45 lines
1.7 KiB
Swift
45 lines
1.7 KiB
Swift
internal import CPlaydate
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/// Internal C-string helpers shared by the wrappers.
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///
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/// Passing strings to C goes through the standard `withCString`, which hands
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/// out a pointer to the string's own null-terminated storage without copying.
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extension String {
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/// Creates a string from a nullable C string, or `nil` if the pointer is null.
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init?(playdateCString pointer: UnsafePointer<CChar>?) {
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guard let pointer else { return nil }
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self.init(cString: pointer)
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}
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/// Copies the string into a newly allocated null-terminated C string.
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/// The caller owns the memory and must free it with `deallocate()`.
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func copiedPlaydateCString() -> UnsafeMutablePointer<CChar> {
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withCString { cString in
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let count = utf8.count + 1
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let buffer = UnsafeMutablePointer<CChar>.allocate(capacity: count)
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buffer.initialize(from: cString, count: count)
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return buffer
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}
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}
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}
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#if hasFeature(Embedded) && !os(macOS)
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/// The Embedded Swift runtime allocates through `posix_memalign(3)`, which
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/// the Playdate device C library does not provide. Memory comes from
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/// `malloc`, which the SDK's setup code routes to the firmware allocator.
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/// The pointer is later released with plain `free`, so it cannot be offset
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/// to adjust alignment; the firmware allocator's natural alignment has to
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/// satisfy the request, which the precondition asserts.
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@c(posix_memalign)
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public func posix_memalign(
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_ memptr: UnsafeMutablePointer<UnsafeMutableRawPointer?>,
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_ alignment: Int,
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_ size: Int
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) -> CInt {
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guard let allocation = malloc(size) else { fatalError() }
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precondition(Int(bitPattern: allocation) % alignment == 0)
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memptr.pointee = allocation
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return 0
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}
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#endif
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