add utils.lua from Penlight

1 files changed, 137 insertions, 0 deletions

diff --git a/pl/compat.lua b/pl/compat.lua
new file mode 100644
index 0000000..7959ac3
--- /dev/null
+++ b/pl/compat.lua
@@ -0,0 +1,137 @@
+----------------

+--- Lua 5.1/5.2 compatibility

+-- Ensures that `table.pack` and `package.searchpath` are available

+-- for Lua 5.1 and LuaJIT.

+-- The exported function `load` is Lua 5.2 compatible.

+-- `compat.setfenv` and `compat.getfenv` are available for Lua 5.2, although

+-- they are not always guaranteed to work.

+-- @module pl.compat

+

+local compat = {}

+

+compat.lua51 = _VERSION == 'Lua 5.1'

+

+--- execute a shell command.

+-- This is a compatibility function that returns the same for Lua 5.1 and Lua 5.2

+-- @param cmd a shell command

+-- @return true if successful

+-- @return actual return code

+function compat.execute (cmd)

+    local res1,res2,res2 = os.execute(cmd)

+    if compat.lua51 then

+        return res1==0,res1

+    else

+        return not not res1,res2

+    end

+end

+

+----------------

+-- Load Lua code as a text or binary chunk.

+-- @param ld code string or loader

+-- @param[opt] source name of chunk for errors

+-- @param[opt] mode 'b', 't' or 'bt'

+-- @param[opt] env environment to load the chunk in

+-- @function compat.load

+

+---------------

+-- Get environment of a function.

+-- With Lua 5.2, may return nil for a function with no global references!

+-- Based on code by [Sergey Rozhenko](http://lua-users.org/lists/lua-l/2010-06/msg00313.html)

+-- @param f a function or a call stack reference

+-- @function compat.setfenv

+

+---------------

+-- Set environment of a function

+-- @param f a function or a call stack reference

+-- @param env a table that becomes the new environment of `f`

+-- @function compat.setfenv

+

+if compat.lua51 then -- define Lua 5.2 style load()

+    if not tostring(assert):match 'builtin' then -- but LuaJIT's load _is_ compatible

+        local lua51_load = load

+        function compat.load(str,src,mode,env)

+            local chunk,err

+            if type(str) == 'string' then

+                if str:byte(1) == 27 and not (mode or 'bt'):find 'b' then

+                    return nil,"attempt to load a binary chunk"

+                end

+                chunk,err = loadstring(str,src)

+            else

+                chunk,err = lua51_load(str,src)

+            end

+            if chunk and env then setfenv(chunk,env) end

+            return chunk,err

+        end

+    else

+        compat.load = load

+    end

+    compat.setfenv, compat.getfenv = setfenv, getfenv

+else

+    compat.load = load

+    -- setfenv/getfenv replacements for Lua 5.2

+    -- by Sergey Rozhenko

+    -- http://lua-users.org/lists/lua-l/2010-06/msg00313.html

+    -- Roberto Ierusalimschy notes that it is possible for getfenv to return nil

+    -- in the case of a function with no globals:

+    -- http://lua-users.org/lists/lua-l/2010-06/msg00315.html

+    function compat.setfenv(f, t)

+        f = (type(f) == 'function' and f or debug.getinfo(f + 1, 'f').func)

+        local name

+        local up = 0

+        repeat

+            up = up + 1

+            name = debug.getupvalue(f, up)

+        until name == '_ENV' or name == nil

+        if name then

+            debug.upvaluejoin(f, up, function() return name end, 1) -- use unique upvalue

+            debug.setupvalue(f, up, t)

+        end

+        if f ~= 0 then return f end

+    end

+

+    function compat.getfenv(f)

+        local f = f or 0

+        f = (type(f) == 'function' and f or debug.getinfo(f + 1, 'f').func)

+        local name, val

+        local up = 0

+        repeat

+            up = up + 1

+            name, val = debug.getupvalue(f, up)

+        until name == '_ENV' or name == nil

+        return val

+    end

+end

+

+--- Lua 5.2 Functions Available for 5.1

+-- @section lua52

+

+--- pack an argument list into a table.

+-- @param ... any arguments

+-- @return a table with field n set to the length

+-- @return the length

+-- @function table.pack

+if not table.pack then

+    function table.pack (...)

+        return {n=select('#',...); ...}

+    end

+end

+

+------

+-- return the full path where a Lua module name would be matched.

+-- @param mod module name, possibly dotted

+-- @param path a path in the same form as package.path or package.cpath

+-- @see path.package_path

+-- @function package.searchpath

+if not package.searchpath then

+    local sep = package.config:sub(1,1)

+    function package.searchpath (mod,path)

+        mod = mod:gsub('%.',sep)

+        for m in path:gmatch('[^;]+') do

+            local nm = m:gsub('?',mod)

+            local f = io.open(nm,'r')

+            if f then f:close(); return nm end

+        end

+    end

+end

+

+return compat