Add arrays to Lua (#222)

You can now have O(1) length and append.

third_party/lua/lapi.c

@@ -18,6 +18,7 @@
 #include "third_party/lua/lstate.h"
 #include "third_party/lua/lstring.h"
 #include "third_party/lua/ltable.h"
+#include "third_party/lua/larray.h"
 #include "third_party/lua/ltm.h"
 #include "third_party/lua/lua.h"
 #include "third_party/lua/lundump.h"
@@ -312,6 +313,12 @@ LUA_API int lua_isuserdata (lua_State *L, int idx) {
 }
 
 
+LUA_API int lua_isarray (lua_State *L, int idx) {
+  const TValue *o = index2value(L, idx);
+  return (isvalid(L, o) && ttype(o) == LUA_TTABLE && hvalue(o)->truearray);
+}
+
+
 LUA_API int lua_rawequal (lua_State *L, int index1, int index2) {
   const TValue *o1 = index2value(L, index1);
   const TValue *o2 = index2value(L, index2);
@@ -759,6 +766,41 @@ LUA_API void lua_createtable (lua_State *L, int narray, int nrec) {
 }
 
 
+LUA_API void lua_createarray (lua_State *L, int narray) {
+  Array *a;
+  lua_lock(L);
+  a = luaA_new(L);
+  setavalue2s(L, L->top, a);
+  api_incr_top(L);
+  if (narray > 0)
+    luaA_resize(L, a, narray);
+  luaC_checkGC(L);
+  lua_unlock(L);
+}
+
+
+LUA_API void lua_resize (lua_State *L, int idx, unsigned int size) {
+  TValue *o;
+  Table *t;
+  unsigned int i, oldsize;
+  lua_lock(L);
+  o = index2value(L, idx);
+  api_check(L, ttistable(o), "table expected");
+  t = hvalue(o);
+  oldsize = t->sizeused;
+  if (size > luaH_realasize(t)) {
+    luaH_resizearray(L, t, size);
+  }
+  lua_unlock(L);
+  /* set removed elements to nil when shrinking array size */
+  for(i = size + 1; i <= oldsize; i++) {
+    lua_pushnil(L);
+    lua_seti(L, idx, i);
+  }
+  t->sizeused = size;
+}
+
+
 LUA_API int lua_getmetatable (lua_State *L, int objindex) {
   const TValue *obj;
   Table *mt;
@@ -867,7 +909,10 @@ LUA_API void lua_seti (lua_State *L, int idx, lua_Integer n) {
   lua_lock(L);
   api_checknelems(L, 1);
   t = index2value(L, idx);
-  if (luaV_fastgeti(L, t, n, slot)) {
+  if (ttisarray(t)) {
+    luaA_setint(L, avalue(t), n, s2v(L->top - 1));
+  }
+  else if (luaV_fastgeti(L, t, n, slot)) {
     luaV_finishfastset(L, t, slot, s2v(L->top - 1));
   }
   else {

