40 lines
1.5 KiB
Lua
40 lines
1.5 KiB
Lua
if not B64 then B64 = {} end
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local encode, decode = {}, { [strbyte("=")] = false }
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for value = 0, 63 do
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local char = strsub('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', value+1, value+1)
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encode[value] = char
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decode[strbyte(char)] = value
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end
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local t = {}
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function B64.Encode(str)
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local j = 1
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for i = 1, strlen(str), 3 do
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local a, b, c = strbyte(str, i, i+2)
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t[j] = encode[bit.rshift(a, 2)]
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t[j+1] = encode[bit.band(bit.lshift(a, 4) + bit.rshift(b or 0, 4), 0x3F)]
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t[j+2] = b and encode[bit.band(bit.lshift(b, 2) + bit.rshift(c or 0, 6), 0x3F)] or "="
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t[j+3] = c and encode[bit.band(c, 0x3F)] or "="
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j = j + 4
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end
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return table.concat(t, "", 1, j-1)
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end
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function B64Decode(str)
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local j = 1
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assert(strlen(str) % 4 == 0, format("invalid data length: %d", strlen(str)))
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for i = 1, strlen(str), 4 do
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local ba, bb, bc, bd = strbyte(str, i, i+3)
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local a, b, c, d = decode[ba], decode[bb], decode[bc], decode[bd]
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assert(a ~= nil, format("invalid data at position %d: '%s'", i, ba))
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assert(b ~= nil, format("invalid data at position %d: '%s'", i+1, bb))
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assert(c ~= nil, format("invalid data at position %d: '%s'", i+2, bc))
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assert(d ~= nil, format("invalid data at position %d: '%s'", i+3, bd))
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t[j] = strchar(bit.lshift(a, 2) + bit.rshift(b, 4))
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t[j+1] = c and strchar(bit.band(bit.lshift(b, 4) + bit.rshift(c, 2), 0xFF)) or ""
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t[j+2] = d and strchar(bit.band(bit.lshift(c, 6) + d, 0xFF)) or ""
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j = j + 3
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end
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return table.concat(t, "", 1, j-1)
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end
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