Add default arguments to CInterface.

A default argument allows a user to specify one or more arguments that
are passed to each function wrapped by the interface before any other
arguments are passed. A default argument is provided by passing a
function that, given a variable name, declares and initializes the
argument.

1 files changed, 14 insertions, 0 deletions

diff --git a/cinterface.lua b/cinterface.lua
index d6c26bb..e8678cc 100644
--- a/cinterface.lua
+++ b/cinterface.lua
@@ -4,6 +4,7 @@ function CInterface.new()
    self = {}
    self.txt = {}
    self.registry = {}
+   self.defaultArguments = {}
    setmetatable(self, {__index=CInterface})
    return self
 end
@@ -16,6 +17,10 @@ function CInterface:print(str)
    table.insert(self.txt, str)
 end
 
+function CInterface:registerDefaultArgument(code)
+  table.insert(self.defaultArguments, code)
+end
+
 function CInterface:wrap(luaname, ...)
    local txt = self.txt
    local varargs = {...}
@@ -29,6 +34,10 @@ function CInterface:wrap(luaname, ...)
    table.insert(txt, "{")
    table.insert(txt, "int narg = lua_gettop(L);")
 
+   for i, defaultArgCode in ipairs(self.defaultArguments) do
+      table.insert(txt, defaultArgCode(string.format("default_arg%d", i)))
+   end
+
    if #varargs == 2 then
       local cfuncname = varargs[1]
       local args = varargs[2]
@@ -104,6 +113,7 @@ end
 function CInterface:clearhistory()
    self.txt = {}
    self.registry = {}
+   self.defaultArguments = {}
 end
 
 function CInterface:tostring()
@@ -277,6 +287,10 @@ end
 function CInterface:__writecall(txt, args, cfuncname, cargs, argcreturned)
    local argtypes = self.argtypes
 
+   for i = 1, #self.defaultArguments do
+      table.insert(cargs, i, string.format('default_arg%d', i))
+   end
+
    for _,arg in ipairs(args) do
       tableinsertcheck(txt, arg:precall())
    end