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add methods to format TimeSpans
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Uses iso 8601 period format. Includes a constructor from a string.
Makes all toString-like methods const
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@maxbla
maxbla committed Mar 10, 2021
1 parent bd43840 commit 1dca08a
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Showing 2 changed files with 177 additions and 7 deletions.
166 changes: 164 additions & 2 deletions RTClib.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -462,7 +462,7 @@ bool DateTime::isValid() const {
*/
/**************************************************************************/

char *DateTime::toString(char *buffer) {
char *DateTime::toString(char *buffer) const {
uint8_t apTag =
(strstr(buffer, "ap") != nullptr) || (strstr(buffer, "AP") != nullptr);
uint8_t hourReformatted = 0, isPM = false;
Expand Down Expand Up @@ -713,7 +713,7 @@ bool DateTime::operator==(const DateTime &right) const {
@return Timestamp string, e.g. "2020-04-16T18:34:56".
*/
/**************************************************************************/
String DateTime::timestamp(timestampOpt opt) {
String DateTime::timestamp(timestampOpt opt) const {
char buffer[25]; // large enough for any DateTime, including invalid ones

// Generate timestamp according to opt
Expand Down Expand Up @@ -765,6 +765,168 @@ TimeSpan::TimeSpan(int16_t days, int8_t hours, int8_t minutes, int8_t seconds)
/**************************************************************************/
TimeSpan::TimeSpan(const TimeSpan &copy) : _seconds(copy._seconds) {}

/*!
@brief Create a new TimeSpan from an iso8601 formatted period string
If the string is entirely malformed (doesn't begin with P or -) this will
construct a TimeSpan of 0 seconds. If parsing fails before the end of the
string, this constuctor will interpret its argument as the longest
well-formed prefix string.
For example, the string P5M10~ will parse the same as P5M
@param iso8601 the formatted string
*/
TimeSpan::TimeSpan(const char *iso8601) : _seconds(0) {
int32_t sign = 1;
const char *cursor = iso8601;
if (*cursor == '-') {
sign = -1;
cursor++;
}
if (*cursor == 'P') {
cursor++;
} else {
return;
}

char *rest;
long num = strtol(cursor, &rest, 10);
cursor = rest;
if (*cursor == 'D') {
_seconds += sign * SECONDS_PER_DAY * num;
cursor++;
}

if (*cursor == 'T') {
cursor++;
num = strtol(cursor, &rest, 10);
cursor = rest;
} else if (*cursor == '\0') {
return;
} else {
// error: malformed iso8601
return;
}

if (*cursor == 'H') {
_seconds += sign * SECS_PER_MIN * MINS_PER_HOUR * num;
cursor++;
num = strtol(cursor, &rest, 10);
cursor = rest;
}

if (*cursor == 'M') {
_seconds += sign * SECS_PER_MIN * num;
cursor++;
num = strtol(cursor, &rest, 10);
cursor = rest;
}

if (*cursor == 'S') {
_seconds += sign * num;
}
}

/*!
@brief Formats this TimeSpan according to iso8601
See toCharArray for more details on the format
@return String of formatted TimeSpan
*/
String TimeSpan::toString() const {
constexpr size_t buflen = 19;
char buf[buflen];
this->toCharArray(buf, buflen);
return String(buf);
}

// Equivalent to left - right unless that would underflow, otherwise 0
//
// At the time of writing, this is only used in logic in TimeSpan::toCharArray
// This function's inclusion is very unfortunate, and if it is used anywhere
// else, should probably use a template
static size_t sat_sub(size_t left, size_t right) {
if (left > right) {
return left - right;
} else {
return 0;
}
}

/*!
@brief Formats this TimeSpan according to iso8601
Fails (returning 0) if buf is too small to store the result. buf size >= 19
will never fail.
Example: TimeSpan t(32, 23, 54, 11) formats to "P32DT23H54M11S".
@param buf char array to write output. Always contains trailing '\0'.
@param len the length of buf. Must be at least 1.
@return number of bytes written excluding trailing '\0' or 0 on failure
*/
size_t TimeSpan::toCharArray(char *buf, size_t len) const {
if (len == 0) {
return 0;
}

size_t written = 0;

if (_seconds == 0) {
written += snprintf(buf, len, "PT0S");
if (written >= len) {
buf[len - 1] = '\0';
return 0;
} else {
return written;
}
}

