'tablib' does not try to use raw operations when possible: fast

track should make standard operations fast enough to forgo
raw accesses

ltablib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ltablib.c,v 1.80 2015/01/13 16:27:29 roberto Exp roberto $
+** $Id: ltablib.c,v 1.81 2015/07/04 16:31:42 roberto Exp roberto $
 ** Library for Table Manipulation
 ** See Copyright Notice in lua.h
 */
@@ -19,42 +19,44 @@
 #include "lualib.h"
 
 
-
 /*
-** Structure with table-access functions
+** Operations that an object must define to mimic a table
+** (some functions only need some of them)
 */
-typedef struct {
-  int (*geti) (lua_State *L, int idx, lua_Integer n);
-  void (*seti) (lua_State *L, int idx, lua_Integer n);
-} TabA;
+#define TAB_R	1
+#define TAB_W	2
+#define TAB_L	4
+#define TAB_RW	(TAB_R | TAB_W)
+
+
+#define aux_getn(L,n,w)	(checktab(L, n, (w) | TAB_L), luaL_len(L, n))
+
+
+static int checkfield (lua_State *L, const char *key, int n) {
+  lua_pushstring(L, key);
+  return (lua_rawget(L, -n) != LUA_TNIL);
+}
 
 
 /*
-** Check that 'arg' has a table and set access functions in 'ta' to raw
-** or non-raw according to the presence of corresponding metamethods.
+** Check that 'arg' either is a table or can behave like one (that is,
+** has a metatable with the required metamethods)
 */
-static void checktab (lua_State *L, int arg, TabA *ta) {
-  ta->geti = NULL; ta->seti = NULL;
-  if (lua_getmetatable(L, arg)) {
-    lua_pushliteral(L, "__index");  /* 'index' metamethod */
-    if (lua_rawget(L, -2) != LUA_TNIL)
-      ta->geti = lua_geti;
-    lua_pushliteral(L, "__newindex");  /* 'newindex' metamethod */
-    if (lua_rawget(L, -3) != LUA_TNIL)
-      ta->seti = lua_seti;
-    lua_pop(L, 3);  /* pop metatable plus both metamethods */
-  }
-  if (ta->geti == NULL || ta->seti == NULL) {
-    luaL_checktype(L, arg, LUA_TTABLE);  /* must be table for raw methods */
-    if (ta->geti == NULL) ta->geti = lua_rawgeti;
-    if (ta->seti == NULL) ta->seti = lua_rawseti;
+static void checktab (lua_State *L, int arg, int what) {
+  if (lua_type(L, arg) != LUA_TTABLE) {  /* is it not a table? */
+    int n = 1;  /* number of elements to pop */
+    if (lua_getmetatable(L, arg) &&  /* must have metatable */
+        (!(what & TAB_R) || checkfield(L, "__index", ++n)) &&
+        (!(what & TAB_W) || checkfield(L, "__newindex", ++n)) &&
+        (!(what & TAB_L) || checkfield(L, "__len", ++n))) {
+      lua_pop(L, n);  /* pop metatable and tested metamethods */
+}
+    else
+      luaL_argerror(L, arg, "table expected");  /* force an error */
   }
 }
 
 
-#define aux_getn(L,n,ta)	(checktab(L, n, ta), luaL_len(L, n))
-
-
 #if defined(LUA_COMPAT_MAXN)
 static int maxn (lua_State *L) {
   lua_Number max = 0;
@@ -74,8 +76,7 @@ static int maxn (lua_State *L) {
 
