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vanvoordenvanvoorden
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[stdlib] string identical
1 parent a782752 commit d26fa93

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6 files changed

+232
-1
lines changed

6 files changed

+232
-1
lines changed

‎benchmark/single-source/StringTests.swift‎

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -40,6 +40,10 @@ public var benchmarks: [BenchmarkInfo] {
4040
runFunction: run_StringHasSuffixUnicode,
4141
tags: [.validation, .api, .String],
4242
legacyFactor: 1000),
43+
BenchmarkInfo(
44+
name: "StringIdentical",
45+
runFunction: run_StringIdentical,
46+
tags: [.validation, .api, .String]),
4347
]
4448

4549
if #available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *) {
@@ -1676,3 +1680,13 @@ public func run_iterateWords(_ n: Int) {
16761680
blackHole(swiftOrgHTML._words)
16771681
}
16781682
}
1683+
1684+
public func run_StringIdentical(_ n: Int) {
1685+
let str1 = "The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. "
1686+
let str2 = str1
1687+
for _ in 0 ..< n {
1688+
for _ in 0 ..< 100_000 {
1689+
check(str1.isIdentical(to: str2))
1690+
}
1691+
}
1692+
}

‎benchmark/single-source/SubstringTest.swift‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,7 @@ public let benchmarks = [
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BenchmarkInfo(name: "SubstringFromLongString2", runFunction: run_SubstringFromLongString, tags: [.validation, .api, .String]),
3131
BenchmarkInfo(name: "SubstringFromLongStringGeneric2", runFunction: run_SubstringFromLongStringGeneric, tags: [.validation, .api, .String]),
3232
BenchmarkInfo(name: "SubstringTrimmingASCIIWhitespace", runFunction: run_SubstringTrimmingASCIIWhitespace, tags: [.validation, .api, .String]),
33+
BenchmarkInfo(name: "SubstringIdentical", runFunction: run_SubstringIdentical, tags: [.validation, .String]),
3334
]
3435

3536
// A string that doesn't fit in small string storage and doesn't fit in Latin-1
@@ -332,3 +333,11 @@ public func run _LessSubstringSubstringGenericStringProtocol(_ n: Int) {
332333
}
333334
}
334335
*/
336+
337+
@inline(never)
338+
public func run_SubstringIdentical(_ n: Int) {
339+
let (a, b) = (ss1, ss1)
340+
for _ in 1...n*500 {
341+
blackHole(a.isIdentical(to: b))
342+
}
343+
}

‎stdlib/public/core/String.swift‎

Lines changed: 19 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1112,4 +1112,22 @@ extension String {
11121112
}
11131113
}
11141114

1115-
1115+
extension String {
1116+
/// Returns a boolean value indicating whether this string is identical to
1117+
/// `other`.
1118+
///
1119+
/// Two string values are identical if there is no way to distinguish between
1120+
/// them.
1121+
///
1122+
/// Comparing strings this way includes comparing (normally) hidden
1123+
/// implementation details such as the memory location of any underlying
1124+
/// string storage object. Therefore, identical strings are guaranteed to
1125+
/// compare equal with `==`, but not all equal strings are considered
1126+
/// identical.
1127+
///
1128+
/// - Performance: O(1)
1129+
@_alwaysEmitIntoClient
1130+
public func isIdentical(to other: Self) -> Bool {
1131+
self._guts.rawBits == other._guts.rawBits
1132+
}
1133+
}

‎stdlib/public/core/Substring.swift‎

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1385,3 +1385,24 @@ extension Substring {
13851385
return Substring(_unchecked: Slice(base: base, bounds: r))
13861386
}
13871387
}
1388+
1389+
extension Substring {
1390+
/// Returns a boolean value indicating whether this substring is identical to
1391+
/// `other`.
1392+
///
1393+
/// Two substring values are identical if there is no way to distinguish
1394+
/// between them.
1395+
///
1396+
/// Comparing substrings this way includes comparing (normally) hidden
1397+
/// implementation details such as the memory location of any underlying
1398+
/// substring storage object. Therefore, identical substrings are guaranteed
1399+
/// to compare equal with `==`, but not all equal substrings are considered
1400+
/// identical.
1401+
///
1402+
/// - Performance: O(1)
1403+
@_alwaysEmitIntoClient
1404+
public func isIdentical(to other: Self) -> Bool {
1405+
self._wholeGuts.rawBits == other._wholeGuts.rawBits &&
1406+
self._offsetRange == other._offsetRange
1407+
}
1408+
}

