std/private/dragonbox

Source Edit

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)

char* output_end = Dtoa(buffer, value);

Converts the given double-precision number into decimal form and stores the result in the given buffer.

The buffer must be large enough, i.e. >= DtoaMinBufferLength. The output format is similar to printf("%g"). The output is _not null-terminted.

The output is optimal, i.e. the output string

rounds back to the input number when read in (using round-to-nearest-even)
is as short as possible,
is as close to the input number as possible.

Note: This function may temporarily write up to DtoaMinBufferLength characters into the buffer.

This file contains an implementation of Junekey Jeon's Dragonbox algorithm.

It is a simplified version of the reference implementation found here: https://github.com/jk-jeon/dragonbox

The reference implementation also works with single-precision floating-point numbers and has options to configure the rounding mode.

namespace Returns floor(x / 2^n).

Technically, right-shift of negative integers is implementation defined... Should easily be optimized into SAR (or equivalent) instruction.

Returns whether value is divisible by 2^e2Returns whether value is divisible by 5^e5Returns (x * y) / 2^128

Imports

digitsutils

Types

BitsType = uint64: Source Edit
Double = object bits*: BitsType: Source Edit
FloatingDecimal64 {.bycopy.} = object significand*: uint64 exponent*: int32: Source Edit
uint64x2 {.bycopy.} = object hi*: uint64 lo*: uint64: Source Edit
ValueType = float: Source Edit

Consts

dtoaMinBufferLength: cint = 64: Source Edit
exponentBias: int32 = 1075'i32: Source Edit
exponentMask: BitsType = 9218868437227405312'u64: Source Edit
hiddenBit: BitsType = 4503599627370496'u64: Source Edit
maxIeeeExponent: BitsType = 2047'u: Source Edit
significandMask: BitsType = 4503599627370495'u64: Source Edit
significandSize: int32 = 53: Source Edit
signMask: BitsType = 9223372036854775808'u64: Source Edit

Procs

proc computeDelta(pow10: uint64x2; betaMinus1: int32): uint32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc computePow10(k: int32): uint64x2 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc constructDouble(bits: BitsType): Double {....raises: [], tags: [], forbids: [].}: Source Edit
proc constructDouble(value: ValueType): Double {....raises: [], tags: [], forbids: [].}: Source Edit
proc decimalLength(v: uint64): int {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc floorDivPow2(x: int32; n: int32): int32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc floorLog2Pow10(e: int32): int32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc floorLog10Pow2(e: int32): int32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc floorLog10ThreeQuartersPow2(e: int32): int32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc formatDigits[T: Ordinal](buffer: var openArray[char]; pos: T; digits: uint64; decimalExponent: int; forceTrailingDotZero = false): int {.inline.}: Source Edit
proc hi32(x: uint64): uint32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc isFinite(this: Double): bool {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc isInf(this: Double): bool {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc isIntegralEndpoint(twoF: uint64; e2: int32; minusK: int32): bool {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc isIntegralMidpoint(twoF: uint64; e2: int32; minusK: int32): bool {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc isNaN(this: Double): bool {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc isZero(this: Double): bool {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc lo32(x: uint64): uint32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc mul128(a: uint64; b: uint64): uint64x2 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc mulParity(twoF: uint64; pow10: uint64x2; betaMinus1: int32): bool {.inline, ...raises: [], tags: [], forbids: [].}: 1 mulx, 1 mul Source Edit
proc mulShift(x: uint64; y: uint64x2): uint64 {.inline, ...raises: [], tags: [], forbids: [].}: 2 mulx Source Edit
proc multipleOfPow2(value: uint64; e2: int32): bool {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc multipleOfPow5(value: uint64; e5: int32): bool {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc physicalExponent(this: Double): BitsType {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc physicalSignificand(this: Double): BitsType {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc printDecimalDigitsBackwards(buf: var openArray[char]; pos: int; output64: uint64): int32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc signBit(this: Double): int {.noSideEffect, ...raises: [], tags: [], forbids: [].}: Source Edit
proc toChars(buffer: var openArray[char]; v: float; forceTrailingDotZero = false): int {. inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc toDecimal64(ieeeSignificand: uint64; ieeeExponent: uint64): FloatingDecimal64 {. inline, ...raises: [], tags: [], forbids: [].}: Source Edit
proc toDecimal64AsymmetricInterval(e2: int32): FloatingDecimal64 {.inline, ...raises: [], tags: [], forbids: [].}: NB: accept_lower_endpoint = true accept_upper_endpoint = true Source Edit
proc utoa8DigitsSkipTrailingZeros(buf: var openArray[char]; pos: int; digits: uint32): int32 {.inline, ...raises: [], tags: [], forbids: [].}: Source Edit

Templates

template dragonbox_Assert(x: untyped): untyped: Source Edit

Docs

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