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+#
+# Run this Tcl script to generate the sqlite.html file.
+#
+set rcsid {$Id: c_interface.tcl,v 1.43 2004/11/19 11:59:24 danielk1977 Exp $}
+source common.tcl
+header {The C language interface to the SQLite library}
+puts {
+<h2>The C language interface to the SQLite library</h2>
+
+<p>The SQLite library is designed to be very easy to use from
+a C or C++ program.  This document gives an overview of the C/C++
+programming interface.</p>
+
+<h3>1.0 The Core API</h3>
+
+<p>The interface to the SQLite library consists of three core functions,
+one opaque data structure, and some constants used as return values.
+The core interface is as follows:</p>
+
+<blockquote><pre>
+typedef struct sqlite sqlite;
+#define SQLITE_OK           0   /* Successful result */
+
+sqlite *sqlite_open(const char *dbname, int mode, char **errmsg);
+
+void sqlite_close(sqlite *db);
+
+int sqlite_exec(
+  sqlite *db,
+  char *sql,
+  int (*xCallback)(void*,int,char**,char**),
+  void *pArg,
+  char **errmsg
+);
+</pre></blockquote>
+
+<p>
+The above is all you really need to know in order to use SQLite
+in your C or C++ programs.  There are other interface functions
+available (and described below) but we will begin by describing
+the core functions shown above.
+</p>
+
+<a name="sqlite_open">
+<h4>1.1 Opening a database</h4>
+
+<p>Use the <b>sqlite_open</b> function to open an existing SQLite
+database or to create a new SQLite database.  The first argument
+is the database name.  The second argument is intended to signal
+whether the database is going to be used for reading and writing
+or just for reading.  But in the current implementation, the
+second argument to <b>sqlite_open</b> is ignored.
+The third argument is a pointer to a string pointer.
+If the third argument is not NULL and an error occurs
+while trying to open the database, then an error message will be
+written to memory obtained from malloc() and *errmsg will be made
+to point to this error message.  The calling function is responsible
+for freeing the memory when it has finished with it.</p>
+
+<p>The name of an SQLite database is the name of a file that will
+contain the database.  If the file does not exist, SQLite attempts
+to create and initialize it.  If the file is read-only (due to
+permission bits or because it is located on read-only media like
+a CD-ROM) then SQLite opens the database for reading only.  The
+entire SQL database is stored in a single file on the disk.  But
+additional temporary files may be created during the execution of
+an SQL command in order to store the database rollback journal or
+temporary and intermediate results of a query.</p>
+
+<p>The return value of the <b>sqlite_open</b> function is a
+pointer to an opaque <b>sqlite</b> structure.  This pointer will
+be the first argument to all subsequent SQLite function calls that
+deal with the same database.  NULL is returned if the open fails
+for any reason.</p>
+
+<a name="sqlite_close">
+<h4>1.2 Closing the database</h4>
+
+<p>To close an SQLite database, call the <b>sqlite_close</b>
+function passing it the sqlite structure pointer that was obtained
+from a prior call to <b>sqlite_open</b>.
+If a transaction is active when the database is closed, the transaction
+is rolled back.</p>
+
+<a name="sqlite_exec">
+<h4>1.3 Executing SQL statements</h4>
+
+<p>The <b>sqlite_exec</b> function is used to process SQL statements
+and queries.  This function requires 5 parameters as follows:</p>
+
+<ol>
+<li><p>A pointer to the sqlite structure obtained from a prior call
+       to <b>sqlite_open</b>.</p></li>
+<li><p>A null-terminated string containing the text of one or more
+       SQL statements and/or queries to be processed.</p></li>
+<li><p>A pointer to a callback function which is invoked once for each
+       row in the result of a query.  This argument may be NULL, in which
+       case no callbacks will ever be invoked.</p></li>
+<li><p>A pointer that is forwarded to become the first argument
+       to the callback function.</p></li>
+<li><p>A pointer to an error string.  Error messages are written to space
+       obtained from malloc() and the error string is made to point to
+       the malloced space.  The calling function is responsible for freeing
+       this space when it has finished with it.
+       This argument may be NULL, in which case error messages are not
+       reported back to the calling function.</p></li>
+</ol>
+
+<p>
+The callback function is used to receive the results of a query.  A
+prototype for the callback function is as follows:</p>
+
+<blockquote><pre>
+int Callback(void *pArg, int argc, char **argv, char **columnNames){
+  return 0;
+}
+</pre></blockquote>
+
+<a name="callback_row_data">
+<p>The first argument to the callback is just a copy of the fourth argument
+to <b>sqlite_exec</b>  This parameter can be used to pass arbitrary
+information through to the callback function from client code.
+The second argument is the number of columns in the query result.
+The third argument is an array of pointers to strings where each string
+is a single column of the result for that record.  Note that the
+callback function reports a NULL value in the database as a NULL pointer,
+which is very different from an empty string.  If the i-th parameter
+is an empty string, we will get:</p>
+<blockquote><pre>
+argv[i][0] == 0
+</pre></blockquote>
+<p>But if the i-th parameter is NULL we will get:</p>
+<blockquote><pre>
+argv[i] == 0
+</pre></blockquote>
+
+<p>The names of the columns are contained in first <i>argc</i>
+entries of the fourth argument.
+If the <a href="pragma.html#pragma_show_datatypes">SHOW_DATATYPES</a> pragma
+is on (it is off by default) then
+the second <i>argc</i> entries in the 4th argument are the datatypes
+for the corresponding columns.