 
 static int tinsert (lua_State *L) {
-  TabA ta;
-  lua_Integer e = aux_getn(L, 1, &ta) + 1;  /* first empty element */
+  lua_Integer e = aux_getn(L, 1, TAB_RW) + 1;  /* first empty element */
   lua_Integer pos;  /* where to insert new element */
   switch (lua_gettop(L)) {
     case 2: {  /* called with only 2 arguments */
@@ -87,8 +88,8 @@ static int tinsert (lua_State *L) {
       pos = luaL_checkinteger(L, 2);  /* 2nd argument is the position */
       luaL_argcheck(L, 1 <= pos && pos <= e, 2, "position out of bounds");
       for (i = e; i > pos; i--) {  /* move up elements */
-        (*ta.geti)(L, 1, i - 1);
-        (*ta.seti)(L, 1, i);  /* t[i] = t[i - 1] */
+        lua_geti(L, 1, i - 1);
+        lua_seti(L, 1, i);  /* t[i] = t[i - 1] */
       }
       break;
     }
@@ -96,42 +97,36 @@ static int tinsert (lua_State *L) {
       return luaL_error(L, "wrong number of arguments to 'insert'");
     }
   }
-  (*ta.seti)(L, 1, pos);  /* t[pos] = v */
+  lua_seti(L, 1, pos);  /* t[pos] = v */
   return 0;
 }
 
 
 static int tremove (lua_State *L) {
-  TabA ta;
-  lua_Integer size = aux_getn(L, 1, &ta);
+  lua_Integer size = aux_getn(L, 1, TAB_RW);
   lua_Integer pos = luaL_optinteger(L, 2, size);
   if (pos != size)  /* validate 'pos' if given */
     luaL_argcheck(L, 1 <= pos && pos <= size + 1, 1, "position out of bounds");
-  (*ta.geti)(L, 1, pos);  /* result = t[pos] */
+  lua_geti(L, 1, pos);  /* result = t[pos] */
   for ( ; pos < size; pos++) {
-    (*ta.geti)(L, 1, pos + 1);
-    (*ta.seti)(L, 1, pos);  /* t[pos] = t[pos + 1] */
+    lua_geti(L, 1, pos + 1);
+    lua_seti(L, 1, pos);  /* t[pos] = t[pos + 1] */
   }
   lua_pushnil(L);
-  (*ta.seti)(L, 1, pos);  /* t[pos] = nil */
+  lua_seti(L, 1, pos);  /* t[pos] = nil */
   return 1;
 }
 
 
 static int tmove (lua_State *L) {
-  TabA ta;
   lua_Integer f = luaL_checkinteger(L, 2);
   lua_Integer e = luaL_checkinteger(L, 3);
   lua_Integer t = luaL_checkinteger(L, 4);
   int tt = !lua_isnoneornil(L, 5) ? 5 : 1;  /* destination table */
+  checktab(L, 1, TAB_R);
+  checktab(L, tt, TAB_W);
   if (e >= f) {  /* otherwise, nothing to move */
     lua_Integer n, i;
-    ta.geti = (luaL_getmetafield(L, 1, "__index") == LUA_TNIL)
-      ? (luaL_checktype(L, 1, LUA_TTABLE), lua_rawgeti)
-      : lua_geti;
-    ta.seti = (luaL_getmetafield(L, tt, "__newindex") == LUA_TNIL)
-      ? (luaL_checktype(L, tt, LUA_TTABLE), lua_rawseti)
-      : lua_seti;
     luaL_argcheck(L, f > 0 || e < LUA_MAXINTEGER + f, 3,
                   "too many elements to move");
     n = e - f + 1;  /* number of elements to move */
@@ -139,14 +134,14 @@ static int tmove (lua_State *L) {
                   "destination wrap around");
     if (t > f) {
       for (i = n - 1; i >= 0; i--) {
-        (*ta.geti)(L, 1, f + i);
-        (*ta.seti)(L, tt, t + i);
+        lua_geti(L, 1, f + i);
+        lua_seti(L, tt, t + i);
       }
     }
     else {
       for (i = 0; i < n; i++) {
-        (*ta.geti)(L, 1, f + i);
-        (*ta.seti)(L, tt, t + i);
+        lua_geti(L, 1, f + i);
+        lua_seti(L, tt, t + i);
       }
     }
   }
@@ -155,8 +150,8 @@ static int tmove (lua_State *L) {
 }
 
