first commit

lib/knife/serialize.lua

@@ -0,0 +1,78 @@
+local tinsert, tconcat, infinity = table.insert, table.concat, math.huge
+
+return function (value)
+    local intro, outro, ready, known = {}, {}, {}, {}
+    local knownCount = 0
+    local writer = {}
+
+    -- get writer delegate for this value's type
+    local function getWriter (value)
+        return writer[type(value)]
+    end
+
+    -- check if a value has a representation yet
+    local function isReady (value)
+        return type(value) ~= 'table' or ready[value]
+    end
+
+    -- serialize tables
+    function writer.table (value)
+        if known[value] then
+            return known[value]
+        end
+
+        knownCount = knownCount + 1
+        local variable = ('v%i'):format(knownCount)
+        known[value] = variable
+
+        local parts = {}
+        for k, v in pairs(value) do
+            local writeKey, writeValue = getWriter(k), getWriter(v)
+            if writeKey and writeValue then
+                local key, value = writeKey(k), writeValue(v)
+                if isReady(k) and isReady(v) then
+                    tinsert(parts, ('[%s]=%s'):format(key, value))
+                else
+                    tinsert(outro, ('%s[%s]=%s'):format(variable, key, value))
+                end
+            end
+        end
+
+        local fields = tconcat(parts, ',')
+        tinsert(intro, ('local %s={%s}'):format(variable, fields))
+        ready[value] = true
+
+        return variable
+    end
+
+    -- preserve sign bit on NaN, since Lua prints "nan" or "-nan"
+    local function writeNan (n)
+        return tostring(n) == tostring(0/0) and '0/0' or '-(0/0)'
+    end
+
+    -- serialize numbers
+    function writer.number (value)
+        return value == infinity and '1/0'
+            or value == -infinity and '-1/0'
+            or value ~= value and writeNan(value)
+            or ('%.17G'):format(value)
+    end
+
+    -- serialize strings
+    function writer.string (value)
+        return ('%q'):format(value)
+    end
+
+    -- serialize booleans
+    writer.boolean = tostring
+
+    -- concatenate array, joined by and terminated with line break
+    local function lines (t)
+        return #t == 0 and '' or tconcat(t, '\n') .. '\n'
+    end
+
+    -- generate serialized result
+    local write = getWriter(value)
+    local result = write and write(value) or 'nil'
+    return lines(intro) .. lines(outro) .. 'return ' .. result
+end