+</p>
+
+<p>If the <a href="pragma.html#pragma_empty_result_callbacks">
+EMPTY_RESULT_CALLBACKS</a> pragma is set to ON and the result of
+a query is an empty set, then the callback is invoked once with the
+third parameter (argv) set to 0.  In other words
+<blockquote><pre>
+argv == 0
+</pre></blockquote>
+The second parameter (argc)
+and the fourth parameter (columnNames) are still valid
+and can be used to determine the number and names of the result
+columns if there had been a result.
+The default behavior is not to invoke the callback at all if the
+result set is empty.</p>
+
+<a name="callback_returns_nonzero">
+<p>The callback function should normally return 0.  If the callback
+function returns non-zero, the query is immediately aborted and 
+<b>sqlite_exec</b> will return SQLITE_ABORT.</p>
+
+<h4>1.4 Error Codes</h4>
+
+<p>
+The <b>sqlite_exec</b> function normally returns SQLITE_OK.  But
+if something goes wrong it can return a different value to indicate
+the type of error.  Here is a complete list of the return codes:
+</p>
+
+<blockquote><pre>
+#define SQLITE_OK           0   /* Successful result */
+#define SQLITE_ERROR        1   /* SQL error or missing database */
+#define SQLITE_INTERNAL     2   /* An internal logic error in SQLite */
+#define SQLITE_PERM         3   /* Access permission denied */
+#define SQLITE_ABORT        4   /* Callback routine requested an abort */
+#define SQLITE_BUSY         5   /* The database file is locked */
+#define SQLITE_LOCKED       6   /* A table in the database is locked */
+#define SQLITE_NOMEM        7   /* A malloc() failed */
+#define SQLITE_READONLY     8   /* Attempt to write a readonly database */
+#define SQLITE_INTERRUPT    9   /* Operation terminated by sqlite_interrupt() */
+#define SQLITE_IOERR       10   /* Some kind of disk I/O error occurred */
+#define SQLITE_CORRUPT     11   /* The database disk image is malformed */
+#define SQLITE_NOTFOUND    12   /* (Internal Only) Table or record not found */
+#define SQLITE_FULL        13   /* Insertion failed because database is full */
+#define SQLITE_CANTOPEN    14   /* Unable to open the database file */
+#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
+#define SQLITE_EMPTY       16   /* (Internal Only) Database table is empty */
+#define SQLITE_SCHEMA      17   /* The database schema changed */
+#define SQLITE_TOOBIG      18   /* Too much data for one row of a table */
+#define SQLITE_CONSTRAINT  19   /* Abort due to contraint violation */
+#define SQLITE_MISMATCH    20   /* Data type mismatch */
+#define SQLITE_MISUSE      21   /* Library used incorrectly */
+#define SQLITE_NOLFS       22   /* Uses OS features not supported on host */
+#define SQLITE_AUTH        23   /* Authorization denied */
+#define SQLITE_ROW         100  /* sqlite_step() has another row ready */
+#define SQLITE_DONE        101  /* sqlite_step() has finished executing */
+</pre></blockquote>
+
+<p>
+The meanings of these various return values are as follows:
+</p>
+
+<blockquote>
+<dl>
+<dt>SQLITE_OK</dt>
+<dd><p>This value is returned if everything worked and there were no errors.
+</p></dd>
+<dt>SQLITE_INTERNAL</dt>
+<dd><p>This value indicates that an internal consistency check within
+the SQLite library failed.  This can only happen if there is a bug in
+the SQLite library.  If you ever get an SQLITE_INTERNAL reply from
+an <b>sqlite_exec</b> call, please report the problem on the SQLite
+mailing list.
+</p></dd>
+<dt>SQLITE_ERROR</dt>
+<dd><p>This return value indicates that there was an error in the SQL
+that was passed into the <b>sqlite_exec</b>.
+</p></dd>
+<dt>SQLITE_PERM</dt>
+<dd><p>This return value says that the access permissions on the database
+file are such that the file cannot be opened.
+</p></dd>
+<dt>SQLITE_ABORT</dt>
+<dd><p>This value is returned if the callback function returns non-zero.
+</p></dd>
+<dt>SQLITE_BUSY</dt>
+<dd><p>This return code indicates that another program or thread has
+the database locked.  SQLite allows two or more threads to read the
+database at the same time, but only one thread can have the database
+open for writing at the same time.  Locking in SQLite is on the
+entire database.</p>
+</p></dd>
+<dt>SQLITE_LOCKED</dt>
+<dd><p>This return code is similar to SQLITE_BUSY in that it indicates
+that the database is locked.  But the source of the lock is a recursive
+call to <b>sqlite_exec</b>.  This return can only occur if you attempt
+to invoke sqlite_exec from within a callback routine of a query
+from a prior invocation of sqlite_exec.  Recursive calls to
+sqlite_exec are allowed as long as they do
+not attempt to write the same table.
+</p></dd>
+<dt>SQLITE_NOMEM</dt>
+<dd><p>This value is returned if a call to <b>malloc</b> fails.
+</p></dd>
+<dt>SQLITE_READONLY</dt>
+<dd><p>This return code indicates that an attempt was made to write to
+a database file that is opened for reading only.
+</p></dd>
+<dt>SQLITE_INTERRUPT</dt>
+<dd><p>This value is returned if a call to <b>sqlite_interrupt</b>
+interrupts a database operation in progress.
+</p></dd>
+<dt>SQLITE_IOERR</dt>
+<dd><p>This value is returned if the operating system informs SQLite
+that it is unable to perform some disk I/O operation.  This could mean
+that there is no more space left on the disk.
+</p></dd>
+<dt>SQLITE_CORRUPT</dt>
+<dd><p>This value is returned if SQLite detects that the database it is
+working on has become corrupted.  Corruption might occur due to a rogue
+process writing to the database file or it might happen due to an 
+perviously undetected logic error in of SQLite. This value is also
+returned if a disk I/O error occurs in such a way that SQLite is forced
+to leave the database file in a corrupted state.  The latter should only
+happen due to a hardware or operating system malfunction.
