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[WIP] [stdlib] Consolidate integer-to-string implementations #14401

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Merged
merged 1 commit into from
Feb 7, 2018
Merged

[WIP] [stdlib] Consolidate integer-to-string implementations #14401

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121 changes: 77 additions & 44 deletions stdlib/public/core/Integers.swift.gyb
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Original file line number Diff line number Diff line change
Expand Up @@ -1678,7 +1678,82 @@ ${operatorComment(x.nonMaskingOperator, False)}

}

// Strideable conformance

//===----------------------------------------------------------------------===//
//===--- CustomStringConvertible conformance ------------------------------===//
//===----------------------------------------------------------------------===//

extension BinaryInteger {
@_inlineable // FIXME(sil-serialize-all)
@_versioned
@_transparent
internal func _description(
radix: Int = 10, uppercase: Bool = false
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I think it would be better to leave out the default values on this internal function, so we can't accidentally forget to pass on the values from the public API.

) -> String {
_precondition(2...36 ~= radix, "Radix must be between 2 and 36")

if bitWidth <= 64 {
let radix_ = Int64(radix)
return Self.isSigned
? _int64ToString(
Int64(truncatingIfNeeded: self), radix: radix_, uppercase: uppercase)
: _uint64ToString(
UInt64(truncatingIfNeeded: self), radix: radix_, uppercase: uppercase)
}

if self == (0 as Self) { return "0" }

// Bit shifting can be faster than division when `radix` is a power of two
// (although not necessarily the case for builtin types).
let isRadixPowerOfTwo = radix.nonzeroBitCount == 1
let radix_ = Magnitude(radix)
let quotientAndRemainder: (Magnitude) -> (Magnitude, Magnitude) = { value in
return isRadixPowerOfTwo
? (value >> radix.trailingZeroBitCount, value & (radix_ - 1))
: value.quotientAndRemainder(dividingBy: radix_)
}

let hasLetters = radix > 10
let ascii: (UInt8) -> UInt8 = { digit in
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Can these be proper inner funcs instead? That would help readability a little, imo.

let base: UInt8
if !hasLetters || digit < 10 {
base = UInt8(("0" as Unicode.Scalar).value)
} else if uppercase {
base = UInt8(("A" as Unicode.Scalar).value) &- 10
} else {
base = UInt8(("a" as Unicode.Scalar).value) &- 10
}
return base &+ digit
}

let isNegative = Self.isSigned && self < (0 as Self)
var value = magnitude
var result: [UInt8] = []
while value != 0 {
let (quotient, remainder) = quotientAndRemainder(value)
result.append(ascii(UInt8(truncatingIfNeeded: remainder)))
value = quotient
}

if isNegative {
result.append(UInt8(("-" as Unicode.Scalar).value))
}
return String._fromWellFormedCodeUnitSequence(
UTF8.self, input: result.reversed())
}

/// A textual representation of this value.
@_inlineable // FIXME(sil-serialize-all)
public var description: String {
return _description()
}
}


//===----------------------------------------------------------------------===//
//===--- Strideable conformance -------------------------------------------===//
//===----------------------------------------------------------------------===//

extension BinaryInteger {
// FIXME(ABI): using Int as the return type is wrong.
/// Returns the distance from this value to the given value, expressed as a
Expand Down Expand Up @@ -1968,6 +2043,7 @@ extension BinaryInteger {

//===----------------------------------------------------------------------===//
//===--- Ambiguity breakers -----------------------------------------------===//
//
// These two versions of the operators are not ordered with respect to one
// another, but the compiler choses the second one, and that results in infinite
// recursion.
Expand Down Expand Up @@ -2694,38 +2770,6 @@ extension UnsignedInteger {
@_inlineable // FIXME(sil-serialize-all)
@_transparent
public static var isSigned: Bool { return false }

/// A textual representation of this value.
@_inlineable // FIXME(sil-serialize-all)
public var description: String {
if self.bitWidth <= ${word_bits} {
return _uint64ToString(UInt64(truncatingIfNeeded: self))
}
if self == (0 as Self) {
return "0"
}
return renderNonZeroDescription()
}

// FIXME(integers): perhaps a faster implementation is possible
@_inlineable // FIXME(sil-serialize-all)
@_versioned // FIXME(sil-serialize-all)
@_transparent
internal func renderNonZeroDescription() -> String {
let ascii0 = 48
var buf: [Unicode.Scalar] = []

var x = self
repeat {
let r = x % 10
x /= 10
buf.append(
Unicode.Scalar(
ascii0 + Int(UInt(truncatingIfNeeded: r)._value))!)
}
while x != (0 as Self)
return String(buf.reversed().lazy.map { Character($0) })
}
}

extension UnsignedInteger where Self : FixedWidthInteger {
Expand Down Expand Up @@ -2828,17 +2872,6 @@ public protocol SignedInteger : BinaryInteger, SignedNumeric {
}

extension SignedInteger {
/// A textual representation of this value.
@_inlineable // FIXME(sil-serialize-all)
public var description: String {
if self.bitWidth <= ${word_bits} {
return _int64ToString(Int64(truncatingIfNeeded: self))
}

let base = magnitude.description
return self < (0 as Self) ? "-" + base : base
}

/// A Boolean value indicating whether this type is a signed integer type.
///
/// This property is always `true` for signed integer types.
Expand Down
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