Allow FFI number types as sizes to ffi.string

For example:
  ffi.string(buf, ffi.new('long', 10))

2 files changed, 16 insertions, 1 deletions

diff --git a/ffi.c b/ffi.c
index 15904b9..91f592a 100644
--- a/ffi.c
+++ b/ffi.c
@@ -2631,7 +2631,11 @@ static int ffi_string(lua_State* L)
     } else if (ct.type == INT8_TYPE && ct.pointers == 1) {
         size_t sz;
 
-        if (!lua_isnil(L, 2)) {
+        if (lua_isuserdata(L, 2)) {
+            if (!cdata_tointeger(L, 2, &sz)) {
+                type_error(L, 2, "int", 0, NULL);
+            }
+        } else if (!lua_isnil(L, 2)) {
             sz = (size_t) luaL_checknumber(L, 2);
 
         } else if (ct.is_array && !ct.is_variable_array) {
diff --git a/test.lua b/test.lua
index f4246ad..c9e036f 100644
--- a/test.lua
+++ b/test.lua
@@ -934,6 +934,17 @@ for i=1,3 do
     assert(structOfStructs.arrays[0].ints[i] == i)
 end
 
+-- Test ffi.string
+local buf = ffi.new('char[5]')
+ffi.fill(buf, 4, 97)
+buf[4] = 0
+
+assert(ffi.string(buf) == 'aaaa')
+assert(ffi.string(buf, 4) == 'aaaa')
+assert(ffi.string(buf, 2) == 'aa')
+assert(ffi.string(buf, 0) == '')
+assert(ffi.string(buf, ffi.new('long long', 2)) == 'aa')
+assert(ffi.string(buf, ffi.new('int', 2)) == 'aa')
 
 print('Test PASSED')