+</p></dd>
+<dt>SQLITE_FULL</dt>
+<dd><p>This value is returned if an insertion failed because there is
+no space left on the disk, or the database is too big to hold any
+more information.  The latter case should only occur for databases
+that are larger than 2GB in size.
+</p></dd>
+<dt>SQLITE_CANTOPEN</dt>
+<dd><p>This value is returned if the database file could not be opened
+for some reason.
+</p></dd>
+<dt>SQLITE_PROTOCOL</dt>
+<dd><p>This value is returned if some other process is messing with
+file locks and has violated the file locking protocol that SQLite uses
+on its rollback journal files.
+</p></dd>
+<dt>SQLITE_SCHEMA</dt>
+<dd><p>When the database first opened, SQLite reads the database schema
+into memory and uses that schema to parse new SQL statements.  If another
+process changes the schema, the command currently being processed will
+abort because the virtual machine code generated assumed the old
+schema.  This is the return code for such cases.  Retrying the
+command usually will clear the problem.
+</p></dd>
+<dt>SQLITE_TOOBIG</dt>
+<dd><p>SQLite will not store more than about 1 megabyte of data in a single
+row of a single table.  If you attempt to store more than 1 megabyte
+in a single row, this is the return code you get.
+</p></dd>
+<dt>SQLITE_CONSTRAINT</dt>
+<dd><p>This constant is returned if the SQL statement would have violated
+a database constraint.
+</p></dd>
+<dt>SQLITE_MISMATCH</dt>
+<dd><p>This error occurs when there is an attempt to insert non-integer
+data into a column labeled INTEGER PRIMARY KEY.  For most columns, SQLite
+ignores the data type and allows any kind of data to be stored.  But
+an INTEGER PRIMARY KEY column is only allowed to store integer data.
+</p></dd>
+<dt>SQLITE_MISUSE</dt>
+<dd><p>This error might occur if one or more of the SQLite API routines
+is used incorrectly.  Examples of incorrect usage include calling
+<b>sqlite_exec</b> after the database has been closed using
+<b>sqlite_close</b> or 
+calling <b>sqlite_exec</b> with the same
+database pointer simultaneously from two separate threads.
+</p></dd>
+<dt>SQLITE_NOLFS</dt>
+<dd><p>This error means that you have attempts to create or access a file
+database file that is larger that 2GB on a legacy Unix machine that
+lacks large file support.
+</p></dd>
+<dt>SQLITE_AUTH</dt>
+<dd><p>This error indicates that the authorizer callback
+has disallowed the SQL you are attempting to execute.
+</p></dd>
+<dt>SQLITE_ROW</dt>
+<dd><p>This is one of the return codes from the
+<b>sqlite_step</b> routine which is part of the non-callback API.
+It indicates that another row of result data is available.
+</p></dd>
+<dt>SQLITE_DONE</dt>
+<dd><p>This is one of the return codes from the
+<b>sqlite_step</b> routine which is part of the non-callback API.
+It indicates that the SQL statement has been completely executed and
+the <b>sqlite_finalize</b> routine is ready to be called.
+</p></dd>
+</dl>
+</blockquote>
+
+<h3>2.0 Accessing Data Without Using A Callback Function</h3>
+
+<p>
+The <b>sqlite_exec</b> routine described above used to be the only
+way to retrieve data from an SQLite database.  But many programmers found
+it inconvenient to use a callback function to obtain results.  So beginning
+with SQLite version 2.7.7, a second access interface is available that
+does not use callbacks.
+</p>
+
+<p>
+The new interface uses three separate functions to replace the single
+<b>sqlite_exec</b> function.
+</p>
+
+<blockquote><pre>
+typedef struct sqlite_vm sqlite_vm;
+
+int sqlite_compile(
+  sqlite *db,              /* The open database */
+  const char *zSql,        /* SQL statement to be compiled */
+  const char **pzTail,     /* OUT: uncompiled tail of zSql */
+  sqlite_vm **ppVm,        /* OUT: the virtual machine to execute zSql */
+  char **pzErrmsg          /* OUT: Error message. */
+);
+
+int sqlite_step(
+  sqlite_vm *pVm,          /* The virtual machine to execute */
+  int *pN,                 /* OUT: Number of columns in result */
+  const char ***pazValue,  /* OUT: Column data */
+  const char ***pazColName /* OUT: Column names and datatypes */
+);
+
+int sqlite_finalize(
+  sqlite_vm *pVm,          /* The virtual machine to be finalized */
+  char **pzErrMsg          /* OUT: Error message */
+);
+</pre></blockquote>
+
+<p>
+The strategy is to compile a single SQL statement using
+<b>sqlite_compile</b> then invoke <b>sqlite_step</b> multiple times,
+once for each row of output, and finally call <b>sqlite_finalize</b>
+to clean up after the SQL has finished execution.
+</p>
+
+<h4>2.1 Compiling An SQL Statement Into A Virtual Machine</h4>
+
+<p>
+The <b>sqlite_compile</b> "compiles" a single SQL statement (specified
+by the second parameter) and generates a virtual machine that is able
+to execute that statement.  
+As with must interface routines, the first parameter must be a pointer
+to an sqlite structure that was obtained from a prior call to
+<b>sqlite_open</b>.
+
+<p>
+A pointer to the virtual machine is stored in a pointer which is passed
+in as the 4th parameter.
+Space to hold the virtual machine is dynamically allocated.  To avoid
+a memory leak, the calling function must invoke
+<b>sqlite_finalize</b> on the virtual machine after it has finished
+with it.
+The 4th parameter may be set to NULL if an error is encountered during
+compilation.