‎test/stdlib/StringAPI.swift‎

Lines changed: 37 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -533,4 +533,41 @@ StringTests.test("hasPrefix/hasSuffix vs Character boundaries") {
533533
expectFalse(s2.hasSuffix("\n"))
534534
}
535535

536+
StringTests.test("isIdentical(to:) small ascii") {
537+
let a = "Hello"
538+
let b = "Hello"
539+
540+
precondition(a == b)
541+
542+
expectTrue(a.isIdentical(to: a))
543+
expectTrue(b.isIdentical(to: b))
544+
expectTrue(a.isIdentical(to: b)) // Both small ASCII strings
545+
expectTrue(b.isIdentical(to: a))
546+
}
547+
548+
StringTests.test("isIdentical(to:) small unicode") {
549+
let a = "Cafe\u{301}"
550+
let b = "Cafe\u{301}"
551+
let c = "Café"
552+
553+
precondition(a == b)
554+
precondition(b == c)
555+
556+
expectTrue(a.isIdentical(to: b))
557+
expectTrue(b.isIdentical(to: a))
558+
expectFalse(a.isIdentical(to: c))
559+
expectFalse(b.isIdentical(to: c))
560+
}
561+
562+
StringTests.test("isIdentical(to:) large ascii") {
563+
let a = String(repeating: "foo", count: 1000)
564+
let b = String(repeating: "foo", count: 1000)
565+
566+
precondition(a == b)
567+
568+
expectFalse(a.isIdentical(to: b)) // Two large, distinct native strings
569+
expectTrue(a.isIdentical(to: a))
570+
expectTrue(b.isIdentical(to: b))
571+
}
572+
536573
runAllTests()

‎test/stdlib/subString.swift‎

Lines changed: 132 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -31,6 +31,41 @@ func checkHasContiguousStorageSubstring(_ x: Substring.UTF8View) {
3131
expectTrue(hasStorage)
3232
}
3333

34+
fileprivate func slices(
35+
_ s: String,
36+
from: Int,
37+
to: Int
38+
) -> (
39+
Substring,
40+
Substring,
41+
Substring
42+
) {
43+
let s1 = s[s.index(s.startIndex, offsetBy: from) ..<
44+
s.index(s.startIndex, offsetBy: to)]
45+
let s2 = s1[s1.startIndex..<s1.endIndex]
46+
let s3 = s2[s1.startIndex..<s1.endIndex]
47+
return (s1, s2, s3)
48+
}
49+
50+
fileprivate func allNotEmpty(
51+
_ s: Substring...
52+
) -> Bool {
53+
s.allSatisfy { $0.isEmpty == false }
54+
}
55+
56+
fileprivate func allEqual(
57+
_ s: Substring...
58+
) -> Bool {
59+
for i in 0..<s.count {
60+
for j in (i + 1)..<s.count {
61+
if s[i] != s[j] {
62+
return false
63+
}
64+
}
65+
}
66+
return true
67+
}
68+
3469
SubstringTests.test("Equality") {
3570
let s = "abcdefg"
3671
let s1 = s[s.index(s.startIndex, offsetBy: 2) ..<
@@ -282,4 +317,101 @@ SubstringTests.test("Substring.base") {
282317
}
283318
}
284319

