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[英]Function that returns int array[] or pointer to int array[] back to calling routine in C
[英]Calling C function with array pointer and int pointer from Swift
我正在创建一个 C 库和一个包装器,以便在 Swift 中轻松使用。 C function 有两个参数,一个数组指针和一个 int 指针:
int crgetproclist(struct kinfo_proc *proc_list, size_t *count) {
int err = 0;
size_t length = 0;
static const int name[] = { CTL_KERN, KERN_PROC, KERN_PROC_ALL, 0 };
// Call sysctl with a NULL buffer to get proper length
err = sysctl((int *)name, (sizeof(name) / sizeof(*name)) - 1, NULL, &length, NULL, 0);
//if (err) return [-1];
// Get the actual process list
err = sysctl((int *)name, (sizeof(name) / sizeof(*name)) - 1, proc_list, &length, NULL, 0);
//if (err) return [-1];
*count = length / sizeof(struct kinfo_proc);
for (int i = 0; i < *count; i++) {
struct kinfo_proc proc = proc_list[i];
proc = proc;
}
return 1;
}
我从我的 Swift 包装器中称其为 function:
var data: [Process] = []
override func viewDidLoad() {
super.viewDidLoad()
let proc_list: UnsafeMutablePointer<kinfo_proc> = UnsafeMutablePointer<kinfo_proc>.allocate(capacity: 500)
var count: size_t = 0
let result = crgetproclist(proc_list, &count)
var foobar: [Process] = []
if (result == 1) {
for i in 1..<count {
var proc: kinfo_proc = proc_list[i]
var process = Process(proc: proc)
foobar.append(process) // <---- works
self.data.append(process) // <---- EXC_BAD_ACCESS ????
}
self.data.sort(by: {
(a: Process, b: Process) -> Bool in
return a.name.lowercased() < b.name.lowercased()
})
self.myTable.reloadData()
}
}
class Process: NSObject {
var _proc: kinfo_proc
var pid: pid_t
var name: String
var icon: NSImage?
var isAlive: Bool = false
var uid: uid_t = 0
init(proc: kinfo_proc) {
self._proc = proc
self.pid = proc.kp_proc.p_pid
self.name = String(cString: crgetprocname(pid))
self.uid = crgetuid(pid)
super.init()
}
}
问题
如何正确创建 UnsafeMutablePointer 并将其传递给 C function? 我硬编码容量:500 哪个有效,但是如果没有硬编码容量,如何正确地做到这一点?
当我尝试 append 它到我的 class 变量数组数据时,它运行到 EXC_BAD_ACCESS,但是当我 append 它到 foobar 时它是相同的类型。 为什么? 如何在没有 memory 错误的情况下将其分配给 class 变量?
我只能回答您问题的第一部分:为了确定进程列表的必要分配计数,您必须允许使用 NULL 参数调用crgetproclist()
(与可以使用sysctl()
调用相同的方式) NULL 参数用于oldp
以获得所需的缓冲区大小):
int crgetproclist(struct kinfo_proc *proc_list, size_t *count) {
int err = 0;
size_t length;
static const int name[] = { CTL_KERN, KERN_PROC, KERN_PROC_ALL };
if (proc_list == NULL) {
// Call sysctl with a NULL buffer to get proper length
length = 0;
err = sysctl((int *)name, (sizeof(name) / sizeof(*name)), NULL, &length, NULL, 0);
} else {
// Get the actual process list
length = *count * sizeof(struct kinfo_proc);
err = sysctl((int *)name, (sizeof(name) / sizeof(*name)), proc_list, &length, NULL, 0);
}
if (err) return -1;
*count = length / sizeof(struct kinfo_proc);
return 1;
}
现在您可以从 Swift 调用 function 两次:首先确定分配计数,然后再次检索进程列表:
var count: size_t = 0
crgetproclist(nil, &count)
let procList = UnsafeMutablePointer<kinfo_proc>.allocate(capacity: count)
if crgetproclist(procList, &count) == 1 {
for i in 0..<count {
let proc = procList[i]
// ...
}
}
procList.deallocate()
另请注意,您可以在纯 Swift 中轻松实现 function:
func getProcessList() -> [kinfo_proc]? {
var name : [Int32] = [ CTL_KERN, KERN_PROC, KERN_PROC_ALL ]
var length = size_t()
sysctl(&name, UInt32(name.count), nil, &length, nil, 0)
let count = length / MemoryLayout<kinfo_proc>.size
var procList = Array(repeating: kinfo_proc(), count: count)
let result = sysctl(&name, UInt32(name.count), &procList, &length, nil, 0)
guard result == 0 else { return nil } // Some error ...
return Array(procList.prefix(length / MemoryLayout<kinfo_proc>.size))
}
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