+</p>
+
+<p>
+If any errors are encountered during compilation, an error message is
+written into memory obtained from <b>malloc</b> and the 5th parameter
+is made to point to that memory.  If the 5th parameter is NULL, then
+no error message is generated.  If the 5th parameter is not NULL, then
+the calling function should dispose of the memory containing the error
+message by calling <b>sqlite_freemem</b>.
+</p>
+
+<p>
+If the 2nd parameter actually contains two or more statements of SQL,
+only the first statement is compiled.  (This is different from the
+behavior of <b>sqlite_exec</b> which executes all SQL statements
+in its input string.)  The 3rd parameter to <b>sqlite_compile</b>
+is made to point to the first character beyond the end of the first
+statement of SQL in the input.  If the 2nd parameter contains only
+a single SQL statement, then the 3rd parameter will be made to point
+to the '\000' terminator at the end of the 2nd parameter.
+</p>
+
+<p>
+On success, <b>sqlite_compile</b> returns SQLITE_OK.
+Otherwise and error code is returned.
+</p>
+
+<h4>2.2 Step-By-Step Execution Of An SQL Statement</h4>
+
+<p>
+After a virtual machine has been generated using <b>sqlite_compile</b>
+it is executed by one or more calls to <b>sqlite_step</b>.  Each
+invocation of <b>sqlite_step</b>, except the last one,
+returns a single row of the result.
+The number of columns in  the result is stored in the integer that
+the 2nd parameter points to.
+The pointer specified by the 3rd parameter is made to point
+to an array of pointers to column values.
+The pointer in the 4th parameter is made to point to an array
+of pointers to column names and datatypes.
+The 2nd through 4th parameters to <b>sqlite_step</b> convey the
+same information as the 2nd through 4th parameters of the
+<b>callback</b> routine when using
+the <b>sqlite_exec</b> interface.  Except, with <b>sqlite_step</b>
+the column datatype information is always included in the in the
+4th parameter regardless of whether or not the
+<a href="pragma.html#pragma_show_datatypes">SHOW_DATATYPES</a> pragma
+is on or off.
+</p>
+
+<p>
+Each invocation of <b>sqlite_step</b> returns an integer code that
+indicates what happened during that step.  This code may be
+SQLITE_BUSY, SQLITE_ROW, SQLITE_DONE, SQLITE_ERROR, or
+SQLITE_MISUSE.
+</p>
+
+<p>
+If the virtual machine is unable to open the database file because
+it is locked by another thread or process, <b>sqlite_step</b>
+will return SQLITE_BUSY.  The calling function should do some other
+activity, or sleep, for a short amount of time to give the lock a
+chance to clear, then invoke <b>sqlite_step</b> again.  This can
+be repeated as many times as desired.
+</p>
+
+<p>
+Whenever another row of result data is available,
+<b>sqlite_step</b> will return SQLITE_ROW.  The row data is
+stored in an array of pointers to strings and the 2nd parameter
+is made to point to this array.
+</p>
+
+<p>
+When all processing is complete, <b>sqlite_step</b> will return
+either SQLITE_DONE or SQLITE_ERROR.  SQLITE_DONE indicates that the
+statement completed successfully and SQLITE_ERROR indicates that there
+was a run-time error.  (The details of the error are obtained from
+<b>sqlite_finalize</b>.)  It is a misuse of the library to attempt
+to call <b>sqlite_step</b> again after it has returned SQLITE_DONE
+or SQLITE_ERROR.
+</p>
+
+<p>
+When <b>sqlite_step</b> returns SQLITE_DONE or SQLITE_ERROR,
+the *pN and *pazColName values are set to the number of columns
+in the result set and to the names of the columns, just as they
+are for an SQLITE_ROW return.  This allows the calling code to
+find the number of result columns and the column names and datatypes
+even if the result set is empty.  The *pazValue parameter is always
+set to NULL when the return codes is SQLITE_DONE or SQLITE_ERROR.
+If the SQL being executed is a statement that does not
+return a result (such as an INSERT or an UPDATE) then *pN will
+be set to zero and *pazColName will be set to NULL.
+</p>
+
+<p>
+If you abuse the library by trying to call <b>sqlite_step</b>
+inappropriately it will attempt return SQLITE_MISUSE.
+This can happen if you call sqlite_step() on the same virtual machine
+at the same
+time from two or more threads or if you call sqlite_step()
+again after it returned SQLITE_DONE or SQLITE_ERROR or if you
+pass in an invalid virtual machine pointer to sqlite_step().
+You should not depend on the SQLITE_MISUSE return code to indicate
+an error.  It is possible that a misuse of the interface will go
+undetected and result in a program crash.  The SQLITE_MISUSE is
+intended as a debugging aid only - to help you detect incorrect
+usage prior to a mishap.  The misuse detection logic is not guaranteed
+to work in every case.
+</p>
+
+<h4>2.3 Deleting A Virtual Machine</h4>
+
+<p>
+Every virtual machine that <b>sqlite_compile</b> creates should
+eventually be handed to <b>sqlite_finalize</b>.  The sqlite_finalize()
+procedure deallocates the memory and other resources that the virtual
+machine uses.  Failure to call sqlite_finalize() will result in 
+resource leaks in your program.
+</p>
+
+<p>
+The <b>sqlite_finalize</b> routine also returns the result code
+that indicates success or failure of the SQL operation that the
+virtual machine carried out.
+The value returned by sqlite_finalize() will be the same as would
+have been returned had the same SQL been executed by <b>sqlite_exec</b>.
+The error message returned will also be the same.
