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Diffstat (limited to 'vendor/github.com/shopspring/decimal/rounding.go')
| -rw-r--r-- | vendor/github.com/shopspring/decimal/rounding.go | 160 |
1 files changed, 0 insertions, 160 deletions
diff --git a/vendor/github.com/shopspring/decimal/rounding.go b/vendor/github.com/shopspring/decimal/rounding.go deleted file mode 100644 index d4b0cd007..000000000 --- a/vendor/github.com/shopspring/decimal/rounding.go +++ /dev/null @@ -1,160 +0,0 @@ -// Copyright 2009 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -// Multiprecision decimal numbers. -// For floating-point formatting only; not general purpose. -// Only operations are assign and (binary) left/right shift. -// Can do binary floating point in multiprecision decimal precisely -// because 2 divides 10; cannot do decimal floating point -// in multiprecision binary precisely. - -package decimal - -type floatInfo struct { - mantbits uint - expbits uint - bias int -} - -var float32info = floatInfo{23, 8, -127} -var float64info = floatInfo{52, 11, -1023} - -// roundShortest rounds d (= mant * 2^exp) to the shortest number of digits -// that will let the original floating point value be precisely reconstructed. -func roundShortest(d *decimal, mant uint64, exp int, flt *floatInfo) { - // If mantissa is zero, the number is zero; stop now. - if mant == 0 { - d.nd = 0 - return - } - - // Compute upper and lower such that any decimal number - // between upper and lower (possibly inclusive) - // will round to the original floating point number. - - // We may see at once that the number is already shortest. - // - // Suppose d is not denormal, so that 2^exp <= d < 10^dp. - // The closest shorter number is at least 10^(dp-nd) away. - // The lower/upper bounds computed below are at distance - // at most 2^(exp-mantbits). - // - // So the number is already shortest if 10^(dp-nd) > 2^(exp-mantbits), - // or equivalently log2(10)*(dp-nd) > exp-mantbits. - // It is true if 332/100*(dp-nd) >= exp-mantbits (log2(10) > 3.32). - minexp := flt.bias + 1 // minimum possible exponent - if exp > minexp && 332*(d.dp-d.nd) >= 100*(exp-int(flt.mantbits)) { - // The number is already shortest. - return - } - - // d = mant << (exp - mantbits) - // Next highest floating point number is mant+1 << exp-mantbits. - // Our upper bound is halfway between, mant*2+1 << exp-mantbits-1. - upper := new(decimal) - upper.Assign(mant*2 + 1) - upper.Shift(exp - int(flt.mantbits) - 1) - - // d = mant << (exp - mantbits) - // Next lowest floating point number is mant-1 << exp-mantbits, - // unless mant-1 drops the significant bit and exp is not the minimum exp, - // in which case the next lowest is mant*2-1 << exp-mantbits-1. - // Either way, call it mantlo << explo-mantbits. - // Our lower bound is halfway between, mantlo*2+1 << explo-mantbits-1. - var mantlo uint64 - var explo int - if mant > 1<<flt.mantbits || exp == minexp { - mantlo = mant - 1 - explo = exp - } else { - mantlo = mant*2 - 1 - explo = exp - 1 - } - lower := new(decimal) - lower.Assign(mantlo*2 + 1) - lower.Shift(explo - int(flt.mantbits) - 1) - - // The upper and lower bounds are possible outputs only if - // the original mantissa is even, so that IEEE round-to-even - // would round to the original mantissa and not the neighbors. - inclusive := mant%2 == 0 - - // As we walk the digits we want to know whether rounding up would fall - // within the upper bound. This is tracked by upperdelta: - // - // If upperdelta == 0, the digits of d and upper are the same so far. - // - // If upperdelta == 1, we saw a difference of 1 between d and upper on a - // previous digit and subsequently only 9s for d and 0s for upper. - // (Thus rounding up may fall outside the bound, if it is exclusive.) - // - // If upperdelta == 2, then the difference is greater than 1 - // and we know that rounding up falls within the bound. - var upperdelta uint8 - - // Now we can figure out the minimum number of digits required. - // Walk along until d has distinguished itself from upper and lower. - for ui := 0; ; ui++ { - // lower, d, and upper may have the decimal points at different - // places. In this case upper is the longest, so we iterate from - // ui==0 and start li and mi at (possibly) -1. - mi := ui - upper.dp + d.dp - if mi >= d.nd { - break - } - li := ui - upper.dp + lower.dp - l := byte('0') // lower digit - if li >= 0 && li < lower.nd { - l = lower.d[li] - } - m := byte('0') // middle digit - if mi >= 0 { - m = d.d[mi] - } - u := byte('0') // upper digit - if ui < upper.nd { - u = upper.d[ui] - } - - // Okay to round down (truncate) if lower has a different digit - // or if lower is inclusive and is exactly the result of rounding - // down (i.e., and we have reached the final digit of lower). - okdown := l != m || inclusive && li+1 == lower.nd - - switch { - case upperdelta == 0 && m+1 < u: - // Example: - // m = 12345xxx - // u = 12347xxx - upperdelta = 2 - case upperdelta == 0 && m != u: - // Example: - // m = 12345xxx - // u = 12346xxx - upperdelta = 1 - case upperdelta == 1 && (m != '9' || u != '0'): - // Example: - // m = 1234598x - // u = 1234600x - upperdelta = 2 - } - // Okay to round up if upper has a different digit and either upper - // is inclusive or upper is bigger than the result of rounding up. - okup := upperdelta > 0 && (inclusive || upperdelta > 1 || ui+1 < upper.nd) - - // If it's okay to do either, then round to the nearest one. - // If it's okay to do only one, do it. - switch { - case okdown && okup: - d.Round(mi + 1) - return - case okdown: - d.RoundDown(mi + 1) - return - case okup: - d.RoundUp(mi + 1) - return - } - } -} |