127 lines
3.5 KiB
Python
127 lines
3.5 KiB
Python
# Eos - Verifiable elections
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# Copyright © 2017 RunasSudo (Yingtong Li)
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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from eos.core.bigint import *
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from eos.core.objects import *
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class BitStream(EosObject):
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def __init__(self, value=None):
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if value:
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self.impl = value
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self.nbits = self.impl.nbits()
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else:
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self.impl = ZERO
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self.nbits = 0
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self.ptr = 0
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self.remaining = self.nbits
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def seek(self, ptr):
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self.ptr = ptr
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self.remaining = self.nbits - self.ptr
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def read(self, nbits=None):
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# 11000110110
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# ^----
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if nbits is None:
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nbits = self.remaining
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if nbits > self.remaining:
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raise Exception('Not enough bits to read from BitString')
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val = (self.impl >> (self.remaining - nbits)) & ((ONE << nbits) - ONE)
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self.ptr += nbits
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self.remaining -= nbits
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return val
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def write(self, bits, nbits=None):
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# 11 0100110
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# 10010
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# ^----
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if nbits is None:
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nbits = bits.nbits()
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if nbits < bits.nbits():
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raise Exception('Too many bits to write to BitString')
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self.impl = ((self.impl >> self.remaining) << (self.remaining + nbits)) | (bits << self.remaining) | (self.impl & ((ONE << self.remaining) - 1))
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self.ptr += nbits
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self.nbits += nbits
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def read_string(self):
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length = self.read(32)
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length = length.__int__() # JS attempts to call this twice if we do it in one line
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if is_python:
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ba = bytearray()
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for i in range(length):
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ba.append(int(self.read(7)))
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return ba.decode('ascii')
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else:
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ba = []
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for i in range(length):
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val = self.read(7)
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val = val.__int__()
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ba.append(val)
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return String.fromCharCode(*ba)
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def write_string(self, strg):
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self.write(BigInt(len(strg)), 32) # TODO: Arbitrary lengths
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# TODO: Support non-ASCII encodings
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if is_python:
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ba = strg.encode('ascii')
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for i in range(len(strg)):
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self.write(BigInt(ba[i]), 7)
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else:
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for i in range(len(strg)):
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self.write(BigInt(strg.charCodeAt(i)), 7)
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# Make the size of this BitStream a multiple of the block_size
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def multiple_of(self, block_size, pad_at_end=False):
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if self.nbits % block_size != 0:
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diff = block_size - (self.nbits % block_size)
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if pad_at_end:
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# Suitable for structured data
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self.seek(self.nbits)
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self.write(ZERO, diff)
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else:
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# Suitable for raw numbers
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self.nbits += diff
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return self # For convenient chaining
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def map(self, func, block_size):
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if self.nbits % block_size != 0:
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raise Exception('The size of the BitStream must be a multiple of block_size')
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self.seek(0)
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result = []
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while self.remaining > 0:
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result.append(func(self.read(block_size)))
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return result
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@classmethod
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def unmap(cls, value, func, block_size):
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bs = cls()
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for x in value:
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bs.write(func(x), block_size)
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bs.seek(0)
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return bs
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def serialise(self):
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return self.impl
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@classmethod
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def deserialise(cls, value):
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return cls(value)
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