NLWriter: use_std::to_chars() #30

Author: glebbelov

nl-writer2/CMakeLists.txt

@@ -25,7 +25,7 @@ set(NLW2_EXAMPLE_PATH ${NLW2_DIR}/examples)
 set(NLW2_LIB_FILES
 	${NLW2_SRC_PATH}/nl-writer2.cc
   ${NLW2_SRC_PATH}/nl-utils.cc
-  ${NLW2_SRC_PATH}/dtoa.cc
+#  ${NLW2_SRC_PATH}/dtoa.cc
 	${NLW2_SRC_PATH}/nl-solver.cc
 )
 set(NLW2_INC_FILES

nl-writer2/src/nl-writer2.cc

@@ -43,6 +43,8 @@
 #include <cmath>
 #include <cstring>
 #include <string>
+#include <charconv>
+#include <system_error>
 
 #include "mp/nl-writer2.h"
 #include "mp/nl-writer2.hpp"
@@ -152,9 +154,20 @@ int TextFormatter::apr(File& f, const char *fmt, ...)
       while (*fmt++ != 'g');
     case 'g':
       x = va_arg(ap, double);
-#ifdef NL_LIB_USE_SPRINTF
-      snprintf(s = buf,
-               sizeof(buf), "%.*g", output_prec, x);
+#define NL_LIB_USE_TO_CHARS
+#ifdef NL_LIB_USE_TO_CHARS
+      std::to_chars_result res;
+      if (output_prec <= 0)             // shortest representation
+        res = std::to_chars(s = buf, buf+sizeof(buf)-1, x);
+      else                              // 24 characters enough IEEE 754
+        res = std::to_chars(s = buf, buf+sizeof(buf)-1, x,
+                            std::chars_format::general,
+                            output_prec);
+      if (res.ec == std::errc())        // OK
+        *res.ptr = '\0';
+      else
+        Utils().myexit("aprintf / to_chars bug: " +
+                       std::make_error_code(res.ec).message());
 #elif NL_LIB_USE_OWN_GFMT
       NL_LIB_GFMT::gfmt(s = buf, sizeof(buf), x, output_prec);
 #else
@@ -306,6 +319,8 @@ apr(File& f, const char *fmt, ...)
 } // namespace mp
 
 
+#ifndef NL_LIB_USE_TO_CHARS
+
 extern "C" {
 char *
 dtoa_r_dmgay(double dd, int mode, int ndigits,
@@ -459,3 +474,5 @@ void gfmt(char *b, size_t sz, double x, int prec) {
 }
 
 }  // namespace NL_LIB_GFMT
+
+#endif  // NL_LIB_USE_TO_CHARS