diff --git a/include/xo/arena/DCircularBuffer.hpp b/include/xo/arena/DCircularBuffer.hpp
index 0cb007a..30a3896 100644
--- a/include/xo/arena/DCircularBuffer.hpp
+++ b/include/xo/arena/DCircularBuffer.hpp
@@ -39,8 +39,8 @@ namespace xo {
             using size_type = std::size_t;
             using byte = std::byte;
             /** a contiguous addres range **/
-            using span_type = span<byte>;
-            using const_span_type = span<const byte>;
+            using span_type = span<char>;
+            using const_span_type = span<const char>;
 
             ///@}
 
@@ -162,7 +162,7 @@ namespace xo {
              *
              *  Require: @p hi < @ref reserved_range_.hi
              **/
-            bool _expand_to(byte * hi);
+            bool _expand_to(char * hi);
 
             /** shrink occupied rnage to the smallest contiguous range that contains both:
              *  all of .input_range_, and all pinned ranges in .pinned_spans_
diff --git a/include/xo/arena/span.hpp b/include/xo/arena/span.hpp
index c038fce..b919266 100644
--- a/include/xo/arena/span.hpp
+++ b/include/xo/arena/span.hpp
@@ -88,6 +88,14 @@ namespace xo {
                 return span(lo, hi);
             }
 
+            /** @brief create span from raw memory **/
+            static span from_memory(span<std::byte> span_memory) {
+                CharT * lo = (CharT *)span_memory.lo();
+                CharT * hi = (CharT *)span_memory.hi();
+
+                return span(lo, hi);
+            }
+
             /** @brief concatenate two contiguous spans */
             static span concat(const span & span1, const span & span2) {
                 if (span1.is_null())
diff --git a/src/arena/DCircularBuffer.cpp b/src/arena/DCircularBuffer.cpp
index 5ad7e02..e00aaaf 100644
--- a/src/arena/DCircularBuffer.cpp
+++ b/src/arena/DCircularBuffer.cpp
@@ -48,17 +48,19 @@ namespace xo {
             log && log(xtag("page_z", page_z),
                        xtag("align_z", align_z));
 
-            auto span = mmap_util::map_aligned_range(config.max_capacity_,
-                                                     align_z,
-                                                     enable_hugepage_flag,
-                                                     config.debug_flag_);
+            auto mapped_span
+                = span<char>::from_memory(mmap_util::map_aligned_range
+                                              (config.max_capacity_,
+                                               align_z,
+                                               enable_hugepage_flag,
+                                               config.debug_flag_));
 
-            if (!span.lo()) {
+            if (!mapped_span.lo()) {
                 throw std::runtime_error(tostr("DCircularBuffer: reserve address range failed",
                                                xtag("size", config.max_capacity_)));
             }
 
-            return DCircularBuffer(config, page_z, align_z, span);
+            return DCircularBuffer(config, page_z, align_z, mapped_span);
         }
 
         DCircularBuffer::DCircularBuffer(const CircularBufferConfig & config,
@@ -302,7 +304,8 @@ namespace xo {
         }
 
         bool
-        DCircularBuffer::_expand_to(byte * hi) {
+        DCircularBuffer::_expand_to(char * hi)
+        {
             scope log(XO_DEBUG(config_.debug_flag_));
 
             if (hi < mapped_range_.hi()) {
@@ -312,7 +315,7 @@ namespace xo {
 
             size_t add_z = hi - mapped_range_.hi();
             size_t add_commit_z = padding::with_padding(add_z, buffer_align_z_);
-            byte * commit_start = mapped_range_.hi();
+            char * commit_start = mapped_range_.hi();
 
             if (::mprotect(commit_start,
                            add_commit_z,
diff --git a/utest/DCircularBuffer.test.cpp b/utest/DCircularBuffer.test.cpp
index be86947..2d8df93 100644
--- a/utest/DCircularBuffer.test.cpp
+++ b/utest/DCircularBuffer.test.cpp
@@ -34,18 +34,16 @@ namespace xo {
             REQUIRE(buf.occupied_range().size() == 0);
             REQUIRE(buf.input_range().size() == 0);
 
-            std::string_view s0 = "abcdefghijk";
+            auto s0 = DCircularBuffer::const_span_type::from_cstr("abcdefghijk");
             /* return value is unaccepted suffix of input */
-            REQUIRE(buf.append(DCircularBuffer::span_type((byte *)s0.begin(),
-                                                          (byte *)s0.end())).empty());
+            REQUIRE(buf.append(s0).empty());
             REQUIRE(buf.verify_ok(verify_policy::log_only()));
             REQUIRE(buf.mapped_range().size() == getpagesize());
             REQUIRE(buf.occupied_range().size() == s0.size());
             REQUIRE(buf.input_range().size() == s0.size());
 
-            std::string_view s1 = "lmnopq";
-            REQUIRE(buf.append(DCircularBuffer::span_type((byte *)s1.begin(),
-                                                          (byte *)s1.end())).empty());
+            auto s1 = DCircularBuffer::const_span_type::from_cstr("lmnopq");
+            REQUIRE(buf.append(s1).empty());
             REQUIRE(buf.mapped_range().size() == getpagesize());
             REQUIRE(buf.occupied_range().size() == s0.size() + s1.size());