// Keep sign separate from tmp to prevent overflow caused by -1 * INT_MIN
int8_t sign = _seconds > 0 ? 1 : -1;
int32_t tmp = _seconds;
int8_t seconds = sign * (tmp % SECS_PER_MIN);
// Fold in sign - while dividing by SECS_PER_MIN, tmp can no longer overflow
tmp /= sign * SECS_PER_MIN;
int8_t minutes = tmp % MINS_PER_HOUR;
tmp /= MINS_PER_HOUR;
int8_t hours = tmp % HOURS_PER_DAY;
int16_t days = tmp / HOURS_PER_DAY;

if (_seconds < 0) {
written += snprintf(buf + written, sat_sub(len, written), "-P");
} else {
written += snprintf(buf + written, sat_sub(len, written), "P");
}

if (days > 0) {
written += snprintf(buf + written, sat_sub(len, written), "%dD", days);
}

if (hours > 0 || minutes > 0 || seconds > 0) {
written += snprintf(buf + written, sat_sub(len, written), "%s", "T");

if (hours > 0) {
written += snprintf(buf + written, sat_sub(len, written), "%dH", hours);
}
if (minutes > 0) {
written += snprintf(buf + written, sat_sub(len, written), "%dM", minutes);
}
if (seconds > 0) {
written += snprintf(buf + written, sat_sub(len, written), "%dS", seconds);
}
}

if (written >= len) {
buf[len - 1] = '\0';
return 0;
} else {
buf[written] = '\0';
return written;
}
}

/**************************************************************************/
/*!
@brief Add two TimeSpans
Expand Down
18 changes: 13 additions & 5 deletions RTClib.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -88,7 +88,7 @@ class DateTime {
DateTime(const __FlashStringHelper *date, const __FlashStringHelper *time);
DateTime(const char *iso8601date);
bool isValid() const;
char *toString(char *buffer);
char *toString(char *buffer) const;

/*!
@brief Return the year.
Expand Down Expand Up @@ -145,7 +145,7 @@ class DateTime {
TIMESTAMP_TIME, //!< `hh:mm:ss`
TIMESTAMP_DATE //!< `YYYY-MM-DD`
};
String timestamp(timestampOpt opt = TIMESTAMP_FULL);
String timestamp(timestampOpt opt = TIMESTAMP_FULL) const;

DateTime operator+(const TimeSpan &span);
DateTime operator-(const TimeSpan &span);
Expand Down Expand Up @@ -215,6 +215,9 @@ class TimeSpan {
TimeSpan(int32_t seconds = 0);
TimeSpan(int16_t days, int8_t hours, int8_t minutes, int8_t seconds);
TimeSpan(const TimeSpan &copy);
TimeSpan(const char *iso8601);
String toString() const;
size_t toCharArray(char *buf, size_t len) const;

/*!
@brief Number of days in the TimeSpan
Expand All @@ -228,21 +231,23 @@ class TimeSpan {
e.g. 4 days, 3 hours - NOT 99 hours
@return int8_t hours
*/
int8_t hours() const { return _seconds / 3600 % 24; }
int8_t hours() const {
return _seconds / (SECS_PER_MIN * MINS_PER_HOUR) % HOURS_PER_DAY;
}
/*!
@brief Number of minutes in the TimeSpan
This is not the total minutes, it includes days/hours
e.g. 4 days, 3 hours, 27 minutes
@return int8_t minutes
*/
int8_t minutes() const { return _seconds / 60 % 60; }
int8_t minutes() const { return _seconds / SECS_PER_MIN % MINS_PER_HOUR; }
/*!
@brief Number of seconds in the TimeSpan
This is not the total seconds, it includes the days/hours/minutes
e.g. 4 days, 3 hours, 27 minutes, 7 seconds
@return int8_t seconds
*/
int8_t seconds() const { return _seconds % 60; }
int8_t seconds() const { return _seconds % SECS_PER_MIN; }
/*!
@brief Total number of seconds in the TimeSpan, e.g. 358027
@return int32_t seconds
Expand All @@ -254,6 +259,9 @@ class TimeSpan {

protected:
int32_t _seconds; ///< Actual TimeSpan value is stored as seconds
static constexpr int32_t SECS_PER_MIN = 60; ///< Number of seconds in a minute
static constexpr int32_t MINS_PER_HOUR = 60; ///< Number of minutes in an hour
static constexpr int32_t HOURS_PER_DAY = 24; ///< Number of hours in a day
};

/** DS1307 SQW pin mode settings */
Expand Down

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