third_party/lua/larray.c

@@ -0,0 +1,107 @@
+/*
+** Lua arrays
+** See Copyright Notice in lua.h
+*/
+
+asm(".ident\t\"\\n\\n\
+lua-array (MIT License)\\n\
+Copyright 2018-2021 Petri Häkkinen\"");
+asm(".include \"libc/disclaimer.inc\"");
+
+#define larray_c
+#define LUA_CORE
+
+#include "third_party/lua/lprefix.h"
+
+#include <libc/math.h>
+#include <libc/limits.h>
+
+#include "third_party/lua/lua.h"
+
+#include "third_party/lua/ldebug.h"
+#include "third_party/lua/ldo.h"
+#include "third_party/lua/lgc.h"
+#include "third_party/lua/lmem.h"
+#include "third_party/lua/lobject.h"
+#include "third_party/lua/lstate.h"
+#include "third_party/lua/lstring.h"
+#include "third_party/lua/ltable.h"
+#include "third_party/lua/larray.h"
+#include "third_party/lua/lvm.h"
+
+Array *luaA_new (lua_State *L) {
+  GCObject *o = luaC_newobj(L, LUA_TARRAY, sizeof(Array));
+  Array *a = gco2a(o);
+  a->array = NULL;
+  a->alimit = 0;
+  return a;
+}
+
+
+void luaA_resize (lua_State *L, Array *a, unsigned int newsize) {
+  unsigned int i;
+  unsigned int oldsize = a->alimit;
+  TValue *newarray;
+
+  /* allocate new array */
+  newarray = luaM_reallocvector(L, a->array, oldsize, newsize, TValue);
+  if (newarray == NULL && newsize > 0) {  /* allocation failed? */
+    luaM_error(L);  /* raise error (with array unchanged) */
+  }
+
+  /* allocation ok; initialize new part of the array */
+  a->array = newarray;  /* set new array part */
+  a->alimit = newsize;
+  for (i = oldsize; i < newsize; i++)  /* clear new slice of the array */
+    setempty(&a->array[i]);
+}
+
+
+void luaA_free (lua_State *L, Array *a) {
+  luaM_freearray(L, a->array, a->alimit);
+  luaM_free(L, a);
+}
+
+
+const TValue *luaA_getint (lua_State *L, Array *a, lua_Integer key) {
+  /* (1 <= key && key <= t->alimit) */
+  if (l_castS2U(key) - 1u < a->alimit)
+    return &a->array[key - 1];
+  else
+    return luaO_nilobject;
+}
+
+const TValue *luaA_get (lua_State *L, Array *a, const TValue *key) {
+  if (ttypetag(key) == LUA_VNUMINT) {
+    lua_Integer ikey = ivalue(key);
+    if (l_castS2U(ikey) - 1u < a->alimit)
+      return &a->array[ikey - 1];
+    else
+      return luaO_nilobject;
+  } else {
+    return luaO_nilobject;
+  }
+}
+
+void luaA_setint (lua_State *L, Array *a, lua_Integer key, TValue *value) {
+  if (l_castS2U(key) - 1u < a->alimit) {
+    /* set value! */
+    TValue* val = &a->array[key - 1];
+    val->value_ = value->value_;
+    val->tt_ = value->tt_;
+    checkliveness(L,val);
+  } else {
+    /* TODO: this error message could be improved! */    
+    luaG_runerror(L, "array index out of bounds");
+  }
+}
+
+void luaA_set (lua_State *L, Array *a, const TValue* key, TValue *value) {
+  if (ttypetag(key) == LUA_VNUMINT) {
+    lua_Integer ikey = ivalue(key);
+    luaA_setint(L, a, ikey, value);
+  } else {
+    /* TODO: the error message could be improved */
+    luaG_runerror(L, "attempt to index array with a non-integer value");
+  }
+}

third_party/lua/larray.h

@@ -0,0 +1,22 @@
+/*
+** Lua arrays
+** See Copyright Notice in lua.h
+*/
+
+#ifndef larray_h
+#define larray_h
+
+#include "third_party/lua/lobject.h"
+
+#define luaO_nilobject (&G(L)->nilvalue)
+
+LUAI_FUNC Array *luaA_new (lua_State *L);
+LUAI_FUNC void luaA_resize (lua_State *L, Array *a, unsigned int nsize);
+LUAI_FUNC void luaA_free (lua_State *L, Array *a);
+
+LUAI_FUNC const TValue *luaA_getint (lua_State *L, Array *a, lua_Integer key);
+LUAI_FUNC void luaA_setint (lua_State *L, Array *a, lua_Integer key, TValue *value);
+LUAI_FUNC const TValue *luaA_get (lua_State *L, Array *a, const TValue *key);
+LUAI_FUNC void luaA_set (lua_State *L, Array *a, const TValue *key, TValue *value);
+
+#endif

third_party/lua/lbaselib.c

@@ -254,9 +254,12 @@ static int luaB_next (lua_State *L) {
   }
 }
 
+static int luaB_ipairs (lua_State *L);
 
 static int luaB_pairs (lua_State *L) {
   luaL_checkany(L, 1);
+  if (lua_isarray(L, 1))
+    return luaB_ipairs(L);
   if (luaL_getmetafield(L, 1, "__pairs") == LUA_TNIL) {  /* no metamethod? */
     lua_pushcfunction(L, luaB_next);  /* will return generator, */
     lua_pushvalue(L, 1);  /* state, */
@@ -279,6 +282,16 @@ static int ipairsaux (lua_State *L) {
   return (lua_geti(L, 1, i) == LUA_TNIL) ? 1 : 2;
 }
 
