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48 lines
1.1 KiB
48 lines
1.1 KiB
4 years ago
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-- Redefine often used functions locally.
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local floor = floor
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-- Redefine often used variables locally.
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local table = table
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-- The characters to be used in the base64 string.
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local digits = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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local base = #digits
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-- A cheat sheet used to easily convert back to decimal.
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local inverse_map = {}
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for i = 1, #digits do
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local c = digits:sub(i,i)
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inverse_map[c] = i - 1
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end
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-- Convert a decimal number to a base64 string.
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function RareTracker.ToBase64(number)
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local t = {}
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if number < 0 then
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number = 0
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end
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repeat
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local d = (number % base) + 1
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number = floor(number / base)
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table.insert(t, 1, digits:sub(d, d))
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until number == 0
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return table.concat(t, "")
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end
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-- Convert a decimal number to a base64 string.
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function RareTracker.ToBase10(base64)
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local n = 0
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local j = 1
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for i = 1, #base64 do
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local k = #base64 - i + 1
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local c = base64:sub(k, k)
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n = n + j * inverse_map[c]
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j = j * base
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end
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return n
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end
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