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-rw-r--r--src/ltablib.c144
1 files changed, 99 insertions, 45 deletions
diff --git a/src/ltablib.c b/src/ltablib.c
index 867ff9df..b3c9a7c5 100644
--- a/src/ltablib.c
+++ b/src/ltablib.c
@@ -1,5 +1,5 @@
/*
-** $Id: ltablib.c,v 1.85 2015/11/12 18:07:25 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
*/
@@ -12,7 +12,7 @@
#include <limits.h>
#include <stddef.h>
-#include <time.h>
+#include <string.h>
#include "lua.h"
@@ -24,10 +24,10 @@
** Operations that an object must define to mimic a table
** (some functions only need some of them)
*/
-#define TAB_R 1
-#define TAB_W 2
-#define TAB_L 4
-#define TAB_RW (TAB_R | TAB_W)
+#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))
@@ -51,7 +51,7 @@ static void checktab (lua_State *L, int arg, int what) {
(!(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 */
}
@@ -168,11 +168,10 @@ static void addfield (lua_State *L, luaL_Buffer *b, lua_Integer i) {
static int tconcat (lua_State *L) {
luaL_Buffer b;
- size_t lsep;
- lua_Integer i;
lua_Integer last = aux_getn(L, 1, TAB_R);
+ size_t lsep;
const char *sep = luaL_optlstring(L, 2, "", &lsep);
- i = luaL_optinteger(L, 3, 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++) {
@@ -206,10 +205,9 @@ static int pack (lua_State *L) {
static int unpack (lua_State *L) {
- lua_Integer i, e;
lua_Unsigned n;
- 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)))
@@ -233,24 +231,68 @@ static int unpack (lua_State *L) {
** =======================================================
*/
-static void set2 (lua_State *L, int i, int 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);
}
@@ -261,9 +303,10 @@ static int sort_comp (lua_State *L, int a, int b) {
** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up]
** returns 'i'.
*/
-static int partition (lua_State *L, int lo, int up) {
- int i = lo; /* will be incremented before first use */
- int j = up - 1; /* will be decremented before first use */
+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 */
@@ -294,23 +337,27 @@ static int partition (lua_State *L, int lo, int up) {
/*
-** Choose a "random" pivot in the middle part of the interval [lo, up].
-** Use 'time' and 'clock' as sources of "randomness".
+** Choose an element in the middle (2nd-3th quarters) of [lo,up]
+** "randomized" by 'rnd'
*/
-static int choosePivot (int lo, int up) {
- unsigned int t = (unsigned int)(unsigned long)time(NULL); /* time */
- unsigned int c = (unsigned int)(unsigned long)clock(); /* clock */
+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 = (c + t) % (r4 * 2) + (lo + r4);
+ unsigned int p = rnd % (r4 * 2) + (lo + r4);
lua_assert(lo + r4 <= p && p <= up - r4);
- return (int)p;
+ return p;
}
-static void auxsort (lua_State *L, int lo, int up) {
+/*
+** 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 */
- int p;
- /* sort elements 'lo', '(lo + up)/2' and 'up' */
+ 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]? */
@@ -319,10 +366,10 @@ static void auxsort (lua_State *L, int lo, int up) {
lua_pop(L, 2); /* remove both values */
if (up - lo == 1) /* only 2 elements? */
return; /* already sorted */
- if (up - lo < 100) /* small interval? */
+ 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);
+ 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]? */
@@ -344,24 +391,31 @@ static void auxsort (lua_State *L, int lo, int up) {
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); /* call recursively for lower interval */
+ 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 {
- auxsort(L, p + 1, up); /* call recursively for upper interval */
+ 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) */
}
- } /* tail call auxsort(L, lo, up) */
+ 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) {
- 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, 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;
}
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