Add to_static_string:

This function converts integers to their decimal
representation as a static string.

In addition, static_string::resize no longer initializes
characters if the new size is larger.

CHANGELOG.md

@@ -1,3 +1,9 @@
+Version 40
+
+* Add to_static_string
+
+--------------------------------------------------------------------------------
+
 Version 39
 
 Beast versions are now identified by a single integer which

doc/quickref.xml

@@ -183,6 +183,7 @@
             <member><link linkend="beast.ref.prepare_buffer">prepare_buffer</link></member>
             <member><link linkend="beast.ref.prepare_buffers">prepare_buffers</link></member>
             <member><link linkend="beast.ref.system_category">system_category</link></member>
+            <member><link linkend="beast.ref.to_static_string">to_static_string</link></member>
           </simplelist>
           <bridgehead renderas="sect3">Macros</bridgehead>
           <simplelist type="vert" columns="1">

include/beast/core/detail/static_string.hpp

@@ -58,6 +58,16 @@ lexicographical_compare(
         s1.data(), s1.size(), s2.data(), s2.size());
 }
 
+// Maximum number of characters in the decimal
+// representation of a binary number
+inline
+std::size_t constexpr
+max_digits(std::size_t bytes)
+{
+    return static_cast<std::size_t>(
+        bytes * 2.41) + 1;
+}
+
 } // detail
 } // beast
 

include/beast/core/impl/static_string.ipp

@@ -450,6 +450,18 @@ copy(CharT* dest, size_type count, size_type pos) const ->
     return str.size();
 }
 
+template<std::size_t N, class CharT, class Traits>
+void
+static_string<N, CharT, Traits>::
+resize(std::size_t n)
+{
+    if(n > max_size())
+        throw detail::make_exception<std::length_error>(
+            "n > max_size()", __FILE__, __LINE__);
+    n_ = n;
+    term();
+}
+
 template<std::size_t N, class CharT, class Traits>
 void
 static_string<N, CharT, Traits>::
@@ -518,6 +530,76 @@ assign_char(CharT ch, std::false_type) ->
         "max_size() == 0", __FILE__, __LINE__);
 }
 
+namespace detail {
+
+template<class Integer>
+static_string<1+max_digits(sizeof(Integer))>
+to_static_string(Integer x, std::true_type)
+{
+    if(x == 0)
+        return {'0'};
+    static_string<1 + detail::max_digits(
+        sizeof(Integer))> s;
+    if(x < 0)
+    {
+        x = -x;
+        char buf[max_digits(sizeof(x))];
+        char* p = buf;
+        for(;x > 0; x /= 10)
+            *p++ = "0123456789"[x % 10];
+        s.resize(1 + p - buf);
+        s[0] = '-';
+        auto d = &s[1];
+        while(p > buf)
+            *d++ = *--p;
+    }
+    else
+    {
+        char buf[max_digits(sizeof(x))];
+        char* p = buf;
+        for(;x > 0; x /= 10)
+            *p++ = "0123456789"[x % 10];
+        s.resize(p - buf);
+        auto d = &s[0];
+        while(p > buf)
+            *d++ = *--p;
+    }
+    return s;
+}
+
+template<class Integer>
+static_string<max_digits(sizeof(Integer))>
+to_static_string(Integer x, std::false_type)
+{
+    if(x == 0)
+        return {'0'};
+    char buf[max_digits(sizeof(x))];
+    char* p = buf;
+    for(;x > 0; x /= 10)
+        *p++ = "0123456789"[x % 10];
+    static_string<detail::max_digits(
+        sizeof(Integer))> s;
+    s.resize(p - buf);
+    auto d = &s[0];
+    while(p > buf)
+        *d++ = *--p;
+    return s;
+}
+
+} // detail
+
+template<class Integer>
+static_string<detail::max_digits(sizeof(Integer))>
+to_static_string(Integer x)
+{
+    static_assert(
+        std::is_integral<Integer>::value,
+        "Integral requirements not met");
+    return detail::to_static_string(
+        x, std::integral_constant<bool,
+            std::is_signed<Integer>::value>{});
+}
+
 } // beast
 
 #endif

include/beast/core/static_string.hpp

@@ -31,6 +31,8 @@ namespace beast {
     imposes a natural small upper limit on the size of a value.
 
     @note The stored string is always null-terminated.
+
+    @see @ref to_static_string 
 */
 template<
     std::size_t N,
@@ -783,13 +785,10 @@ public:
     /** Changes the number of characters stored.
 
         If the resulting string is larger, the new
-        characters are initialized to zero.
+        characters are uninitialized.
     */
     void
-    resize(std::size_t n)
-    {
-        resize(n, 0);
-    }
+    resize(std::size_t n);
 
     /** Changes the number of characters stored.
 
@@ -1098,6 +1097,23 @@ operator<<(std::basic_ostream<CharT, Traits>& os,
         beast::basic_string_view<CharT, Traits>>(str);
 }
 
+//
+// Numeric conversions
+//
+
+/** Returns a static string representing an integer as a decimal.
+
+    @param x The signed or unsigned integer to convert.
+    This must be an integral type.
+
+    @return A @ref static_string with an implementation defined
+    maximum size large enough to hold the longest possible decimal
+    representation of any integer of the given type.
+*/
+template<class Integer>
+static_string<detail::max_digits(sizeof(Integer))>
+to_static_string(Integer x);
+
 } // beast
 
 #include <beast/core/impl/static_string.ipp>

test/core/static_string.cpp

@@ -1433,7 +1433,29 @@ public:
         pass();
     }
 
-    void run() override
+    void
+    testToStaticString()
+    {
+        BEAST_EXPECT(to_static_string<long>(0) == "0");
+        BEAST_EXPECT(to_static_string<long>(1) == "1");
+        BEAST_EXPECT(to_static_string<long>(0xffff) == "65535");
+        BEAST_EXPECT(to_static_string<long>(0x10000) == "65536");
+        BEAST_EXPECT(to_static_string<long long>(0xffffffff) == "4294967295");
+
+        BEAST_EXPECT(to_static_string<long>(-1) == "-1");
+        BEAST_EXPECT(to_static_string<long>(-65535) == "-65535");
+        BEAST_EXPECT(to_static_string<long>(-65536) == "-65536");
+        BEAST_EXPECT(to_static_string<long long>(-4294967295ll) == "-4294967295");
+
+        BEAST_EXPECT(to_static_string<unsigned long>(0) == "0");
+        BEAST_EXPECT(to_static_string<unsigned long>(1) == "1");
+        BEAST_EXPECT(to_static_string<unsigned long>(0xffff) == "65535");
+        BEAST_EXPECT(to_static_string<unsigned long>(0x10000) == "65536");
+        BEAST_EXPECT(to_static_string<unsigned long>(0xffffffff) == "4294967295");
+    }
+
+    void
+    run() override
     {
         testConstruct();
         testAssign();
@@ -1445,6 +1467,7 @@ public:
         testSwap();
 
         testGeneral();
+        testToStaticString();
     }
 };