1 files changed, 235 insertions, 143 deletions

diff --git a/ltablib.c b/ltablib.c
index 8f78afb..b3c9a7c 100644
--- a/ltablib.c
+++ b/ltablib.c
@@ -1,5 +1,5 @@
 /*
-** $Id: ltablib.c,v 1.79 2014/11/02 19:19:04 roberto Exp $
+** $Id: ltablib.c,v 1.90 2015/11/25 12:48:57 roberto Exp $
 ** Library for Table Manipulation
 ** See Copyright Notice in lua.h
 */
@@ -12,6 +12,7 @@
 
 #include <limits.h>
 #include <stddef.h>
+#include <string.h>
 
 #include "lua.h"
 
@@ -19,42 +20,44 @@
 #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                       /* read */
+#define TAB_W   2                       /* write */
+#define TAB_L   4                       /* length */
+#define TAB_RW  (TAB_R | TAB_W)         /* read/write */
+
+
+#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 +77,7 @@ 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 +89,8 @@ 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;
     }
@@ -96,55 +98,57 @@ 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;
 }
 
 
+/*
+** Copy elements (1[f], ..., 1[e]) into (tt[t], tt[t+1], ...). Whenever
+** possible, copy in increasing order, which is better for rehashing.
+** "possible" means destination after original range, or smaller
+** than origin, or copying to another table.
+*/
 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 */
-  /* the following restriction avoids several problems with overflows */
-  luaL_argcheck(L, f > 0, 2, "initial position must be positive");
+  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 */
-    if (t > f) {
-      for (i = n - 1; i >= 0; i--) {
-        (*ta.geti)(L, 1, f + i);
-        (*ta.seti)(L, tt, t + i);
+    luaL_argcheck(L, t <= LUA_MAXINTEGER - n + 1, 4,
+                  "destination wrap around");
+    if (t > e || t <= f || tt != 1) {
+      for (i = 0; i < n; 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);
+      for (i = n - 1; i >= 0; i--) {
+        lua_geti(L, 1, f + i);
+        lua_seti(L, tt, t + i);
       }
     }
   }
@@ -153,8 +157,8 @@ 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);
@@ -163,21 +167,19 @@ 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;
+  lua_Integer last = aux_getn(L, 1, TAB_R);
   size_t lsep;
-  lua_Integer i, last;
   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));
+  lua_Integer i = luaL_optinteger(L, 3, 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;
 }
@@ -195,7 +197,7 @@ 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 */
@@ -203,20 +205,17 @@ 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));
+  lua_Integer i = luaL_optinteger(L, 2, 1);
+  lua_Integer e = luaL_opt(L, luaL_checkinteger, 3, luaL_len(L, 1));
   if (i > e) return 0;  /* empty range */
   n = (lua_Unsigned)e - i;  /* number of elements minus 1 (avoid overflows) */
   if (n >= (unsigned int)INT_MAX  || !lua_checkstack(L, (int)(++n)))
     return luaL_error(L, "too many results to unpack");
-  do {  /* must have at least one element */
-    (*ta.geti)(L, 1, i);  /* push arg[i..e] */
-  } while (i++ < e); 
-
+  for (; i < e; i++) {  /* push arg[i..e - 1] (to avoid overflows) */
+    lua_geti(L, 1, i);
+  }
+  lua_geti(L, 1, e);  /* push last element */
   return (int)n;
 }
 
@@ -233,97 +232,190 @@ 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);
+/*
+** Produce a "random" 'unsigned int' to randomize pivot choice. This
+** macro is used only when 'sort' detects a big imbalance in the result
+** of a partition. (If you don't want/need this "randomness", ~0 is a
+** good choice.)
+*/
+#if !defined(l_randomizePivot)          /* { */
+
+#include <time.h>
+
+/* size of 'e' measured in number of 'unsigned int's */
+#define sof(e)          (sizeof(e) / sizeof(unsigned int))
+
+/*
+** Use 'time' and 'clock' as sources of "randomness". Because we don't
+** know the types 'clock_t' and 'time_t', we cannot cast them to
+** anything without risking overflows. A safe way to use their values
+** is to copy them to an array of a known type and use the array values.
+*/
+static unsigned int l_randomizePivot (void) {
+  clock_t c = clock();
+  time_t t = time(NULL);
+  unsigned int buff[sof(c) + sof(t)];
+  unsigned int i, rnd = 0;
+  memcpy(buff, &c, sof(c) * sizeof(unsigned int));
+  memcpy(buff + sof(c), &t, sof(t) * sizeof(unsigned int));
+  for (i = 0; i < sof(buff); i++)
+    rnd += buff[i];
+  return rnd;
+}
+
+#endif                                  /* } */
+
+
+/* arrays larger than 'RANLIMIT' may use randomized pivots */
+#define RANLIMIT        100u
+
+
+static void set2 (lua_State *L, unsigned int i, unsigned int j) {
+  lua_seti(L, 1, i);
+  lua_seti(L, 1, j);
 }
 
