AWK/b91dec.awk

   1 #!/usr/bin/awk -f
   2
   3 # basE91 decoder
   4 # Copyright (c) 2000-2006 Joachim Henke
   5 # http://base91.sourceforge.net/
   6
   7 BEGIN {
   8         b = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!#$%&()*+,./:;<=>?@[]^_`{|}~\""
   9         for (i = 0; i < 256; ++i) {
  10                 --d[sprintf("%c", i)]
  11         }
  12         for (i = 0; i < 91; ++i) {
  13                 d[substr(b, i + 1, 1)] = i
  14         }
  15         b = 0
  16         n = 0
  17         v = -1
  18 }
  19
  20 {
  21         l = length($0)
  22         for (i = 1; i <= l; ++i) {
  23                 c = d[substr($0, i, 1)]
  24                 if (c < 0) {
  25                         continue
  26                 }
  27                 if (v < 0) {
  28                         v = c
  29                 } else {
  30                         v += c * 91
  31                         b += v * 2 ^ n
  32                         n += v % 8192 > 88 ? 13 : 14
  33                         do {
  34                                 b -= c = b % 256
  35                                 printf "%c", c
  36                                 b /= 256
  37                                 n -= 8
  38                         } while (n > 7)
  39                         v = -1
  40                 }
  41         }
  42 }
  43
  44 END {
  45         if (v + 1) {
  46                 printf "%c", b + v * 2 ^ n
  47         }
  48 }