build: directly use __TIMESTAMP__

avoid weird conversion from string -> time_t -> string

remove magic inline macros converting string value to time_t.
instead, just pick specific string regions and explicitly constexpr'ify conversion
(ref. https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html)

ntp could lose the value, since we never use it properly
(although, ctime functions do; it is rather tricky with timezones, though)

nofuss could use any value, might as well use the string that is already
provided by the compiler that has the same property as the used timestamp

code/espurna/build.cpp

@@ -244,9 +244,154 @@ alignas(4) static constexpr char Name[] PROGMEM = APP_NAME;
 alignas(4) static constexpr char Version[] PROGMEM = APP_VERSION;
 alignas(4) static constexpr char Author[] PROGMEM = APP_AUTHOR;
 alignas(4) static constexpr char Website[] PROGMEM = APP_WEBSITE;
+alignas(4) static constexpr char BuildTime[] PROGMEM = __TIMESTAMP__;
 
 } // namespace internal
 
+// ref. https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html
+// > __TIMESTAMP__
+// > This macro expands to a string constant that describes the date and time of the last modification of the current source file.
+// > The string constant contains abbreviated day of the week, month, day of the month, time in hh:mm:ss form, year and looks like
+// > "Sun Sep 16 01:03:52 1973". If the day of the month is less than 10, it is padded with a space on the left.
+// >
+// > If GCC cannot determine the current date, it will emit a warning message (once per compilation) and __TIMESTAMP__ will expand to
+// > "??? ??? ?? ??:??:?? ????".
+namespace time {
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^^
+constexpr StringView raw_weekday() {
+ return StringView(&internal::BuildTime[0], &internal::BuildTime[3]);
+}
+static_assert(raw_weekday().length() == 3, "");
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^^
+constexpr StringView raw_month() {
+ return StringView(&internal::BuildTime[4], &internal::BuildTime[7]);
+}
+static_assert(raw_month().length() == 3, "");
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^ (with space, or without)
+constexpr StringView raw_day() {
+ return (internal::BuildTime[8] == ' ')
+ ? StringView(&internal::BuildTime[9], &internal::BuildTime[10])
+ : StringView(&internal::BuildTime[8], &internal::BuildTime[10]);
+}
+static_assert(raw_day().length() < 3, "");
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^
+constexpr StringView raw_hour() {
+ return StringView(&internal::BuildTime[11], &internal::BuildTime[13]);
+}
+static_assert(raw_hour().length() == 2, "");
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^
+constexpr StringView raw_minute() {
+ return StringView(&internal::BuildTime[14], &internal::BuildTime[16]);
+}
+static_assert(raw_minute().length() == 2, "");
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^
+constexpr StringView raw_second() {
+ return StringView(&internal::BuildTime[17], &internal::BuildTime[19]);
+}
+static_assert(raw_second().length() == 2, "");
+
+// "Thu Jan 1 03:00:00 1970"
+// ^^^^
+constexpr StringView raw_year() {
+ return StringView(&internal::BuildTime[20], &internal::BuildTime[24]);
+}
+static_assert(raw_year().length() == 4, "");
+
+#define STRING_EQUALS(EXPECTED, ACTUAL)\
+ (__builtin_memcmp((ACTUAL).c_str(), (EXPECTED), (ACTUAL).length()) == 0)
+
+constexpr int from_raw_weekday(StringView weekday) {
+ return STRING_EQUALS("Sun", weekday) ? 1 :
+ STRING_EQUALS("Mon", weekday) ? 2 :
+ STRING_EQUALS("Tue", weekday) ? 3 :
+ STRING_EQUALS("Wed", weekday) ? 4 :
+ STRING_EQUALS("Thu", weekday) ? 5 :
+ STRING_EQUALS("Fri", weekday) ? 6 :
+ STRING_EQUALS("Sat", weekday) ? 7 : 0;
+}
+
+constexpr int weekday() {
+ return from_raw_weekday(raw_weekday());
+}
+
+constexpr int from_raw_month(StringView month) {
+ return STRING_EQUALS("Jan", month) ? 1 :
+ STRING_EQUALS("Feb", month) ? 2 :
+ STRING_EQUALS("Mar", month) ? 3 :
+ STRING_EQUALS("Apr", month) ? 4 :
+ STRING_EQUALS("May", month) ? 5 :
+ STRING_EQUALS("Jun", month) ? 6 :
+ STRING_EQUALS("Jul", month) ? 7 :
+ STRING_EQUALS("Aug", month) ? 8 :
+ STRING_EQUALS("Sep", month) ? 9 :
+ STRING_EQUALS("Oct", month) ? 10 :
+ STRING_EQUALS("Nov", month) ? 11 :
+ STRING_EQUALS("Dec", month) ? 12 : 0;
+}
+#undef STRING_EQUALS
+
+constexpr int month() {
+ return from_raw_month(raw_month());
+}
+
+constexpr int from_one_digit(char value) {
+ return ((value >= '0') && (value <= '9'))
+ ? (value - '0')
+ : 0;
+}
+
+constexpr int from_two_digits(StringView value) {
+ return (from_one_digit(value.c_str()[0]) * 10)
+ + from_one_digit(value.c_str()[1]);
+}
+
+constexpr int from_raw_day(StringView day) {
+ return (day.length() == 2)
+ ? from_two_digits(day)
+ : from_one_digit(*day.c_str());
+}
+
+constexpr int day() {
+ return from_raw_day(raw_day());
+}
+
+constexpr int hour() {
+ return from_two_digits(raw_hour());
+}
+
+constexpr int minute() {
+ return from_two_digits(raw_minute());
+}
+
+constexpr int second() {
+ return from_two_digits(raw_second());
+}
+
+constexpr int from_raw_year(StringView year) {
+ return (from_one_digit(year.c_str()[0]) * 1000)
+ + (from_one_digit(year.c_str()[1]) * 100)
+ + (from_one_digit(year.c_str()[2]) * 10)
+ + from_one_digit(year.c_str()[3]);
+}
+
+constexpr int year() {
+ return from_raw_year(raw_year());
+}
+
+} // namespace time
+
 constexpr StringView modules() {
  return internal::Modules;
 }
@@ -267,47 +412,34 @@ constexpr StringView website() {
  return internal::Website;
 }
 