+
+/*
+** Return true iff value at stack index 'a' is less than the value at
+** index 'b' (according to the order of the sort).
+*/
 static int sort_comp (lua_State *L, int a, int b) {
-  if (!lua_isnil(L, 2)) {  /* function? */
+  if (lua_isnil(L, 2))  /* no function? */
+    return lua_compare(L, a, b, LUA_OPLT);  /* a < b */
+  else {  /* function */
     int res;
-    lua_pushvalue(L, 2);
+    lua_pushvalue(L, 2);    /* push function */
     lua_pushvalue(L, a-1);  /* -1 to compensate function */
     lua_pushvalue(L, b-2);  /* -2 to compensate function and 'a' */
-    lua_call(L, 2, 1);
-    res = lua_toboolean(L, -1);
-    lua_pop(L, 1);
+    lua_call(L, 2, 1);      /* call function */
+    res = lua_toboolean(L, -1);  /* get result */
+    lua_pop(L, 1);          /* pop result */
     return res;
   }
-  else  /* a < b? */
-    return lua_compare(L, a, b, LUA_OPLT);
 }
 
-static void auxsort (lua_State *L, TabA *ta, 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);
-    if (sort_comp(L, -1, -2))  /* a[u] < a[l]? */
-      set2(L, ta, l, u);  /* swap a[l] - a[u] */
+
+/*
+** Does the partition: Pivot P is at the top of the stack.
+** precondition: a[lo] <= P == a[up-1] <= a[up],
+** so it only needs to do the partition from lo + 1 to up - 2.
+** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up]
+** returns 'i'.
+*/
+static unsigned int partition (lua_State *L, unsigned int lo,
+                                             unsigned int up) {
+  unsigned int i = lo;  /* will be incremented before first use */
+  unsigned int j = up - 1;  /* will be decremented before first use */
+  /* loop invariant: a[lo .. i] <= P <= a[j .. up] */
+  for (;;) {
+    /* next loop: repeat ++i while a[i] < P */
+    while (lua_geti(L, 1, ++i), sort_comp(L, -1, -2)) {
+      if (i == up - 1)  /* a[i] < P  but a[up - 1] == P  ?? */
+        luaL_error(L, "invalid order function for sorting");
+      lua_pop(L, 1);  /* remove a[i] */
+    }
+    /* after the loop, a[i] >= P and a[lo .. i - 1] < P */
+    /* next loop: repeat --j while P < a[j] */
+    while (lua_geti(L, 1, --j), sort_comp(L, -3, -1)) {
+      if (j < i)  /* j < i  but  a[j] > P ?? */
+        luaL_error(L, "invalid order function for sorting");
+      lua_pop(L, 1);  /* remove a[j] */
+    }
+    /* after the loop, a[j] <= P and a[j + 1 .. up] >= P */
+    if (j < i) {  /* no elements out of place? */
+      /* a[lo .. i - 1] <= P <= a[j + 1 .. i .. up] */
+      lua_pop(L, 1);  /* pop a[j] */
+      /* swap pivot (a[up - 1]) with a[i] to satisfy pos-condition */
+      set2(L, up - 1, i);
+      return i;
+    }
+    /* otherwise, swap a[i] - a[j] to restore invariant and repeat */
+    set2(L, i, j);
+  }
+}
+
+
+/*
+** Choose an element in the middle (2nd-3th quarters) of [lo,up]
+** "randomized" by 'rnd'
+*/
+static unsigned int choosePivot (unsigned int lo, unsigned int up,
+                                 unsigned int rnd) {
+  unsigned int r4 = (unsigned int)(up - lo) / 4u;  /* range/4 */
+  unsigned int p = rnd % (r4 * 2) + (lo + r4);
+  lua_assert(lo + r4 <= p && p <= up - r4);
+  return p;
+}
+
+
+/*
+** QuickSort algorithm (recursive function)
+*/
+static void auxsort (lua_State *L, unsigned int lo, unsigned int up,
+                                   unsigned int rnd) {
+  while (lo < up) {  /* loop for tail recursion */
+    unsigned int p;  /* Pivot index */
+    unsigned int n;  /* to be used later */
+    /* sort elements 'lo', 'p', and 'up' */
+    lua_geti(L, 1, lo);
+    lua_geti(L, 1, up);
+    if (sort_comp(L, -1, -2))  /* a[up] < a[lo]? */