+</p>
+
+<p>
+It is acceptable to call <b>sqlite_finalize</b> on a virtual machine
+before <b>sqlite_step</b> has returned SQLITE_DONE.  Doing so has
+the effect of interrupting the operation in progress.  Partially completed
+changes will be rolled back and the database will be restored to its
+original state (unless an alternative recovery algorithm is selected using
+an ON CONFLICT clause in the SQL being executed.)  The effect is the
+same as if a callback function of <b>sqlite_exec</b> had returned
+non-zero.
+</p>
+
+<p>
+It is also acceptable to call <b>sqlite_finalize</b> on a virtual machine
+that has never been passed to <b>sqlite_step</b> even once.
+</p>
+
+<h3>3.0 The Extended API</h3>
+
+<p>Only the three core routines described in section 1.0 are required to use
+SQLite.  But there are many other functions that provide 
+useful interfaces.  These extended routines are as follows:
+</p>
+
+<blockquote><pre>
+int sqlite_last_insert_rowid(sqlite*);
+
+int sqlite_changes(sqlite*);
+
+int sqlite_get_table(
+  sqlite*,
+  char *sql,
+  char ***result,
+  int *nrow,
+  int *ncolumn,
+  char **errmsg
+);
+
+void sqlite_free_table(char**);
+
+void sqlite_interrupt(sqlite*);
+
+int sqlite_complete(const char *sql);
+
+void sqlite_busy_handler(sqlite*, int (*)(void*,const char*,int), void*);
+
+void sqlite_busy_timeout(sqlite*, int ms);
+
+const char sqlite_version[];
+
+const char sqlite_encoding[];
+
+int sqlite_exec_printf(
+  sqlite*,
+  char *sql,
+  int (*)(void*,int,char**,char**),
+  void*,
+  char **errmsg,
+  ...
+);
+
+int sqlite_exec_vprintf(
+  sqlite*,
+  char *sql,
+  int (*)(void*,int,char**,char**),
+  void*,
+  char **errmsg,
+  va_list
+);
+
+int sqlite_get_table_printf(
+  sqlite*,
+  char *sql,
+  char ***result,
+  int *nrow,
+  int *ncolumn,
+  char **errmsg,
+  ...
+);
+
+int sqlite_get_table_vprintf(
+  sqlite*,
+  char *sql,
+  char ***result,
+  int *nrow,
+  int *ncolumn,
+  char **errmsg,
+  va_list
+);
+
+char *sqlite_mprintf(const char *zFormat, ...);
+
+char *sqlite_vmprintf(const char *zFormat, va_list);
+
+void sqlite_freemem(char*);
+
+void sqlite_progress_handler(sqlite*, int, int (*)(void*), void*);
+
+</pre></blockquote>
+
+<p>All of the above definitions are included in the "sqlite.h"
+header file that comes in the source tree.</p>
+
+<h4>3.1 The ROWID of the most recent insert</h4>
+
+<p>Every row of an SQLite table has a unique integer key.  If the
+table has a column labeled INTEGER PRIMARY KEY, then that column
+serves as the key.  If there is no INTEGER PRIMARY KEY column then
+the key is a unique integer.  The key for a row can be accessed in
+a SELECT statement or used in a WHERE or ORDER BY clause using any
+of the names "ROWID", "OID", or "_ROWID_".</p>
+
+<p>When you do an insert into a table that does not have an INTEGER PRIMARY
+KEY column, or if the table does have an INTEGER PRIMARY KEY but the value
+for that column is not specified in the VALUES clause of the insert, then
+the key is automatically generated.  You can find the value of the key
+for the most recent INSERT statement using the
+<b>sqlite_last_insert_rowid</b> API function.</p>
+
+<h4>3.2 The number of rows that changed</h4>
+
+<p>The <b>sqlite_changes</b> API function returns the number of rows
+that have been inserted, deleted, or modified since the database was
+last quiescent.  A "quiescent" database is one in which there are
+no outstanding calls to <b>sqlite_exec</b> and no VMs created by
+<b>sqlite_compile</b> that have not been finalized by <b>sqlite_finalize</b>.
+In common usage, <b>sqlite_changes</b> returns the number
+of rows inserted, deleted, or modified by the most recent <b>sqlite_exec</b>
+call or since the most recent <b>sqlite_compile</b>.  But if you have
+nested calls to <b>sqlite_exec</b> (that is, if the callback routine
+of one <b>sqlite_exec</b> invokes another <b>sqlite_exec</b>) or if
+you invoke <b>sqlite_compile</b> to create a new VM while there is
+still another VM in existance, then
+the meaning of the number returned by <b>sqlite_changes</b> is more
+complex.
+The number reported includes any changes
+that were later undone by a ROLLBACK or ABORT.  But rows that are
+deleted because of a DROP TABLE are <em>not</em> counted.</p>
+
+<p>SQLite implements the command "<b>DELETE FROM table</b>" (without
+a WHERE clause) by dropping the table then recreating it.  
+This is much faster than deleting the elements of the table individually.
