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%%% Copyright (C) 2008 - Will Glozer. All rights reserved.
-module(pgsql_fdatetime).
-export([decode/2, encode/2]).
-define(int32, 1/big-signed-unit:32).
-define(postgres_epoc_jdate, 2451545).
-define(mins_per_hour, 60).
-define(secs_per_day, 86400.0).
-define(secs_per_hour, 3600.0).
-define(secs_per_minute, 60.0).
decode(date, <<J:1/big-signed-unit:32>>) -> j2date(?postgres_epoc_jdate + J);
decode(time, <<N:1/big-float-unit:64>>) -> f2time(N);
decode(timetz, <<N:1/big-float-unit:64, TZ:?int32>>) -> {f2time(N), TZ};
decode(timestamp, <<N:1/big-float-unit:64>>) -> f2timestamp(N);
decode(timestamptz, <<N:1/big-float-unit:64>>) -> f2timestamp(N);
decode(interval, <<N:1/big-float-unit:64, D:?int32, M:?int32>>) -> {f2time(N), D, M}.
encode(date, D) -> <<4:?int32, (date2j(D) - ?postgres_epoc_jdate):1/big-signed-unit:32>>;
encode(time, T) -> <<8:?int32, (time2f(T)):1/big-float-unit:64>>;
encode(timetz, {T, TZ}) -> <<12:?int32, (time2f(T)):1/big-float-unit:64, TZ:?int32>>;
encode(timestamp, TS) -> <<8:?int32, (timestamp2f(TS)):1/big-float-unit:64>>;
encode(timestamptz, TS) -> <<8:?int32, (timestamp2f(TS)):1/big-float-unit:64>>;
encode(interval, {T, D, M}) -> <<16:?int32, (time2f(T)):1/big-float-unit:64, 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.
f2time(N) ->
{R1, Hour} = tmodulo(N, ?secs_per_hour),
{R2, Min} = tmodulo(R1, ?secs_per_minute),
{R3, Sec} = tmodulo(R2, 1.0),
case timeround(R3) of
US when US >= 1.0 -> f2time(ceiling(N));
US -> {Hour, Min, Sec + US}
end.
time2f({H, M, S}) ->
((H * ?mins_per_hour + M) * ?secs_per_minute) + S.
f2timestamp(N) ->
case tmodulo(N, ?secs_per_day) of
{T, D} when T < 0 -> f2timestamp2(D - 1 + ?postgres_epoc_jdate, T + ?secs_per_day);
{T, D} -> f2timestamp2(D + ?postgres_epoc_jdate, T)
end.
f2timestamp2(D, T) ->
{_H, _M, S} = Time = f2time(T),
Date = j2date(D),
case tsround(S - trunc(S)) of
N when N >= 1.0 ->
case ceiling(T) of
T2 when T2 > ?secs_per_day -> f2timestamp2(D + 1, 0.0);
T2 -> f2timestamp2(T2, D)
end;
_ -> ok
end,
{Date, Time}.
timestamp2f({Date, Time}) ->
D = date2j(Date) - ?postgres_epoc_jdate,
D * ?secs_per_day + time2f(Time).
tmodulo(T, U) ->
case T < 0 of
true -> Q = ceiling(T / U);
false -> Q = floor(T / U)
end,
case Q of
0 -> {T, Q};
_ -> {T - rint(Q * U), Q}
end.
rint(N) -> round(N) * 1.0.
timeround(J) -> rint(J * 10000000000.0) / 10000000000.0.
tsround(J) -> rint(J * 1000000.0) / 1000000.0.
floor(X) ->
T = erlang:trunc(X),
case (X - T) of
N when N < 0 -> T - 1;
N when N > 0 -> T;
_ -> T
end.
ceiling(X) ->
T = erlang:trunc(X),
case (X - T) of
N when N < 0 -> T;
N when N > 0 -> T + 1;
_ -> T
end.
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