+      set2(L, lo, up);  /* swap a[lo] - a[up] */
     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);
-    if (sort_comp(L, -2, -1))  /* a[i]<a[l]? */
-      set2(L, ta, i, l);
+      lua_pop(L, 2);  /* remove both values */
+    if (up - lo == 1)  /* only 2 elements? */
+      return;  /* already sorted */
+    if (up - lo < RANLIMIT || rnd == 0)  /* small interval or no randomize? */
+      p = (lo + up)/2;  /* middle element is a good pivot */
+    else  /* for larger intervals, it is worth a random pivot */
+      p = choosePivot(lo, up, rnd);
+    lua_geti(L, 1, p);
+    lua_geti(L, 1, lo);
+    if (sort_comp(L, -2, -1))  /* a[p] < a[lo]? */
+      set2(L, p, lo);  /* swap a[p] - a[lo] */
     else {
-      lua_pop(L, 1);  /* remove a[l] */
-      (*ta->geti)(L, 1, u);
-      if (sort_comp(L, -1, -2))  /* a[u]<a[i]? */
-        set2(L, ta, i, u);
+      lua_pop(L, 1);  /* remove a[lo] */
+      lua_geti(L, 1, up);
+      if (sort_comp(L, -1, -2))  /* a[up] < a[p]? */
+        set2(L, p, up);  /* swap a[up] - a[p] */
       else
         lua_pop(L, 2);
     }
-    if (u-l == 2) break;  /* only 3 elements */
-    (*ta->geti)(L, 1, i);  /* Pivot */
-    lua_pushvalue(L, -1);
-    (*ta->geti)(L, 1, u-1);
-    set2(L, ta, 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)) {
-        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)) {
-        if (j<=l) luaL_error(L, "invalid order function for sorting");
-        lua_pop(L, 1);  /* remove a[j] */
-      }
-      if (j<i) {
-        lua_pop(L, 3);  /* pop pivot, a[i], a[j] */
-        break;
-      }
-      set2(L, ta, 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] */
-    /* 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) {
-      j=l; i=i-1; l=i+2;
+    if (up - lo == 2)  /* only 3 elements? */
+      return;  /* already sorted */
+    lua_geti(L, 1, p);  /* get middle element (Pivot) */
+    lua_pushvalue(L, -1);  /* push Pivot */
+    lua_geti(L, 1, up - 1);  /* push a[up - 1] */
+    set2(L, p, up - 1);  /* swap Pivot (a[p]) with a[up - 1] */
+    p = partition(L, lo, up);
+    /* a[lo .. p - 1] <= a[p] == P <= a[p + 1 .. up] */
+    if (p - lo < up - p) {  /* lower interval is smaller? */
+      auxsort(L, lo, p - 1, rnd);  /* call recursively for lower interval */
+      n = p - lo;  /* size of smaller interval */
+      lo = p + 1;  /* tail call for [p + 1 .. up] (upper interval) */
     }
     else {
-      j=i+1; i=u; u=j-2;
+      auxsort(L, p + 1, up, rnd);  /* call recursively for upper interval */
+      n = up - p;  /* size of smaller interval */
+      up = p - 1;  /* tail call for [lo .. p - 1]  (lower interval) */
     }
-    auxsort(L, ta, j, i);  /* call recursively the smaller one */
-  }  /* repeat the routine for the larger one */
+    if ((up - lo) / 128u > n) /* partition too imbalanced? */
+      rnd = l_randomizePivot();  /* try a new randomization */
+  }  /* tail call auxsort(L, lo, up, rnd) */
 }
 
+
 static int sort (lua_State *L) {
-  TabA ta;
-  int n = (int)aux_getn(L, 1, &ta);
-  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);
+  lua_Integer n = aux_getn(L, 1, TAB_RW);
+  if (n > 1) {  /* non-trivial interval? */
+    luaL_argcheck(L, n < INT_MAX, 1, "array too big");
+    luaL_checkstack(L, 40, "");  /* assume array is smaller than 2^40 */
+    if (!lua_isnoneornil(L, 2))  /* is there a 2nd argument? */
+      luaL_checktype(L, 2, LUA_TFUNCTION);  /* must be a function */
+    lua_settop(L, 2);  /* make sure there are two arguments */
+    auxsort(L, 1, (unsigned int)n, 0u);
+  }
   return 0;
 }