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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-05 17:28:19 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-05 17:28:19 +0000 |
commit | 18657a960e125336f704ea058e25c27bd3900dcb (patch) | |
tree | 17b438b680ed45a996d7b59951e6aa34023783f2 /ext/misc/remember.c | |
parent | Initial commit. (diff) | |
download | sqlite3-upstream.tar.xz sqlite3-upstream.zip |
Adding upstream version 3.40.1.upstream/3.40.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'ext/misc/remember.c')
-rw-r--r-- | ext/misc/remember.c | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/ext/misc/remember.c b/ext/misc/remember.c new file mode 100644 index 0000000..18f6ede --- /dev/null +++ b/ext/misc/remember.c @@ -0,0 +1,72 @@ +/* +** 2016-08-09 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** +** This file demonstrates how to create an SQL function that is a pass-through +** for integer values (it returns a copy of its argument) but also saves the +** value that is passed through into a C-language variable. The address of +** the C-language variable is supplied as the second argument. +** +** This allows, for example, a counter to incremented and the original +** value retrieved, atomically, using a single statement: +** +** UPDATE counterTab SET cnt=remember(cnt,$PTR)+1 WHERE id=$ID +** +** Prepare the above statement once. Then to use it, bind the address +** of the output variable to $PTR using sqlite3_bind_pointer() with a +** pointer type of "carray" and bind the id of the counter to $ID and +** run the prepared statement. +** +** This implementation of the remember() function uses a "carray" +** pointer so that it can share pointers with the carray() extension. +** +** One can imagine doing similar things with floating-point values and +** strings, but this demonstration extension will stick to using just +** integers. +*/ +#include "sqlite3ext.h" +SQLITE_EXTENSION_INIT1 +#include <assert.h> + +/* +** remember(V,PTR) +** +** Return the integer value V. Also save the value of V in a +** C-language variable whose address is PTR. +*/ +static void rememberFunc( + sqlite3_context *pCtx, + int argc, + sqlite3_value **argv +){ + sqlite3_int64 v; + sqlite3_int64 *ptr; + assert( argc==2 ); + v = sqlite3_value_int64(argv[0]); + ptr = sqlite3_value_pointer(argv[1], "carray"); + if( ptr ) *ptr = v; + sqlite3_result_int64(pCtx, v); +} + +#ifdef _WIN32 +__declspec(dllexport) +#endif +int sqlite3_remember_init( + sqlite3 *db, + char **pzErrMsg, + const sqlite3_api_routines *pApi +){ + int rc = SQLITE_OK; + SQLITE_EXTENSION_INIT2(pApi); + rc = sqlite3_create_function(db, "remember", 2, SQLITE_UTF8, 0, + rememberFunc, 0, 0); + return rc; +} |