gears.sort: Import

The difference to table.sort() is that this is guranteed to be stable.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/gears/init.lua.in

@@ -5,6 +5,7 @@
 ---------------------------------------------------------------------------
 
 require("gears.color")
+require("gears.sort")
 
 module("gears")
 

lib/gears/sort.lua.in

@@ -0,0 +1,83 @@
+---------------------------------------------------------------------------
+-- @author Uli Schlachter
+-- @copyright 2010 Uli Schlachter
+-- @release @AWESOME_VERSION@
+---------------------------------------------------------------------------
+
+local setmetatable = setmetatable
+local ipairs = ipairs
+local table = table
+local error = error
+
+module("gears.sort")
+
+local function less_than_comp(a, b)
+    return a < b
+end
+
+-- Sort a table. This interface should be identical to table.sort().
+-- The difference to table.sort() is that this sort is stable.
+-- @param list The table to sort (we do an in-place sort!).
+-- @param comp Comparator used for the sorting
+function sort(list, comp)
+    local comp = comp or less_than_comp
+
+    -- A table could contain non-integer keys which we have to ignore.
+    local num = 0
+    for k, v in ipairs(list) do
+        num = num + 1
+    end
+
+    if num <= 1 then
+        -- Nothing to do
+        return
+    end
+
+    -- Sort until everything is sorted :)
+    local sorted = false
+    local n = num
+    while not sorted do
+        sorted = true
+        for i = 1, n - 1 do
+            -- Two equal elements won't be swapped -> we are stable
+            if comp(list[i+1], list[i]) then
+                local tmp = list[i]
+                list[i] = list[i+1]
+                list[i+1] = tmp
+
+                sorted = false
+            end
+        end
+        -- The last element is now guaranteed to be in the right spot
+        n = n - 1
+    end
+end
+
+function test()
+    local function test_one(t)
+        local len = #t
+        sort(t)
+        if len ~= #t then
+            error("Table lost entries during sort!")
+        end
+        if len > 1 then
+            local cur = table.remove(t, 1)
+            len = len - 1
+            while len > 0 do
+                local next = table.remove(t, 1)
+                if cur > next then
+                    error("Table not sorted!")
+                end
+                cur = next
+                len = len -1
+            end
+        end
+    end
+    test_one({1, 2, 3, 4, 5, 6})
+    test_one({6, 5, 4, 3, 2, 1})
+    return true
+end
+
+setmetatable(_M, { __call = function (_, ...) return sort(...) end })
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=80