testing precision

src/datetime_io_core.cpp

@@ -0,0 +1,151 @@
+#include "datetime_io_core.hpp"
+#include <cctype>
+#include <charconv>
+#include <cstdio>
+
+inline const char *skipws(const char *line) noexcept {
+  const char *c = line;
+  while (*c && (*c == ' ' || *c == '/' || *c == '-' || *c == 'T' || *c == ':'))
+    ++c;
+  return c;
+}
+
+/** @brief Count decimal digits in a float
+ *
+ * Examples:
+ * assert(count_decimal_digits(".123456789") == 9);
+ * assert(count_decimal_digits("  .123456789") == 9);
+ * assert(count_decimal_digits("12.123456789") == 9);
+ * assert(count_decimal_digits("12.123456789.123") == 9);
+ * assert(count_decimal_digits("12.123456789.A23") == 9);
+ * assert(count_decimal_digits("12.123456789EA23") == 9);
+ */
+inline int count_decimal_digits(const char *fltstr) noexcept {
+  /* go to decimal part */
+  while (fltstr && *fltstr != '.')
+    ++fltstr;
+  if (fltstr && *fltstr == '.') {
+    /* count digits */
+    ++fltstr;
+    const char *dgtc = fltstr;
+    while (std::isdigit(*dgtc))
+      ++dgtc;
+    return (dgtc - fltstr);
+  } else {
+    /* no decimal digits */
+    return 0;
+  }
+}
+
+int dso::datetime_io_core::get_two_ints(const char *str, int *ints,
+                                        int max_chars,
+                                        const char **end) noexcept {
+  if (end)
+    *end = str;
+  const char *start = skipws(str);
+  const char *c = str;
+
+  /* resolve the three ints */
+  for (int i = 0; i < 2; ++i) {
+    auto tres = std::from_chars(skipws(c), start + max_chars, ints[i]);
+    if (tres.ec != std::errc{}) {
+      return i + 1;
+    }
+    c = tres.ptr;
+  }
+
+  /* assign pointer to first non-parsed character */
+  if (end)
+    *end = c;
+
+  return 0;
+}
+
+int dso::datetime_io_core::get_three_ints(const char *str, int *ints,
+                                          int max_chars,
+                                          const char **end) noexcept {
+  if (end)
+    *end = str;
+  const char *c = str;
+  const char *start = skipws(str);
+
+  /* resolve the three ints */
+  for (int i = 0; i < 3; ++i) {
+    auto tres = std::from_chars(skipws(c), start + max_chars, ints[i]);
+    if (tres.ec != std::errc{}) {
+      return i + 1;
+    }
+    c = tres.ptr;
+  }
+
+  /* assign pointer to first non-parsed character */
+  if (end)
+    *end = c;
+
+  return 0;
+}
+
+int dso::datetime_io_core::get_three_ints(const char *str, long *ints,
+                                          int max_chars,
+                                          const char **end) noexcept {
+  if (end)
+    *end = str;
+  const char *c = str;
+  const char *start = skipws(str);
+
+  /* resolve the three long ints */
+  for (int i = 0; i < 3; ++i) {
+    auto tres = std::from_chars(skipws(c), start + max_chars, ints[i]);
+    if (tres.ec != std::errc{}) {
+      return i + 1;
+    }
+    c = tres.ptr;
+  }
+
+  /* assign pointer to first non-parsed character */
+  if (end)
+    *end = c;
+
+  return 0;
+}
+
+int dso::datetime_io_core::get_two_ints_double(const char *str, int *ints,
+                                               double &flt, int max_chars,
+                                               const char **end) noexcept {
+  if (end)
+    *end = str;
+  const char *c = str;
+  const char *start = skipws(str);
+
+  /* resolve the two ints */
+  for (int i = 0; i < 2; ++i) {
+    auto tres = std::from_chars(skipws(c), start + max_chars, ints[i]);
+    if (tres.ec != std::errc{}) {
+      return i + 1;
+    }
+    c = tres.ptr;
+  }
+
+  /* before parsing the next floating point number, count its decimal digits
+   * If more than nanoseconds, issue a warning
+   */
+  if (count_decimal_digits(skipws(c)) > 12) {
+    fprintf(stderr, "[WARNING] Reading in date with resolution larger than "
+                    "nanoseconds will lead to loss of precision!\n");
+    fprintf(stderr,
+            "[WARNING] Date/Time resolved from string \'%s\' (traceback: %s)\n",
+            str, __func__);
+  }
+
+  /* resolve one double */
+  auto tres = std::from_chars(skipws(c), start + max_chars, flt);
+  if (tres.ec != std::errc{}) {
+    return 3;
+  }
+
+  /* assign pointer to first non-parsed character */
+  if (end)
+    *end = tres.ptr;
+
+  return 0;
+}

src/datetime_io_core.hpp

@@ -1,4 +1,5 @@
-/** Datetime input/output (i.e. read/write) core utilities and definitions.
+/** @file 
+ * Datetime input/output (i.e. read/write) core utilities and definitions.
  */
 
 #ifndef __DSO_DATETIME_IO_CORE_HPP__
@@ -7,6 +8,21 @@
 namespace dso {
 enum class YMDFormat { YYYYMMDD, DDMMYYYY, YYYYDDD, YYMMDD, DDMMYY };
 enum class HMSFormat { HHMMSS, HHMMSSF };
+
+namespace datetime_io_core {
+int get_two_ints(const char *str, int *ints, int max_chars,
+                 const char **end) noexcept;
+
+int get_three_ints(const char *str, int *ints, int max_chars,
+                   const char **end) noexcept;
+
+int get_three_ints(const char *str, long *ints, int max_chars,
+                   const char **end) noexcept;
+
+int get_two_ints_double(const char *str, int *ints, double &flt, int max_chars,
+                        const char **end) noexcept;
+} /* namespace datetime_io_core */
+
 } /* namespace dso */
 
 #endif