Index: third_party/sqlite/src/ext/misc/remember.c |
diff --git a/third_party/sqlite/src/ext/misc/remember.c b/third_party/sqlite/src/ext/misc/remember.c |
new file mode 100644 |
index 0000000000000000000000000000000000000000..aa3eff8a3f8bc47e22a182d925a2990075b3c0c1 |
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+++ b/third_party/sqlite/src/ext/misc/remember.c |
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+/* |
+** 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 and the id of the counter to $ID and |
+** run the prepared statement. |
+** |
+** 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_int64(argv[1]); |
+ *((sqlite3_int64*)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; |
+} |