clean up integer_to_str() function

include/libtorrent/bencode.hpp

@@ -97,15 +97,13 @@ namespace detail {
 			static_assert(sizeof(entry::integer_type) <= 8, "64 bit integers required");
 			static_assert(sizeof(data) <= sizeof(entry::integer_type), "input data too big, see entry::integer_type");
 			char buf[21];
-			int ret = 0;
-			for (char const* str = integer_to_str(buf, 21, val);
-				*str != 0; ++str)
+			auto const str = integer_to_str(buf, val);
+			for (char const c : str)
 			{
-				*out = *str;
+				*out = c;
 				++out;
-				++ret;
 			}
-			return ret;
+			return static_cast<int>(str.size());
 		}
 
 		template <class OutIt>

include/libtorrent/entry.hpp

@@ -342,9 +342,9 @@ namespace aux {
 
 namespace detail {
 
-		TORRENT_EXPORT char const* integer_to_str(char* buf, int size
+	TORRENT_EXTRA_EXPORT string_view integer_to_str(span<char> buf
 		, entry::integer_type val);
-	}
+}
 
 #if TORRENT_USE_IOSTREAM
 	// prints the bencoded structure to the ostream as a JSON-style structure.

src/entry.cpp

@@ -45,7 +45,7 @@ namespace libtorrent {
 
 namespace detail {
 
-	char const* integer_to_str(char* buf, int size
+	string_view integer_to_str(span<char> buf
 		, entry::integer_type val)
 	{
 		int sign = 0;
@@ -54,15 +54,17 @@ namespace detail {
 			sign = 1;
 			val = -val;
 		}
-		buf[--size] = '\0';
-		if (val == 0) buf[--size] = '0';
-		while (size > sign && val != 0)
+		char* ptr = &buf.back();
+		*ptr-- = '\0';
+		if (val == 0) *ptr-- = '0';
+		while (ptr > buf.data() + sign && val != 0)
 		{
-			buf[--size] = '0' + char(val % 10);
+			*ptr-- = '0' + char(val % 10);
 			val /= 10;
 		}
-		if (sign) buf[--size] = '-';
-		return buf + size;
+		if (sign) *ptr-- = '-';
+		++ptr;
+		return {ptr, static_cast<std::size_t>(&buf.back() - ptr)};
 	}
 } // detail
 

test/test_bencoding.cpp

@@ -228,6 +228,18 @@ TORRENT_TEST(print_deep_dict)
 	TEST_EQUAL(e.to_string(), "{\n 'a': 'foobar',\n 'ints': [\n   1,\n   2,\n   3 ],\n 'strings': [\n   'foo',\n   'bar' ] }");
 }
 
+TORRENT_TEST(integer_to_str)
+{
+	using lt::detail::integer_to_str;
+
+	char buf[30];
+	TEST_CHECK(integer_to_str(buf, 0) == "0"_sv);
+	TEST_CHECK(integer_to_str(buf, 1234) == "1234"_sv);
+	TEST_CHECK(integer_to_str(buf, -1234) == "-1234"_sv);
+	TEST_CHECK(integer_to_str(buf, 123456789012345678LL) == "123456789012345678"_sv);
+	TEST_CHECK(integer_to_str(buf, -123456789012345678LL) == "-123456789012345678"_sv);
+}
+
 TORRENT_TEST(lazy_entry)
 {
 	{