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    1 /*
    2 ** $Id: ltablib.c $
    3 ** Library for Table Manipulation
    4 ** See Copyright Notice in lua.h
    5 */
    6 
    7 #define ltablib_c
    8 #define LUA_LIB
    9 
   10 #include "lprefix.h"
   11 
   12 
   13 #include <limits.h>
   14 #include <stddef.h>
   15 #include <string.h>
   16 
   17 #include "lua.h"
   18 
   19 #include "lauxlib.h"
   20 #include "lualib.h"
   21 
   22 
   23 /*
   24 ** Operations that an object must define to mimic a table
   25 ** (some functions only need some of them)
   26 */
   27 #define TAB_R   1           /* read */
   28 #define TAB_W   2           /* write */
   29 #define TAB_L   4           /* length */
   30 #define TAB_RW  (TAB_R | TAB_W)     /* read/write */
   31 
   32 
   33 #define aux_getn(L,n,w) (checktab(L, n, (w) | TAB_L), luaL_len(L, n))
   34 
   35 
   36 static int checkfield (lua_State *L, const char *key, int n) {
   37   lua_pushstring(L, key);
   38   return (lua_rawget(L, -n) != LUA_TNIL);
   39 }
   40 
   41 
   42 /*
   43 ** Check that 'arg' either is a table or can behave like one (that is,
   44 ** has a metatable with the required metamethods)
   45 */
   46 static void checktab (lua_State *L, int arg, int what) {
   47   if (lua_type(L, arg) != LUA_TTABLE) {  /* is it not a table? */
   48     int n = 1;  /* number of elements to pop */
   49     if (lua_getmetatable(L, arg) &&  /* must have metatable */
   50         (!(what & TAB_R) || checkfield(L, "__index", ++n)) &&
   51         (!(what & TAB_W) || checkfield(L, "__newindex", ++n)) &&
   52         (!(what & TAB_L) || checkfield(L, "__len", ++n))) {
   53       lua_pop(L, n);  /* pop metatable and tested metamethods */
   54     }
   55     else
   56       luaL_checktype(L, arg, LUA_TTABLE);  /* force an error */
   57   }
   58 }
   59 
   60 
   61 static int tinsert (lua_State *L) {
   62   lua_Integer e = aux_getn(L, 1, TAB_RW) + 1;  /* first empty element */
   63   lua_Integer pos;  /* where to insert new element */
   64   switch (lua_gettop(L)) {
   65     case 2: {  /* called with only 2 arguments */
   66       pos = e;  /* insert new element at the end */
   67       break;
   68     }
   69     case 3: {
   70       lua_Integer i;
   71       pos = luaL_checkinteger(L, 2);  /* 2nd argument is the position */
   72       /* check whether 'pos' is in [1, e] */
   73       luaL_argcheck(L, (lua_Unsigned)pos - 1u < (lua_Unsigned)e, 2,
   74                        "position out of bounds");
   75       for (i = e; i > pos; i--) {  /* move up elements */
   76         lua_geti(L, 1, i - 1);
   77         lua_seti(L, 1, i);  /* t[i] = t[i - 1] */
   78       }
   79       break;
   80     }
   81     default: {
   82       return luaL_error(L, "wrong number of arguments to 'insert'");
   83     }
   84   }
   85   lua_seti(L, 1, pos);  /* t[pos] = v */
   86   return 0;
   87 }
   88 
   89 
   90 static int tremove (lua_State *L) {
   91   lua_Integer size = aux_getn(L, 1, TAB_RW);
   92   lua_Integer pos = luaL_optinteger(L, 2, size);
   93   if (pos != size)  /* validate 'pos' if given */
   94     /* check whether 'pos' is in [1, size + 1] */
   95     luaL_argcheck(L, (lua_Unsigned)pos - 1u <= (lua_Unsigned)size, 1,
   96                      "position out of bounds");
   97   lua_geti(L, 1, pos);  /* result = t[pos] */
   98   for ( ; pos < size; pos++) {
   99     lua_geti(L, 1, pos + 1);
  100     lua_seti(L, 1, pos);  /* t[pos] = t[pos + 1] */
  101   }
  102   lua_pushnil(L);
  103   lua_seti(L, 1, pos);  /* remove entry t[pos] */
  104   return 1;
  105 }
  106 
  107 
  108 /*
  109 ** Copy elements (1[f], ..., 1[e]) into (tt[t], tt[t+1], ...). Whenever
  110 ** possible, copy in increasing order, which is better for rehashing.
  111 ** "possible" means destination after original range, or smaller
  112 ** than origin, or copying to another table.