320+
SubstringTests.test("isIdentical(to:) small ascii") {
321+
let (a1, a2, a3) = slices("Hello", from: 2, to: 4)
322+
let (b1, b2, b3) = slices("Hello", from: 2, to: 4)
323+
324+
precondition(allNotEmpty(a1, a2, a3, b1, b2, b3))
325+
precondition(allEqual(a1, a2, a3, b1, b2, b3))
326+
327+
expectTrue(a1.isIdentical(to: a1))
328+
expectTrue(a1.isIdentical(to: a2))
329+
expectTrue(a1.isIdentical(to: a3))
330+
expectTrue(a1.isIdentical(to: b1))
331+
expectTrue(a1.isIdentical(to: b2))
332+
expectTrue(a1.isIdentical(to: b3))
333+
334+
expectTrue(a2.isIdentical(to: a1))
335+
expectTrue(a2.isIdentical(to: a2))
336+
expectTrue(a2.isIdentical(to: a3))
337+
expectTrue(a2.isIdentical(to: b1))
338+
expectTrue(a2.isIdentical(to: b2))
339+
expectTrue(a2.isIdentical(to: b3))
340+
341+
expectTrue(a3.isIdentical(to: a1))
342+
expectTrue(a3.isIdentical(to: a2))
343+
expectTrue(a3.isIdentical(to: a3))
344+
expectTrue(a3.isIdentical(to: b1))
345+
expectTrue(a3.isIdentical(to: b2))
346+
expectTrue(a3.isIdentical(to: b3))
347+
}
348+
349+
SubstringTests.test("isIdentical(to:) small unicode") {
350+
let (a1, a2, a3) = slices("Hello Cafe\u{301}", from: 2, to: 4)
351+
let (b1, b2, b3) = slices("Hello Cafe\u{301}", from: 2, to: 4)
352+
let (c1, c2, c3) = slices("Hello Café", from: 2, to: 4)
353+
354+
precondition(allNotEmpty(a1, a2, a3, b1, b2, b3, c1, c2, c3))
355+
precondition(allEqual(a1, a2, a3, b1, b2, b3, c1, c2, c3))
356+
357+
expectTrue(a1.isIdentical(to: a1))
358+
expectTrue(a1.isIdentical(to: a2))
359+
expectTrue(a1.isIdentical(to: a3))
360+
expectTrue(a1.isIdentical(to: b1))
361+
expectTrue(a1.isIdentical(to: b2))
362+
expectTrue(a1.isIdentical(to: b3))
363+
expectFalse(a1.isIdentical(to: c1))
364+
expectFalse(a1.isIdentical(to: c2))
365+
expectFalse(a1.isIdentical(to: c3))
366+
367+
expectTrue(a2.isIdentical(to: a1))
368+
expectTrue(a2.isIdentical(to: a2))
369+
expectTrue(a2.isIdentical(to: a3))
370+
expectTrue(a2.isIdentical(to: b1))
371+
expectTrue(a2.isIdentical(to: b2))
372+
expectTrue(a2.isIdentical(to: b3))
373+
expectFalse(a2.isIdentical(to: c1))
374+
expectFalse(a2.isIdentical(to: c2))
375+
expectFalse(a2.isIdentical(to: c3))
376+
377+
expectTrue(a3.isIdentical(to: a1))
378+
expectTrue(a3.isIdentical(to: a2))
379+
expectTrue(a3.isIdentical(to: a3))
380+
expectTrue(a3.isIdentical(to: b1))
381+
expectTrue(a3.isIdentical(to: b2))
382+
expectTrue(a3.isIdentical(to: b3))
383+
expectFalse(a3.isIdentical(to: c1))
384+
expectFalse(a3.isIdentical(to: c2))
385+
expectFalse(a3.isIdentical(to: c3))
386+
}
387+
388+
SubstringTests.test("isIdentical(to:) large ascii") {
389+
let (a1, a2, a3) = slices(String(repeating: "Hello", count: 1000), from: 2, to: 4)
390+
let (b1, b2, b3) = slices(String(repeating: "Hello", count: 1000), from: 2, to: 4)
391+
392+
precondition(allNotEmpty(a1, a2, a3, b1, b2, b3))
393+
precondition(allEqual(a1, a2, a3, b1, b2, b3))
394+
395+
expectTrue(a1.isIdentical(to: a1))
396+
expectTrue(a1.isIdentical(to: a2))
397+
expectTrue(a1.isIdentical(to: a3))
398+
expectFalse(a1.isIdentical(to: b1))
399+
expectFalse(a1.isIdentical(to: b2))
400+
expectFalse(a1.isIdentical(to: b3))
401+
402+
expectTrue(a2.isIdentical(to: a1))
403+
expectTrue(a2.isIdentical(to: a2))
404+
expectTrue(a2.isIdentical(to: a3))
405+
expectFalse(a2.isIdentical(to: b1))
406+
expectFalse(a2.isIdentical(to: b2))
407+
expectFalse(a2.isIdentical(to: b3))
408+
409+
expectTrue(a3.isIdentical(to: a1))
410+
expectTrue(a3.isIdentical(to: a2))
411+
expectTrue(a3.isIdentical(to: a3))
412+
expectFalse(a3.isIdentical(to: b1))
413+
expectFalse(a3.isIdentical(to: b2))
414+
expectFalse(a3.isIdentical(to: b3))
415+
}
416+
285417
runAllTests()

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