[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
我正在創建一個 C 庫和一個包裝器,以便在 Swift 中輕松使用。 C function 有兩個參數,一個數組指針和一個 int 指針:
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;
}
我從我的 Swift 包裝器中稱其為 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()
}
}
問題
如何正確創建 UnsafeMutablePointer 並將其傳遞給 C function? 我硬編碼容量:500 哪個有效,但是如果沒有硬編碼容量,如何正確地做到這一點?
當我嘗試 append 它到我的 class 變量數組數據時,它運行到 EXC_BAD_ACCESS,但是當我 append 它到 foobar 時它是相同的類型。 為什么? 如何在沒有 memory 錯誤的情況下將其分配給 class 變量?
我只能回答您問題的第一部分:為了確定進程列表的必要分配計數,您必須允許使用 NULL 參數調用crgetproclist()
(與可以使用sysctl()
調用相同的方式) NULL 參數用於oldp
以獲得所需的緩沖區大小):
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;
}
現在您可以從 Swift 調用 function 兩次:首先確定分配計數,然后再次檢索進程列表:
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()
另請注意,您可以在純 Swift 中輕松實現 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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