  113 */
  114 static int tmove (lua_State *L) {
  115   lua_Integer f = luaL_checkinteger(L, 2);
  116   lua_Integer e = luaL_checkinteger(L, 3);
  117   lua_Integer t = luaL_checkinteger(L, 4);
  118   int tt = !lua_isnoneornil(L, 5) ? 5 : 1;  /* destination table */
  119   checktab(L, 1, TAB_R);
  120   checktab(L, tt, TAB_W);
  121   if (e >= f) {  /* otherwise, nothing to move */
  122     lua_Integer n, i;
  123     luaL_argcheck(L, f > 0 || e < LUA_MAXINTEGER + f, 3,
  124                   "too many elements to move");
  125     n = e - f + 1;  /* number of elements to move */
  126     luaL_argcheck(L, t <= LUA_MAXINTEGER - n + 1, 4,
  127                   "destination wrap around");
  128     if (t > e || t <= f || (tt != 1 && !lua_compare(L, 1, tt, LUA_OPEQ))) {
  129       for (i = 0; i < n; i++) {
  130         lua_geti(L, 1, f + i);
  131         lua_seti(L, tt, t + i);
  132       }
  133     }
  134     else {
  135       for (i = n - 1; i >= 0; i--) {
  136         lua_geti(L, 1, f + i);
  137         lua_seti(L, tt, t + i);
  138       }
  139     }
  140   }
  141   lua_pushvalue(L, tt);  /* return destination table */
  142   return 1;
  143 }
  144 
  145 
  146 static void addfield (lua_State *L, luaL_Buffer *b, lua_Integer i) {
  147   lua_geti(L, 1, i);
  148   if (l_unlikely(!lua_isstring(L, -1)))
  149     luaL_error(L, "invalid value (%s) at index %I in table for 'concat'",
  150                   luaL_typename(L, -1), i);
  151   luaL_addvalue(b);
  152 }
  153 
  154 
  155 static int tconcat (lua_State *L) {
  156   luaL_Buffer b;
  157   lua_Integer last = aux_getn(L, 1, TAB_R);
  158   size_t lsep;
  159   const char *sep = luaL_optlstring(L, 2, "", &lsep);
  160   lua_Integer i = luaL_optinteger(L, 3, 1);
  161   last = luaL_optinteger(L, 4, last);
  162   luaL_buffinit(L, &b);
  163   for (; i < last; i++) {
  164     addfield(L, &b, i);
  165     luaL_addlstring(&b, sep, lsep);
  166   }
  167   if (i == last)  /* add last value (if interval was not empty) */
  168     addfield(L, &b, i);
  169   luaL_pushresult(&b);
  170   return 1;
  171 }
  172 
  173 
  174 /*
  175 ** {======================================================
  176 ** Pack/unpack
  177 ** =======================================================
  178 */
  179 
  180 static int tpack (lua_State *L) {
  181   int i;
  182   int n = lua_gettop(L);  /* number of elements to pack */
  183   lua_createtable(L, n, 1);  /* create result table */
  184   lua_insert(L, 1);  /* put it at index 1 */
  185   for (i = n; i >= 1; i--)  /* assign elements */
  186     lua_seti(L, 1, i);
  187   lua_pushinteger(L, n);
  188   lua_setfield(L, 1, "n");  /* t.n = number of elements */
  189   return 1;  /* return table */
  190 }
  191 
  192 
  193 static int tunpack (lua_State *L) {
  194   lua_Unsigned n;
  195   lua_Integer i = luaL_optinteger(L, 2, 1);
  196   lua_Integer e = luaL_opt(L, luaL_checkinteger, 3, luaL_len(L, 1));
  197   if (i > e) return 0;  /* empty range */
  198   n = (lua_Unsigned)e - i;  /* number of elements minus 1 (avoid overflows) */
  199   if (l_unlikely(n >= (unsigned int)INT_MAX  ||
  200                  !lua_checkstack(L, (int)(++n))))
  201     return luaL_error(L, "too many results to unpack");
  202   for (; i < e; i++) {  /* push arg[i..e - 1] (to avoid overflows) */
  203     lua_geti(L, 1, i);
  204   }
  205   lua_geti(L, 1, e);  /* push last element */
  206   return (int)n;
  207 }
  208 
  209 /* }====================================================== */
  210 
  211 
  212 
  213 /*
  214 ** {======================================================
  215 ** Quicksort
  216 ** (based on 'Algorithms in MODULA-3', Robert Sedgewick;
  217 **  Addison-Wesley, 1993.)
  218 ** =======================================================
  219 */
  220 
  221 
  222 /* type for array indices */
  223 typedef unsigned int IdxT;
  224 
  225 
  226 /*
  227 ** Produce a "random" 'unsigned int' to randomize pivot choice. This
  228 ** macro is used only when 'sort' detects a big imbalance in the result
  229 ** of a partition. (If you don't want/need this "randomness", ~0 is a
  230 ** good choice.)
