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 1.254 2007/09/01 18:17:22 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++.

** using [sqlite3_step()], then destroyed using [sqlite3_finalize()].
**
** If one or more of the SQL statements are queries, then
** the callback function specified by the 3rd parameter is
** invoked once for each row of the query result.  This callback
** should normally return 0.  If the callback returns a non-zero
** value then the query is aborted, all subsequent SQL statements
** are skipped and the sqlite3_exec() function returns the [SQLITE_ABORT].
**
** The 4th parameter to this interface is an arbitrary pointer that is
** passed through to the callback function as its first parameter.
**
** The 2nd parameter to the callback function is the number of
** columns in the query result.  The 3rd parameter to the callback
** is an array of strings holding the values for each column
** as extracted using [sqlite3_column_text()].
** The 4th parameter to the callback is an array of strings
** obtained using [sqlite3_column_name()] and holding
** the names of each column.
**
** The callback function may be NULL, even for queries.  A NULL
** callback is not an error.  It just means that no callback
** will be invoked.
**
** If an error occurs while parsing or evaluating the SQL (but
** not while executing the callback) then an appropriate error
** message is written into memory obtained from [sqlite3_malloc()] and
** *errmsg is made to point to that message.  The calling function
** is responsible for freeing the memory using [sqlite3_free()].

** If errmsg==NULL, then no error message is ever written.
**
** The return value is is SQLITE_OK if there are no errors and
** some other [SQLITE_OK | return code] if there is an error.  
** The particular return value depends on the type of error. 
**
*/
int sqlite3_exec(

/*
** CAPI3REF: OS Interface Open File Handle
**
** An [sqlite3_file] object represents an open file in the OS
** interface layer.  Individual OS interface implementations will
** want to subclass this object by appending additional fields
** for their own use.  The pMethods entry is a pointer to an
** [sqlite3_io_methods] object that defines methods for performing
** I/O operations on the open file.
*/
typedef struct sqlite3_file sqlite3_file;
struct sqlite3_file {
  const struct sqlite3_io_methods *pMethods;  /* Methods for an open file */
};

/*
** CAPI3REF: OS Interface File Virtual Methods Object
**
** Every file opened by the [sqlite3_vfs] xOpen method contains a pointer to
** an instance of the this object.  This object defines the
** methods used to perform various operations against the open file.
**
** The flags argument to xSync may be one of [SQLITE_SYNC_NORMAL] or
** [SQLITE_SYNC_FULL].  The first choice is the normal fsync().


*  The second choice is an
** OS-X style fullsync.  The SQLITE_SYNC_DATA flag may be ORed in to
** indicate that only the data of the file and not its inode needs to be
** synced.
** 
** The integer values to xLock() and xUnlock() are one of
** <ul>
** <li> [SQLITE_LOCK_NONE],
** <li> [SQLITE_LOCK_READ],
** <li> [SQLITE_LOCK_RESERVED],
** <li> [SQLITE_LOCK_PENDING], or
** <li> [SQLITE_LOCK_EXCLUSIVE].
** </ul>
** xLock() increases the lock. xUnlock() decreases the lock.  
** The xCheckReservedLock() method looks
** to see if any database connection, either in this
** process or in some other process, is holding an RESERVED,
** PENDING, or EXCLUSIVE lock on the file.  It returns true
** if such a lock exists and false if not.
** 
** The xFileControl() method is a generic interface that allows custom
** VFS implementations to directly control an open file using the
** [sqlite3_file_control()] interface.  The second "op" argument
** is an integer opcode.   The third
** argument is a generic pointer which is intended to be a pointer
** to a structure that may contain arguments or space in which to
** write return values.  Potential uses for xFileControl() might be
** functions to enable blocking locks with timeouts, to change the
** locking strategy (for example to use dot-file locks), to inquire
** about the status of a lock, or to break stale locks.  The SQLite
** core reserves opcodes less than 100 for its own use. 
** A [SQLITE_FCNTL_LOCKSTATE | list of opcodes] less than 100 is available.
** Applications that define a custom xFileControl method should use opcodes 
** greater than 100 to avoid conflicts.
**
** The xSectorSize() method returns the sector size of the
** device that underlies the file.  The sector size is the
** minimum write that can be performed without disturbing
** other bytes in the file.  The xDeviceCharacteristics()
** method returns a bit vector describing behaviors of the
** underlying device:
**
** <ul>
** <li> [SQLITE_IOCAP_ATOMIC]
** <li> [SQLITE_IOCAP_ATOMIC512]
** <li> [SQLITE_IOCAP_ATOMIC1K]
** <li> [SQLITE_IOCAP_ATOMIC2K]
** <li> [SQLITE_IOCAP_ATOMIC4K]
** <li> [SQLITE_IOCAP_ATOMIC8K]
** <li> [SQLITE_IOCAP_ATOMIC16K]
** <li> [SQLITE_IOCAP_ATOMIC32K]
** <li> [SQLITE_IOCAP_ATOMIC64K]
** <li> [SQLITE_IOCAP_SAFE_APPEND]
** <li> [SQLITE_IOCAP_SEQUENTIAL]
** </ul>
**
** The SQLITE_IOCAP_ATOMIC property means that all writes of
** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
** mean that writes of blocks that are nnn bytes in size and
** are aligned to an address which is an integer multiple of
** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means

