Add an implementation of `lua_getextraspace()`.

5 files changed, 92 insertions, 6 deletions

diff --git a/README.md b/README.md
index b986584..ea2f079 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,7 @@ For Lua 5.1 additionally:
 * `lua_KContext` (see [here][14])
 * `lua_KFunction` (see [here][14])
 * `lua_dump` (extra `strip` parameter, ignored, see [here][15])
+* `lua_getextraspace` (limited compatibilitiy, may throw out-of-memory errors)
 * `lua_getfield` (return value)
 * `lua_geti` and `lua_seti`
 * `lua_getglobal` (return value)
@@ -186,7 +187,6 @@ For Lua 5.1 additionally:
   [`lua-compat-5.2`][2] for a detailed list.
 * the following C API functions/macros:
   * `lua_isyieldable`
-  * `lua_getextraspace`
   * `lua_arith` (new operators missing)
   * `lua_push(v)fstring` (new formats missing)
   * `lua_upvalueid` (5.1)
diff --git a/c-api/compat-5.3.c b/c-api/compat-5.3.c
index bf81673..590e3c8 100644
--- a/c-api/compat-5.3.c
+++ b/c-api/compat-5.3.c
@@ -720,6 +720,63 @@ COMPAT53_API int lua_geti (lua_State *L, int index, lua_Integer i) {
 }
 
 
+#ifndef LUA_EXTRASPACE
+#define LUA_EXTRASPACE (sizeof(void*))
+#endif
+
+COMPAT53_API void *lua_getextraspace (lua_State *L) {
+  int is_main = 0;
+  void *ptr = NULL;
+  luaL_checkstack(L, 4, "not enough stack slots available");
+  lua_pushliteral(L, "__compat53_extraspace");
+  lua_pushvalue(L, -1);
+  lua_rawget(L, LUA_REGISTRYINDEX);
+  if (!lua_istable(L, -1)) {
+    lua_pop(L, 1);
+    lua_createtable(L, 0, 2);
+    lua_createtable(L, 0, 1);
+    lua_pushliteral(L, "k");
+    lua_setfield(L, -2, "__mode");
+    lua_setmetatable(L, -2);
+    lua_pushvalue(L, -2);
+    lua_pushvalue(L, -2);
+    lua_rawset(L, LUA_REGISTRYINDEX);
+  }
+  lua_replace(L, -2);
+  is_main = lua_pushthread(L);
+  lua_rawget(L, -2);
+  ptr = lua_touserdata(L, -1);
+  if (!ptr) {
+    lua_pop(L, 1);
+    ptr = lua_newuserdata(L, LUA_EXTRASPACE);
+    if (is_main) {
+      memset(ptr, '\0', LUA_EXTRASPACE);
+      lua_pushthread(L);
+      lua_pushvalue(L, -2);
+      lua_rawset(L, -4);
+      lua_pushboolean(L, 1);
+      lua_pushvalue(L, -2);
+      lua_rawset(L, -4);
+    } else {
+      void* mptr = NULL;
+      lua_pushboolean(L, 1);
+      lua_rawget(L, -3);
+      mptr = lua_touserdata(L, -1);
+      if (mptr)
+        memcpy(ptr, mptr, LUA_EXTRASPACE);
+      else
+        memset(ptr, '\0', LUA_EXTRASPACE);
+      lua_pop(L, 1);
+      lua_pushthread(L);
+      lua_pushvalue(L, -2);
+      lua_rawset(L, -4);
+    }
+  }
+  lua_pop(L, 2);
+  return ptr;
+}
+
+
 COMPAT53_API int lua_isinteger (lua_State *L, int index) {
   if (lua_type(L, index) == LUA_TNUMBER) {
     lua_Number n = lua_tonumber(L, index);
diff --git a/c-api/compat-5.3.h b/c-api/compat-5.3.h
index 8e10893..082a6a0 100644
--- a/c-api/compat-5.3.h
+++ b/c-api/compat-5.3.h
@@ -293,6 +293,9 @@ typedef int (*lua_KFunction)(lua_State *L, int status, lua_KContext ctx);
 #define lua_geti COMPAT53_CONCAT(COMPAT53_PREFIX, _geti)
 COMPAT53_API int lua_geti (lua_State *L, int index, lua_Integer i);
 
