Add 'base91-python/' from commit '749aa78cf12496cca4b9bf3eafe045809fc0da10'

[secnet.git] / base91-python / base91 / __init__.py

diff --git a/base91-python/base91/__init__.py b/base91-python/base91/__init__.py
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+# Base91 encode/decode for Python 2 and Python 3
+#
+# Copyright (c) 2012 Adrien Beraud
+# Copyright (c) 2015 Guillaume Jacquenot
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#   * Redistributions of source code must retain the above copyright notice,
+#     this list of conditions and the following disclaimer.
+#   * Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions and the following disclaimer in the documentation
+#     and/or other materials provided with the distribution.
+#   * Neither the name of Adrien Beraud, Wisdom Vibes Pte. Ltd., nor the names
+#     of its contributors may be used to endorse or promote products derived
+#     from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+import struct
+
+base91_alphabet = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+                   'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+                   'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
+                   'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+                   '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '#', '$',
+                   '%', '&', '(', ')', '*', '+', ',', '.', '/', ':', ';', '<', '=',
+                   '>', '?', '@', '[', ']', '^', '_', '`', '{', '|', '}', '~', '"']
+
+decode_table = dict((v, k) for k, v in enumerate(base91_alphabet))
+
+
+def decode(encoded_str):
+    ''' Decode Base91 string to a bytearray '''
+    v = -1
+    b = 0
+    n = 0
+    out = bytearray()
+    for strletter in encoded_str:
+        if not strletter in decode_table:
+            continue
+        c = decode_table[strletter]
+        if (v < 0):
+            v = c
+        else:
+            v += c * 91
+            b |= v << n
+            n += 13 if (v & 8191) > 88 else 14
+            while True:
+                out += struct.pack('B', b & 255)
+                b >>= 8
+                n -= 8
+                if not n > 7:
+                    break
+            v = -1
+    if v + 1:
+        out += struct.pack('B', (b | v << n) & 255)
+    return out
+
+
+def encode(bindata):
+    ''' Encode a bytearray to a Base91 string '''
+    b = 0
+    n = 0
+    out = ''
+    for count in range(len(bindata)):
+        byte = bindata[count:count + 1]
+        b |= struct.unpack('B', byte)[0] << n
+        n += 8
+        if n > 13:
+            v = b & 8191
+            if v > 88:
+                b >>= 13
+                n -= 13
+            else:
+                v = b & 16383
+                b >>= 14
+                n -= 14
+            out += base91_alphabet[v % 91] + base91_alphabet[v // 91]
+    if n:
+        out += base91_alphabet[b % 91]
+        if n > 7 or b > 90:
+            out += base91_alphabet[b // 91]
+    return out