Use value_type in CDataStream where possible

Also, simplify unit tests with the CDataStream::str method.

src/streams.h

@@ -226,7 +226,7 @@ public:
         : nType{nTypeIn},
           nVersion{nVersionIn} {}
 
-    explicit CDataStream(Span<const uint8_t> sp, int nTypeIn, int nVersionIn)
+    explicit CDataStream(Span<const value_type> sp, int nTypeIn, int nVersionIn)
         : vch(sp.data(), sp.data() + sp.size()),
           nType{nTypeIn},
           nVersion{nVersionIn} {}
@@ -254,17 +254,17 @@ public:
     iterator end()                                   { return vch.end(); }
     size_type size() const                           { return vch.size() - nReadPos; }
     bool empty() const                               { return vch.size() == nReadPos; }
-    void resize(size_type n, value_type c=0)         { vch.resize(n + nReadPos, c); }
+    void resize(size_type n, value_type c = value_type{}) { vch.resize(n + nReadPos, c); }
     void reserve(size_type n)                        { vch.reserve(n + nReadPos); }
     const_reference operator[](size_type pos) const  { return vch[pos + nReadPos]; }
     reference operator[](size_type pos)              { return vch[pos + nReadPos]; }
     void clear()                                     { vch.clear(); nReadPos = 0; }
-    iterator insert(iterator it, const uint8_t x) { return vch.insert(it, x); }
-    void insert(iterator it, size_type n, const uint8_t x) { vch.insert(it, n, x); }
+    iterator insert(iterator it, const value_type x) { return vch.insert(it, x); }
+    void insert(iterator it, size_type n, const value_type x) { vch.insert(it, n, x); }
     value_type* data()                               { return vch.data() + nReadPos; }
     const value_type* data() const                   { return vch.data() + nReadPos; }
 
-    void insert(iterator it, std::vector<uint8_t>::const_iterator first, std::vector<uint8_t>::const_iterator last)
+    void insert(iterator it, std::vector<value_type>::const_iterator first, std::vector<value_type>::const_iterator last)
     {
         if (last == first) return;
         assert(last - first > 0);
@@ -278,7 +278,7 @@ public:
             vch.insert(it, first, last);
     }
 
-    void insert(iterator it, const char* first, const char* last)
+    void insert(iterator it, const value_type* first, const value_type* last)
     {
         if (last == first) return;
         assert(last - first > 0);

src/test/streams_tests.cpp

@@ -172,7 +172,7 @@ BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
     ds.Xor(key);
     BOOST_CHECK_EQUAL(
             std::string(expected_xor.begin(), expected_xor.end()),
-            std::string(ds.begin(), ds.end()));
+            ds.str());
 
     in.push_back('\x0f');
     in.push_back('\xf0');
@@ -189,7 +189,7 @@ BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
     ds.Xor(key);
     BOOST_CHECK_EQUAL(
             std::string(expected_xor.begin(), expected_xor.end()),
-            std::string(ds.begin(), ds.end()));
+            ds.str());
 
     // Multi character key
 
@@ -210,7 +210,7 @@ BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
     ds.Xor(key);
     BOOST_CHECK_EQUAL(
             std::string(expected_xor.begin(), expected_xor.end()),
-            std::string(ds.begin(), ds.end()));
+            ds.str());
 }
 
 BOOST_AUTO_TEST_CASE(streams_buffered_file)