fix bitfield m_buf null pointer (#1526)

fix operations on empty bitfield

ChangeLog

@@ -1,3 +1,4 @@
+	* fix crash caused by empty bitfield 
 	* removed disk-access-log build configuration
 	* removed mmap_cache feature
 	* strengthened type safety in handling of piece and file indices

include/libtorrent/bitfield.hpp

@@ -105,6 +105,8 @@ namespace libtorrent
 
 		bool none_set() const
 		{
+			if(size() == 0) return true;
+
 			const int words = num_words();
 			std::uint32_t const* b = buf();
 			for (int i = 0; i < words; ++i)
@@ -126,7 +128,7 @@ namespace libtorrent
 		}
 
 		// returns true if the bitfield has zero size.
-		bool empty() const { return m_buf == nullptr ? true : m_buf[0] == 0; }
+		bool empty() const { return size() == 0; }
 
 		// returns a pointer to the internal buffer of the bitfield.
 		char const* data() const { return m_buf ? reinterpret_cast<char const*>(&m_buf[1]) : nullptr; }
@@ -226,13 +228,13 @@ namespace libtorrent
 		// set all bits in the bitfield to 1 (set_all) or 0 (clear_all).
 		void set_all()
 		{
-			if (m_buf == nullptr) return;
+			if (size() == 0) return;
 			std::memset(buf(), 0xff, size_t(num_words() * 4));
 			clear_trailing_bits();
 		}
 		void clear_all()
 		{
-			if (m_buf == nullptr) return;
+			if (size() == 0) return;
 			std::memset(buf(), 0x00, size_t(num_words() * 4));
 		}
 

src/bitfield.cpp

@@ -41,6 +41,8 @@ namespace libtorrent
 {
 	bool bitfield::all_set() const
 	{
+		if(size() == 0) return false;
+
 		int const words = size() / 32;
 		for (int i = 1; i < words + 1; ++i)
 		{

test/test_bitfield.cpp

@@ -355,3 +355,51 @@ TORRENT_TEST(find_last_clear_misc)
 	test4.clear_bit(89);
 	TEST_EQUAL(test4.find_last_clear(), 91);
 }
+
+TORRENT_TEST(not_initialized)
+{
+	// check a not initialized empty bitfield
+	bitfield test1(0);
+	TEST_EQUAL(test1.none_set(), true);
+	TEST_EQUAL(test1.all_set(), false);
+	TEST_EQUAL(test1.size(), 0);
+	TEST_EQUAL(test1.num_words(), 0);
+	TEST_EQUAL(test1.empty(), true);
+	TEST_CHECK(test1.data() == nullptr);
+	TEST_EQUAL(test1.count(), 0);
+	TEST_EQUAL(test1.find_first_set(), -1);
+	TEST_EQUAL(test1.find_last_clear(), -1);
+
+	test1.clear_all();
+	TEST_EQUAL(test1.size(), 0);
+
+	test1.clear();
+	TEST_EQUAL(test1.size(), 0);
+
+	test1.set_all();
+	TEST_EQUAL(test1.size(), 0);
+
+	// don't test methods which aren't defined for empty sets:
+	// get_bit, clear_bit, set_bit
+}
+
+TORRENT_TEST(not_initialized_assign)
+{
+	// check a not initialized empty bitfield
+	bitfield test1(0);
+	std::uint8_t b1[] = { 0xff };
+	test1.assign((char*)b1, 8);
+	TEST_EQUAL(test1.count(), 8);
+}
+
+TORRENT_TEST(not_initialized_resize)
+{
+	// check a not initialized empty bitfield
+	bitfield test1(0);
+	test1.resize(8, true);
+	TEST_EQUAL(test1.count(), 8);
+
+	bitfield test2(0);
+	test2.resize(8);
+	TEST_EQUAL(test2.size(), 8);
+}