+But it also means that the value returned from <b>sqlite_changes</b>
+will be zero regardless of the number of elements that were originally
+in the table.  If an accurate count of the number of elements deleted
+is necessary, use "<b>DELETE FROM table WHERE 1</b>" instead.</p>
+
+<h4>3.3 Querying into memory obtained from malloc()</h4>
+
+<p>The <b>sqlite_get_table</b> function is a wrapper around
+<b>sqlite_exec</b> that collects all the information from successive
+callbacks and writes it into memory obtained from malloc().  This
+is a convenience function that allows the application to get the
+entire result of a database query with a single function call.</p>
+
+<p>The main result from <b>sqlite_get_table</b> is an array of pointers
+to strings.  There is one element in this array for each column of
+each row in the result.  NULL results are represented by a NULL
+pointer. In addition to the regular data, there is an added row at the 
+beginning of the array that contains the name of each column of the
+result.</p>
+
+<p>As an example, consider the following query:</p>
+
+<blockquote>
+SELECT employee_name, login, host FROM users WHERE login LIKE 'd%';
+</blockquote>
+
+<p>This query will return the name, login and host computer name
+for every employee whose login begins with the letter "d".  If this
+query is submitted to <b>sqlite_get_table</b> the result might
+look like this:</p>
+
+<blockquote>
+nrow = 2<br>
+ncolumn = 3<br>
+result[0] = "employee_name"<br>
+result[1] = "login"<br>
+result[2] = "host"<br>
+result[3] = "dummy"<br>
+result[4] = "No such user"<br>
+result[5] = 0<br>
+result[6] = "D. Richard Hipp"<br>
+result[7] = "drh"<br>
+result[8] = "zadok"
+</blockquote>
+
+<p>Notice that the "host" value for the "dummy" record is NULL so
+the result[] array contains a NULL pointer at that slot.</p>
+
+<p>If the result set of a query is empty, then by default
+<b>sqlite_get_table</b> will set nrow to 0 and leave its
+result parameter is set to NULL.  But if the EMPTY_RESULT_CALLBACKS
+pragma is ON then the result parameter is initialized to the names
+of the columns only.  For example, consider this query which has
+an empty result set:</p>
+
+<blockquote>
+SELECT employee_name, login, host FROM users WHERE employee_name IS NULL;
+</blockquote>
+
+<p>
+The default behavior gives this results:
+</p>
+
+<blockquote>
+nrow = 0<br>
+ncolumn = 0<br>
+result = 0<br>
+</blockquote>
+
+<p>
+But if the EMPTY_RESULT_CALLBACKS pragma is ON, then the following
+is returned:
+</p>
+
+<blockquote>
+nrow = 0<br>
+ncolumn = 3<br>
+result[0] = "employee_name"<br>
+result[1] = "login"<br>
+result[2] = "host"<br>
+</blockquote>
+
+<p>Memory to hold the information returned by <b>sqlite_get_table</b>
+is obtained from malloc().  But the calling function should not try
+to free this information directly.  Instead, pass the complete table
+to <b>sqlite_free_table</b> when the table is no longer needed.
+It is safe to call <b>sqlite_free_table</b> with a NULL pointer such
+as would be returned if the result set is empty.</p>
+
+<p>The <b>sqlite_get_table</b> routine returns the same integer
+result code as <b>sqlite_exec</b>.</p>
+
+<h4>3.4 Interrupting an SQLite operation</h4>
+
+<p>The <b>sqlite_interrupt</b> function can be called from a
+different thread or from a signal handler to cause the current database
+operation to exit at its first opportunity.  When this happens,
+the <b>sqlite_exec</b> routine (or the equivalent) that started
+the database operation will return SQLITE_INTERRUPT.</p>
+
+<h4>3.5 Testing for a complete SQL statement</h4>
+
+<p>The next interface routine to SQLite is a convenience function used
+to test whether or not a string forms a complete SQL statement.
+If the <b>sqlite_complete</b> function returns true when its input
+is a string, then the argument forms a complete SQL statement.
+There are no guarantees that the syntax of that statement is correct,
+but we at least know the statement is complete.  If <b>sqlite_complete</b>
+returns false, then more text is required to complete the SQL statement.</p>
+
+<p>For the purpose of the <b>sqlite_complete</b> function, an SQL
+statement is complete if it ends in a semicolon.</p>
+
+<p>The <b>sqlite</b> command-line utility uses the <b>sqlite_complete</b>
+function to know when it needs to call <b>sqlite_exec</b>.  After each
+line of input is received, <b>sqlite</b> calls <b>sqlite_complete</b>
+on all input in its buffer.  If <b>sqlite_complete</b> returns true, 
+then <b>sqlite_exec</b> is called and the input buffer is reset.  If
+<b>sqlite_complete</b> returns false, then the prompt is changed to
+the continuation prompt and another line of text is read and added to
+the input buffer.</p>
+
+<h4>3.6 Library version string</h4>
+
+<p>The SQLite library exports the string constant named
+<b>sqlite_version</b> which contains the version number of the
+library.  The header file contains a macro SQLITE_VERSION
+with the same information.  If desired, a program can compare
+the SQLITE_VERSION macro against the <b>sqlite_version</b>
+string constant to verify that the version number of the
+header file and the library match.</p> 
+
+<h4>3.7 Library character encoding</h4>
+
+<p>By default, SQLite assumes that all data uses a fixed-size
+8-bit character (iso8859).  But if you give the --enable-utf8 option
+to the configure script, then the library assumes UTF-8 variable
+sized characters.  This makes a difference for the LIKE and GLOB
+operators and the LENGTH() and SUBSTR() functions.  The static
+string <b>sqlite_encoding</b> will be set to either "UTF-8" or
+"iso8859" to indicate how the library was compiled.  In addition,
+the <b>sqlite.h</b> header file will define one of the
+macros <b>SQLITE_UTF8</b> or <b>SQLITE_ISO8859</b>, as appropriate.</p>
+
+<p>Note that the character encoding mechanism used by SQLite cannot
+be changed at run-time.  This is a compile-time option only.  The
+<b>sqlite_encoding</b> character string just tells you how the library
+was compiled.</p>
+
+<h4>3.8 Changing the library's response to locked files</h4>
+
+<p>The <b>sqlite_busy_handler</b> procedure can be used to register
+a busy callback with an open SQLite database.  The busy callback will
+be invoked whenever SQLite tries to access a database that is locked.