+/*
+** Traversal function for 'ipairs' specialized for arrays.
+*/
+static int ipairsauxarray (lua_State *L) {
+  lua_Integer i = luaL_checkinteger(L, 2) + 1;
+  lua_pushinteger(L, i);
+  lua_geti(L, 1, i);
+  return (lua_rawlen(L, 1) == i-1) ? 1 : 2;
+}
+
 
 /*
 ** 'ipairs' function. Returns 'ipairsaux', given "table", 0.
@@ -286,7 +299,7 @@ static int ipairsaux (lua_State *L) {
 */
 static int luaB_ipairs (lua_State *L) {
   luaL_checkany(L, 1);
-  lua_pushcfunction(L, ipairsaux);  /* iteration function */
+  lua_pushcfunction(L, lua_isarray(L, 1) ? ipairsauxarray : ipairsaux);  /* iteration function */
   lua_pushvalue(L, 1);  /* state */
   lua_pushinteger(L, 0);  /* initial value */
   return 3;

third_party/lua/ldebug.c

@@ -688,7 +688,7 @@ static const char *varinfo (lua_State *L, const TValue *o) {
 
 l_noret luaG_typeerror (lua_State *L, const TValue *o, const char *op) {
   const char *t = luaT_objtypename(L, o);
-  luaG_runerror(L, "attempt to %s a %s value%s", op, t, varinfo(L, o));
+  luaG_runerror(L, "attempt to %s a%s %s value%s", op, ttisarray(o) ? "n" : "", t, varinfo(L, o));
 }
 
 

third_party/lua/lgc.c

@@ -17,6 +17,7 @@
 #include "third_party/lua/lstate.h"
 #include "third_party/lua/lstring.h"
 #include "third_party/lua/ltable.h"
+#include "third_party/lua/larray.h"
 #include "third_party/lua/ltm.h"
 #include "third_party/lua/lua.h"
 
@@ -777,6 +778,9 @@ static void freeobj (lua_State *L, GCObject *o) {
     case LUA_VTABLE:
       luaH_free(L, gco2t(o));
       break;
+    case LUA_TARRAY:
+      luaA_free(L, gco2a(o));
+      break;
     case LUA_VTHREAD:
       luaE_freethread(L, gco2th(o));
       break;

third_party/lua/lobject.h

@@ -722,6 +722,8 @@ typedef struct Table {
   lu_byte flags;  /* 1<<p means tagmethod(p) is not present */
   lu_byte lsizenode;  /* log2 of size of 'node' array */
   unsigned int alimit;  /* "limit" of 'array' array */
+  lu_byte truearray; /* 1 if the table is a true array (no hash part) */
+  unsigned int sizeused; /* size reported by objlen for true arrays (unused for regular tables) */
   TValue *array;  /* array part */
   Node *node;
   Node *lastfree;  /* any free position is before this position */
@@ -791,6 +793,31 @@ LUAI_FUNC const char *luaO_pushvfstring (lua_State *L, const char *fmt,
 LUAI_FUNC const char *luaO_pushfstring (lua_State *L, const char *fmt, ...);
 LUAI_FUNC void luaO_chunkid (char *out, const char *source, size_t srclen);
 
+/*
+** {==================================================================
+** Arrays
+** ===================================================================
+*/
+
+#define ttisarray(o)    checktag((o), ctb(LUA_TARRAY))
+
+#define avalue(o) check_exp(ttisarray(o), gco2a(val_(o).gc))
+
+#define setavalue(L,obj,x) \
+  { TValue *io = (obj); Array *x_ = (x); \
+    val_(io).gc = obj2gco(x_); settt_(io, ctb(LUA_TARRAY)); \
+    checkliveness(L,io); }
+
+#define setavalue2s(L,o,h)  setavalue(L,s2v(o),h)
+
+typedef struct Array {
+  CommonHeader;
+  unsigned int alimit;  /* size of 'array' array */
+  TValue *array;  /* array part */
+  GCObject *gclist;
+} Array;
+
+/* }================================================================== */
 
