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176 | with Ada.Calendar.Formatting;
package body ULID is
-- Crockford's Base32 (5 bits per symbol):
crockford : constant String (1 .. 32) := "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
function Decode (Text : String) return ULID_Number is
index : Integer;
reverse_crockford : array (Character) of Integer;
single_digit : Integer;
invalid : constant := -1;
result : ULID_Number := 0;
begin
case Text'Length is
when 26 =>
reverse_crockford := (others => invalid);
for i in crockford'Range loop
reverse_crockford (crockford (i)) := i - 1;
end loop;
for c of Text loop
single_digit := reverse_crockford (c);
if single_digit = invalid then
raise Invalid_Text
with "Error in Crockford's Base32 representation";
end if;
result := result * 32 + ULID_Number (single_digit);
end loop;
when 36 =>
index := Text'First;
for hexa_digit in 1 .. 16 loop
single_digit :=
Integer'Value ("16#" & Text (index .. index + 1) & '#');
index := index + 2;
if index <= Text'Last and then Text (index) = '-' then
if index not in 8 + Text'First | 13 + Text'First |
18 + Text'First | 23 + Text'First
then
raise Invalid_Text
with "Misplaced dash in 8-4-4-4-12 representation";
end if;
index := index + 1;
end if;
result := result * 256 + ULID_Number (single_digit);
end loop;
when 38 =>
if Text (Text'First) = '{' and then Text (Text'Last) = '}' then
return Decode (Text (Text'First + 1 .. Text'Last - 1));
else
raise Invalid_Text
with "Expecting bracketed 8-4-4-4-12 format for 38 characters";
end if;
when others =>
raise Invalid_Text with "Invalid UILD / UUID text representation";
end case;
return result;
end Decode;
function Encode (Code : ULID_Number) return String is
result : String (1 .. 26);
-- ^ The first 10 characters contain a time information (50 bits,
-- of them 48 are used); the 16 other characters represent a random
-- number (80 bits).
x : ULID_Number := Code;
begin
for c of reverse result loop
c := crockford (1 + Integer (x and 31));
x := x / 32;
end loop;
return result;
end Encode;
function Encode_as_8_4_4_4_12 (Code : in ULID_Number) return String is
result : String (1 .. 36);
index : Integer := result'Last;
base : constant := 16;
hexa : constant String (1 .. base) := "0123456789abcdef";
work : ULID_Number := Code;
b : Integer;
begin
for i in reverse 1 .. 16 loop
b := Integer (work and 255);
work := work / 256;
result (index - 1) := hexa (b / base + 1);
result (index) := hexa (b mod base + 1);
index := index - 2;
-- Insert dashes
if i = 5 or else i = 7 or else i = 9 or else i = 11 then
result (index) := '-';
index := index - 1;
end if;
end loop;
return result;
end Encode_as_8_4_4_4_12;
procedure Reset (Generator : Random_Generator) is
begin
Random_Numbers.Reset (Random_Numbers.Generator (Generator));
end Reset;
procedure Reset (Generator : Random_Generator; Seed : Integer) is
begin
Random_Numbers.Reset (Random_Numbers.Generator (Generator), Seed);
end Reset;
function Generate_Time_Part
(Leap_Second : Boolean;
Offset : Ada.Calendar.Time_Zones.Time_Offset)
return ULID_Number
is
use Ada.Calendar;
unix_epoch : constant Time :=
Ada.Calendar.Formatting.Time_Of
(1970, 1, 1, 0.0, Leap_Second, Offset);
milliseconds_clock : constant ULID_Number :=
ULID_Number (1000.0 * (Clock - unix_epoch));
begin
return milliseconds_clock * 2 ** 80;
end Generate_Time_Part;
function
Generate_Random_Part (Generator : Random_Generator) return ULID_Number
is
begin
return ULID_Number
(Random_Numbers.Random
(Random_Numbers.Generator (Generator)));
end Generate_Random_Part;
function Generate
(Generator : Random_Generator;
Leap_Second : Boolean := False;
Offset : Ada.Calendar.Time_Zones.Time_Offset := 0)
return ULID_Number
is
(Generate_Time_Part (Leap_Second, Offset) +
Generate_Random_Part (Generator));
function Generate_Monotonic
(Previous : ULID_Number;
Generator : Random_Generator;
Leap_Second : Boolean := False;
Offset : Ada.Calendar.Time_Zones.Time_Offset := 0)
return ULID_Number
is
-- Mask for erasing the random part:
mask : constant := (2 ** 128 - 1) - (2 ** 80 - 1);
old_time_part : constant ULID_Number := Previous and mask;
new_time_part : constant ULID_Number :=
Generate_Time_Part (Leap_Second, Offset);
begin
if new_time_part > old_time_part then
return new_time_part + Generate_Random_Part (Generator);
else
-- New time is not new enough: we increment previous value.
return Previous + 1;
end if;
end Generate_Monotonic;
function Network_Byte_Order (Code : ULID_Number) return Byte_Array is
result : Byte_Array;
rest : ULID_Number := Code;
begin
for i in reverse result'Range loop
result (i) := Byte (rest and 255);
rest := rest / 256;
end loop;
return result;
end Network_Byte_Order;
end ULID;
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