Add assertions to get_target
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@ -50,7 +50,11 @@ class Blockchain(util.PrintError):
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self.print_error("prev hash mismatch: %s vs %s"
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% (prev_hash, header.get('prev_block_hash')))
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return False
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bits, target = self.get_target(height/2016, chain)
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try:
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bits, target = self.get_target(height/2016, chain)
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except AssertionError as e:
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self.print_error("target calculation error: %s" % (str(e)))
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return False
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if bits != header.get('bits'):
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self.print_error("bits mismatch: %s vs %s"
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% (bits, header.get('bits')))
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@ -190,36 +194,33 @@ class Blockchain(util.PrintError):
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if h.get('block_height') == index*2016-1:
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last = h
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# bits to target
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bits = last.get('bits')
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bitsN = (bits >> 24) & 0xff
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assert bitsN >= 0x03 and bitsN <= 0x1d, "First part of bits should be in [0x03, 0x1d]"
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bitsBase = bits & 0xffffff
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assert bitsN >= 0x8000 and bitsN <= 0x7fffff, "Second part of bits should be in [0x8000, 0x7fffff]"
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target = bitsBase << (8*(bitsN-3))
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# new target
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nActualTimespan = last.get('timestamp') - first.get('timestamp')
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nTargetTimespan = 14*24*60*60
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nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
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nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
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new_target = min(max_target, (target * nActualTimespan)/nTargetTimespan)
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bits = last.get('bits')
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# convert to bignum
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MM = 256*256*256
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a = bits%MM
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if a < 0x8000:
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a *= 256
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target = (a) * pow(2, 8 * (bits/MM - 3))
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# new target
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new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
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# convert it to bits
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c = ("%064X"%new_target)[2:]
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i = 31
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while c[0:2]=="00":
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# convert new target to bits
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c = ("%064x" % new_target)[2:]
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while c[:2] == '00' and len(c) > 6:
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c = c[2:]
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i -= 1
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c = int('0x'+c[0:6],16)
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if c >= 0x800000:
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c /= 256
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i += 1
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bitsN, bitsBase = len(c)/2, int('0x'+c[:6], 16)
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if bitsBase >= 0x800000:
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bitsN += 1
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bitsBase >>= 8
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new_bits = c + MM * i
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return new_bits, new_target
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new_bits = bitsN << 24 | bitsBase
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return new_bits, bitsBase << (8*(bitsN-3))
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def connect_header(self, chain, header):
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'''Builds a header chain until it connects. Returns True if it has
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