 
-static void addfield (lua_State *L, luaL_Buffer *b, TabA *ta, lua_Integer i) {
-  (*ta->geti)(L, 1, i);
+static void addfield (lua_State *L, luaL_Buffer *b, lua_Integer i) {
+  lua_geti(L, 1, i);
   if (!lua_isstring(L, -1))
     luaL_error(L, "invalid value (%s) at index %d in table for 'concat'",
                   luaL_typename(L, -1), i);
@@ -165,21 +160,20 @@ static void addfield (lua_State *L, luaL_Buffer *b, TabA *ta, lua_Integer i) {
 
 
 static int tconcat (lua_State *L) {
-  TabA ta;
   luaL_Buffer b;
   size_t lsep;
-  lua_Integer i, last;
+  lua_Integer i;
+  lua_Integer last = aux_getn(L, 1, TAB_R);
   const char *sep = luaL_optlstring(L, 2, "", &lsep);
-  checktab(L, 1, &ta);
   i = luaL_optinteger(L, 3, 1);
-  last = luaL_opt(L, luaL_checkinteger, 4, luaL_len(L, 1));
+  last = luaL_opt(L, luaL_checkinteger, 4, last);
   luaL_buffinit(L, &b);
   for (; i < last; i++) {
-    addfield(L, &b, &ta, i);
+    addfield(L, &b, i);
     luaL_addlstring(&b, sep, lsep);
   }
   if (i == last)  /* add last value (if interval was not empty) */
-    addfield(L, &b, &ta, i);
+    addfield(L, &b, i);
   luaL_pushresult(&b);
   return 1;
 }
@@ -197,7 +191,7 @@ static int pack (lua_State *L) {
   lua_createtable(L, n, 1);  /* create result table */
   lua_insert(L, 1);  /* put it at index 1 */
   for (i = n; i >= 1; i--)  /* assign elements */
-    lua_rawseti(L, 1, i);
+    lua_seti(L, 1, i);
   lua_pushinteger(L, n);
   lua_setfield(L, 1, "n");  /* t.n = number of elements */
   return 1;  /* return table */
@@ -205,10 +199,8 @@ static int pack (lua_State *L) {
 
 
 static int unpack (lua_State *L) {
-  TabA ta;
   lua_Integer i, e;
   lua_Unsigned n;
-  checktab(L, 1, &ta);
   i = luaL_optinteger(L, 2, 1);
   e = luaL_opt(L, luaL_checkinteger, 3, luaL_len(L, 1));
   if (i > e) return 0;  /* empty range */
@@ -216,9 +208,9 @@ static int unpack (lua_State *L) {
   if (n >= (unsigned int)INT_MAX  || !lua_checkstack(L, (int)(++n)))
     return luaL_error(L, "too many results to unpack");
   for (; i < e; i++) {  /* push arg[i..e - 1] (to avoid overflows) */
-    (*ta.geti)(L, 1, i);
+    lua_geti(L, 1, i);
   }
-  (*ta.geti)(L, 1, e);  /* push last element */
+  lua_geti(L, 1, e);  /* push last element */
   return (int)n;
 }
 
@@ -235,9 +227,9 @@ static int unpack (lua_State *L) {
 */
 
 
-static void set2 (lua_State *L, TabA *ta, int i, int j) {
-  (*ta->seti)(L, 1, i);
-  (*ta->seti)(L, 1, j);
+static void set2 (lua_State *L, int i, int j) {
+  lua_seti(L, 1, i);
+  lua_seti(L, 1, j);
 }
 
 static int sort_comp (lua_State *L, int a, int b) {
@@ -255,45 +247,45 @@ static int sort_comp (lua_State *L, int a, int b) {
     return lua_compare(L, a, b, LUA_OPLT);
 }
 
