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Updates to the documentation. Changed version number to 2.4.0-beta1 (CVS 417)

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FossilOrigin-Name: 36a8fe0ad0ee2a67afafc04125dcc085ec1b5a13
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drh
2002-03-04 02:26:15 +00:00
parent 4ff6dfa7de
commit ef2daf547d
9 changed files with 268 additions and 61 deletions
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78
www/c_interface.tcl
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@@ -1,7 +1,7 @@
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: c_interface.tcl,v 1.24 2002/02/19 22:42:06 drh Exp $}
set rcsid {$Id: c_interface.tcl,v 1.25 2002/03/04 02:26:17 drh Exp $}
puts {<html>
<head>
@@ -642,6 +642,82 @@ 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>
<h2>Adding New SQL Functions</h2>
<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.
</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>
<h2>Usage Examples</h2>
<p>For examples of how the SQLite C/C++ interface can be used,