zstring_span: fix for Expects, simplify functions

- `s[s.size() - 1]` is wrong for empty `s`, so `Expects(s.size() > 0)`
- no hard coded `'\0'`but `value_type{}`
- hard code `empty()` to return `false`
- simplify `as_string_span`: can never be `empty`
- clarify comment on `ensure_z`

1 files changed, 6 insertions, 7 deletions

diff --git a/include/gsl/string_span b/include/gsl/string_span
index ba125b7..506001f 100644
--- a/include/gsl/string_span
+++ b/include/gsl/string_span
@@ -120,9 +120,8 @@ span<T, dynamic_extent> ensure_sentinel(T* seq,
 }

 

 //

-// ensure_z - creates a span for a zero terminated strings.

-// Will fail fast if a null-terminator cannot be found before

-// the limit of size_type.

+// ensure_z - creates a span for a zero terminated strings. The span will not contain the zero termination.

+// Will fail fast if a null-terminator cannot be found before the limit of size_type.

 //

 template <typename CharT>

 span<CharT, dynamic_extent> ensure_z(CharT* const& sz,

@@ -395,7 +394,8 @@ public:
     constexpr basic_zstring_span(impl_type s) : span_(s)

     {

         // expects a zero-terminated span

-        Expects(s[s.size() - 1] == '\0');

+        Expects(s.size() > 0);

+        Expects(s[s.size() - 1] == value_type{});

     }

 

     // copy

@@ -410,12 +410,11 @@ public:
     // move assign

     constexpr basic_zstring_span& operator=(basic_zstring_span&& other) = default;

 

-    constexpr bool empty() const noexcept { return span_.size() == 0; }

+    constexpr bool empty() const noexcept { return false; }

 

     constexpr string_span_type as_string_span() const noexcept

     {

-        const auto sz = span_.size();

-        return {span_.data(), sz > 1 ? sz - 1 : 0};

+        return {span_.data(), span_.size() - 1};

     }

     constexpr string_span_type ensure_z() const { return gsl::ensure_z(span_); }