Add to_hex::buffer

contrib/epee/include/hex.h

@@ -67,6 +67,9 @@ namespace epee
       return out;
     }
 
+    //! Write `src` as hex to `out`. `out` must be exactly 2x in size.
+    static bool buffer(span<char> out, const span<const std::uint8_t> src) noexcept;
+
     //! Append `src` as hex to `out`.
     static void buffer(std::ostream& out, const span<const std::uint8_t> src);
 

contrib/epee/src/hex.cpp

@@ -69,6 +69,14 @@ namespace epee
   std::string to_hex::string(const span<const std::uint8_t> src) { return convert<std::string>(src); }
   epee::wipeable_string to_hex::wipeable_string(const span<const std::uint8_t> src) { return convert<epee::wipeable_string>(src); }
 
+  bool to_hex::buffer(span<char> out, const span<const std::uint8_t> src) noexcept
+  {
+    if (out.size() % 2 != 0 || out.size() / 2 != src.size())
+      return false;
+    to_hex::buffer_unchecked(out.data(), src);
+    return true;
+  }
+
   void to_hex::buffer(std::ostream& out, const span<const std::uint8_t> src)
   {
     write_hex(std::ostreambuf_iterator<char>{out}, src);

tests/unit_tests/epee_utils.cpp

@@ -1241,6 +1241,22 @@ TEST(ToHex, ArrayFromPod)
   );
 }
 
+TEST(ToHex, Buffer)
+{
+  static constexpr const std::uint8_t source[] = {0xFF, 0x00, 0xAB, 0x01};
+  const std::vector<char> expected{'f', 'f', '0', '0', 'a', 'b', '0', '1'};
+
+  std::vector<char> buffer;
+  buffer.resize(expected.size());
+  EXPECT_TRUE(epee::to_hex::buffer(epee::to_mut_span(buffer), source));
+  EXPECT_EQ(expected, buffer);
+
+  buffer.pop_back();
+  EXPECT_FALSE(epee::to_hex::buffer(epee::to_mut_span(buffer), source));
+  buffer.pop_back();
+  EXPECT_FALSE(epee::to_hex::buffer(epee::to_mut_span(buffer), source));
+}
+
 TEST(ToHex, Ostream)
 {
   std::stringstream out;