  231 */
  232 #if !defined(l_randomizePivot)      /* { */
  233 
  234 #include <time.h>
  235 
  236 /* size of 'e' measured in number of 'unsigned int's */
  237 #define sof(e)      (sizeof(e) / sizeof(unsigned int))
  238 
  239 /*
  240 ** Use 'time' and 'clock' as sources of "randomness". Because we don't
  241 ** know the types 'clock_t' and 'time_t', we cannot cast them to
  242 ** anything without risking overflows. A safe way to use their values
  243 ** is to copy them to an array of a known type and use the array values.
  244 */
  245 static unsigned int l_randomizePivot (void) {
  246   clock_t c = clock();
  247   time_t t = time(NULL);
  248   unsigned int buff[sof(c) + sof(t)];
  249   unsigned int i, rnd = 0;
  250   memcpy(buff, &c, sof(c) * sizeof(unsigned int));
  251   memcpy(buff + sof(c), &t, sof(t) * sizeof(unsigned int));
  252   for (i = 0; i < sof(buff); i++)
  253     rnd += buff[i];
  254   return rnd;
  255 }
  256 
  257 #endif                  /* } */
  258 
  259 
  260 /* arrays larger than 'RANLIMIT' may use randomized pivots */
  261 #define RANLIMIT    100u
  262 
  263 
  264 static void set2 (lua_State *L, IdxT i, IdxT j) {
  265   lua_seti(L, 1, i);
  266   lua_seti(L, 1, j);
  267 }
  268 
  269 
  270 /*
  271 ** Return true iff value at stack index 'a' is less than the value at
  272 ** index 'b' (according to the order of the sort).
  273 */
  274 static int sort_comp (lua_State *L, int a, int b) {
  275   if (lua_isnil(L, 2))  /* no function? */
  276     return lua_compare(L, a, b, LUA_OPLT);  /* a < b */
  277   else {  /* function */
  278     int res;
  279     lua_pushvalue(L, 2);    /* push function */
  280     lua_pushvalue(L, a-1);  /* -1 to compensate function */
  281     lua_pushvalue(L, b-2);  /* -2 to compensate function and 'a' */
  282     lua_call(L, 2, 1);      /* call function */
  283     res = lua_toboolean(L, -1);  /* get result */
  284     lua_pop(L, 1);          /* pop result */
  285     return res;
  286   }
  287 }
  288 
  289 
  290 /*
  291 ** Does the partition: Pivot P is at the top of the stack.
  292 ** precondition: a[lo] <= P == a[up-1] <= a[up],
  293 ** so it only needs to do the partition from lo + 1 to up - 2.
  294 ** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up]
  295 ** returns 'i'.
  296 */
  297 static IdxT partition (lua_State *L, IdxT lo, IdxT up) {
  298   IdxT i = lo;  /* will be incremented before first use */
  299   IdxT j = up - 1;  /* will be decremented before first use */
  300   /* loop invariant: a[lo .. i] <= P <= a[j .. up] */
  301   for (;;) {
  302     /* next loop: repeat ++i while a[i] < P */
  303     while ((void)lua_geti(L, 1, ++i), sort_comp(L, -1, -2)) {
  304       if (l_unlikely(i == up - 1))  /* a[i] < P  but a[up - 1] == P  ?? */
  305         luaL_error(L, "invalid order function for sorting");
  306       lua_pop(L, 1);  /* remove a[i] */
  307     }
  308     /* after the loop, a[i] >= P and a[lo .. i - 1] < P */
  309     /* next loop: repeat --j while P < a[j] */
  310     while ((void)lua_geti(L, 1, --j), sort_comp(L, -3, -1)) {
  311       if (l_unlikely(j < i))  /* j < i  but  a[j] > P ?? */
  312         luaL_error(L, "invalid order function for sorting");
  313       lua_pop(L, 1);  /* remove a[j] */
  314     }
  315     /* after the loop, a[j] <= P and a[j + 1 .. up] >= P */
  316     if (j < i) {  /* no elements out of place? */
  317       /* a[lo .. i - 1] <= P <= a[j + 1 .. i .. up] */
  318       lua_pop(L, 1);  /* pop a[j] */
  319       /* swap pivot (a[up - 1]) with a[i] to satisfy pos-condition */
  320       set2(L, up - 1, i);
  321       return i;
  322     }
  323     /* otherwise, swap a[i] - a[j] to restore invariant and repeat */
  324     set2(L, i, j);
  325   }
  326 }
  327 
  328 
  329 /*
  330 ** Choose an element in the middle (2nd-3th quarters) of [lo,up]