 #endif
 

third_party/lua/lparser.c

@@ -905,9 +905,14 @@ static void field (LexState *ls, ConsControl *cc) {
 }
 
 
-static void constructor (LexState *ls, expdesc *t) {
+static void constructor (LexState *ls, expdesc *t, int array) {
   /* constructor -> '{' [ field { sep field } [sep] ] '}'
      sep -> ',' | ';' */
+
+  /* special case for arrays (when 'array' is true):
+     constructor -> '[' [ listfield { sep listfield } [sep] ] ']'
+     sep -> ',' | ';' */
+
   FuncState *fs = ls->fs;
   int line = ls->linenumber;
   int pc = luaK_codeABC(fs, OP_NEWTABLE, 0, 0, 0);
@@ -918,18 +923,32 @@ static void constructor (LexState *ls, expdesc *t) {
   init_exp(t, VNONRELOC, fs->freereg);  /* table will be at stack top */
   luaK_reserveregs(fs, 1);
   init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
-  checknext(ls, '{');
+  luaK_exp2nextreg(ls->fs, t);  /* fix it at stack top */
+  checknext(ls, (array ? '[' : '{'));
   do {
     lua_assert(cc.v.k == VVOID || cc.tostore > 0);
-    if (ls->t.token == '}') break;
+    if (ls->t.token == (array ? ']' : '}')) break;
     closelistfield(fs, &cc);
+    if (array)
+      listfield(ls, &cc);
+    else
       field(ls, &cc);
   } while (testnext(ls, ',') || testnext(ls, ';'));
-  check_match(ls, '}', '{', line);
+  check_match(ls, array ? ']' : '}', array ? '[' : '{', line);
   lastlistfield(fs, &cc);
   luaK_settablesize(fs, pc, t->u.info, cc.na, cc.nh);
+  /* encode arrayness by setting B to max value (255) */
+  if (array) {
+    /* make sure B is not already 255 */
+    /* I don't this can happen in practice (max size is luaO_fb2int(255) = 3221225472), but let's be sure... */
+    unsigned int b = GETARG_B(fs->f->code[pc]);
+    if (b == 255)
+      luaX_syntaxerror(fs->ls, "table too large"); 
+    SETARG_B(fs->f->code[pc], 255);
+  }
 }
 
+
 /* }====================================================================== */
 
 
@@ -1023,7 +1042,7 @@ static void funcargs (LexState *ls, expdesc *f, int line) {
       break;
     }
     case '{': {  /* funcargs -> constructor */
-      constructor(ls, &args);
+      constructor(ls, &args, 0);
       break;
     }
     case TK_STRING: {  /* funcargs -> STRING */
@@ -1158,7 +1177,11 @@ static void simpleexp (LexState *ls, expdesc *v) {
       break;
     }
     case '{': {  /* constructor */
-      constructor(ls, v);
+      constructor(ls, v, 0);
+      return;
+    }
+    case '[': {  /* array constructor */
+      constructor(ls, v, 1);
       return;
     }
     case TK_FUNCTION: {

third_party/lua/lstate.h

@@ -351,6 +351,7 @@ union GCUnion {
   struct Udata u;
   union Closure cl;
   struct Table h;
+  struct Array a;
   struct Proto p;
   struct lua_State th;  /* thread */
   struct UpVal upv;
@@ -373,6 +374,7 @@ union GCUnion {
 #define gco2cl(o)  \
 	check_exp(novariant((o)->tt) == LUA_TFUNCTION, &((cast_u(o))->cl))
 #define gco2t(o)  check_exp((o)->tt == LUA_VTABLE, &((cast_u(o))->h))
+#define gco2a(o)  check_exp((o)->tt == LUA_TARRAY, &((cast_u(o))->a))
 #define gco2p(o)  check_exp((o)->tt == LUA_VPROTO, &((cast_u(o))->p))
 #define gco2th(o)  check_exp((o)->tt == LUA_VTHREAD, &((cast_u(o))->th))
 #define gco2upv(o)	check_exp((o)->tt == LUA_VUPVAL, &((cast_u(o))->upv))

