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Optimize parsing microseconds and offset in calendar #14169

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Merged
merged 2 commits into from
Jan 10, 2025
Merged

Optimize parsing microseconds and offset in calendar #14169

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e8679d6
dk_optimize_parsing_microseconds_and_offset
dkuku Jan 10, 2025
5731c43
drop ms precision > 6
dkuku Jan 10, 2025
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64 changes: 35 additions & 29 deletions lib/elixir/lib/calendar/iso.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -1279,15 +1279,16 @@ defmodule Calendar.ISO do
def microseconds_to_iodata(microsecond, 6), do: zero_pad(microsecond, 6)

def microseconds_to_iodata(microsecond, precision) do
num = div(microsecond, div_factor(precision))
num = div(microsecond, scale_factor(precision))
zero_pad(num, precision)
end

defp div_factor(1), do: 100_000
defp div_factor(2), do: 10_000
defp div_factor(3), do: 1_000
defp div_factor(4), do: 100
defp div_factor(5), do: 10
defp scale_factor(1), do: 100_000
defp scale_factor(2), do: 10_000
defp scale_factor(3), do: 1_000
defp scale_factor(4), do: 100
defp scale_factor(5), do: 10
defp scale_factor(6), do: 1

defp time_to_iodata_format(hour, minute, second, :extended) do
[zero_pad(hour, 2), ?:, zero_pad(minute, 2), ?: | zero_pad(second, 2)]
Expand Down Expand Up @@ -1988,16 +1989,13 @@ defmodule Calendar.ISO do
end

defp parse_microsecond("." <> rest) do
case parse_microsecond(rest, 0, "") do
{"", 0, _} ->
case parse_microsecond(rest, 0, []) do
{[], 0, _} ->
:error

{microsecond, precision, rest} when precision in 1..6 ->
pad = String.duplicate("0", 6 - byte_size(microsecond))
{{String.to_integer(microsecond <> pad), precision}, rest}

{microsecond, _precision, rest} ->
{{String.to_integer(binary_part(microsecond, 0, 6)), 6}, rest}
{microsecond, precision, rest} ->
scale = scale_factor(precision)
{{:erlang.list_to_integer(microsecond) * scale, precision}, rest}
end
end

Expand All @@ -2009,34 +2007,42 @@ defmodule Calendar.ISO do
{{0, 0}, rest}
end

defp parse_microsecond(<<head, tail::binary>>, 6, acc) when head in ?0..?9,
do: parse_microsecond(tail, 6, acc)

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@dkuku dkuku Jan 10, 2025 •
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when there is more than 6 digits of milliseconds we just drop the head and continue.
It does not require special handling in the caller

defp parse_microsecond(<<head, tail::binary>>, precision, acc) when head in ?0..?9,
do: parse_microsecond(tail, precision + 1, <<acc::binary, head>>)
do: parse_microsecond(tail, precision + 1, [head | acc])

defp parse_microsecond(rest, precision, acc), do: {acc, precision, rest}
defp parse_microsecond(rest, precision, acc) do
{:lists.reverse(acc), precision, rest}
end

defp parse_offset(""), do: {nil, ""}
defp parse_offset("Z"), do: {0, ""}
defp parse_offset("-00:00"), do: :error

defp parse_offset(<<?+, hour::2-bytes, ?:, min::2-bytes, rest::binary>>),
do: parse_offset(1, hour, min, rest)
defp parse_offset(<<?+, h1, h2, ?:, m1, m2, rest::binary>>),
do: parse_offset(1, h1, h2, m1, m2, rest)

defp parse_offset(<<?-, hour::2-bytes, ?:, min::2-bytes, rest::binary>>),
do: parse_offset(-1, hour, min, rest)
defp parse_offset(<<?-, h1, h2, ?:, m1, m2, rest::binary>>),
do: parse_offset(-1, h1, h2, m1, m2, rest)

defp parse_offset(<<?+, hour::2-bytes, min::2-bytes, rest::binary>>),
do: parse_offset(1, hour, min, rest)
defp parse_offset(<<?+, h1, h2, m1, m2, rest::binary>>),
do: parse_offset(1, h1, h2, m1, m2, rest)

defp parse_offset(<<?-, hour::2-bytes, min::2-bytes, rest::binary>>),
do: parse_offset(-1, hour, min, rest)
defp parse_offset(<<?-, h1, h2, m1, m2, rest::binary>>),
do: parse_offset(-1, h1, h2, m1, m2, rest)

defp parse_offset(<<?+, hour::2-bytes, rest::binary>>), do: parse_offset(1, hour, "00", rest)
defp parse_offset(<<?-, hour::2-bytes, rest::binary>>), do: parse_offset(-1, hour, "00", rest)
defp parse_offset(<<?+, h1, h2, rest::binary>>), do: parse_offset(1, h1, h2, ?0, ?0, rest)
defp parse_offset(<<?-, h1, h2, rest::binary>>), do: parse_offset(-1, h1, h2, ?0, ?0, rest)
defp parse_offset(_), do: :error

defp parse_offset(sign, hour, min, rest) do
with {hour, ""} when hour < 24 <- Integer.parse(hour),
{min, ""} when min < 60 <- Integer.parse(min) do
defp parse_offset(sign, h1, h2, m1, m2, rest) do
with true <- h1 in ?0..?2 and h2 in ?0..?9,
true <- m1 in ?0..?5 and m2 in ?0..?9,
hour = (h1 - ?0) * 10 + h2 - ?0,
min = (m1 - ?0) * 10 + m2 - ?0,
true <- hour < 24 do
{(hour * 60 + min) * 60 * sign, rest}
else
_ -> :error
Expand Down
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