite3_shutdown().  Appropriate
** implementations for sqlite3_os_init() and sqlite3_os_end()
** are built into SQLite when it is compiled for unix, windows, or os/2.
** When built for other platforms (using the SQLITE_OS_OTHER=1 compile-time
** option) the application must supply a suitable implementation for
** sqlite3_os_init() and sqlite3_os_end().  An application-supplied
** implementation of sqlite3_os_init() or sqlite3_os_end()

** must return SQLITE_OK on success and some other [error code] upon
** failure.
*/
int sqlite3_initialize(void);
int sqlite3_shutdown(void);
int sqlite3_os_init(void);
int sqlite3_os_end(void);

/*
** CAPI3REF: Configuring The SQLite Library {F10145}
**
** The sqlite3_config() interface is used to make global configuration
** changes to SQLite in order to tune SQLite to the specific needs of
** the application.  The default configuration is recommended for most

** to [database connections] and [prepared statements] so that the
** application is free to use the same [database connection] or the
** same [prepared statement] in different threads at the same time.</dd>
**
** <dt>SQLITE_CONFIG_MALLOC</dt>
** <dd>This option takes four arguments.  The first three
** arguments are pointers to functions that emulate malloc(), free(),
** and realloc(), respectively.  The fourth argument must be a pointer to
** a function that returns the size of a prior allocation when handed a pointer

** to the allocation. This option is used to replace the default memory
** allocator with an application-defined memory allocator.</dd>
**
** <dt>SQLITE_CONFIG_MEMSTATS</dt>
** <dd>This option takes single boolean argument which enables or disables
** the collection of memory allocation statistics.  When disabled, the
** following SQLite interfaces become non-operational:
**   <ul>

** macro defined (with "-DSQLITE_MUTEX_APPDEF=1"), then no mutex
** implementation is included with the library.  The
** mutex interface routines defined here become external
** references in the SQLite library for which implementations
** must be provided by the application.  This facility allows an
** application that links against SQLite to provide its own mutex
** implementation without having to modify the SQLite core.
**
** {F17001} The sqlite3_mutex_init() routine is called once by each
** effective call to [sqlite3_initialize()].  The sqlite3_mutex_init()
** interface initializes the mutex subsystem.  The application should
** never call sqlite3_mutex_init() directly but only indirectly by
** invoking [sqlite3_initialize()].
**
** {F17003} The sqlite3_mutex_end() routine undoes the effect of
** sqlite3_mutex_init().  The sqlite3_mutex_end() interface is called
** by [sqlite3_shutdown()].  The application should never call 
** sqlite3_mutex_end() directly but only indirectly through
** [sqlite3_shutdown()].
**
** {F17011} The sqlite3_mutex_alloc() routine allocates a new
** mutex and returns a pointer to it. {F17012} If it returns NULL
** that means that a mutex could not be allocated. {F17013} SQLite
** will unwind its stack and return an error. {F17014} The argument
** to sqlite3_mutex_alloc() is one of these integer constants:
**

** upon successful entry.  {F17026} Mutexes created using
** SQLITE_MUTEX_RECURSIVE can be entered multiple times by the same thread.
** {F17027} In such cases the,
** mutex must be exited an equal number of times before another thread
** can enter.  {U17028} If the same thread tries to enter any other
** kind of mutex more than once, the behavior is undefined.
** {F17029} SQLite will never exhibit
** such behavior in its own use of mutexes.
**
** Some systems (ex: windows95) do not support the operation implemented by
** sqlite3_mutex_try().  On those systems, sqlite3_mutex_try() will
** always return SQLITE_BUSY.  {F17030} The SQLite core only ever uses
** sqlite3_mutex_try() as an optimization so this is acceptable behavior.
**
** {F17031} The sqlite3_mutex_leave() routine exits a mutex that was
** previously entered by the same thread.  {U17032} The behavior
** is undefined if the mutex is not currently entered by the
** calling thread or is not currently allocated.  {F17033} SQLite will
** never do either. {END}
**
** See also: [sqlite3_mutex_held()] and [sqlite3_mutex_notheld()].
*/
int sqlite3_mutex_init();
sqlite3_mutex *sqlite3_mutex_alloc(int);
void sqlite3_mutex_free(sqlite3_mutex*);
void sqlite3_mutex_enter(sqlite3_mutex*);
int sqlite3_mutex_try(sqlite3_mutex*);
void sqlite3_mutex_leave(sqlite3_mutex*);
int sqlite_mutex_end();

/*
** CAPI3REF: Mutex Verifcation Routines {F17080}
**
** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routines
** are intended for use inside assert() statements. {F17081} The SQLite core
** never uses these routines except inside an assert() and applications

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.308 2008/06/12 00:07:29 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

        bestFlags = flags;
        bestNEq = nEq;
        bestJ = j;
        pLevel->pBestIdx = pIndex;
      }
      if( doNotReorder ) break;
    }
    WHERETRACE(("*** Optimizer selects table %d for loop %d\n", bestJ,
           pLevel-pWInfo->a));
    if( (bestFlags & WHERE_ORDERBY)!=0 ){
      *ppOrderBy = 0;
    }
    andFlags &= bestFlags;
    pLevel->flags = bestFlags;
    pLevel->pIdx = pBest;