module pg #flag -lpq #flag linux -I/usr/include/postgresql #flag darwin -I/opt/local/include/postgresql11 #flag windows -I @VROOT/thirdparty/pg/include #flag windows -L @VROOT/thirdparty/pg/win64 #include pub struct DB { mut: conn &C.PGconn } pub struct Row { pub mut: vals []string } struct C.PGResult pub struct Config { pub: host string port int = 5432 user string password string dbname string } fn C.PQconnectdb(a byteptr) &C.PGconn fn C.PQerrorMessage(voidptr) byteptr fn C.PQgetvalue(&C.PGResult, int, int) byteptr fn C.PQstatus(voidptr) int fn C.PQresultStatus(voidptr) int fn C.PQntuples(&C.PGResult) int fn C.PQnfields(&C.PGResult) int fn C.PQexec(voidptr) &C.PGResult fn C.PQexecParams(voidptr) &C.PGResult fn C.PQclear(&C.PGResult) voidptr fn C.PQfinish(voidptr) // connect makes a new connection to the database server using // the parameters from the `Config` structure, returning // a connection error when something goes wrong pub fn connect(config Config) ?DB { conninfo := 'host=$config.host port=$config.port user=$config.user dbname=$config.dbname password=$config.password' conn := C.PQconnectdb(conninfo.str) if conn == 0 { return error('libpq memory allocation error') } status := C.PQstatus(conn) if status != C.CONNECTION_OK { // We force the construction of a new string as the // error message will be freed by the next `PQfinish` // call c_error_msg := unsafe {C.PQerrorMessage(conn).vstring()} error_msg := '$c_error_msg' C.PQfinish(conn) return error('Connection to a PG database failed: $error_msg') } return DB{ conn: conn } } fn res_to_rows(res voidptr) []Row { nr_rows := C.PQntuples(res) nr_cols := C.PQnfields(res) mut rows := []Row{} for i in 0 .. nr_rows { mut row := Row{} for j in 0 .. nr_cols { val := C.PQgetvalue(res, i, j) sval := unsafe {val.vstring()} row.vals << sval } rows << row } C.PQclear(res) return rows } // close frees the underlaying resource allocated by the database connection pub fn (db DB) close() { C.PQfinish(db.conn) } // q_int submit a command to the database server and // returns an the first field in the first tuple // converted to an int. If no row is found or on // command failure, an error is returned pub fn (db DB) q_int(query string) ?int { rows := db.exec(query) ? if rows.len == 0 { return error('q_int "$query" not found') } row := rows[0] if row.vals.len == 0 { return 0 } val := row.vals[0] return val.int() } // q_int submit a command to the database server and // returns an the first field in the first tuple // as a string. If no row is found or on // command failure, an error is returned pub fn (db DB) q_string(query string) ?string { rows := db.exec(query) ? if rows.len == 0 { return error('q_string "$query" not found') } row := rows[0] if row.vals.len == 0 { return '' } val := row.vals[0] return val } // q_strings submit a command to the database server and // returns the resulting row set. Alias of `exec` pub fn (db DB) q_strings(query string) ?[]Row { return db.exec(query) } // exec submit a command to the database server and wait // for the result, returning an error on failure and a // row set on success pub fn (db DB) exec(query string) ?[]Row { res := C.PQexec(db.conn, query.str) return db.handle_error_or_result(res, 'exec') } fn rows_first_or_empty(rows []Row) ?Row { if rows.len == 0 { return error('no row') } return rows[0] } pub fn (db DB) exec_one(query string) ?Row { res := C.PQexec(db.conn, query.str) e := unsafe {C.PQerrorMessage(db.conn).vstring()} if e != '' { return error('pg exec error: "$e"') } row := rows_first_or_empty(res_to_rows(res)) ? return row } // exec_param_many executes a query with the provided parameters pub fn (db DB) exec_param_many(query string, params []string) ?[]Row { mut param_vals := []charptr{ len: params.len } for i in 0 .. params.len { param_vals[i] = params[i].str } res := C.PQexecParams(db.conn, query.str, params.len, 0, param_vals.data, 0, 0, 0) return db.handle_error_or_result(res, 'exec_param_many') } pub fn (db DB) exec_param2(query string, param string, param2 string) ?[]Row { return db.exec_param_many(query, [param, param2]) } pub fn (db DB) exec_param(query string, param string) ?[]Row { return db.exec_param_many(query, [param]) } fn (db DB) handle_error_or_result(res voidptr, elabel string) ?[]Row { e := unsafe {C.PQerrorMessage(db.conn).vstring()} if e != '' { C.PQclear(res) return error('pg $elabel error:\n$e') } return res_to_rows(res) }