Fixed bugs for take_slice and byte_stream->byte_slice

contrib/epee/src/byte_slice.cpp

@@ -173,9 +173,14 @@ namespace epee
   byte_slice::byte_slice(byte_stream&& stream) noexcept
     : storage_(nullptr), portion_(stream.data(), stream.size())
   {
-    std::uint8_t* const data = stream.take_buffer().release() - sizeof(raw_byte_slice);
-    new (data) raw_byte_slice{};
-    storage_.reset(reinterpret_cast<raw_byte_slice*>(data));
+    if (stream.size())
+    {
+      std::uint8_t* const data = stream.take_buffer().release() - sizeof(raw_byte_slice);
+      new (data) raw_byte_slice{};
+      storage_.reset(reinterpret_cast<raw_byte_slice*>(data));
+    }
+    else
+      portion_ = nullptr;
   }
 
   byte_slice::byte_slice(byte_slice&& source) noexcept
@@ -205,14 +210,17 @@ namespace epee
   byte_slice byte_slice::take_slice(const std::size_t max_bytes) noexcept
   {
     byte_slice out{};
-    std::uint8_t const* const ptr = data();
-    out.portion_ = {ptr, portion_.remove_prefix(max_bytes)};
 
-    if (portion_.empty())
-      out.storage_ = std::move(storage_); // no atomic inc/dec
-    else
-      out = {storage_.get(), out.portion_};
+    if (max_bytes)
+    {
+      std::uint8_t const* const ptr = data();
+      out.portion_ = {ptr, portion_.remove_prefix(max_bytes)};
 
+      if (portion_.empty())
+        out.storage_ = std::move(storage_); // no atomic inc/dec
+      else
+        out = {storage_.get(), out.portion_};
+    }
     return out;
   }
 

tests/unit_tests/epee_utils.cpp

@@ -667,6 +667,23 @@ TEST(ByteSlice, TakeSlice)
   EXPECT_TRUE(boost::range::equal(base_string, slice));
 
   const epee::span<const std::uint8_t> original = epee::to_span(slice);
+  const epee::byte_slice empty_slice = slice.take_slice(0);
+  EXPECT_EQ(original.begin(), slice.begin());
+  EXPECT_EQ(slice.begin(), slice.cbegin());
+  EXPECT_EQ(original.end(), slice.end());
+  EXPECT_EQ(slice.end(), slice.cend());
+
+  EXPECT_EQ(nullptr, empty_slice.begin());
+  EXPECT_EQ(nullptr, empty_slice.cbegin());
+  EXPECT_EQ(nullptr, empty_slice.end());
+  EXPECT_EQ(nullptr, empty_slice.cend());
+  EXPECT_EQ(nullptr, empty_slice.data());
+  EXPECT_TRUE(empty_slice.empty());
+  EXPECT_EQ(0u, empty_slice.size());
+
+  EXPECT_FALSE(slice.empty());
+  EXPECT_EQ(slice.cbegin(), slice.data());
+
   const epee::byte_slice slice2 = slice.take_slice(remove_size);
 
   EXPECT_EQ(original.begin() + remove_size, slice.begin());
@@ -1061,6 +1078,20 @@ TEST(ByteStream, ToByteSlice)
   EXPECT_EQ(nullptr, stream.data());
   EXPECT_EQ(nullptr, stream.tellp());
   EXPECT_TRUE(equal(source, slice));
+
+  stream = epee::byte_stream{};
+  stream.reserve(1);
+  EXPECT_NE(nullptr, stream.data());
+  EXPECT_NE(nullptr, stream.tellp());
+
+  const epee::byte_slice empty_slice{std::move(stream)};
+  EXPECT_TRUE(empty_slice.empty());
+  EXPECT_EQ(0u, empty_slice.size());
+  EXPECT_EQ(nullptr, empty_slice.begin());
+  EXPECT_EQ(nullptr, empty_slice.cbegin());
+  EXPECT_EQ(nullptr, empty_slice.end());
+  EXPECT_EQ(nullptr, empty_slice.cend());
+  EXPECT_EQ(nullptr, empty_slice.data());
 }
 
 TEST(ToHex, String)