在 iOS/MacOS 中调用本机函数时，如何将复杂的 swift 数据类型传递给 C 数据类型？

Question

我设法获得了一个基本的 dylib，我已将其包含在一个框架中，该框架允许我传入一个 Int 和 returns 以及 Int 工作但我将如何传递并且 return 更复杂从 swift 到 C dylib?

的指针、字节数组或实际数据结构等数据类型

是否有任何教程或资源 map/pass/convert 从 swift 数据类型到 C 数据类型，反之亦然，例如在 JNI 中 java？

Answer 1

解释 C 结构并从 Swift 端的 c-dylib 动态提取函数的示例如下所示：

.c 文件

Person *get_person() {
    Person *p = malloc(sizeof(Person));
    p->first_name = strdup("Branford");
    p->last_name = strdup("Marsalis");
    p->age = 60;
    return p;
}

void free_person(Person *person) {
    free(person->first_name);
    free(person->last_name);
    free(person);
}

.h 文件

typedef struct {
    char *first_name;
    char *last_name;
    int age;
} Person;

Swift

typealias getPersonFunc = @convention(c) () -> UnsafeMutablePointer<Person>
typealias freePersonFunc = @convention(c) (UnsafeMutablePointer<Person>) -> Void

...

let handle = dlopen("libsimple.dylib", RTLD_LOCAL|RTLD_NOW)
let get_person_sym = dlsym(handle, "get_person")
let getPerson = unsafeBitCast(get_person_sym, to: getPersonFunc.self)
let cPerson = getPerson()
let person = cPerson.withMemoryRebound(to: Person.self, capacity: 1) { [=12=].pointee }
let firstName = String(cString: UnsafeRawPointer(person.first_name).assumingMemoryBound(to: CChar.self))
let lastName = String(cString: UnsafeRawPointer(person.last_name).assumingMemoryBound(to: CChar.self))

print(firstName)
print(lastName)
print(person.age)

let free_person_sym = dlsym(handle, "free_person")
let freePerson = unsafeBitCast(free_person_sym, to: freePersonFunc.self)
freePerson(cPerson)

dlclose(handle)

测试

此示例的调试控制台输出如下所示：

Branford
Marsalis
60

从Swift到C

假设在 .c 中：

void print_person(Person *person) {
    printf("%s %s is %d years old\n",
           person->first_name,
           person->last_name,
           person->age);
}

然后在 Swift 一侧可以写：

typealias printPersonFunc = @convention(c) (UnsafeMutablePointer<Person>) -> Void
...
let newPerson = UnsafeMutablePointer<Person>.allocate(capacity: 1)
newPerson.pointee.first_name = UnsafeMutablePointer<Int8>(mutating: ("Norah" as NSString).utf8String)
newPerson.pointee.last_name = UnsafeMutablePointer<Int8>(mutating: ("Jones" as NSString).utf8String)
newPerson.pointee.age = 41
let print_person_sym = dlsym(handle, "print_person")
let printPerson = unsafeBitCast(print_person_sym, to: printPersonFunc.self)
printPerson(newPerson)
newPerson.deallocate()

这将在控制台上产生以下输出：

Norah Jones is 41 years old

在 iOS/MacOS 中调用本机函数时，如何将复杂的 swift 数据类型传递给 C 数据类型？

How can I pass complex swift datatypes to C datatypes when calling native functions in iOS/MacOS?

c

macos

dylib

ios

swift