-static void auxsort (lua_State *L, TabA *ta, int l, int u) {
+static void auxsort (lua_State *L, int l, int u) {
   while (l < u) {  /* for tail recursion */
     int i, j;
     /* sort elements a[l], a[(l+u)/2] and a[u] */
-    (*ta->geti)(L, 1, l);
-    (*ta->geti)(L, 1, u);
+    lua_geti(L, 1, l);
+    lua_geti(L, 1, u);
     if (sort_comp(L, -1, -2))  /* a[u] < a[l]? */
-      set2(L, ta, l, u);  /* swap a[l] - a[u] */
+      set2(L, l, u);  /* swap a[l] - a[u] */
     else
       lua_pop(L, 2);
     if (u-l == 1) break;  /* only 2 elements */
     i = (l+u)/2;
-    (*ta->geti)(L, 1, i);
-    (*ta->geti)(L, 1, l);
+    lua_geti(L, 1, i);
+    lua_geti(L, 1, l);
     if (sort_comp(L, -2, -1))  /* a[i]<a[l]? */
-      set2(L, ta, i, l);
+      set2(L, i, l);
     else {
       lua_pop(L, 1);  /* remove a[l] */
-      (*ta->geti)(L, 1, u);
+      lua_geti(L, 1, u);
       if (sort_comp(L, -1, -2))  /* a[u]<a[i]? */
-        set2(L, ta, i, u);
+        set2(L, i, u);
       else
         lua_pop(L, 2);
     }
     if (u-l == 2) break;  /* only 3 elements */
-    (*ta->geti)(L, 1, i);  /* Pivot */
+    lua_geti(L, 1, i);  /* Pivot */
     lua_pushvalue(L, -1);
-    (*ta->geti)(L, 1, u-1);
-    set2(L, ta, i, u-1);
+    lua_geti(L, 1, u-1);
+    set2(L, i, u-1);
     /* a[l] <= P == a[u-1] <= a[u], only need to sort from l+1 to u-2 */
     i = l; j = u-1;
     for (;;) {  /* invariant: a[l..i] <= P <= a[j..u] */
       /* repeat ++i until a[i] >= P */
-      while ((*ta->geti)(L, 1, ++i), sort_comp(L, -1, -2)) {
+      while (lua_geti(L, 1, ++i), sort_comp(L, -1, -2)) {
         if (i>=u) luaL_error(L, "invalid order function for sorting");
         lua_pop(L, 1);  /* remove a[i] */
       }
       /* repeat --j until a[j] <= P */
-      while ((*ta->geti)(L, 1, --j), sort_comp(L, -3, -1)) {
+      while (lua_geti(L, 1, --j), sort_comp(L, -3, -1)) {
         if (j<=l) luaL_error(L, "invalid order function for sorting");
         lua_pop(L, 1);  /* remove a[j] */
       }
@@ -301,11 +293,11 @@ static void auxsort (lua_State *L, TabA *ta, int l, int u) {
         lua_pop(L, 3);  /* pop pivot, a[i], a[j] */
         break;
       }
-      set2(L, ta, i, j);
+      set2(L, i, j);
     }
-    (*ta->geti)(L, 1, u-1);
-    (*ta->geti)(L, 1, i);
-    set2(L, ta, u-1, i);  /* swap pivot (a[u-1]) with a[i] */
+    lua_geti(L, 1, u-1);
+    lua_geti(L, 1, i);
+    set2(L, u-1, i);  /* swap pivot (a[u-1]) with a[i] */
     /* a[l..i-1] <= a[i] == P <= a[i+1..u] */
     /* adjust so that smaller half is in [j..i] and larger one in [l..u] */
     if (i-l < u-i) {
@@ -314,18 +306,17 @@ static void auxsort (lua_State *L, TabA *ta, int l, int u) {
     else {
       j=i+1; i=u; u=j-2;
     }
-    auxsort(L, ta, j, i);  /* call recursively the smaller one */
+    auxsort(L, j, i);  /* call recursively the smaller one */
   }  /* repeat the routine for the larger one */
 }
 
 static int sort (lua_State *L) {
-  TabA ta;
-  int n = (int)aux_getn(L, 1, &ta);
+  int n = (int)aux_getn(L, 1, TAB_RW);
   luaL_checkstack(L, 50, "");  /* assume array is smaller than 2^50 */
   if (!lua_isnoneornil(L, 2))  /* is there a 2nd argument? */
     luaL_checktype(L, 2, LUA_TFUNCTION);
   lua_settop(L, 2);  /* make sure there are two arguments */
-  auxsort(L, &ta, 1, n);
+  auxsort(L, 1, n);
   return 0;
 }