+The callback will typically do some other useful work, or perhaps sleep,
+in order to give the lock a chance to clear.  If the callback returns
+non-zero, then SQLite tries again to access the database and the cycle
+repeats.  If the callback returns zero, then SQLite aborts the current
+operation and returns SQLITE_BUSY.</p>
+
+<p>The arguments to <b>sqlite_busy_handler</b> are the opaque
+structure returned from <b>sqlite_open</b>, a pointer to the busy
+callback function, and a generic pointer that will be passed as
+the first argument to the busy callback.  When SQLite invokes the
+busy callback, it sends it three arguments:  the generic pointer
+that was passed in as the third argument to <b>sqlite_busy_handler</b>,
+the name of the database table or index that the library is trying
+to access, and the number of times that the library has attempted to
+access the database table or index.</p>
+
+<p>For the common case where we want the busy callback to sleep,
+the SQLite library provides a convenience routine <b>sqlite_busy_timeout</b>.
+The first argument to <b>sqlite_busy_timeout</b> is a pointer to
+an open SQLite database and the second argument is a number of milliseconds.
+After <b>sqlite_busy_timeout</b> has been executed, the SQLite library
+will wait for the lock to clear for at least the number of milliseconds 
+specified before it returns SQLITE_BUSY.  Specifying zero milliseconds for
+the timeout restores the default behavior.</p>
+
+<h4>3.9 Using the <tt>_printf()</tt> wrapper functions</h4>
+
+<p>The four utility functions</p>
+
+<p>
+<ul>
+<li><b>sqlite_exec_printf()</b></li>
+<li><b>sqlite_exec_vprintf()</b></li>
+<li><b>sqlite_get_table_printf()</b></li>
+<li><b>sqlite_get_table_vprintf()</b></li>
+</ul>
+</p>
+
+<p>implement the same query functionality as <b>sqlite_exec</b>
+and <b>sqlite_get_table</b>.  But instead of taking a complete
+SQL statement as their second argument, the four <b>_printf</b>
+routines take a printf-style format string.  The SQL statement to
+be executed is generated from this format string and from whatever
+additional arguments are attached to the end of the function call.</p>
+
+<p>There are two advantages to using the SQLite printf
+functions instead of <b>sprintf</b>.  First of all, with the
+SQLite printf routines, there is never a danger of overflowing a
+static buffer as there is with <b>sprintf</b>.  The SQLite
+printf routines automatically allocate (and later frees)
+as much memory as is 
+necessary to hold the SQL statements generated.</p>
+
+<p>The second advantage the SQLite printf routines have over
+<b>sprintf</b> are two new formatting options specifically designed
+to support string literals in SQL.  Within the format string,
+the %q formatting option works very much like %s in that it
+reads a null-terminated string from the argument list and inserts
+it into the result.  But %q translates the inserted string by
+making two copies of every single-quote (') character in the
+substituted string.  This has the effect of escaping the end-of-string
+meaning of single-quote within a string literal. The %Q formatting
+option works similar; it translates the single-quotes like %q and
+additionally encloses the resulting string in single-quotes.
+If the argument for the %Q formatting options is a NULL pointer,
+the resulting string is NULL without single quotes.
+</p>
+
+<p>Consider an example.  Suppose you are trying to insert a string
+value into a database table where the string value was obtained from
+user input.  Suppose the string to be inserted is stored in a variable
+named zString.  The code to do the insertion might look like this:</p>
+
+<blockquote><pre>
+sqlite_exec_printf(db,
+  "INSERT INTO table1 VALUES('%s')",
+  0, 0, 0, zString);
+</pre></blockquote>
+
+<p>If the zString variable holds text like "Hello", then this statement
+will work just fine.  But suppose the user enters a string like 
+"Hi y'all!".  The SQL statement generated reads as follows:
+
+<blockquote><pre>
+INSERT INTO table1 VALUES('Hi y'all')
+</pre></blockquote>
+
+<p>This is not valid SQL because of the apostrophy in the word "y'all".
+But if the %q formatting option is used instead of %s, like this:</p>
+
+<blockquote><pre>
+sqlite_exec_printf(db,
+  "INSERT INTO table1 VALUES('%q')",
+  0, 0, 0, zString);
+</pre></blockquote>
+
+<p>Then the generated SQL will look like the following:</p>
+
+<blockquote><pre>
+INSERT INTO table1 VALUES('Hi y''all')
+</pre></blockquote>
+
+<p>Here the apostrophy has been escaped and the SQL statement is well-formed.
+When generating SQL on-the-fly from data that might contain a
+single-quote character ('), it is always a good idea to use the
+SQLite printf routines and the %q formatting option instead of <b>sprintf</b>.
+</p>
+
+<p>If the %Q formatting option is used instead of %q, like this:</p>
+
+<blockquote><pre>
+sqlite_exec_printf(db,
+  "INSERT INTO table1 VALUES(%Q)",
+  0, 0, 0, zString);
+</pre></blockquote>
+
+<p>Then the generated SQL will look like the following:</p>
+
+<blockquote><pre>
+INSERT INTO table1 VALUES('Hi y''all')
+</pre></blockquote>
+
+<p>If the value of the zString variable is NULL, the generated SQL
+will look like the following:</p>
+
+<blockquote><pre>
+INSERT INTO table1 VALUES(NULL)
+</pre></blockquote>
+
+<p>All of the _printf() routines above are built around the following
+two functions:</p>
+
+<blockquote><pre>
+char *sqlite_mprintf(const char *zFormat, ...);
+char *sqlite_vmprintf(const char *zFormat, va_list);
+</pre></blockquote>
+
+<p>The <b>sqlite_mprintf()</b> routine works like the the standard library
+<b>sprintf()</b> except that it writes its results into memory obtained
+from malloc() and returns a pointer to the malloced buffer.  
+<b>sqlite_mprintf()</b> also understands the %q and %Q extensions described
+above.  The <b>sqlite_vmprintf()</b> is a varargs version of the same
+routine.  The string pointer that these routines return should be freed
+by passing it to <b>sqlite_freemem()</b>.
