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defmodule SData do
@moduledoc """
Utility functions
Compare functions are functions that compares stored items and provides a total order.
They must return:
- `:after` if the first argument is more recent
- `:duplicate` if the two items are the same
- `:before` if the first argument is older
These functions must only return :duplicate for equal items.
"""
@doc """
Calculate the hash of an Erlang term by first converting it to its
binary representation.
"""
def term_hash(term, algo \\ :sha256) do
:crypto.hash(algo, (:erlang.term_to_binary term))
end
def term_bin(term) do
:erlang.term_to_binary term
end
def bin_hash(bin, algo \\ :sha256) do
:crypto.hash(algo, bin)
end
def term_unbin(bin) do
:erlang.binary_to_term(bin, [:safe])
end
@doc"""
Compare function for arbitrary terms using the Erlang order
"""
def cmp_term(a, b) do
cond do
a > b -> :after
a < b -> :before
a == b -> :duplicate
end
end
@doc"""
Compare function for timestamped strings
"""
def cmp_ts_str({ts1, str1}, {ts2, str2}) do
cond do
ts1 > ts2 -> :after
ts1 < ts2 -> :before
str1 > str2 -> :after
str1 < str2 -> :before
true -> :duplicate
end
end
@doc"""
Merge function for nils
"""
def merge_true(true, true), do: true
end
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