[base] Added function to convert long to string with fixed output length

Signed-off-by: S. Kozyr <s.trump@gmail.com>

base/base_tests/string_utils_test.cpp

@@ -678,6 +678,17 @@ UNIT_TEST(to_string_dac)
   TEST_EQUAL(strings::to_string_dac(1.0 + 1.0E-14, 15), "1.00000000000001", ());
 }
 
+UNIT_TEST(to_string_prec)
+{
+  TEST_EQUAL(strings::to_string_prec(123, 5), "00123", ());
+  TEST_EQUAL(strings::to_string_prec(99, 3), "099", ());
+  TEST_EQUAL(strings::to_string_prec(0, 4), "0000", ());
+  TEST_EQUAL(strings::to_string_prec(-10, 4), "-0010", ());
+  TEST_EQUAL(strings::to_string_prec(545, 1), "545", ());
+  TEST_EQUAL(strings::to_string_prec(1073741824, 0), "1073741824", ());
+}
+
+
 struct FunctorTester
 {
   size_t & m_index;

base/string_utils.cpp

@@ -408,6 +408,33 @@ std::string to_string_dac(double d, int dac)
   return ss.str();
 }
 
+std::string to_string_prec(long l, int prec)
+{
+  long absL = abs(l);
+  int digs = 0;
+  while (absL > 0L)
+  {
+    absL /= 10;
+    ++digs;
+  }
+  if (digs == 0)
+      digs = 1;
+
+  std::ostringstream ss;
+  if (l<0)
+      ss << '-';
+
+  while(prec > digs)
+  {
+      ss << '0';
+      --prec;
+  }
+
+  ss << l;
+
+  return ss.str();
+}
+
 bool IsHTML(std::string const & utf8)
 {
   std::string::const_iterator it = utf8.begin();

base/string_utils.hpp

@@ -566,6 +566,9 @@ inline std::string to_string(uint64_t i) { return std::to_string(i); }
 std::string to_string_dac(double d, int dac);
 //@}
 
+// Get string with fixed count of digits. Extra '0' are added at the begining to fit size.
+std::string to_string_prec(long l, int prec);
+
 template <typename IterT1, typename IterT2>
 bool StartsWith(IterT1 beg, IterT1 end, IterT2 begPrefix, IterT2 endPrefix)
 {