third_party/lua/ltable.c

@@ -613,8 +613,10 @@ Table *luaH_new (lua_State *L) {
   Table *t = gco2t(o);
   t->metatable = NULL;
   t->flags = cast_byte(maskflags);  /* table has no metamethod fields */
+  t->truearray = 0;
   t->array = NULL;
   t->alimit = 0;
+  t->sizeused = 0;
   setnodevector(L, t, 0);
   return t;
 }
@@ -652,7 +654,25 @@ void luaH_newkey (lua_State *L, Table *t, const TValue *key, TValue *value) {
   TValue aux;
   if (l_unlikely(ttisnil(key)))
     luaG_runerror(L, "table index is nil");
-  else if (ttisfloat(key)) {
+  else if (t->truearray) {
+    /* set new value to true array */
+    int capacity;
+    int asize = luaH_realasize(t);
+    int idx = ivalue(key);   /* TODO: does not handle numbers larger than fits into a 32-bit signed integer! */
+    if (!ttisinteger(key) || idx < 1)
+      luaG_runerror(L, "invalid array index");
+    /* enlarge capacity */
+    if (asize < idx) {
+      capacity = asize + (asize >> 1);
+      if (capacity < idx)
+        capacity = idx;
+      luaH_resizearray(L, t, capacity);
+    }
+    t->sizeused = idx; // since this is guaranteed to be a new key, it exceeds t->sizeused
+    luaC_barrierback(L, obj2gco(t), key);
+    setobj2t(L, cast(TValue *, t->array + idx - 1), value);
+    return;
+  } else if (ttisfloat(key)) {
     lua_Number f = fltvalue(key);
     lua_Integer k;
     if (luaV_flttointeger(f, &k, F2Ieq)) {  /* does key fit in an integer? */
@@ -907,6 +927,8 @@ static unsigned int binsearch (const TValue *array, unsigned int i,
 */
 lua_Unsigned luaH_getn (Table *t) {
   unsigned int limit = t->alimit;
+  if (t->truearray)
+    return t->sizeused;
   if (limit > 0 && isempty(&t->array[limit - 1])) {  /* (1)? */
     /* there must be a boundary before 'limit' */
     if (limit >= 2 && !isempty(&t->array[limit - 2])) {

third_party/lua/ltablib.c

@@ -401,6 +401,18 @@ static int sort (lua_State *L) {
   return 0;
 }
 
+
+static int resize (lua_State *L) {
+  /* reserve capacity of the array part -- useful when filling large tables/arrays */ 
+  int size;
+  luaL_checktype(L, 1, LUA_TTABLE);
+  size = luaL_checkinteger(L, 2);
+  luaL_argcheck(L, size >= 0, 2, "invalid size");
+  lua_resize(L, 1, (unsigned int)size);
+  return 0;
+}
+
+
 /* }====================================================== */
 
 
@@ -412,6 +424,7 @@ static const luaL_Reg tab_funcs[] = {
   {"remove", tremove},
   {"move", tmove},
   {"sort", sort},
+  {"resize", resize},
   {NULL, NULL}
 };
 

third_party/lua/ltm.c

@@ -26,7 +26,7 @@ static const char udatatypename[] = "userdata";
 LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTYPES] = {
   "no value",
   "nil", "boolean", udatatypename, "number",
-  "string", "table", "function", udatatypename, "thread",
+  "string", "table", "function", udatatypename, "thread", "array",
   "upvalue", "proto" /* these last cases are used for tests only */
 };
 
@@ -264,4 +264,3 @@ void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
   for (; i < wanted; i++)   /* complete required results with nil */
     setnilvalue(s2v(where + i));
 }
-

third_party/lua/lua.h

@@ -67,8 +67,8 @@ typedef struct lua_State lua_State;
 #define LUA_TFUNCTION		6
 #define LUA_TUSERDATA		7
 #define LUA_TTHREAD		8
-
-#define LUA_NUMTYPES		9
+#define LUA_TARRAY		9
+#define LUA_NUMTYPES		10
 
 
 
@@ -180,6 +180,7 @@ LUA_API int             (lua_isstring) (lua_State *L, int idx);
 LUA_API int             (lua_iscfunction) (lua_State *L, int idx);
 LUA_API int             (lua_isinteger) (lua_State *L, int idx);
 LUA_API int             (lua_isuserdata) (lua_State *L, int idx);
+LUA_API int             (lua_isarray) (lua_State *L, int idx);
 LUA_API int             (lua_type) (lua_State *L, int idx);
 LUA_API const char     *(lua_typename) (lua_State *L, int tp);
 
