Timezone database

Read access to the timezone database stored in resources. More...

Data Structures
struct	TimezoneDSTRule
	Transition between standard time and DST. More...

Enumerations
enum	DSTRuleFlags { TIMEZONE_FLAG_DAY_DECREMENT = 1 << 0 , TIMEZONE_FLAG_STANDARD_TIME = 1 << 1 , TIMEZONE_FLAG_UTC_TIME = 1 << 2 }
	Flags of a TimezoneDSTRule. More...

Functions
int	timezone_database_get_region_count (void)
	Get the number of regions in the database.
bool	timezone_database_load_region_info (uint16_t region_id, TimezoneInfo *tz_info)
	Load the timezone information of a region.
bool	timezone_database_load_region_name (uint16_t region_id, char *region_name)
	Load the name of a region.
bool	timezone_database_load_dst_rule (uint8_t dst_id, TimezoneDSTRule *start, TimezoneDSTRule *end)
	Load the pair of DST rules of a DST id.
int	timezone_database_find_region_by_name (const char *region_name, int region_name_length)
	Find a region by name.

Detailed Description

Read access to the timezone database stored in resources.

The database holds the regions (continent/city name, UTC offset, abbreviation and DST rule index), pairs of DST rules, and links mapping legacy region names to regions.

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Data Structure Documentation

TimezoneDSTRule

struct TimezoneDSTRule

Transition between standard time and DST.

Matches the storage format exactly; do not change it without changing the database format.

Data Fields
char	ds_label	'D' when entering DST, 'S' when entering standard time, or a NUL character if the timezone does not observe DST.
uint8_t	flag	DSTRuleFlags bits.
uint8_t	hour	Hour of the day; values of 24 and above roll over to the following days.
uint8_t	mday	Day of the month, starting at 1.
uint8_t	minute	Minute of the hour.
uint8_t	month	Month, 0 being January.
uint8_t	wday	Day of the week, 0 being Sunday, or 255 for any day.

Enumeration Type Documentation

DSTRuleFlags

enum DSTRuleFlags

Flags of a TimezoneDSTRule.

Enumerator
TIMEZONE_FLAG_DAY_DECREMENT	Search backwards, rather than forwards, from TimezoneDSTRule::mday for the weekday.
TIMEZONE_FLAG_STANDARD_TIME	The transition time is in standard time rather than wall-clock time.
TIMEZONE_FLAG_UTC_TIME	The transition time is in UTC rather than wall-clock time.

Function Documentation

timezone_database_find_region_by_name()

int timezone_database_find_region_by_name	(	const char *	region_name,
		int	region_name_length
	)

Find a region by name.

Region names are matched on their first region_name_length characters. Links are searched next, as phones may send legacy names such as "US/Pacific".

Parameters

region_name	Name to look up, need not be NUL terminated.
region_name_length	Length of region_name.

Returns

Region id, or -1 if not found.

timezone_database_get_region_count()

int timezone_database_get_region_count

(

void

)

Get the number of regions in the database.

Returns

Number of regions.

timezone_database_load_dst_rule()

bool timezone_database_load_dst_rule	(	uint8_t	dst_id,
		TimezoneDSTRule *	start,
		TimezoneDSTRule *	end
	)

Load the pair of DST rules of a DST id.

Parameters

	dst_id	DST rule index, starting at 1.
[out]	start	Rule entering DST.
[out]	end	Rule leaving DST.

Returns

True on success, false if dst_id is invalid, the timezone does not observe DST or the database is malformed.

timezone_database_load_region_info()

bool timezone_database_load_region_info	(	uint16_t	region_id,
		TimezoneInfo *	tz_info
	)

Load the timezone information of a region.

TimezoneInfo::dst_start and TimezoneInfo::dst_end are set to 0; the DST period is not computed.

Parameters

	region_id	Region to look up.
[out]	tz_info	Timezone information.

Returns

True on success, false if the database could not be read.

timezone_database_load_region_name()

bool timezone_database_load_region_name	(	uint16_t	region_id,
		char *	region_name
	)

Load the name of a region.

Parameters

	region_id	Region to look up.
[out]	region_name	NUL terminated "continent/city" name, in a buffer of at least TIMEZONE_NAME_LENGTH bytes.

Returns

True on success, false if region_id is invalid.