+#define lua_getextraspace COMPAT53_CONCAT(COMPAT53_PREFIX, _getextraspace)
+COMPAT53_API void *lua_getextraspace (lua_State *L);
+
 #define lua_isinteger COMPAT53_CONCAT(COMPAT53_PREFIX, _isinteger)
 COMPAT53_API int lua_isinteger (lua_State *L, int index);
 
@@ -339,7 +342,6 @@ COMPAT53_API void luaL_requiref (lua_State *L, const char *modname,
 
 /* XXX not implemented:
  * lua_isyieldable
- * lua_getextraspace
  * lua_arith (new operators)
  * lua_pushfstring (new formats)
  */
diff --git a/tests/test.lua b/tests/test.lua
index c2c0abf..9bb08da 100755
--- a/tests/test.lua
+++ b/tests/test.lua
@@ -664,14 +664,12 @@ print("isinteger", mod.isinteger(12.3))
 print("isinteger", mod.isinteger(math.huge))
 print("isinteger", mod.isinteger(math.sqrt(-1)))
 
-
 ___''
 print("rotate", mod.rotate(1, 1, 2, 3, 4, 5, 6))
 print("rotate", mod.rotate(-1, 1, 2, 3, 4, 5, 6))
 print("rotate", mod.rotate(4, 1, 2, 3, 4, 5, 6))
 print("rotate", mod.rotate(-4, 1, 2, 3, 4, 5, 6))
 
-
 ___''
 print("strtonum", mod.strtonum("+123"))
 print("strtonum", mod.strtonum(" 123 "))
@@ -679,7 +677,6 @@ print("strtonum", mod.strtonum("-1.23"))
 print("strtonum", mod.strtonum(" 123 abc"))
 print("strtonum", mod.strtonum("jkl"))
 
-
 ___''
 local a, b, c = mod.requiref()
 print("requiref", type(a), type(b), type(c),
@@ -687,6 +684,20 @@ print("requiref", type(a), type(b), type(c),
       type(requiref1), type(requiref2), type(requiref3))
 
 ___''
+mod.extraspace("abc")
+print("getextraspace", mod.extraspace("xyz"))
+local c = coroutine.wrap(function()
+  print("getextraspace", mod.extraspace("uvw"))
+  print("getextraspace", mod.extraspace("123"))
+  coroutine.yield()
+  print("getextraspace", mod.extraspace("asd"))
+end)
+c()
+print("getextraspace", mod.extraspace("456"))
+c()
+print("getextraspace", mod.extraspace("789"))
+
+___''
 local proxy, backend = {}, {}
 setmetatable(proxy, { __index = backend, __newindex = backend })
 print("geti/seti", rawget(proxy, 1), rawget(backend, 1))
@@ -705,7 +716,7 @@ print("tonumber", mod.tonumber("error"))
 
 ___''
 print("tointeger", mod.tointeger(12))
-print("tointeger", mod.tointeger(-12))
+print("tointeger", mod.tointeger(12))
 print("tointeger", mod.tointeger(12.1))
 print("tointeger", mod.tointeger(12.9))
 print("tointeger", mod.tointeger(-12.1))
diff --git a/tests/testmod.c b/tests/testmod.c
index cd56e76..345a8c9 100644
--- a/tests/testmod.c
+++ b/tests/testmod.c
@@ -63,6 +63,21 @@ static int test_getseti (lua_State *L) {
 }
 
 
+#ifndef LUA_EXTRASPACE
+#define LUA_EXTRASPACE (sizeof(void*))
+#endif
+
+static int test_getextraspace (lua_State *L) {
+  size_t len = 0;
+  char const* s = luaL_optlstring(L, 1, NULL, &len);
+  void* p = lua_getextraspace(L);
+  lua_pushstring(L, p);
+  if (s)
+    memcpy(p, s, len > LUA_EXTRASPACE-1 ? LUA_EXTRASPACE-1 : len+1);
+  return 1;
+}
+
+
 /* additional tests for Lua5.1 */
 #define NUP 3
 
@@ -307,6 +322,7 @@ static const luaL_Reg funcs[] = {
   { "strtonum", test_str2num },
   { "requiref", test_requiref },
   { "getseti", test_getseti },
+  { "extraspace", test_getextraspace },
   { "newproxy", test_newproxy },
   { "arith", test_arith },
   { "compare", test_compare },