Optimized processing of tables with numeric indexes.

README.md

@@ -162,6 +162,7 @@ See LICENSE file.
 
 ### v0.25 (Sep 29 2013)
   - Added `maxnum` option to limit the number of elements in tables.
+  - Optimized processing of tables with numeric indexes.
 
 ### v0.24 (Jun 12 2013)
   - Fixed an issue with missing numerical keys (fixes #8).

src/serpent.lua

@@ -44,7 +44,7 @@ local function s(t, opts)
       ((type(name) == "number") and '' or name..space..'='..space) or
       (name ~= nil and sname..space..'='..space or '')
     if seen[t] then -- already seen this element
-      table.insert(sref, spath..space..'='..space..seen[t])
+      sref[#sref+1] = spath..space..'='..space..seen[t]
       return tag..'nil'..comment('ref', level) end
     if type(mt) == 'table' and (mt.__serialize or mt.__tostring) then -- knows how to serialize itself
       seen[t] = insref or spath
@@ -54,10 +54,10 @@ local function s(t, opts)
       if level >= maxl then return tag..'{}'..comment('max', level) end
       seen[t] = insref or spath
       if next(t) == nil then return tag..'{}'..comment(t, level) end -- table empty
-      local maxn, o, out = #t, {}, {}
-      for key = 1, maxn do table.insert(o, key) end
-      for key in pairs(t) do if not o[key] or key > maxn then table.insert(o, key) end end
-      if opts.sortkeys then alphanumsort(o, t, opts.sortkeys) end
+      local maxn, o, out, maxt = math.min(#t, opts.maxnum or #t), {}, {}, #t > 0 and #t or nil
+      for key = 1, maxn do o[key] = key end
+      for key in next, t, maxt do if not o[key] or key > maxn then o[#o+1] = key end end
+      if opts.sortkeys and next(t, maxt) ~= nil then alphanumsort(o, t, opts.sortkeys) end
       if opts.maxnum and #o > opts.maxnum then o[opts.maxnum+1] = nil end
       for n, key in ipairs(o) do
         local value, ktype, plainindex = t[key], type(key), n <= maxn and not sparse
@@ -67,14 +67,14 @@ local function s(t, opts)
         or sparse and value == nil then -- skipping nils; do nothing
         elseif ktype == 'table' or ktype == 'function' or badtype[ktype] then
           if not seen[key] and not globals[key] then
-            table.insert(sref, 'placeholder')
+            sref[#sref+1] = 'placeholder'
             local sname = safename(iname, gensym(key)) -- iname is table for local variables
             sref[#sref] = val2str(key,sname,indent,sname,iname,true) end
-          table.insert(sref, 'placeholder')
+          sref[#sref+1] = 'placeholder'
           local path = seen[t]..'['..(seen[key] or globals[key] or gensym(key))..']'
           sref[#sref] = path..space..'='..space..(seen[value] or val2str(value,nil,indent,path))
         else
-          table.insert(out,val2str(value,key,indent,insref,seen[t],plainindex,level+1))
+          out[#out+1] = val2str(value,key,indent,insref,seen[t],plainindex,level+1)
         end
       end
       local prefix = string.rep(indent or '', level)

t/test.lua

@@ -158,7 +158,7 @@ do
 end
 
 -- test userdata with __tostring method that returns type starting with digits
-do
+if _VERSION == 'Lua 5.1' then
   local userdata = newproxy(true)
   getmetatable(userdata).__tostring = function() return "1234 <Userdata>" end
   local a = {hi = "there", [{}] = 123, [userdata] = 23}
@@ -168,7 +168,7 @@ do
 end
 
 -- test userdata with __tostring method that returns a table
-do
+if _VERSION == 'Lua 5.1' then
   local userdata = newproxy(true)
   getmetatable(userdata).__tostring = function() return {3,4,5} end
   local a = {hi = "there", [{}] = 123, [userdata] = 23, ud = userdata}
@@ -181,7 +181,7 @@ do
 end
 
 -- test userdata with __tostring method that includes another userdata
-do
+if _VERSION == 'Lua 5.1' then
   local userdata1 = newproxy(true)
   local userdata2 = newproxy(true)
   getmetatable(userdata1).__tostring = function() return {1,2,ud = userdata2} end
@@ -197,7 +197,7 @@ do
 end
 
 -- test userdata with __serialize method that includes another userdata
-do
+if _VERSION == 'Lua 5.1' then
   local userdata1 = newproxy(true)
   local userdata2 = newproxy(true)
   getmetatable(userdata1).__serialize = function() return {1,2,ud = userdata2} end