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%%% Copyright (C) 2008 - Will Glozer. All rights reserved.
-module(pgsql_idatetime).
-export([decode/2, encode/2]).
-define(int32, 1/big-signed-unit:32).
-define(int64, 1/big-signed-unit:64).
-define(postgres_epoc_jdate, 2451545).
-define(postgres_epoc_usecs, 946684800000000).
-define(mins_per_hour, 60).
-define(secs_per_minute, 60).
-define(usecs_per_day, 86400000000).
-define(usecs_per_hour, 3600000000).
-define(usecs_per_minute, 60000000).
-define(usecs_per_sec, 1000000).
decode(date, <<J:?int32>>) -> j2date(?postgres_epoc_jdate + J);
decode(time, <<N:?int64>>) -> i2time(N);
decode(timetz, <<N:?int64, TZ:?int32>>) -> {i2time(N), TZ};
decode(timestamp, <<N:?int64>>) -> i2timestamp(N);
decode(timestamptz, <<N:?int64>>) -> i2timestamp(N);
decode(interval, <<N:?int64, D:?int32, M:?int32>>) -> {i2time(N), D, M}.
encode(date, D) -> <<4:?int32, (date2j(D) - ?postgres_epoc_jdate):?int32>>;
encode(time, T) -> <<8:?int32, (time2i(T)):?int64>>;
encode(timetz, {T, TZ}) -> <<12:?int32, (time2i(T)):?int64, TZ:?int32>>;
encode(timestamp, TS = {_, _, _}) -> <<8:?int32, (now2i(TS)):?int64>>;
encode(timestamp, TS) -> <<8:?int32, (timestamp2i(TS)):?int64>>;
encode(timestamptz, TS = {_, _, _}) -> <<8:?int32, (now2i(TS)):?int64>>;
encode(timestamptz, TS) -> <<8:?int32, (timestamp2i(TS)):?int64>>;
encode(interval, {T, D, M}) -> <<16:?int32, (time2i(T)):?int64, D:?int32, M:?int32>>.
j2date(N) ->
J = N + 32044,
Q1 = J div 146097,
Extra = (J - Q1 * 146097) * 4 + 3,
J2 = J + 60 + Q1 * 3 + Extra div 146097,
Q2 = J2 div 1461,
J3 = J2 - Q2 * 1461,
Y = J3 * 4 div 1461,
case Y of
0 -> J4 = ((J3 + 306) rem 366) + 123;
_ -> J4 = ((J3 + 305) rem 365) + 123
end,
Year = (Y + Q2 * 4) - 4800,
Q3 = J4 * 2141 div 65536,
Day = J4 - 7834 * Q3 div 256,
Month = (Q3 + 10) rem 12 + 1,
{Year, Month, Day}.
date2j({Y, M, D}) ->
case M > 2 of
true ->
M2 = M + 1,
Y2 = Y + 4800;
false ->
M2 = M + 13,
Y2 = Y + 4799
end,
C = Y2 div 100,
J1 = Y2 * 365 - 32167,
J2 = J1 + (Y2 div 4 - C + C div 4),
J2 + 7834 * M2 div 256 + D.
i2time(N) ->
Hour = N div ?usecs_per_hour,
R1 = N - Hour * ?usecs_per_hour,
Min = R1 div ?usecs_per_minute,
R2 = R1 - Min * ?usecs_per_minute,
Sec = R2 div ?usecs_per_sec,
US = R2 - Sec * ?usecs_per_sec,
{Hour, Min, Sec + US / ?usecs_per_sec}.
time2i({H, M, S}) ->
US = trunc(round(S * ?usecs_per_sec)),
((H * ?mins_per_hour + M) * ?secs_per_minute) * ?usecs_per_sec + US.
i2timestamp(N) ->
case tmodulo(N, ?usecs_per_day) of
{T, D} when T < 0 -> i2timestamp2(D - 1 + ?postgres_epoc_jdate, T + ?usecs_per_day);
{T, D} -> i2timestamp2(D + ?postgres_epoc_jdate, T)
end.
i2timestamp2(D, T) ->
{j2date(D), i2time(T)}.
timestamp2i({Date, Time}) ->
D = date2j(Date) - ?postgres_epoc_jdate,
D * ?usecs_per_day + time2i(Time).
now2i({MegaSecs, Secs, MicroSecs}) ->
(MegaSecs * 1000000 + Secs) * 1000000 + MicroSecs - ?postgres_epoc_usecs.
tmodulo(T, U) ->
case T div U of
0 -> {T, 0};
Q -> {T - (Q * U), Q}
end.
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