+</p>
+
+<h4>3.10 Performing background jobs during large queries</h3>
+
+<p>The <b>sqlite_progress_handler()</b> routine can be used to register a
+callback routine with an SQLite database to be invoked periodically during long
+running calls to <b>sqlite_exec()</b>, <b>sqlite_step()</b> and the various
+wrapper functions.
+</p>
+
+<p>The callback is invoked every N virtual machine operations, where N is
+supplied as the second argument to <b>sqlite_progress_handler()</b>. The third
+and fourth arguments to <b>sqlite_progress_handler()</b> are a pointer to the
+routine to be invoked and a void pointer to be passed as the first argument to
+it.
+</p>
+
+<p>The time taken to execute each virtual machine operation can vary based on
+many factors.  A typical value for a 1 GHz PC is between half and three million
+per second but may be much higher or lower, depending on the query.  As such it
+is difficult to schedule background operations based on virtual machine
+operations. Instead, it is recommended that a callback be scheduled relatively
+frequently (say every 1000 instructions) and external timer routines used to
+determine whether or not background jobs need to be run.  
+</p>
+
+<a name="cfunc">
+<h3>4.0 Adding New SQL Functions</h3>
+
+<p>Beginning with version 2.4.0, SQLite allows the SQL language to be
+extended with new functions implemented as C code.  The following interface
+is used:
+</p>
+
+<blockquote><pre>
+typedef struct sqlite_func sqlite_func;
+
+int sqlite_create_function(
+  sqlite *db,
+  const char *zName,
+  int nArg,
+  void (*xFunc)(sqlite_func*,int,const char**),
+  void *pUserData
+);
+int sqlite_create_aggregate(
+  sqlite *db,
+  const char *zName,
+  int nArg,
+  void (*xStep)(sqlite_func*,int,const char**),
+  void (*xFinalize)(sqlite_func*),
+  void *pUserData
+);
+
+char *sqlite_set_result_string(sqlite_func*,const char*,int);
+void sqlite_set_result_int(sqlite_func*,int);
+void sqlite_set_result_double(sqlite_func*,double);
+void sqlite_set_result_error(sqlite_func*,const char*,int);
+
+void *sqlite_user_data(sqlite_func*);
+void *sqlite_aggregate_context(sqlite_func*, int nBytes);
+int sqlite_aggregate_count(sqlite_func*);
+</pre></blockquote>
+
+<p>
+The <b>sqlite_create_function()</b> interface is used to create 
+regular functions and <b>sqlite_create_aggregate()</b> is used to
+create new aggregate functions.  In both cases, the <b>db</b>
+parameter is an open SQLite database on which the functions should
+be registered, <b>zName</b> is the name of the new function,
+<b>nArg</b> is the number of arguments, and <b>pUserData</b> is
+a pointer which is passed through unchanged to the C implementation
+of the function.  Both routines return 0 on success and non-zero
+if there are any errors.
+</p>
+
+<p>
+The length of a function name may not exceed 255 characters.
+Any attempt to create a function whose name exceeds 255 characters
+in length will result in an error.
+</p>
+
+<p>
+For regular functions, the <b>xFunc</b> callback is invoked once
+for each function call.  The implementation of xFunc should call
+one of the <b>sqlite_set_result_...</b> interfaces to return its
+result.  The <b>sqlite_user_data()</b> routine can be used to
+retrieve the <b>pUserData</b> pointer that was passed in when the
+function was registered.
+</p>
+
+<p>
+For aggregate functions, the <b>xStep</b> callback is invoked once
+for each row in the result and then <b>xFinalize</b> is invoked at the
+end to compute a final answer.  The xStep routine can use the
+<b>sqlite_aggregate_context()</b> interface to allocate memory that
+will be unique to that particular instance of the SQL function.
+This memory will be automatically deleted after xFinalize is called.
+The <b>sqlite_aggregate_count()</b> routine can be used to find out
+how many rows of data were passed to the aggregate.  The xFinalize
+callback should invoke one of the <b>sqlite_set_result_...</b>
+interfaces to set the final result of the aggregate.
+</p>
+
+<p>
+SQLite now implements all of its built-in functions using this
+interface.  For additional information and examples on how to create
+new SQL functions, review the SQLite source code in the file
+<b>func.c</b>.
+</p>
+
+<h3>5.0 Multi-Threading And SQLite</h3>
+
+<p>
+If SQLite is compiled with the THREADSAFE preprocessor macro set to 1,
+then it is safe to use SQLite from two or more threads of the same process
+at the same time.  But each thread should have its own <b>sqlite*</b>
+pointer returned from <b>sqlite_open</b>.  It is never safe for two
+or more threads to access the same <b>sqlite*</b> pointer at the same time.
+</p>
+
+<p>
+In precompiled SQLite libraries available on the website, the Unix
+versions are compiled with THREADSAFE turned off but the windows
+versions are compiled with THREADSAFE turned on.  If you need something
+different that this you will have to recompile.
+</p>
+
+<p>
+Under Unix, an <b>sqlite*</b> pointer should not be carried across a
+<b>fork()</b> system call into the child process.  The child process
+should open its own copy of the database after the <b>fork()</b>.
+</p>
+
+<h3>6.0 Usage Examples</h3>
+
+<p>For examples of how the SQLite C/C++ interface can be used,
+refer to the source code for the <b>sqlite</b> program in the
+file <b>src/shell.c</b> of the source tree.
+Additional information about sqlite is available at
+<a href="sqlite.html">sqlite.html</a>.
+See also the sources to the Tcl interface for SQLite in
+the source file <b>src/tclsqlite.c</b>.</p>
+}
+footer $rcsid