-constexpr time_t time() {
- return __UNIX_TIMESTAMP__;
-}
-
-StringView time_string() {
- static const String out = ([]() -> String {
- char buf[32];
-
-#if NTP_SUPPORT
- const time_t ts = time();
- tm now;
-
- gmtime_r(&ts, &now);
- now.tm_year += 1900;
- now.tm_mon += 1;
-#else
- constexpr tm now {
- .tm_year = __TIME_YEAR__,
- .tm_mon = __TIME_MONTH__,
- .tm_mday = __TIME_DAY__,
- .tm_hour = __TIME_HOUR__,
- .tm_min = __TIME_MINUTE__,
- .tm_sec = __TIME_SECOND__,
- };
-#endif
- snprintf_P(buf, sizeof(buf),
- PSTR("%04d-%02d-%02d %02d:%02d:%02d"),
- now.tm_year, now.tm_mon, now.tm_mday,
- now.tm_hour, now.tm_min, now.tm_sec);
-
- return buf;
- })();
-
- return out;
+StringView build_time() {
+ // 1234-56-78 01:02:03
+ static char out[20] = {0};
+
+ if (out[0] == '\0') {
+ // workaround for gcc4.8, explicitly mark as constexpr
+ // otherwise, we will read progmem'ed string at runtime
+ // (double-check the asm when changing anything here)
+ constexpr int year = time::year();
+ constexpr int month = time::month();
+ constexpr int day = time::day();
+ constexpr int hour = time::hour();
+ constexpr int minute = time::minute();
+ constexpr int second = time::second();
+ snprintf_P(out, sizeof(out),
+ PSTR("%4d-%02d-%02d %02d:%02d:%02d"),
+ year, month, day,
+ hour, minute, second);
+ }
+
+ return StringView(out, sizeof(out) - 1);
 }
 
 App get() {
  return App{
  .name = name(),
  .version = version(),
- .build_time = time_string(),
+ .build_time = build_time(),
  .author = author(),
  .website = website(),
  };
@@ -327,8 +459,8 @@ Info info() {
 } // namespace build
 } // namespace espurna
 
-time_t buildTime() {
- return espurna::build::app::time();
+espurna::StringView buildTime() {
+ return espurna::build::app::build_time();
 }
 
 espurna::build::Sdk buildSdk() {

code/espurna/build.h

@@ -41,8 +41,7 @@ struct Info {
 } // namespace build
 } // namespace espruna
 
-time_t buildTime();
-
+espurna::StringView buildTime();
 espurna::build::Info buildInfo();
 
 espurna::build::Sdk buildSdk();

code/espurna/config/all.h

@@ -30,7 +30,6 @@
 #include "custom.h"
 #endif
 
-#include "buildtime.h"
 #include "version.h"
 #include "types.h"
 #include "arduino.h"

code/espurna/nofuss.cpp

@@ -63,9 +63,9 @@ void _nofussConfigure() {
 
  const auto info = buildInfo();
  String device;
- device += info.app.name;
+ device += String(info.app.name);
  device += '_';
- device += info.hardware.device;
+ device += String(info.hardware.device);
  NoFUSSClient.setDevice(device);
 
  const auto version = String(info.app.version);

code/espurna/ntp.cpp

@@ -32,8 +32,6 @@ static_assert(
  "lwip must be configured with SNTP_SERVER_DNS"
 );
 
-#include "config/buildtime.h"
-
 #include "ntp.h"
 #include "ntp_timelib.h"
 #include "utils.h"
@@ -50,10 +48,6 @@ T randomizeDuration(T base, T offset) {
 
 namespace build {
 
-// not strictly necessary, but allow ::time() to return something else than 0
-// (but, still report as 'not synced' to the outside APIs related to time)
-static constexpr time_t InitialTimestamp { __UNIX_TIMESTAMP__ };
-
 // per the lwip recommendations, we delay the actual sntp app start
 // by default, this is expected to be `LWIP_RAND % 5000` (aka [0...5) seconds)
 static constexpr auto StartMin = espurna::duration::Seconds { 1 };
@@ -815,10 +809,6 @@ void setup() {
  DEBUG_MSG_P(PSTR("[NTP] Startup delay: %u (s), Update interval: %u (s)\n"),
  internal::start_delay.count(), internal::update_interval.count());
 
- // start up with some reasonable timestamp already available
- // (notice that this may not be in UTC, if the machine used to build this has a local timezone set)
- setTimestamp(build::InitialTimestamp);
-
  // will be called every time after ntp syncs AND loop() finishes
  settimeofday_cb(onSystemTimeSynced);