json: optimize writing strings

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/json/serialization_write.nit b/lib/json/serialization_write.nit
index 43987e8..28e79a8 100644 (file)
--- a/lib/json/serialization_write.nit
+++ b/lib/json/serialization_write.nit
@@ -144,26 +144,49 @@ redef class Text
        redef fun accept_json_serializer(v)
        do
                v.stream.write "\""
+
+               var start_i = 0
+               var escaped = null
                for i in [0 .. self.length[ do
                        var char = self[i]
                        if char == '\\' then
-                               v.stream.write "\\\\"
+                               escaped = "\\\\"
                        else if char == '\"' then
-                               v.stream.write "\\\""
+                               escaped = "\\\""
                        else if char < ' ' then
                                if char == '\n' then
-                                       v.stream.write "\\n"
+                                       escaped = "\\n"
                                else if char == '\r' then
-                                       v.stream.write "\\r"
+                                       escaped = "\\r"
                                else if char == '\t' then
-                                       v.stream.write "\\t"
+                                       escaped = "\\t"
                                else
-                                       v.stream.write char.escape_to_utf16
+                                       escaped = char.escape_to_utf16
                                end
+                       end
+
+                       if escaped != null then
+                               # Write open non-escaped string
+                               if start_i <= i then
+                                       v.stream.write substring(start_i, i-start_i)
+                               end
+
+                               # Write escaped character
+                               v.stream.write escaped
+                               escaped = null
+                               start_i = i+1
+                       end
+               end
+
+               # Write remaining non-escaped string
+               if start_i < length then
+                       if start_i == 0 then
+                               v.stream.write self
                        else
-                               v.stream.write char.to_s
+                               v.stream.write substring(start_i, length-start_i)
                        end
                end
+
                v.stream.write "\""
        end
 end