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/*
Creates an array of C-strings that can be passed to C functions and automatically deallocated
Copyright 2020 Robert Salesas
*/
public struct CStringArray {
public let pointer: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?>
public let count: Int
private var data: Data
public init(_ array: [String]) {
let count = array.count
// Allocate memory to hold the CStrings and a terminating nil
let pointer = UnsafeMutablePointer<UnsafeMutablePointer<CChar>?>.allocate(capacity: count + 1)
pointer.initialize(repeating: nil, count: count + 1) // Implicit terminating nil at the end of the array
// Populate the allocated memory with pointers to CStrings
var e = 0
array.forEach {
pointer[e] = strdup($0)
e += 1
}
// This uses the deallocator available on the data structure as a solution to the fact that structs do not have `deinit`
self.data = Data(bytesNoCopy: pointer, count: MemoryLayout<UnsafeMutablePointer<CChar>>.size * count, deallocator: .custom({_,_ in
for i in 0...count - 1 {
free(pointer[i])
}
pointer.deallocate()
}))
self.pointer = pointer
self.count = array.count
}
public subscript(index: Data.Index) -> UnsafeMutablePointer<CChar>? {
get {
precondition(index >= 0 && index < count, "Index out of range")
return pointer[index]
}
}
public subscript(index: Data.Index) -> String? {
get {
precondition(index >= 0 && index < count, "Index out of range")
if let pointee = pointer[index] {
return String(cString: pointee)
}
return nil
}
}
}
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