src/include/pgtime.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pgtime.h
   4  *        PostgreSQL internal timezone library
   5  *
   6  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *        src/include/pgtime.h
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #ifndef _PGTIME_H
  14 #define _PGTIME_H
  15
  16
  17 /*
  18  * The API of this library is generally similar to the corresponding
  19  * C library functions, except that we use pg_time_t which (we hope) is
  20  * 64 bits wide, and which is most definitely signed not unsigned.
  21  */
  22
  23 typedef int64 pg_time_t;
  24
  25 /*
  26  * Data structure representing a broken-down timestamp.
  27  *
  28  * CAUTION: the IANA timezone library (src/timezone/) follows the POSIX
  29  * convention that tm_mon counts from 0 and tm_year is relative to 1900.
  30  * However, Postgres' datetime functions generally treat tm_mon as counting
  31  * from 1 and tm_year as relative to 1 BC.  Be sure to make the appropriate
  32  * adjustments when moving from one code domain to the other.
  33  */
  34 struct pg_tm
  35 {
  36         int                     tm_sec;
  37         int                     tm_min;
  38         int                     tm_hour;
  39         int                     tm_mday;
  40         int                     tm_mon;                 /* see above */
  41         int                     tm_year;                /* see above */
  42         int                     tm_wday;
  43         int                     tm_yday;
  44         int                     tm_isdst;
  45         long int        tm_gmtoff;
  46         const char *tm_zone;
  47 };
  48
  49 /* These structs are opaque outside the timezone library */
  50 typedef struct pg_tz pg_tz;
  51 typedef struct pg_tzenum pg_tzenum;
  52
  53 /* Maximum length of a timezone name (not including trailing null) */
  54 #define TZ_STRLEN_MAX 255
  55
  56 /* these functions are in localtime.c */
  57
  58 extern struct pg_tm *pg_localtime(const pg_time_t *timep, const pg_tz *tz);
  59 extern struct pg_tm *pg_gmtime(const pg_time_t *timep);
  60 extern int      pg_next_dst_boundary(const pg_time_t *timep,
  61                                                                  long int *before_gmtoff,
  62                                                                  int *before_isdst,
  63                                                                  pg_time_t *boundary,
  64                                                                  long int *after_gmtoff,
  65                                                                  int *after_isdst,
  66                                                                  const pg_tz *tz);
  67 extern bool pg_interpret_timezone_abbrev(const char *abbrev,
  68                                                                                  const pg_time_t *timep,
  69                                                                                  long int *gmtoff,
  70                                                                                  int *isdst,
  71                                                                                  const pg_tz *tz);
  72 extern bool pg_get_timezone_offset(const pg_tz *tz, long int *gmtoff);
  73 extern const char *pg_get_timezone_name(pg_tz *tz);
  74 extern bool pg_tz_acceptable(pg_tz *tz);
  75
  76 /* these functions are in strftime.c */
  77
  78 extern size_t pg_strftime(char *s, size_t maxsize, const char *format,
  79                                                   const struct pg_tm *t);
  80
  81 /* these functions and variables are in pgtz.c */
  82
  83 extern PGDLLIMPORT pg_tz *session_timezone;
  84 extern PGDLLIMPORT pg_tz *log_timezone;
  85
  86 extern void pg_timezone_initialize(void);
  87 extern pg_tz *pg_tzset(const char *tzname);
  88 extern pg_tz *pg_tzset_offset(long gmtoffset);
  89
  90 extern pg_tzenum *pg_tzenumerate_start(void);
  91 extern pg_tz *pg_tzenumerate_next(pg_tzenum *dir);
  92 extern void pg_tzenumerate_end(pg_tzenum *dir);
  93
  94 #endif                                                  /* _PGTIME_H */