Skip to content

Raw UUID Comparisons #216

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jun 19, 2024
Merged

Raw UUID Comparisons #216

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
c9ddba3
Added a raw UUID comparison thats always available
dimitribouniol Jun 19, 2024
46704b5
Updated the recommended version in the README
dimitribouniol Jun 19, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@ Please check the [releases](https://github.com/mochidev/CodableDatastore/release
dependencies: [
.package(
url: "https://github.com/mochidev/CodableDatastore.git",
.upToNextMinor(from: "0.3.3")
.upToNextMinor(from: "0.3.4")
),
],
...
Expand Down
48 changes: 23 additions & 25 deletions Sources/CodableDatastore/Indexes/UUID+Comparable.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -15,44 +15,42 @@ extension UUID: @retroactive Comparable {
@inlinable
@_disfavoredOverload
public static func < (lhs: UUID, rhs: UUID) -> Bool {
lhs.isLessThan(rhs: rhs)
lhs.uuid < rhs.uuid
}
}
#else
extension UUID: Comparable {
@inlinable
@_disfavoredOverload
public static func < (lhs: UUID, rhs: UUID) -> Bool {
lhs.isLessThan(rhs: rhs)
lhs.uuid < rhs.uuid
}
}
#endif
#endif

extension UUID {
/// Make UUIDs comparable, so that they can be used transparently as an index.
///
/// - SeeAlso: https://github.com/apple/swift-foundation/blob/5388acf1d929865d4df97d3c50e4d08bc4c6bdf0/Sources/FoundationEssentials/UUID.swift#L135-L156
@usableFromInline
func isLessThan(rhs: UUID) -> Bool {
var leftUUID = self.uuid
var rightUUID = rhs.uuid
var result: Int = 0
var diff: Int = 0
withUnsafeBytes(of: &leftUUID) { leftPtr in
withUnsafeBytes(of: &rightUUID) { rightPtr in
for offset in (0 ..< MemoryLayout<uuid_t>.size).reversed() {
diff = Int(leftPtr.load(fromByteOffset: offset, as: UInt8.self)) -
Int(rightPtr.load(fromByteOffset: offset, as: UInt8.self))
// Constant time, no branching equivalent of
// if (diff != 0) {
// result = diff;
// }
result = (result & (((diff - 1) & ~diff) >> 8)) | diff
}
/// Make UUIDs comparable, so that they can be used transparently as an index.
///
/// - SeeAlso: https://github.com/apple/swift-foundation/blob/5388acf1d929865d4df97d3c50e4d08bc4c6bdf0/Sources/FoundationEssentials/UUID.swift#L135-L156
@inlinable
public func < (lhs: uuid_t, rhs: uuid_t) -> Bool {
var lhs = lhs
var rhs = rhs
var result: Int = 0
var diff: Int = 0
withUnsafeBytes(of: &lhs) { leftPtr in
withUnsafeBytes(of: &rhs) { rightPtr in
for offset in (0 ..< MemoryLayout<uuid_t>.size).reversed() {
diff = Int(leftPtr.load(fromByteOffset: offset, as: UInt8.self)) -
Int(rightPtr.load(fromByteOffset: offset, as: UInt8.self))
// Constant time, no branching equivalent of
// if (diff != 0) {
// result = diff;
// }
result = (result & (((diff - 1) & ~diff) >> 8)) | diff
}
}

return result < 0
}

return result < 0
}