* array.c (rb_ary_shuffle_bang): bail out from modification during

  shuffle.

* array.c (rb_ary_sample): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29108 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 46 insertions, 18 deletions

diff --git a/array.c b/array.c
index 0e51bb0b98..8a828c506c 100644
--- a/array.c
+++ b/array.c
@@ -20,6 +20,8 @@
 #endif
 #include <assert.h>
 
+#define numberof(array) (int)(sizeof(array) / sizeof((array)[0]))
+
 VALUE rb_cArray;
 
 static ID id_cmp;
@@ -3748,8 +3750,8 @@ static VALUE sym_random;
 static VALUE
 rb_ary_shuffle_bang(int argc, VALUE *argv, VALUE ary)
 {
-    VALUE *ptr, opts, randgen = rb_cRandom;
-    long i = RARRAY_LEN(ary);
+    VALUE *ptr, opts, *snap_ptr, randgen = rb_cRandom;
+    long i, snap_len;
 
     if (OPTHASH_GIVEN_P(opts)) {
 	randgen = rb_hash_lookup2(opts, sym_random, randgen);
@@ -3758,10 +3760,17 @@ rb_ary_shuffle_bang(int argc, VALUE *argv, VALUE ary)
 	rb_raise(rb_eArgError, "wrong number of arguments (%d for 0)", argc);
     }
     rb_ary_modify(ary);
+    i = RARRAY_LEN(ary);
     ptr = RARRAY_PTR(ary);
+    snap_len = i;
+    snap_ptr = ptr;
     while (i) {
 	long j = RAND_UPTO(i);
-	VALUE tmp = ptr[--i];
+	VALUE tmp;
+	if (snap_len != RARRAY_LEN(ary) || snap_ptr != RARRAY_PTR(ary)) {
+	    rb_raise(rb_eRuntimeError, "modified during shuffle");
+	}
+	tmp = ptr[--i];
 	ptr[i] = ptr[j];
 	ptr[j] = tmp;
     }
@@ -3814,37 +3823,54 @@ static VALUE
 rb_ary_sample(int argc, VALUE *argv, VALUE ary)
 {
     VALUE nv, result, *ptr;
-    VALUE opts, randgen = rb_cRandom;
+    VALUE opts, snap, randgen = rb_cRandom;
     long n, len, i, j, k, idx[10];
+    double rnds[numberof(idx)];
 
-    len = RARRAY_LEN(ary);
     if (OPTHASH_GIVEN_P(opts)) {
 	randgen = rb_hash_lookup2(opts, sym_random, randgen);
     }
+    ptr = RARRAY_PTR(ary);
+    len = RARRAY_LEN(ary);
     if (argc == 0) {
 	if (len == 0) return Qnil;
-	i = len == 1 ? 0 : RAND_UPTO(len);
+	if (len == 1) {
+	    i = 0;
+	}
+	else {
+	    double x = rb_random_real(randgen);
+	    if ((len = RARRAY_LEN(ary)) == 0) return Qnil;
+	    i = (long)(x * len);
+	}
 	return RARRAY_PTR(ary)[i];
     }
     rb_scan_args(argc, argv, "1", &nv);
     n = NUM2LONG(nv);
     if (n < 0) rb_raise(rb_eArgError, "negative sample number");
-    ptr = RARRAY_PTR(ary);
+    if (n > len) n = len;
+    if (n <= numberof(idx)) {
+	for (i = 0; i < n; ++i) {
+	    rnds[i] = rb_random_real(randgen);
+	}
+    }
     len = RARRAY_LEN(ary);
+    ptr = RARRAY_PTR(ary);
     if (n > len) n = len;
     switch (n) {
-      case 0: return rb_ary_new2(0);
+      case 0:
+	return rb_ary_new2(0);
       case 1:
-	return rb_ary_new4(1, &ptr[RAND_UPTO(len)]);
+	i = (long)(rnds[0] * len);
+	return rb_ary_new4(1, &ptr[i]);
       case 2:
-	i = RAND_UPTO(len);
-	j = RAND_UPTO(len-1);
+	i = (long)(rnds[0] * len);
+	j = (long)(rnds[1] * (len-1));
 	if (j >= i) j++;
 	return rb_ary_new3(2, ptr[i], ptr[j]);
       case 3:
-	i = RAND_UPTO(len);
-	j = RAND_UPTO(len-1);
-	k = RAND_UPTO(len-2);
+	i = (long)(rnds[0] * len);
+	j = (long)(rnds[1] * (len-1));
+	k = (long)(rnds[2] * (len-2));
 	{
 	    long l = j, g = i;
 	    if (j >= i) l = i, g = ++j;
@@ -3852,12 +3878,12 @@ rb_ary_sample(int argc, VALUE *argv, VALUE ary)
 	}
 	return rb_ary_new3(3, ptr[i], ptr[j], ptr[k]);
     }
-    if ((size_t)n < sizeof(idx)/sizeof(idx[0])) {
+    if (n <= numberof(idx)) {
 	VALUE *ptr_result;
-	long sorted[sizeof(idx)/sizeof(idx[0])];
-	sorted[0] = idx[0] = RAND_UPTO(len);
+	long sorted[numberof(idx)];
+	sorted[0] = idx[0] = (long)(rnds[0] * len);
 	for (i=1; i<n; i++) {
-	    k = RAND_UPTO(--len);
+	    k = (long)(rnds[i] * --len);
 	    for (j = 0; j < i; ++j) {
 		if (k < sorted[j]) break;
 		++k;
@@ -3874,6 +3900,7 @@ rb_ary_sample(int argc, VALUE *argv, VALUE ary)
     else {
 	VALUE *ptr_result;
 	result = rb_ary_new4(len, ptr);
+	RBASIC(result)->klass = 0;
 	ptr_result = RARRAY_PTR(result);
 	RB_GC_GUARD(ary);
 	for (i=0; i<n; i++) {
@@ -3882,6 +3909,7 @@ rb_ary_sample(int argc, VALUE *argv, VALUE ary)
 	    ptr_result[j] = ptr_result[i];
 	    ptr_result[i] = nv;
 	}
+	RBASIC(result)->klass = rb_cArray;
     }
     ARY_SET_LEN(result, n);