Custom overload for to_string(uint64_t) - speedup feature reading.

2 files changed, 86 insertions, 7 deletions

diff --git a/base/base_tests/string_utils_test.cpp b/base/base_tests/string_utils_test.cpp
index b42d9bf70d..be6d3cbfef 100644
--- a/base/base_tests/string_utils_test.cpp
+++ b/base/base_tests/string_utils_test.cpp
@@ -218,10 +218,23 @@ UNIT_TEST(to_int64)
 
 UNIT_TEST(to_string)
 {
+  TEST_EQUAL(strings::to_string(0), "0", ());
+  TEST_EQUAL(strings::to_string(-0), "0", ());
+  TEST_EQUAL(strings::to_string(1), "1", ());
   TEST_EQUAL(strings::to_string(-1), "-1", ());
   TEST_EQUAL(strings::to_string(1234567890), "1234567890", ());
+  TEST_EQUAL(strings::to_string(-987654321), "-987654321", ());
   TEST_EQUAL(strings::to_string(0.56), "0.56", ());
   TEST_EQUAL(strings::to_string(-100.2), "-100.2", ());
+
+  // 6 digits after the comma with rounding - it's a default behavior
+  TEST_EQUAL(strings::to_string(-0.66666666), "-0.666667", ());
+
+  TEST_EQUAL(strings::to_string(-1.0E2), "-100", ());
+  TEST_EQUAL(strings::to_string(1.0E-2), "0.01", ());
+
+  TEST_EQUAL(strings::to_string(123456789123456789ULL), "123456789123456789", ());
+  TEST_EQUAL(strings::to_string(-987654321987654321LL), "-987654321987654321", ());
 }
 
 struct FunctorTester
diff --git a/base/string_utils.hpp b/base/string_utils.hpp
index 474b186cb9..98dd14544e 100644
--- a/base/string_utils.hpp
+++ b/base/string_utils.hpp
@@ -5,6 +5,7 @@
 #include "../std/string.hpp"
 #include "../std/stdint.hpp"
 #include "../std/sstream.hpp"
+#include "../std/limits.hpp"
 
 #include "../3party/utfcpp/source/utf8/unchecked.h"
 
@@ -154,23 +155,88 @@ template <class T, size_t N, class TT> bool IsInArray(T (&arr) [N], TT const & t
   return false;
 }
 
+/// @name From string to numeric.
+//@{
 bool to_int(char const * s, int & i);
 bool to_uint64(char const * s, uint64_t & i);
 bool to_int64(char const * s, int64_t & i);
 bool to_double(char const * s, double & d);
 
-template <class T>
-string to_string(T i)
+inline bool to_int(string const & s, int & i) { return to_int(s.c_str(), i); }
+inline bool to_uint64(string const & s, uint64_t & i) { return to_uint64(s.c_str(), i); }
+inline bool to_int64(string const & s, int64_t & i) { return to_int64(s.c_str(), i); }
+inline bool to_double(string const & s, double & d) { return to_double(s.c_str(), d); }
+//@}
+
+/// @name From numeric to string.
+//@{
+inline string to_string(string const & s)
+{
+  return s;
+}
+
+inline string to_string(char const * s)
+{
+  return s;
+}
+
+template <typename T> string to_string(T t)
 {
   ostringstream ss;
-  ss << i;
+  ss << t;
   return ss.str();
 }
 
-inline bool to_int(string const & s, int & i) { return to_int(s.c_str(), i); }
-inline bool to_uint64(string const & s, uint64_t & i) { return to_uint64(s.c_str(), i); }
-inline bool to_int64(string const & s, int64_t & i) { return to_int64(s.c_str(), i); }
-inline bool to_double(string const & s, double & d) { return to_double(s.c_str(), d); }
+namespace impl
+{
+
+template <typename T> char * to_string_digits(char * buf, T i)
+{
+  do
+  {
+    --buf;
+    *buf = static_cast<char>(i % 10) + '0';
+    i = i / 10;
+  } while (i != 0);
+  return buf;
+}
+
+template <typename T> string to_string_signed(T i)
+{
+  bool const negative = i < 0;
+  int const sz = numeric_limits<T>::digits10 + 1;
+  char buf[sz];
+  char * end = buf + sz;
+  char * beg = to_string_digits(end, negative ? -i : i);
+  if (negative)
+  {
+    --beg;
+    *beg = '-';
+  }
+  return string(beg, end - beg);
+}
+
+template <typename T> string to_string_unsigned(T i)
+{
+  int const sz = numeric_limits<T>::digits10;
+  char buf[sz];
+  char * end = buf + sz;
+  char * beg = to_string_digits(end, i);
+  return string(beg, end - beg);
+}
+
+}
+
+inline string to_string(int64_t i)
+{
+  return impl::to_string_signed(i);
+}
+
+inline string to_string(uint64_t i)
+{
+  return impl::to_string_unsigned(i);
+}
+//@}
 
 /*
 template <typename ItT, typename DelimiterT>