franta-hg@57: #include <cstdio>
franta-hg@57: #include <sqlite3ext.h>
franta-hg@57: #include <unistd.h>
franta-hg@57: 
franta-hg@57: /**
franta-hg@57:  * This is just an example – use official documentation: https://www.sqlite.org/loadext.html
franta-hg@57:  */
franta-hg@57: 
franta-hg@57: #define C_API extern "C"
franta-hg@57: #define SQL_FN(functionName) C_API void functionName (sqlite3_context* ctx, int valueCount, sqlite3_value** values)
franta-hg@57: 
franta-hg@57: SQLITE_EXTENSION_INIT1
franta-hg@57: 
franta-hg@57: /**
franta-hg@57:  * Returns number of values passed to the SQL function.
franta-hg@57:  */
franta-hg@57: SQL_FN(valueCount) {
franta-hg@57: 	sqlite3_result_int(ctx, valueCount);
franta-hg@57: }
franta-hg@57: 
franta-hg@57: /**
franta-hg@57:  * Returns current PID (process id).
franta-hg@57:  */
franta-hg@57: SQL_FN(getPID) {
franta-hg@57: 	sqlite3_result_int(ctx, getpid());
franta-hg@57: }
franta-hg@57: 
franta-hg@57: /**
franta-hg@57:  * Returns multiplication of all arguments or zero, if there are no arguments.
franta-hg@57:  */
franta-hg@57: SQL_FN(multiply) {
franta-hg@57: 	sqlite3_int64 result = valueCount == 0 ? 0 : 1;
franta-hg@57: 	for (int i = 0; i < valueCount; i++) result *= sqlite3_value_int64(values[i]);
franta-hg@57: 	sqlite3_result_int64(ctx, result);
franta-hg@57: }
franta-hg@57: 
franta-hg@57: /**
franta-hg@57:  * Function name should match the library file name: libdemo.so → sqlite3_demo_init.
franta-hg@57:  * Or we can specify different entry point when loading the module.
franta-hg@57:  */
franta-hg@57: C_API int sqlite3_demo_init(sqlite3* db, char** error, const sqlite3_api_routines* api) {
franta-hg@57: 	SQLITE_EXTENSION_INIT2(api);
franta-hg@57: 
franta-hg@57: 	sqlite3_create_function(db, "value_count", -1, SQLITE_UTF8, nullptr, valueCount, nullptr, nullptr);
franta-hg@57: 	sqlite3_create_function(db, "get_pid", 0, SQLITE_UTF8, nullptr, getPID, nullptr, nullptr);
franta-hg@57: 	sqlite3_create_function(db, "multiply", -1, SQLITE_UTF8, nullptr, multiply, nullptr, nullptr);
franta-hg@57: 	// -1 = function accepts arbitrary number of arguments
franta-hg@57: 
franta-hg@57: 	return SQLITE_OK;
franta-hg@57: }