Start work on introducing machine-readable error codes.

This commit introduces a new type 'ErrNo', implementing the error
interface.  Constants for all sqlite3 error codes are provided
in the new source file "error.go".

sqlite3.go

@@ -132,7 +132,7 @@ func (c *SQLiteConn) exec(cmd string) error {
 	defer C.free(unsafe.Pointer(pcmd))
 	rv := C.sqlite3_exec(c.db, pcmd, nil, nil, nil)
 	if rv != C.SQLITE_OK {
-		return errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
+		return ErrNo(rv)
 	}
 	return nil
 }
@@ -145,6 +145,10 @@ func (c *SQLiteConn) Begin() (driver.Tx, error) {
 	return &SQLiteTx{c}, nil
 }
 
+func errorString(err ErrNo) string {
+	return C.GoString(C.sqlite3_errstr(C.int(err)))
+}
+
 // Open database and return a new connection.
 // You can specify DSN string with URI filename.
 //   test.db
@@ -165,7 +169,7 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 			C.SQLITE_OPEN_CREATE,
 		nil)
 	if rv != 0 {
-		return nil, errors.New(C.GoString(C.sqlite3_errmsg(db)))
+		return nil, ErrNo(rv)
 	}
 	if db == nil {
 		return nil, errors.New("sqlite succeeded without returning a database")
@@ -173,7 +177,7 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 
 	rv = C.sqlite3_busy_timeout(db, 5000)
 	if rv != C.SQLITE_OK {
-		return nil, errors.New(C.GoString(C.sqlite3_errmsg(db)))
+		return nil, ErrNo(rv)
 	}
 
 	return &SQLiteConn{db}, nil
@@ -188,7 +192,7 @@ func (c *SQLiteConn) Close() error {
 	}
 	rv := C.sqlite3_close(c.db)
 	if rv != C.SQLITE_OK {
-		return errors.New("error while closing sqlite database connection")
+		return ErrNo(rv)
 	}
 	c.db = nil
 	return nil
@@ -202,7 +206,7 @@ func (c *SQLiteConn) Prepare(query string) (driver.Stmt, error) {
 	var perror *C.char
 	rv := C.sqlite3_prepare_v2(c.db, pquery, -1, &s, &perror)
 	if rv != C.SQLITE_OK {
-		return nil, errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
+		return nil, ErrNo(rv)
 	}
 	var t string
 	if perror != nil && C.strlen(perror) > 0 {
@@ -222,7 +226,7 @@ func (s *SQLiteStmt) Close() error {
 	}
 	rv := C.sqlite3_finalize(s.s)
 	if rv != C.SQLITE_OK {
-		return errors.New(C.GoString(C.sqlite3_errmsg(s.c.db)))
+		return ErrNo(rv)
 	}
 	return nil
 }
@@ -235,7 +239,7 @@ func (s *SQLiteStmt) NumInput() int {
 func (s *SQLiteStmt) bind(args []driver.Value) error {
 	rv := C.sqlite3_reset(s.s)
 	if rv != C.SQLITE_ROW && rv != C.SQLITE_OK && rv != C.SQLITE_DONE {
-		return errors.New(C.GoString(C.sqlite3_errmsg(s.c.db)))
+		return ErrNo(rv)
 	}
 
 	for i, v := range args {
@@ -280,7 +284,7 @@ func (s *SQLiteStmt) bind(args []driver.Value) error {
 			rv = C._sqlite3_bind_text(s.s, n, (*C.char)(unsafe.Pointer(&b[0])), C.int(len(b)))
 		}
 		if rv != C.SQLITE_OK {
-			return errors.New(C.GoString(C.sqlite3_errmsg(s.c.db)))
+			return ErrNo(rv)
 		}
 	}
 	return nil
@@ -311,7 +315,7 @@ func (s *SQLiteStmt) Exec(args []driver.Value) (driver.Result, error) {
 	}
 	rv := C.sqlite3_step(s.s)
 	if rv != C.SQLITE_ROW && rv != C.SQLITE_OK && rv != C.SQLITE_DONE {
-		return nil, errors.New(C.GoString(C.sqlite3_errmsg(s.c.db)))
+		return nil, ErrNo(rv)
 	}
 
 	res := &SQLiteResult{
@@ -325,7 +329,7 @@ func (s *SQLiteStmt) Exec(args []driver.Value) (driver.Result, error) {
 func (rc *SQLiteRows) Close() error {
 	rv := C.sqlite3_reset(rc.s.s)
 	if rv != C.SQLITE_OK {
-		return errors.New(C.GoString(C.sqlite3_errmsg(rc.s.c.db)))
+		return ErrNo(rv)
 	}
 	return nil
 }
@@ -348,7 +352,7 @@ func (rc *SQLiteRows) Next(dest []driver.Value) error {
 		return io.EOF
 	}
 	if rv != C.SQLITE_ROW {
-		return errors.New(C.GoString(C.sqlite3_errmsg(rc.s.c.db)))
+		return ErrNo(rv)
 	}
 
 	if rc.decltype == nil {