Revision 776ddced6b0f56d695d189716eedd6f4042bf9dd authored by Katharine Hyatt on 06 March 2019, 14:28:16 UTC, committed by Fredrik Ekre on 06 March 2019, 14:28:15 UTC
1 parent 6552521
fastprecision.jl
# This file is a part of Julia, but is derived from
# https://github.com/google/double-conversion which has the following license
#
# Copyright 2006-2014, the V8 project authors. 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 Google Inc. 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.
function roundweed(buffer,len,rest,tk,unit,kappa)
unit >= tk && return false, kappa
tk - unit <= unit && return false, kappa
tk - rest > rest && (tk - 2 * rest >= 2 * unit) && return true, kappa
if rest > unit && (tk - (rest - unit) <= (rest - unit))
buffer[len-1] += 1
for i = (len-1):-1:2
buffer[i] != 0x30 + 10 && break
buffer[i] = 0x30
buffer[i-1] += 1
end
if buffer[1] == 0x30 + 10
buffer[1] = 0x31
kappa += 1
end
return true, kappa
end
return false, kappa
end
function digitgen(w,buffer,requested_digits=1000)
unit::UInt64 = 1
one = Float(unit << -w.e, w.e)
integrals = w.s >> -one.e
fractionals = w.s & (one.s-1)
divisor, kappa = bigpowten(integrals, 64 + one.e)
len = 1
rest = 0
while kappa > 0
digit = div(integrals,divisor)
buffer[len] = 0x30 + digit
len += 1
requested_digits -= 1
integrals %= divisor
kappa -= 1
if requested_digits == 0
rest = (UInt64(integrals) << -one.e) + fractionals
r, kappa = roundweed(buffer, len, rest, UInt64(divisor) << -one.e,
unit,kappa)
return r, kappa, len
end
divisor = div(divisor,10)
end
while requested_digits > 0 && fractionals > unit
fractionals *= 10
unit *= 10
digit = fractionals >> -one.e
buffer[len] = 0x30 + digit
len += 1
requested_digits -= 1
fractionals &= one.s - 1
kappa -= 1
end
requested_digits != 0 && return false, kappa, len
r, kappa = roundweed(buffer,len,fractionals,one.s,
unit,kappa)
return r, kappa, len
end
function fastprecision(v, requested_digits, buffer = Vector{UInt8}(undef, 100))
f = normalize(Float64(v))
ten_mk_min_exp = kMinExp - (f.e + FloatSignificandSize)
ten_mk_max_exp = kMaxExp - (f.e + FloatSignificandSize)
cp = binexp_cache(ten_mk_min_exp,ten_mk_max_exp)
scaled_w = f * cp
r, kappa, len = digitgen(scaled_w,buffer,requested_digits)
decimal_exponent = -cp.de + kappa
return r, len, decimal_exponent+len-1
end
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