zfec: rearrange files

[tahoe-lafs/zfec.git] / zfec / easyfec.py

diff --git a/zfec/easyfec.py b/zfec/easyfec.py
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+++ b/zfec/easyfec.py
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+# zfec -- a fast C implementation of Reed-Solomon erasure coding with
+# command-line, C, and Python interfaces
+
+import zfec
+
+# div_ceil() was copied from the pyutil library.
+def div_ceil(n, d):
+    """
+    The smallest integer k such that k*d >= n.
+    """
+    return (n/d) + (n%d != 0)
+
+from base64 import b32encode
+def ab(x): # debuggery
+    if len(x) >= 3:
+        return "%s:%s" % (len(x), b32encode(x[-3:]),)
+    elif len(x) == 2:
+        return "%s:%s" % (len(x), b32encode(x[-2:]),)
+    elif len(x) == 1:
+        return "%s:%s" % (len(x), b32encode(x[-1:]),)
+    elif len(x) == 0:
+        return "%s:%s" % (len(x), "--empty--",)
+
+class Encoder(object):
+    def __init__(self, k, m):
+        self.fec = zfec.Encoder(k, m)
+
+    def encode(self, data):
+        """
+        @param data: string
+
+        @return: a sequence of m blocks -- any k of which suffice to
+            reconstruct the input data
+        """
+        chunksize = div_ceil(len(data), self.fec.k)
+        l = [ data[i*chunksize:(i+1)*chunksize] + "\x00" * min(chunksize, (((i+1)*chunksize)-len(data))) for i in range(self.fec.k) ]
+        assert len(l) == self.fec.k, (len(l), self.fec.k,)
+        assert (not l) or (not [ x for x in l if len(x) != len(l[0]) ], (len(l), [ ab(x) for x in l ], chunksize, self.fec.k, len(data),))
+        return self.fec.encode(l)
+        
+class Decoder(object):
+    def __init__(self, k, m):
+        self.fec = zfec.Decoder(k, m)
+
+    def decode(self, blocks, sharenums, padlen):
+        """
+        @param padlen: the number of bytes of padding to strip off;  Note that
+            the padlen is always equal to (blocksize times k) minus the length
+            of data.  (Therefore, padlen can be 0.)
+        """
+        data = ''.join(self.fec.decode(blocks, sharenums))
+        if padlen:
+            return data[:-padlen]
+        else:
+            return data
+
+# zfec -- fast forward error correction library with Python interface
+# 
+# Copyright (C) 2007 Allmydata, Inc.
+# Author: Zooko Wilcox-O'Hearn
+# 
+# This file is part of zfec.
+# 
+# See README.rst for licensing information.