util.json: New, improved, fixed codepoint to UTF-8 conversion.

diff --git a/util/json.lua b/util/json.lua
index e8de4d2d49952afa2a846efec356a09bfae90b8a..9c2dd2c6127b6d9275ffba29639eab079ca82d52 100644 (file)
--- a/util/json.lua
+++ b/util/json.lua
@@ -2,8 +2,6 @@
 -- Copyright (C) 2008-2010 Matthew Wild
 -- Copyright (C) 2008-2010 Waqas Hussain
 --
--- utf8char copyright (C) 2007 Rici Lake
---
 -- This project is MIT/X11 licensed. Please see the
 -- COPYING file in the source package for more information.
 --
@@ -41,32 +39,19 @@ for i=0,31 do
        if not escapes[ch] then escapes[ch] = ("\\u%.4X"):format(i); end
 end
 
-local function utf8char(i)
-       if i >= 0 then
-               i = i - i%1
-               if i < 128 then
-                       return s_char(i)
-               else
-                       local c1 = i % 64
-                       i = (i - c1) / 64
-                       if i < 32 then
-                               return s_char(0xC0+i, 0x80+c1)
-                       else
-                               local c2 = i % 64
-                               i = (i - c2) / 64
-                               if i < 16 and (i ~= 13 or c2 < 32) then
-                                       return s_char(0xE0+i, 0x80+c2, 0x80+c1)
-                               elseif i >= 16 and i < 0x110 then
-                                       local c3 = i % 64
-                                       i = (i - c3) / 64
-                                       return s_char(0xF0+i, 0x80+c3, 0x80+c2, 0x80+c1)
-                               end
-                       end
-               end
+local function codepoint_to_utf8(code)
+       if code < 0x80 then return s_char(code); end
+       local bits0_6 = code % 64;
+       if code < 0x800 then
+               local bits6_5 = (code - bits0_6) / 64;
+               return s_char(0x80 + 0x40 + bits6_5, 0x80 + bits0_6);
        end
+       local bits0_12 = code % 4096;
+       local bits6_6 = (bits0_12 - bits0_6) / 64;
+       local bits12_4 = (code - bits0_12) / 4096;
+       return s_char(0x80 + 0x40 + 0x20 + bits12_4, 0x80 + bits6_6, 0x80 + bits0_6);
 end
 
-
 local valid_types = {
        number  = true,
        string  = true,
@@ -292,7 +277,7 @@ function json.decode(json)
                                                if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end
                                                seq = seq..ch;
                                        end
-                                       s = s..utf8char(tonumber(seq, 16));
+                                       s = s..codepoint_to_utf8(tonumber(seq, 16));
                                        next();
                                else error("invalid escape sequence in string"); end
                        end