119 lines
4.5 KiB
Julia
119 lines
4.5 KiB
Julia
# This file is a part of Julia, but is derived from
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# https://github.com/google/double-conversion which has the following license
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#
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# Copyright 2006-2014, the V8 project authors. All rights reserved.
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are
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# met:
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#
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials provided
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# with the distribution.
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# * Neither the name of Google Inc. nor the names of its
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# contributors may be used to endorse or promote products derived
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# from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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const kMinExp = -60
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const kMaxExp = -32
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function roundweed(buffer,len,rest,tk,unit,kappa,too_high::UInt64,unsafe_interval::UInt64)
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small = too_high - unit
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big = too_high + unit
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while rest < small &&
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unsafe_interval - rest >= tk &&
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(rest + tk < small ||
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small - rest >= rest + tk - small)
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buffer[len-1] -= 1
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rest += tk
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end
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if rest < big &&
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unsafe_interval - rest >= tk &&
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(rest + tk < big ||
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big - rest > rest + tk - big)
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return false, kappa
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end
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return (2 * unit <= rest) && (rest <= unsafe_interval - 4 * unit), kappa
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end
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const SmallPowersOfTen = [
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0, 1, 10, 100, 1000, 10000, 100000,
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1000000, 10000000, 100000000, 1000000000]
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function bigpowten(n,n_bits)
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guess = (n_bits + 1) * 1233 >> 12
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guess += 1
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i = SmallPowersOfTen[guess+1]
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return n < i ? (SmallPowersOfTen[guess], guess-1) : (i,guess)
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end
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function digitgen(low,w,high,buffer)
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unit::UInt64 = 1
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one = Float(unit << -w.e, w.e)
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too_high = Float(high.s+unit,high.e)
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unsafe_interval = too_high - Float(low.s-unit,low.e)
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integrals = too_high.s >> -one.e
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fractionals = too_high.s & (one.s-1)
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divisor, kappa = bigpowten(integrals, 64 + one.e)
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len = 1
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rest = UInt64(0)
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while kappa > 0
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digit = div(integrals,divisor)
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buffer[len] = 0x30 + digit
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len += 1
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integrals %= divisor
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kappa -= 1
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rest = (UInt64(integrals) << -one.e) + fractionals
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if rest < unsafe_interval.s
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r, kappa = roundweed(buffer, len, rest, UInt64(divisor) << -one.e,
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unit,kappa,(too_high - w).s,unsafe_interval.s)
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return r, kappa, len
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end
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divisor = div(divisor,10)
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end
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while true
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fractionals *= 10
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unit *= 10
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unsafe_interval = Float(unsafe_interval.s*10,unsafe_interval.e)
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digit = fractionals >> -one.e
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buffer[len] = 0x30 + digit
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len += 1
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fractionals &= one.s - 1
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kappa -= 1
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if fractionals < unsafe_interval.s
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r, kappa = roundweed(buffer,len,fractionals,one.s,
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unit,kappa,(too_high - w).s*unit,unsafe_interval.s)
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return r, kappa, len
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end
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end
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end
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function fastshortest(v, buffer = Vector{UInt8}(17))
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f = normalize(Float64(v))
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bound_minus, bound_plus = normalizedbound(v)
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ten_mk_min_exp = kMinExp - (f.e + FloatSignificandSize)
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ten_mk_max_exp = kMaxExp - (f.e + FloatSignificandSize)
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cp = binexp_cache(ten_mk_min_exp,ten_mk_max_exp)
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scaled_w = f * cp
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scaled_bound_minus = bound_minus * cp
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scaled_bound_plus = bound_plus * cp
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r, kappa, len = digitgen(scaled_bound_minus,scaled_w,
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scaled_bound_plus,buffer)
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decimal_exponent = -cp.de + kappa
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return r, len, decimal_exponent+len-1
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end
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