我有一个C结构(旧的库,等等),其中包含一个C字符串,现在我需要将CFString和Swift字符串转换为该C字符串。就像是
struct Product{ char name[50]; char code[20]; }
所以我正在尝试将其分配为
productName.getCString(&myVarOfStructProduct.name, maxLength: 50, encoding: NSUTF8StringEncoding)
但是编译器给我以下错误:无法将类型(int8,int8,int8 ....)转换为[CChar]。
可能的解决方案:
withUnsafeMutablePointer(&myVarOfStructProduct.name) { strlcpy(UnsafeMutablePointer($0), productName, UInt(sizeofValue(myVarOfStructProduct.name))) }
在该块内部,$0是一个指向元组的(可变)指针。该指针UnsafeMutablePointer<Int8>将按BSD库函数的strlcpy()预期 转换为。
$0
UnsafeMutablePointer<Int8>
strlcpy()
它还使用了这样的事实:Swift字符串productName会自动UnsafePointer<UInt8> 按照 UnsafePointer<UInt8> 函数参数行为的字符串值中的说明进行操作。如该线程的注释中所述,这是通过创建一个临时UInt8数组(或序列?)来完成的。所以, _或者_你可以明确地列举了UTF-8字节,并把它们放到目的地:
productName
UnsafePointer<UInt8>
UInt8
withUnsafeMutablePointer(&myVarOfStructProduct.name) { tuplePtr -> Void in var uint8Ptr = UnsafeMutablePointer<UInt8>(tuplePtr) let size = sizeofValue(myVarOfStructProduct.name) var idx = 0 if size == 0 { return } // C array has zero length. for u in productName.utf8 { if idx == size - 1 { break } uint8Ptr[idx++] = u } uint8Ptr[idx] = 0 // NUL-terminate the C string in the array. }
另一个可能的解决方案(带有中间NSData对象):
NSData
withUnsafeMutablePointer(&myVarOfStructProduct.name) { tuplePtr -> Void in let tmp = productName + String(UnicodeScalar(0)) // Add NUL-termination let data = tmp.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)! data.getBytes(tuplePtr, length: sizeofValue(myVarOfStructProduct.name)) }
Swift 3更新:
withUnsafeMutablePointer(to: &myVarOfStructProduct.name) { $0.withMemoryRebound(to: Int8.self, capacity: MemoryLayout.size(ofValue: myVarOfStructProduct.name)) { _ = strlcpy($0, productName, MemoryLayout.size(ofValue: myVarOfStructProduct.name)) } }