** SQLite core and the underlying operating system.  The "vfs"
** in the name of the object stands for "virtual file system".
**
** The iVersion field is initially 1 but may be larger for future
** versions of SQLite.  Additional fields may be appended to this
** object when the iVersion value is increased.
**
** The szOsFile field is the size of the subclassed [sqlite3_file]
** structure used by this VFS.  mxPathname is the maximum length of
** a pathname in this VFS.
**
** Registered vfs modules are kept on a linked list formed by
** the pNext pointer.  The [sqlite3_register_vfs()]
** and [sqlite3_unregister_vfs()] interfaces manage this list
** in a thread-safe way.  The [sqlite3_find_vfs()] interface

** SQLite will guarantee that the zFilename string passed to
** xOpen() is a full pathname as generated by xFullPathname() and
** that the string will be valid and unchanged until xClose() is
** called.  So the [sqlite3_file] can store a pointer to the
** filename if it needs to remember the filename for some reason.
**
** The flags argument to xOpen() is a copy of the flags argument
** to [sqlite3_open_v2()].  If [sqlite3_open()] or [sqlite3_open16()]
** is used, then flags is [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE].
** If xOpen() opens a file read-only then it sets *pOutFlags to
** include [SQLITE_OPEN_READONLY].  Other bits in *pOutFlags may be
** set.
** 
** SQLite will also add one of the following flags to the xOpen()
** call, depending on the object being opened:
** 
** <ul>
** <li>  [SQLITE_OPEN_MAIN_DB]

** for the main database file.
** 
** Space to hold the  [sqlite3_file] structure passed as the third 
** argument to xOpen is allocated by caller (the SQLite core). 
** szOsFile bytes are allocated for this object.  The xOpen method
** fills in the allocated space.
** 
** The flags argument to xAccess() may be [SQLITE_ACCESS_EXISTS] 
** to test for the existance of a file,
** or [SQLITE_ACCESS_READWRITE] to test to see
** if a file is readable and writable, or [SQLITE_ACCESS_READ]
** to test to see if a file is at least readable.  The file can be a 
** directory.
** 
** SQLite will always allocate at least mxPathname+1 byte for
** the output buffers for xGetTempName and xFullPathname.
** 
** The xRandomness(), xSleep(), and xCurrentTime() interfaces
** are not strictly a part of the filesystem, but they are
** included in the VFS structure for completeness.
** The xRandomness() function attempts to return nBytes bytes
** of good-quality randomness into zOut.  The return value is
** the actual number of bytes of randomness obtained.  The
** xSleep() method cause the calling thread to sleep for at
** least the number of microseconds given.  The xCurrentTime()
** method returns a Julian Day Number for the current date and
** time.
*/
typedef struct sqlite3_vfs sqlite3_vfs;
struct sqlite3_vfs {

