String Primitives

Null-terminated platform string storage for Swift — a String namespace of ~Copyable owned strings, non-escapable borrowed views, and platform-native code units, with zero Foundation dependency.

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Quick Start

String_Primitives.String is an owned, null-terminated platform string. It owns a single heap allocation and frees it exactly once on deinit; being ~Copyable, the compiler rejects accidental double-ownership at compile time rather than at run time. The code unit is platform-native — UInt8 (UTF-8) on POSIX, UInt16 (UTF-16) on Windows — so one type spans every target without Foundation.String or C string bridging.

import String_Primitives

// An owned, null-terminated platform string — UTF-8 on POSIX, UTF-16 on Windows.
// `~Copyable` means the heap buffer is owned by exactly one value and freed once.
let greeting = String_Primitives.String(ascii: "hello")

print(greeting.count)         // 5  — code units, excluding the null terminator
print(greeting.view.length)   // 5  — a non-escapable borrowed view, no copy

String.Borrowed is the non-escapable (~Escapable) view returned by view: it carries a pointer and a length but owns nothing, and the compiler forbids it from outliving the String it borrows. Because the storage is ~Copyable and tag-neutral, a Tagged phantom type can distinguish two platform strings that share a representation but not a meaning — a filesystem path versus an environment-variable name, for instance:

import String_Primitives
import Tagged_Primitives

// A path and an env-var name share a representation but not a meaning.
// A phantom `Tagged` tag keeps the two from being confused at compile time.
enum PathTag {}

let path = Tagged<PathTag, String_Primitives.String>(ascii: "/usr/local/bin")
print(path.count)   // 14

Storage can be created by adopting: an existing allocation, copying: a borrowed view, from a Swift.Span of code units, or from an ascii: literal; ownership is handed back out with the consuming take(). The module name is String_Primitives and the type is String, so qualify as String_Primitives.String where it would shadow Swift.String.

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Installation

dependencies: [
    .package(url: "https://github.com/swift-primitives/swift-string-primitives.git", branch: "main")
]

.target(
    name: "App",
    dependencies: [
        .product(name: "String Primitives", package: "swift-string-primitives"),
    ]
)

Requires Swift 6.3.1 and macOS 26 / iOS 26 / tvOS 26 / watchOS 26 / visionOS 26 (or the matching Linux / Windows toolchain).

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Architecture

Two library products. Depends only on the Memory.Heap, Span.Protocol, Tagged, and Ownership.Borrow primitives.

Product	Target	Purpose
String Primitives	Sources/String Primitives/	The String namespace: owned ~Copyable String, the non-escapable String.Borrowed view, platform Char / CodeUnit code units, String.length(of:), and Tagged integration for phantom-typed platform strings.
String Primitives Test Support	Tests/Support/	Re-exports the main target (and the Tagged test support) for test consumers.

Foundation-free.

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Platform Support

Platform	Status
macOS 26	Full support
Linux	Full support
Windows	Full support
iOS / tvOS / watchOS / visionOS	Supported

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Community

License

Apache 2.0. See LICENSE.md.