用於執行Carbon FSExchangeObjectsCompat調用的Cocoa方法是什麼？

Question

舊的MoreFilesX，FSExchangeObjectsCompat中有這樣一個功能，即「在兩個文件之間交換數據」。它通常用作安全保存方法的一部分，在該方法中寫入臨時文件，然後調用FSExchangeObjectsCompat將新保存的臨時文件與舊的「原始」文件進行交換。它保留了所有的元數據，特權等

我看到高Sierra上的這個函數在APFS捲上出現故障，這在HFS +捲上從未失敗。沒有什麼大驚喜 - 其中很多電話都被棄用了。

但是做同樣的事情的Cocoa NSFileManager方法是什麼？

Answer 1

您可以使用較低級別的功能做類似的事情。這是我寫的與10.12之前的SDK一起使用的代碼。如果您針對10.12 SDK或更高版本進行編譯，則可以使其更簡單，如果您的部署目標爲10.12或更高版本，則更簡單。

#ifndef RENAME_SWAP 
#define RENAME_SWAP 0x00000002 
#endif 

/*! 
    @function ExchangeFiles 

    @abstract Given full paths to two files on the same volume, 
       swap their contents. 

    @discussion This is often part of a safe-save strategy. 

    @param  inOldFile Full path to a file. 
    @param  inNewFile Full path to a file. 
    @result  0 if all went well, -1 otherwise. 
*/ 
int ExchangeFiles(const char* inOldFile, const char* inNewFile) 
{ 
    int result = -1; 
    static dispatch_once_t sOnce = 0; 
    static renameFuncType sRenameFunc = NULL; 
    // Try to get a function pointer to renamex_np, which is available in OS 10.12 and later. 
    dispatch_once(&sOnce, 
     ^{ 
      sRenameFunc = (renameFuncType) dlsym(RTLD_DEFAULT, "renamex_np"); 
     }); 

    // renamex_np is only available on OS 10.12 and later, and does not work on HFS+ volumes 
    // but does work on APFS volumes. Being the latest and greatest, we try it first. 
    if (sRenameFunc != NULL) 
    { 
     result = (*sRenameFunc)(inOldFile, inNewFile, RENAME_SWAP); 
    } 

    if (result != 0) 
    { 
     // exchangedata is an older function that works on HFS+ but not APFS. 
     result = exchangedata(inOldFile, inNewFile, 0); 
    } 

    if (result != 0) 
    { 
     // Neither function worked, we must go old school. 
     std::string nameTemplate(inOldFile); 
     nameTemplate += "-swapXXXX"; 
     // Make a mutable copy of the template 
     std::vector<char> workPath(nameTemplate.size() + 1); 
     memcpy(&workPath[0], nameTemplate.c_str(), nameTemplate.size() + 1); 
     mktemp(&workPath[0]); 
     std::string tempPath(&workPath[0]); 

     // Make the old file have a temporary name 
     result = rename(inOldFile, tempPath.c_str()); 

     // Put the new file data under the old name. 
     if (result == 0) 
     { 
      result = rename(inNewFile, inOldFile); 
     } 

     // Put the old data under the new name. 
     if (result == 0) 
     { 
      result = rename(tempPath.c_str(), inNewFile); 
     } 
    } 

    return result; 
} 

Answer 2

你想要-[NSFileManager replaceItemAtURL:withItemAtURL:backupItemName:options:resultingItemURL:error:]。