string: add snprintf

Signed-off-by: Simon Rozman <simon@rozman.si>

UnitTests/string.cpp

@@ -42,4 +42,31 @@ namespace UnitTests
 		Assert::AreEqual(str.c_str(), stdex::sprintf("%s", locale, str.data()).c_str());
 		Assert::AreEqual(str.size(), stdex::sprintf("%s", locale, str.data()).size());
 	}
+
+	void string::snprintf()
+	{
+		stdex::locale locale(stdex::create_locale(LC_ALL, "en_US.UTF-8"));
+
+		{
+			wchar_t buf[0x100];
+			Assert::IsTrue(stdex::snprintf(buf, _countof(buf), L"This is %ls.", locale, L"a test") == 15);
+			Assert::AreEqual(L"This is a test.", buf);
+		}
+		{
+			char buf[0x100];
+			Assert::IsTrue(stdex::snprintf(buf, _countof(buf), "This is %s.", locale, "a test") == 15);
+			Assert::AreEqual("This is a test.", buf);
+		}
+
+		{
+			wchar_t buf[8];
+			Assert::IsTrue(stdex::snprintf(buf, _countof(buf), L"This is %ls.", locale, L"a test") == 8);
+			Assert::IsTrue(stdex::strncmp(L"This is a test.", buf, _countof(buf)) == 0);
+		}
+		{
+			char buf[8];
+			Assert::IsTrue(stdex::snprintf(buf, _countof(buf), "This is %s.", locale, "a test") == 8);
+			Assert::IsTrue(stdex::strncmp("This is a test.", buf, _countof(buf)) == 0);
+		}
+	}
 }