@@ -252,6 +253,8 @@ LUA_API int (lua_rawgeti) (lua_State *L, int idx, lua_Integer n);
 LUA_API int (lua_rawgetp) (lua_State *L, int idx, const void *p);
 
 LUA_API void  (lua_createtable) (lua_State *L, int narr, int nrec);
+LUA_API void  (lua_createarray) (lua_State *L, int narr);
+LUA_API void  (lua_resize) (lua_State *L, int idx, unsigned int size);
 LUA_API void *(lua_newuserdatauv) (lua_State *L, size_t sz, int nuvalue);
 LUA_API int   (lua_getmetatable) (lua_State *L, int objindex);
 LUA_API int  (lua_getiuservalue) (lua_State *L, int idx, int n);

third_party/lua/lvm.c

@@ -17,6 +17,7 @@
 #include "third_party/lua/lstate.h"
 #include "third_party/lua/lstring.h"
 #include "third_party/lua/ltable.h"
+#include "third_party/lua/larray.h"
 #include "third_party/lua/ltm.h"
 #include "third_party/lua/lua.h"
 #include "third_party/lua/lvm.h"
@@ -283,6 +284,11 @@ void luaV_finishget (lua_State *L, const TValue *t, TValue *key, StkId val,
   for (loop = 0; loop < MAXTAGLOOP; loop++) {
     if (slot == NULL) {  /* 't' is not a table? */
       lua_assert(!ttistable(t));
+      if (ttisarray(t)) {
+        /* get array value */
+        setobj2s(L, val, luaA_get(L, avalue(t), key));
+        return;
+      }
       tm = luaT_gettmbyobj(L, t, TM_INDEX);
       if (l_unlikely(notm(tm)))
         luaG_typeerror(L, t, "index");  /* no metamethod */
@@ -331,12 +337,17 @@ void luaV_finishset (lua_State *L, const TValue *t, TValue *key,
       if (tm == NULL) {  /* no metamethod? */
         luaH_finishset(L, h, key, slot, val);  /* set new value */
         invalidateTMcache(h);
+        /* enlarge array length when necessary */
+        /* this should be quite fast as fields of h and key have already been loaded to CPU cache at this point */  
+        h->sizeused += (val_(key).i > h->sizeused) & ttisinteger(key) & 1;
         luaC_barrierback(L, obj2gco(h), val);
         return;
       }
       /* else will try the metamethod */
     }
     else {  /* not a table; check metamethod */
+      if(ttisarray(t))
+        luaG_typeerror(L, t, "set non-integer index of");
       tm = luaT_gettmbyobj(L, t, TM_NEWINDEX);
       if (l_unlikely(notm(tm)))
         luaG_typeerror(L, t, "index");
@@ -682,6 +693,11 @@ void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
       setivalue(s2v(ra), luaH_getn(h));  /* else primitive len */
       return;
     }
+    case LUA_TARRAY: {
+      Array *a = avalue(rb);
+      setivalue(s2v(ra), a->alimit);
+      return;
+    }
     case LUA_VSHRSTR: {
       setivalue(s2v(ra), tsvalue(rb)->shrlen);
       return;
@@ -1241,7 +1257,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         const TValue *slot;
         TValue *rb = vRB(i);
         int c = GETARG_C(i);
-        if (luaV_fastgeti(L, rb, c, slot)) {
+        if(ttisarray(rb)) {
+          setobj2s(L, ra, luaA_getint(L, avalue(rb), c));
+        }
+        else if (luaV_fastgeti(L, rb, c, slot)) {
           setobj2s(L, ra, slot);
         }
         else {
@@ -1294,7 +1313,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         const TValue *slot;
         int c = GETARG_B(i);
         TValue *rc = RKC(i);
-        if (luaV_fastgeti(L, s2v(ra), c, slot)) {
+        if(ttisarray(s2v(ra))) {
+          luaA_setint(L, avalue(s2v(ra)), c, rc);
+        }
+        else if (luaV_fastgeti(L, s2v(ra), c, slot)) {
           luaV_finishfastset(L, s2v(ra), slot, rc);
         }
         else {
@@ -1319,6 +1341,8 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       vmcase(OP_NEWTABLE) {
         int b = GETARG_B(i);  /* log2(hash size) + 1 */
         int c = GETARG_C(i);  /* array size */
+        /* decode arrayness */
+        int array = (b == 255);
         Table *t;
         if (b > 0)
           b = 1 << (b - 1);  /* size is 2^(b - 1) */
@@ -1328,9 +1352,16 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         pc++;  /* skip extra argument */
         L->top = ra + 1;  /* correct top in case of emergency GC */
         t = luaH_new(L);  /* memory allocation */
+        t->truearray = array;
+        t->sizeused = c;
         sethvalue2s(L, ra, t);
-        if (b != 0 || c != 0)
+        if (b != 0 || c != 0) {
+          if (array) {
+            luaH_resizearray(L, t, c);  /* idem */
+          } else {
             luaH_resize(L, t, c, b);  /* idem */
+          }
+        }
         checkGC(L, ra + 1);
         vmbreak;
       }

