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[stdlib] Further simplify string-to-integer parsing and change some inlining choices.

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This commit is contained in:
Xiaodi Wu
2021-03-29 12:08:28 -04:00
parent 0319bdc966
commit 5d943f46bd
1 changed files with 30 additions and 42 deletions
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72
stdlib/public/core/IntegerParsing.swift
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@@ -16,49 +16,37 @@ internal func _parseASCIIDigits<Result: FixedWidthInteger>(
) -> Result? {
_internalInvariant(radix >= 2 && radix <= 36)
guard _fastPath(!codeUnits.isEmpty) else { return nil }
let numericalUpperBound, uppercaseUpperBound, lowercaseUpperBound: UInt8
if radix <= 10 {
numericalUpperBound = 48 /* "0" */ &+ UInt8(radix)
uppercaseUpperBound = 65
lowercaseUpperBound = 97
} else {
numericalUpperBound = 58
uppercaseUpperBound = 65 /* "A" */ &+ UInt8(radix &- 10)
lowercaseUpperBound = 97 /* "a" */ &+ UInt8(radix &- 10)
}
let multiplicand = Result(radix)
var result = 0 as Result
if radix <= 10 {
let upperBound = 48 /* "0" */ &+ UInt8(radix)
for digit in codeUnits {
let digitValue: Result
if _fastPath(digit >= 48 && digit < upperBound) {
digitValue = Result(digit &- 48)
} else {
return nil
}
let (temporary, overflow1) =
result.multipliedReportingOverflow(by: multiplicand)
guard _fastPath(!overflow1) else { return nil }
let (nextResult, overflow2) = isNegative
? temporary.subtractingReportingOverflow(digitValue)
: temporary.addingReportingOverflow(digitValue)
guard _fastPath(!overflow2) else { return nil }
result = nextResult
}
} else {
let uppercaseUpperBound = 65 /* "A" */ &+ UInt8(radix &- 10)
let lowercaseUpperBound = 97 /* "a" */ &+ UInt8(radix &- 10)
for digit in codeUnits {
let digitValue: Result
if _fastPath(digit >= 48 /* "0" */ && digit < 58) {
digitValue = Result(digit &- 48)
} else if _fastPath(digit >= 65 && digit < uppercaseUpperBound) {
digitValue = Result(digit &- 65 &+ 10)
} else if _fastPath(digit >= 97 && digit < lowercaseUpperBound) {
digitValue = Result(digit &- 97 &+ 10)
} else {
return nil
}
let (temporary, overflow1) =
result.multipliedReportingOverflow(by: multiplicand)
guard _fastPath(!overflow1) else { return nil }
let (nextResult, overflow2) = isNegative
? temporary.subtractingReportingOverflow(digitValue)
: temporary.addingReportingOverflow(digitValue)
guard _fastPath(!overflow2) else { return nil }
result = nextResult
for digit in codeUnits {
let digitValue: Result
if _fastPath(digit >= 48 && digit < numericalUpperBound) {
digitValue = Result(digit &- 48)
} else if _fastPath(digit >= 65 && digit < uppercaseUpperBound) {
digitValue = Result(digit &- 65 &+ 10)
} else if _fastPath(digit >= 97 && digit < lowercaseUpperBound) {
digitValue = Result(digit &- 97 &+ 10)
} else {
return nil
}
let (temporary, overflow1) =
result.multipliedReportingOverflow(by: multiplicand)
guard _fastPath(!overflow1) else { return nil }
let (nextResult, overflow2) = isNegative
? temporary.subtractingReportingOverflow(digitValue)
: temporary.addingReportingOverflow(digitValue)
guard _fastPath(!overflow2) else { return nil }
result = nextResult
}
return result
}
@@ -83,6 +71,7 @@ internal func _parseASCII<Result: FixedWidthInteger>(
}
@_alwaysEmitIntoClient
@inline(never)
internal func _parseASCII<S: StringProtocol, Result: FixedWidthInteger>(
_ text: S, radix: Int
) -> Result? {
@@ -124,8 +113,7 @@ extension FixedWidthInteger {
/// - radix: The radix, or base, to use for converting `text` to an integer
/// value. `radix` must be in the range `2...36`. The default is 10.
@inlinable
@_specialize(kind: partial, where S == String)
@_specialize(kind: partial, where S == Substring)
@inline(__always)
public init?<S: StringProtocol>(_ text: S, radix: Int = 10) {
_precondition(2...36 ~= radix, "Radix not in range 2...36")
guard _fastPath(!text.isEmpty) else { return nil }