84 lines
1.7 KiB
Nim
84 lines
1.7 KiB
Nim
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#
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# Nim's Unofficial Library
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# (c) Copyright 2015 Huy Doan
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#
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# See the file "LICENSE", included in this
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# distribution, for details about the copyright.
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#
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## This module implements a base32 encoder and decoder.
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const
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VERSION* = "0.1.2"
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base32Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567="
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proc encode*(s: openArray[char]; pad=true): string =
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var i, j, idx, digit: int = 0
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var current, next: int
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var len = (s.len * 8 / 5).int
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if len mod 8 != 0:
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len += 8 - (len mod 8)
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result = newString(len)
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while i < s.len:
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current = s[i].ord
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if idx > 3:
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if i + 1 < s.len:
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next = s[i+1].ord
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else:
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next = 0
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digit = current and (0xFF shr idx)
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idx = (idx + 5) mod 8
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digit = digit shl idx
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digit = digit or (next shr (8 - idx))
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i += 1
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else:
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digit = (current shr (8 - (idx + 5))) and 0x1F
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idx = (idx + 5) mod 8
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if idx == 0:
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i += 1
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result[j] = base32Chars[digit]
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j += 1
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if pad:
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for i in j..<len:
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result[i] = base32Chars[32]
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else:
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result.setLen j
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proc decode*(s: openArray[char]): string =
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var ch, idx, bits, buf: int = 0
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let len = (s.len * 5 / 8).int
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result = newString(len)
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for i in 0..s.len-1:
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ch = s[i].ord
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case ch
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of 0x41..0x5A, 0x61..0x7A:
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ch = (ch and 0x1F) - 1
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of 0x32..0x37:
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ch -= 0x32 - 26
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of 0x3D:
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continue
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else:
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raise newException(ValueError, "Non-base32 digit found: " & $ch)
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buf = buf shl 5
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buf = buf xor ch
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bits += 5
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if bits >= 8:
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bits -= 8
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result[idx] = char(buf shr bits and 0xFF)
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idx += 1
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if idx < len:
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setLen(result, idx)
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