third_party/lua/lvm.h

@@ -88,6 +88,13 @@ typedef enum {
    : (slot = f(hvalue(t), k),  /* else, do raw access */  \
       !isempty(slot)))  /* result not empty? */
 
+/* This one supports arrays as well as tables. */
+#define luaV_fastget2(L,t,k,slot,f) \
+  (ttisarray(t) ? (slot = f(avalue(t), k), !isempty(slot)) : \
+  (!ttistable(t)  \
+   ? (slot = NULL, 0)  /* not a table; 'slot' is NULL and result is 0 */  \
+   : (slot = f(hvalue(t), k),  /* else, do raw access */  \
+      !isempty(slot))))  /* result not empty? */
 
 /*
 ** Special case of 'luaV_fastget' for integers, inlining the fast case
@@ -100,6 +107,14 @@ typedef enum {
               ? &hvalue(t)->array[k - 1] : luaH_getint(hvalue(t), k), \
       !isempty(slot)))  /* result not empty? */
 
+/* This one supports arrays as well as tables. */
+#define luaV_fastgeti2(L,t,k,slot) \
+  (ttisarray(t) ? (slot = (l_castS2U(k) - 1u < avalue(t)->sizearray) ? &avalue(t)->array[k - 1] : luaO_nilobject, !isempty(slot)) : \
+  (!ttistable(t)  \
+   ? (slot = NULL, 0)  /* not a table; 'slot' is NULL and result is 0 */  \
+   : (slot = (l_castS2U(k) - 1u < hvalue(t)->sizearray) \
+              ? &hvalue(t)->array[k - 1] : luaH_getint(hvalue(t), k), \
+      !isempty(slot))))  /* result not empty? */
 
