Errors, files, refactor.

error.go

@@ -0,0 +1,32 @@
+package sqlite3
+
+import (
+	"strconv"
+	"strings"
+)
+
+type Error struct {
+	Code         int
+	ExtendedCode int
+	str          string
+	msg          string
+}
+
+func (e Error) Error() string {
+	var b strings.Builder
+	b.WriteString("sqlite3: ")
+
+	if e.str != "" {
+		b.WriteString(e.str)
+	} else {
+		b.WriteString(strconv.Itoa(e.Code))
+	}
+
+	if e.msg != "" {
+		b.WriteByte(':')
+		b.WriteByte(' ')
+		b.WriteString(e.msg)
+	}
+
+	return b.String()
+}