/*
** CAPI3REF: Compiling An SQL Statement
**
** To execute an SQL query, it must first be compiled into a byte-code
** program using one of these routines. 
**
** The first argument "db" is an [sqlite3 | SQLite database handle] 
** obtained from a prior call to [sqlite3_open()], [sqlite3_open_v2()]
** or [sqlite3_open16()].
** The second argument "zSql" is the statement to be compiled, encoded
** as either UTF-8 or UTF-16.  The sqlite3_prepare() and sqlite3_prepare_v2()
** interfaces uses UTF-8 and sqlite3_prepare16() and sqlite3_prepare16_v2()
** use UTF-16.
**
** If the nByte argument is less
** than zero, then zSql is read up to the first zero terminator.  If

**
** If this global variable is made to point to a string which is
** the name of a folder (a.ka. directory), then all temporary files
** created by SQLite will be placed in that directory.  If this variable
** is NULL pointer, then SQLite does a search for an appropriate temporary
** file directory.
**
** It is not safe to modify this variable once a database connection
** has been opened.  It is intended that this variable be set once
** as part of process initialization and before any SQLite interface
** routines have been call and remain unchanged thereafter.
*/
SQLITE_EXTERN char *sqlite3_temp_directory;

/*
** CAPI3REF:  Test To See If The Database Is In Auto-Commit Mode
**
** Test to see whether or not the database connection is in autocommit
** mode.  Return TRUE if it is and FALSE if not.  Autocommit mode is on
** by default.  Autocommit is disabled by a BEGIN statement and reenabled
** by the next COMMIT or ROLLBACK.
**
** If another thread changes the autocommit status of the database

**
** The cache sharing mode set by this interface effects all subsequent
** calls to [sqlite3_open()], [sqlite3_open_v2()], and [sqlite3_open16()].
** Existing database connections continue use the sharing mode that was
** in effect at the time they were opened.
**
** Virtual tables cannot be used with a shared cache.  When shared
** cache is enabled, the [sqlite3_create_module()] API used to register
** virtual tables will always return an error.
**
** This routine returns [SQLITE_OK] if shared cache was
** enabled or disabled successfully.  An [SQLITE_ERROR | error code]
** is returned otherwise.
**
** Shared cache is disabled by default.  But this might change in
** future releases of SQLite.  Applications that care about shared
** cache setting should set it explicitly.
*/
int sqlite3_enable_shared_cache(int);

/*
** CAPI3REF:  Attempt To Free Heap Memory
**
** Attempt to free N bytes of heap memory by deallocating non-essential
** memory allocations held by the database library (example: memory 
** used to cache database pages to improve performance).



*/
int sqlite3_release_memory(int);

/*
** CAPI3REF:  Impose A Limit On Heap Size
**
** Place a "soft" limit on the amount of heap memory that may be allocated

** memory alarm interface it will interfere with the operation of the
** soft heap limit and undefined behavior will result.  
**
** Prior to SQLite version 3.5.0, this routine only constrained the memory
** allocated by a single thread - the same thread in which this routine
** runs.  Beginning with SQLite version 3.5.0, the soft heap limit is
** applied to all threads.  The value specified for the soft heap limit
** is an upper bound on the total memory allocation for all threads.  In
** version 3.5.0 there is no mechanism for limiting the heap usage for
** individual threads.
*/
void sqlite3_soft_heap_limit(int);

/*
** CAPI3REF:  Extract Metadata About A Column Of A Table

** If the second parameter (zDbName) does not match the name of any
** open database file, then SQLITE_ERROR is returned.  This error
** code is not remembered and will not be recalled by [sqlite3_errcode()]
** or [sqlite3_errmsg()].  The underlying xFileControl method might
** also return SQLITE_ERROR.  There is no way to distinguish between
** an incorrect zDbName and an SQLITE_ERROR return from the underlying
** xFileControl method.
**
** See also: [SQLITE_FCNTL_LOCKSTATE]
*/
int sqlite3_file_control(sqlite3*, const char *zDbName, int op, void*);

/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
*/