CStringArray.swift (3082B)
1 // MIT License 2 // Copyright 2020 Robert Salesas 3 // 4 // Permission is hereby granted, free of charge, to any person obtaining a copy of this software 5 // and associated documentation files (the "Software"), to deal in the Software without restriction, 6 // including without limitation the rights to use, copy, modify, merge, publish, distribute, 7 // sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is 8 // furnished to do so, subject to the following conditions: 9 // 10 // The above copyright notice and this permission notice shall be included in all copies or 11 // substantial portions of the Software. 12 // 13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 14 // BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 15 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 16 // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 17 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 18 // 19 import Foundation 20 21 /// `CStringArray` represents a C null-terminated array of pointers to C strings. 22 /// 23 /// The lifetime of the C strings will correspond to the lifetime of the `CStringArray` 24 /// instance so be careful about copying the buffer as it may contain dangling pointers. 25 26 public struct CStringArray { 27 public let pointer: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?> 28 public let count: Int 29 private var data: Data 30 31 public init(_ array: [String]) { 32 let count = array.count 33 34 // Allocate memory to hold the CStrings and a terminating nil 35 let pointer = UnsafeMutablePointer<UnsafeMutablePointer<CChar>?>.allocate(capacity: count + 1) 36 pointer.initialize(repeating: nil, count: count + 1) // Implicit terminating nil at the end of the array 37 38 // Populate the allocated memory with pointers to CStrings 39 var e = 0 40 array.forEach { 41 pointer[e] = strdup($0) 42 e += 1 43 } 44 45 // This uses the deallocator available on the data structure as a solution to the fact that structs do not have `deinit` 46 self.data = Data(bytesNoCopy: pointer, count: MemoryLayout<UnsafeMutablePointer<CChar>>.size * count, deallocator: .custom({_,_ in 47 for i in 0...count - 1 { 48 free(pointer[i]) 49 } 50 pointer.deallocate() 51 })) 52 53 self.pointer = pointer 54 self.count = array.count 55 } 56 57 public subscript(index: Data.Index) -> UnsafeMutablePointer<CChar>? { 58 get { 59 precondition(index >= 0 && index < count, "Index out of range") 60 return pointer[index] 61 } 62 } 63 64 public subscript(index: Data.Index) -> String? { 65 get { 66 precondition(index >= 0 && index < count, "Index out of range") 67 if let pointee = pointer[index] { 68 return String(cString: pointee) 69 } 70 71 return nil 72 } 73 } 74 }