cocoa + dmg文件+回溯其路径

Question

我遇到这样一种情况，即我的.dmg文件将存储在包含我的应用程序的可移动存储设备上。当我双击它时，它将被挂载到我的本地计算机上，在挂载的卷中将是我的.app (应用程序文件)。现在，我希望我的应用程序在我的本地计算机上挂载dmg文件后自动启动。另外，现在我的应用程序需要关于实际dmg文件所在位置的信息，比如它在可移动存储设备上的路径。这是可能的吗?如果可能，我如何找到从中挂载卷的dmg文件的路径。

谢谢

Answer 1

在Mac中，

1. 不能自动启动应用程序。有一些安全原因。唯一可以自动启动的是.pkg文件，而且只能通过Safari AFAIK。

1. 可以确定应用程序所在的DMG文件。为此，您必须使用IOKit。试着玩玩IORegistryExplorer.

一些可能对您有帮助的代码

这是我第一次尝试使用IOKit，这是另一个目的，但它应该会有所帮助。

// hopefully all needed headers
#include <sys/stat.h>

#include <IOKit/IOKitLib.h>
#include <IOKit/IOBSD.h>
#include <CoreFoundation/CoreFoundation.h>

/* First we want to get the major and minor BSD number
 * of the DMG that our app is residing on.
 *
 * char *path is the path of a file that resides on the disk image.
 * It is like this: /Volumes/Partition Name/SomeFile
 * The simplest method to get such a path is to ask
 * NSBundle for the path of the executable.
 */

// look up device number with stat
char *path = "path/to/app";

struct stat stats;
if (stat(path, &stats) != 0) {
    return;
}
int bsd_major = major(stats.st_dev);
int bsd_minor = minor(stats.st_dev);

/* Now that we've got the BSD numbers we have to locate the
 * IOService that has those numbers. IOKit works with
 * CoreFoundation types.
 */

CFTypeRef keys[2] = { CFSTR(kIOBSDMajorKey), CFSTR(kIOBSDMinorKey) };
CFTypeRef values[2];
values[0] = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &bsd_major);
values[1] = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &bsd_minor);

CFDictionaryRef matchingDictionary;
matchingDictionary = CFDictionaryCreate(kCFAllocatorDefault,
                                        &keys, &values,
                                        sizeof(keys) / sizeof(*keys),
                                        &kCFTypeDictionaryKeyCallBacks,
                                        &kCFTypeDictionaryValueCallBacks);
    
CFRelease(values[0]);
CFRelease(values[1]);
// IOServiceGetMatchingService uses up one reference to the dictionary
io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault,
                                                   matchingDictionary);
    
if (!service) {
    return;
}

/* Now this part is quite different from what I need
 * for my application. I'm not sure how this works
 * because I'm currently not at my Mac and cannot try it.
 * 
 * You need to go up the IOService chain. It looks like this:
  +-o IOHDIXHDDriveOutKernelUserClient
    +-o IODiskImageBlockStorageDeviceOutKernel   <---- You want to get up here
      +-o IOBlockStorageDriver
        +-o Apple UDIF read-only compressed (zlib) Media
          +-o IOMediaBSDClient
          +-o IOApplePartitionScheme
            +-o Apple@1
            | +-o IOMediaBSDClient
            +-o disk image@2               <---- This is the matched IOService!
              +-o IOMediaBSDClient
 *
 * IODiskImage... has a property "Protocol Characteristics" which is a
 * dictionary that has the key "Virtual Interface Location Path" which is  
 * the path to the disk image. There are probably #defines somewhere in
 * IOKit for those keys.
 *
 * This code is NOT tested. It's out of my head and the documentation.
 * This goes up 4 times in the hierarchy. Hopefully there aren't more
 * than 1 parents.
 */

for (int i = 0; i < 4; i++) {
    io_service_t parent;
    IORegistryEntryGetParentEntry(service, kIOServicePlane, &parent);
    IOObjectRelease(service);
    service = parent;
}

 /* Getting the property from the IOService is the last step:
  */

 CFDictionaryRef characteristics;
 characteristics = (CFDictionaryRef)IORegistryEntryCreateCFProperty(service,
                                          CFSTR("Protocol Characteristics"),
                                          kCFAllocatorDefault, 0)

 CFStringRef *dmgPath = CFDictionaryGetValue(characteristics,
                                    CFSTR("Virtual Interface Location Path"));
 // clean up
 IOObjectRelease(service);
 CFRetain(dmgPath);
 CFRelease(characteristics);

 // Use the path

 // later
 CFRelease(dmgPath);

由于免费的桥接支持，大部分操作都可以使用基础类而不是CoreFoundation类来完成。这使得它更容易和更易读。

如果IOBlockStorageDriver的父IOService为IODiskImageBlockStorageDeviceOutKernel，则上面的示例代码可以正常工作。如果父IOService的名称是"AppleDiskImageDevice"，则IOService链看起来有点不同：

  +-o IOHDIXHDDriveOutKernelUserClient
    +-o AppleDiskImageDevice        <---- You want to get up here
      +-o IOBlockStorageDriver
        +-o Apple Disk Image Media  <---- This is different
          +-o IOMediaBSDClient
          +-o IOApplePartitionScheme
            +-o Apple@1
            | +-o IOMediaBSDClient
            +-o disk image@2        <---- This is the matched IOService!
              +-o IOMediaBSDClient

通过上面的for循环，您可以获得如下所示的图片文件路径URL字符串：

CFMutableDictionaryRef properties = nil;
IORegistryEntryCreateCFProperties(service, &properties, kCFAllocatorDefault, kNilOptions);
if (properties) {
    CFStringRef url = CFDictionaryGetValue(properties, CFSTR("DiskImageURL"));
    CFRelease(properties);
}
IOObjectRelease(service);