Allow non-string, non-userdata subjects in Lua 5.1

2 files changed, 20 insertions, 21 deletions

diff --git a/doc/manual.txt b/doc/manual.txt
index ab68394..f7d063c 100644
--- a/doc/manual.txt
+++ b/doc/manual.txt
@@ -38,15 +38,15 @@ Notes
    too. In this case, the cf_ and larg_ arguments are ignored (should
    be either supplied as nils or omitted).
 
-6. All functions that take a string-type subject accept a table (in Lua >= 5.2)
-   or userdata that has a ``topointer`` method and ``__len`` metamethod, and
-   take the subject to be a block of memory starting at the address returned by
+6. All functions that take a string-type subject accept a table or userdata that
+   has a ``topointer`` method and ``__len`` metamethod, and take the subject to
+   be a block of memory starting at the address returned by
    ``subject:topointer()`` and of length ``#subject``. This works with buffers
    objects from the alien library (https://github.com/mascarenhas/alien). Note
    that special attention is needed with POSIX regex libraries that do not
    support ``REG_STARTEND``, and hence need NUL-terminated subjects: the NUL is
-   not included in the string length, so alien buffers must be wrapped to
-   report a length that excludes the NUL.
+   not included in the string length, so alien buffers must be wrapped to report
+   a length that excludes the NUL.
 
 .. _cf:
 
diff --git a/src/algo.h b/src/algo.h
index 5d25330..3bea806 100644
--- a/src/algo.h
+++ b/src/algo.h
@@ -119,13 +119,8 @@ static void check_subject (lua_State *L, int pos, TArgExec *argE)
   int stype;
   argE->text = lua_tolstring (L, pos, &argE->textlen);
   stype = lua_type (L, pos);
-#if LUA_VERSION_NUM == 501
-  if (stype != LUA_TSTRING && stype != LUA_TUSERDATA) {
-    luaL_typerror (L, pos, "string or userdata");
-#else
   if (stype != LUA_TSTRING && stype != LUA_TTABLE && stype != LUA_TUSERDATA) {
     luaL_typerror (L, pos, "string, table or userdata");
-#endif
   } else if (argE->text == NULL) {
     int type;
     lua_getfield (L, pos, "topointer");
@@ -140,19 +135,23 @@ static void check_subject (lua_State *L, int pos, TArgExec *argE)
     argE->text = lua_touserdata (L, -1);
     lua_pop (L, 1);
 #if LUA_VERSION_NUM == 501
-    if (!luaL_getmetafield (L, pos, "__len") || lua_type (L, -1) != LUA_TFUNCTION)
-      luaL_argerror (L, pos, "the userdata has no valid __len metafield");
-    lua_pushvalue (L, pos);
-    lua_call (L, 1, 1);
+    if (stype == LUA_TSTRING || stype == LUA_TTABLE)
+      argE->textlen = lua_objlen (L, pos);
+    else {
+      if (!luaL_getmetafield (L, pos, "__len") || lua_type (L, -1) != LUA_TFUNCTION)
+        luaL_argerror (L, pos, "the userdata has no valid __len metafield");
+      lua_pushvalue (L, pos);
+      lua_call (L, 1, 1);
+      type = lua_type (L, -1);
+      if (type != LUA_TNUMBER)
+        luaL_error (L, "subject's length is %s (expected number)",
+                   lua_typename (L, type));
+      argE->textlen = lua_tointeger (L, -1);
+      lua_pop (L, 1);
+    }
 #else
-    lua_len (L, pos);
+    argE->textlen = luaL_len (L, pos);
 #endif
-    type = lua_type (L, -1);
-    if (type != LUA_TNUMBER)
-      luaL_error (L, "subject's length is %s (expected number)",
-                  lua_typename (L, type));
-    argE->textlen = lua_tointeger (L, -1);
-    lua_pop (L, 1);
   }
 }