  331 ** "randomized" by 'rnd'
  332 */
  333 static IdxT choosePivot (IdxT lo, IdxT up, unsigned int rnd) {
  334   IdxT r4 = (up - lo) / 4;  /* range/4 */
  335   IdxT p = rnd % (r4 * 2) + (lo + r4);
  336   lua_assert(lo + r4 <= p && p <= up - r4);
  337   return p;
  338 }
  339 
  340 
  341 /*
  342 ** Quicksort algorithm (recursive function)
  343 */
  344 static void auxsort (lua_State *L, IdxT lo, IdxT up,
  345                                    unsigned int rnd) {
  346   while (lo < up) {  /* loop for tail recursion */
  347     IdxT p;  /* Pivot index */
  348     IdxT n;  /* to be used later */
  349     /* sort elements 'lo', 'p', and 'up' */
  350     lua_geti(L, 1, lo);
  351     lua_geti(L, 1, up);
  352     if (sort_comp(L, -1, -2))  /* a[up] < a[lo]? */
  353       set2(L, lo, up);  /* swap a[lo] - a[up] */
  354     else
  355       lua_pop(L, 2);  /* remove both values */
  356     if (up - lo == 1)  /* only 2 elements? */
  357       return;  /* already sorted */
  358     if (up - lo < RANLIMIT || rnd == 0)  /* small interval or no randomize? */
  359       p = (lo + up)/2;  /* middle element is a good pivot */
  360     else  /* for larger intervals, it is worth a random pivot */
  361       p = choosePivot(lo, up, rnd);
  362     lua_geti(L, 1, p);
  363     lua_geti(L, 1, lo);
  364     if (sort_comp(L, -2, -1))  /* a[p] < a[lo]? */
  365       set2(L, p, lo);  /* swap a[p] - a[lo] */
  366     else {
  367       lua_pop(L, 1);  /* remove a[lo] */
  368       lua_geti(L, 1, up);
  369       if (sort_comp(L, -1, -2))  /* a[up] < a[p]? */
  370         set2(L, p, up);  /* swap a[up] - a[p] */
  371       else
  372         lua_pop(L, 2);
  373     }
  374     if (up - lo == 2)  /* only 3 elements? */
  375       return;  /* already sorted */
  376     lua_geti(L, 1, p);  /* get middle element (Pivot) */
  377     lua_pushvalue(L, -1);  /* push Pivot */
  378     lua_geti(L, 1, up - 1);  /* push a[up - 1] */
  379     set2(L, p, up - 1);  /* swap Pivot (a[p]) with a[up - 1] */
  380     p = partition(L, lo, up);
  381     /* a[lo .. p - 1] <= a[p] == P <= a[p + 1 .. up] */
  382     if (p - lo < up - p) {  /* lower interval is smaller? */
  383       auxsort(L, lo, p - 1, rnd);  /* call recursively for lower interval */
  384       n = p - lo;  /* size of smaller interval */
  385       lo = p + 1;  /* tail call for [p + 1 .. up] (upper interval) */
  386     }
  387     else {
  388       auxsort(L, p + 1, up, rnd);  /* call recursively for upper interval */
  389       n = up - p;  /* size of smaller interval */
  390       up = p - 1;  /* tail call for [lo .. p - 1]  (lower interval) */
  391     }
  392     if ((up - lo) / 128 > n) /* partition too imbalanced? */
  393       rnd = l_randomizePivot();  /* try a new randomization */
  394   }  /* tail call auxsort(L, lo, up, rnd) */
  395 }
  396 
  397 
  398 static int sort (lua_State *L) {
  399   lua_Integer n = aux_getn(L, 1, TAB_RW);
  400   if (n > 1) {  /* non-trivial interval? */
  401     luaL_argcheck(L, n < INT_MAX, 1, "array too big");
  402     if (!lua_isnoneornil(L, 2))  /* is there a 2nd argument? */
  403       luaL_checktype(L, 2, LUA_TFUNCTION);  /* must be a function */
  404     lua_settop(L, 2);  /* make sure there are two arguments */
  405     auxsort(L, 1, (IdxT)n, 0);
  406   }
  407   return 0;
  408 }
  409 
  410 /* }====================================================== */
  411 
  412 
  413 static const luaL_Reg tab_funcs[] = {
  414   {"concat", tconcat},
  415   {"insert", tinsert},
  416   {"pack", tpack},
  417   {"unpack", tunpack},
  418   {"remove", tremove},
  419   {"move", tmove},
  420   {"sort", sort},
  421   {NULL, NULL}
  422 };
  423 
  424 
  425 LUAMOD_API int luaopen_table (lua_State *L) {
  426   luaL_newlib(L, tab_funcs);
  427   return 1;
  428 }
  429