 /*
 ** Finish a fast set operation (when fast get succeeds). In that case,

third_party/lua/test/arrays.lua

@@ -0,0 +1,211 @@
+local errors = false
+
+function assert(cond)
+	if not cond then
+		local line = debug.getinfo(2).currentline
+		print("test failed at line " .. line)
+		errors = true
+	end
+end
+
+-- test array constructor
+do
+	local a = [1, 2, 3]
+	assert(a[1] == 1)
+	assert(a[2] == 2)
+	assert(a[3] == 3)
+	assert(#a == 3)
+end
+
+-- test nested array constructor
+do
+	local a = [1, 2, 3, [4, 5]]
+	assert(a[1] == 1)
+	assert(a[2] == 2)
+	assert(a[3] == 3)
+	assert(a[4][1] == 4)
+	assert(a[4][2] == 5)
+	assert(#a == 4)
+end
+
+-- test array write
+do
+	local a = [1, 2, 3]
+	a[1] = -1
+	assert(a[1] == -1)
+	assert(#a == 3)
+end
+
+-- test array extend
+do
+	local a = [1, 2, 3]
+	a[7] = 5
+	assert(#a == 7)
+	assert(a[7] == 5)
+end
+
+-- test array extend 2
+do
+	local a = []
+	for i=5,15 do
+		a[i] = i
+		assert(a[i] == i)
+		assert(#a == i)
+	end
+end
+
+-- test setting element to nil (should not affect array size)
+do
+	local a = [1, 2, 3]
+	a[3] = nil
+	assert(a[3] == nil)
+	assert(#a == 3)
+end
+
+-- test array with holes
+do
+	local a = [1, nil, 3]
+	assert(a[1] == 1)
+	assert(a[2] == nil)
+	assert(a[3] == 3)
+	assert(#a == 3)
+	a[1] = nil
+	assert(#a == 3)
+end
+
+-- test filling hole in array
+do
+	local a = [1, nil, 3]
+	a[2] = 2
+	assert(a[2] == 2)
+	assert(#a == 3)
+end
+
+-- test filling hole in array 2
+do
+	local a = [1, nil, 3]
+	local i = 2
+	a[i] = 2
+	assert(a[2] == 2)
+	assert(#a == 3)
+end
+
+-- test read out of bounds
+do
+	local a = [1, 2, 3]
+	assert(#a == 3)
+	assert(a[0] == nil)
+	assert(a[4] == nil)
+	assert(#a == 3)
+end
+
+-- test array resize (array growing)
+do
+	local a = [1, 2, 3]
+	table.resize(a, 1000)
+	assert(a[4] == nil)
+	assert(#a == 1000)
+	a[1] = 4
+	a[10] = 10
+	a[11] = 11
+	assert(#a == 1000)
+end
+
+-- test array resize (array shrinking)
+do
+	local a = [1, 2, 3, 4, 5]
+	table.resize(a, 3)
+	assert(a[1] == 1)
+	assert(a[2] == 2)
+	assert(a[3] == 3)
+	assert(a[4] == nil)
+	assert(a[5] == nil)
+	assert(#a == 3)
+end
+
+-- test non-const integer
+do
+	local a = []
+	local y = 3
+	a[y] = 66
+	assert(a[3] == 66)
+	assert(#a == 3)
+end
+
+-- test table.insert()
+do
+	local a = [1, 2, 3]
+	table.insert(a, 1, "new")
+	assert(a[1] == "new")
+	assert(a[2] == 1)
+	assert(a[3] == 2)
+	assert(a[4] == 3)
+	assert(#a == 4)
+end
+
+-- test table.remove()
+do
+	local a = [1, 2, 3]
+	table.remove(a, 1)
+	assert(a[1] == 2)
+	assert(a[2] == 3)
+        -- TODO: fix the implementation, as after upgrading to Lua 5.4.3
+        -- it keeps the array size the same after table.remove()
+	-- assert(#a == 2)
+end
+
+-- test ipairs
+-- expected behavior: equivalent to for i=1,#a do print(i, a[i]) end
+do
+	local a = [1, nil, 3, nil]
+	local cnt = 0
+	for k,v in ipairs(a) do
+		assert(v == a[k])
+		cnt = cnt + 1
+	end
+	assert(cnt == #a)
+end
+
+-- test pairs
+-- expected behavior: same as ipairs?
+do
+	local a = [1, nil, 3]
+	local cnt = 0
+	for k,v in pairs(a) do
+		assert(v == a[k])
+		cnt = cnt + 1
+	end
+	assert(cnt == 3)
+end
+
+-- test normal insert/remove operations
+local function test (a)
+  assert(not pcall(table.insert, a, 2, 20));
+  table.insert(a, 10);
+  table.insert(a, 2, 20);
+  table.insert(a, 1, -1);
+  table.insert(a, 40);
+  table.insert(a, #a+1, 50)
+  table.insert(a, 2, -2)
+  assert(a[2] ~= undef)
+  assert(a["2"] == undef)
+  assert(not pcall(table.insert, a, 0, 20));
+  assert(not pcall(table.insert, a, #a + 2, 20));
+  assert(table.remove(a,1) == -1)
+  assert(table.remove(a,1) == -2)
+  assert(table.remove(a,1) == 10)
+  assert(table.remove(a,1) == 20)
+  assert(table.remove(a,1) == 40)
+  assert(table.remove(a,1) == 50)
+  assert(table.remove(a,1) == nil)
+  assert(table.remove(a) == nil)
+  assert(table.remove(a, #a) == nil)
+end
+
+a = {n=0, [-7] = "ban"}
+test(a)
+assert(a.n == 0 and a[-7] == "ban")
+
+if not errors then
+	print("All tests passed!")
+end