in hash nodes, keys are stored in separate pieces to avoid wasting

space with alignments

lobject.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.h,v 2.120 2017/04/30 20:43:26 roberto Exp roberto $
+** $Id: lobject.h,v 2.121 2017/06/01 20:24:05 roberto Exp roberto $
 ** Type definitions for Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -122,6 +122,7 @@ typedef struct lua_TValue {
 
 
 #define val_(o)		((o)->value_)
+#define valraw(o)	(&val_(o))
 
 
 /* raw type tag of a TValue */
@@ -131,7 +132,8 @@ typedef struct lua_TValue {
 #define novariant(x)	((x) & 0x0F)
 
 /* type tag of a TValue (bits 0-3 for tags + variant bits 4-5) */
-#define ttype(o)	(rttype(o) & 0x3F)
+#define ttyperaw(t)	((t) & 0x3F)
+#define ttype(o)	ttyperaw(rttype(o))
 
 /* type tag of a TValue with no variants (bits 0-3) */
 #define ttnov(o)	(novariant(rttype(o)))
@@ -157,7 +159,19 @@ typedef struct lua_TValue {
 #define ttislcf(o)		checktag((o), LUA_TLCF)
 #define ttisfulluserdata(o)	checktag((o), ctb(LUA_TUSERDATA))
 #define ttisthread(o)		checktag((o), ctb(LUA_TTHREAD))
-#define ttisdeadkey(o)		checktag((o), LUA_TDEADKEY)
+
+
+/*
+** Macros to access unstructured values (may come both from
+** 'TValue's and table keys)
+*/
+#define ivalueraw(v)	((v).i)
+#define fltvalueraw(v)	((v).n)
+#define gcvalueraw(v)	((v).gc)
+#define pvalueraw(v)	((v).p)
+#define tsvalueraw(v)	(gco2ts((v).gc))
+#define fvalueraw(v)	((v).f)
+#define bvalueraw(v)	((v).b)
 
 
 /* Macros to access values */
@@ -176,8 +190,6 @@ typedef struct lua_TValue {
 #define hvalue(o)	check_exp(ttistable(o), gco2t(val_(o).gc))
 #define bvalue(o)	check_exp(ttisboolean(o), val_(o).b)
 #define thvalue(o)	check_exp(ttisthread(o), gco2th(val_(o).gc))
-/* a dead value may get the 'gc' field, but cannot access its contents */
-#define deadvalue(o)	check_exp(ttisdeadkey(o), cast(void *, val_(o).gc))
 
 #define l_isfalse(o)	(ttisnil(o) || (ttisboolean(o) && bvalue(o) == 0))
 
@@ -185,6 +197,12 @@ typedef struct lua_TValue {
 #define iscollectable(o)	(rttype(o) & BIT_ISCOLLECTABLE)
 
 
+/*
+** Protected access to objects in values
+*/
+#define gcvalueN(o)	(iscollectable(o) ? gcvalue(o) : NULL)
+
+
 /* Macros for internal tests */
 #define righttt(obj)		(ttype(obj) == gcvalue(obj)->tt)
 
@@ -253,8 +271,6 @@ typedef struct lua_TValue {
     val_(io).gc = obj2gco(x_); settt_(io, ctb(LUA_TTABLE)); \
     checkliveness(L,io); }
 
-#define setdeadvalue(obj)	settt_(obj, LUA_TDEADKEY)
-
 
 
 #define setobj(L,obj1,obj2) \
@@ -485,26 +501,37 @@ typedef union Closure {
 ** Tables
 */
 
-typedef union TKey {
-  struct {
-    TValuefields;
-    int next;  /* for chaining (offset for next node) */
-  } nk;
-  TValue tvk;
-} TKey;
+
+/*
+** Nodes for Hash tables. A pack of two TValue's (key-value pairs)
+** plus a 'next' field to link colliding entries. The distribuition
+** of the key's fields ('key_tt' and 'key_val') not forming a proper
+** 'TValue' allows for a smaller size for 'Node' both in 4-byte
+** and 8-byte alignments.
+*/
+typedef union Node {
+  struct NodeKey {
+    TValuefields;  /* fields for value */
+    lu_byte key_tt;  /* key type */
+    int next;  /* for chaining */
+    Value key_val;  /* key value */
+  } u;
+  TValue i_val;  /* direct access to node's value as a proper 'TValue' */
+} Node;
 
 
-/* copy a value into a key without messing up field 'next' */
-#define setnodekey(L,key,obj) \
-	{ TKey *k_=(key); const TValue *io_=(obj); \
-	  k_->nk.value_ = io_->value_; k_->nk.tt_ = io_->tt_; \
+/* copy a value into a key */
+#define setnodekey(L,node,obj) \
+	{ Node *n_=(node); const TValue *io_=(obj); \
+	  n_->u.key_val = io_->value_; n_->u.key_tt = io_->tt_; \
 	  (void)L; checkliveness(L,io_); }
 
 
-typedef struct Node {
-  TValue i_val;
-  TKey i_key;
-} Node;
+/* copy a value from a key */
+#define getnodekey(L,obj,node) \
+	{ TValue *io_=(obj); const Node *n_=(node); \
+	  io_->value_ = n_->u.key_val; io_->tt_ = n_->u.key_tt; \
+	  (void)L; checkliveness(L,io_); }
 
 
 typedef struct Table {
@@ -520,6 +547,33 @@ typedef struct Table {
 } Table;
 
 
+/*
+** Macros to manipulate keys inserted in nodes
+*/
+#define keytt(node)		((node)->u.key_tt)
+#define keyval(node)		((node)->u.key_val)
+
+#define keyisnil(node)		(keytt(node) == LUA_TNIL)
+#define keyisinteger(node)	(keytt(node) == LUA_TNUMINT)
+#define keyival(node)		(keyval(node).i)
+#define keyisshrstr(node)	(keytt(node) == ctb(LUA_TSHRSTR))
+#define keystrval(node)		(gco2ts(keyval(node).gc))
+
+#define keyisdead(node)		(keytt(node) == LUA_TDEADKEY)
+
+#define setnilkey(node)		(keytt(node) = LUA_TNIL)
+#define setdeadkey(node)	(keytt(node) = LUA_TDEADKEY)
+
+/* a dead value may get the 'gc' field, but cannot access its contents */
+#define deadkey(n)  \
+  check_exp(keytt(n) == LUA_TDEADKEY, cast(void *, keyval(n).gc))
+
+#define keyiscollectable(n)	(keytt(n) & BIT_ISCOLLECTABLE)
+
+#define gckey(n)	(keyval(n).gc)
+#define gckeyN(n)	(keyiscollectable(n) ? gckey(n) : NULL)
+
+
 
 /*
 ** 'module' operation for hashing (size is always a power of 2)