NS和CF

iOS底层和内部：

底层有两套东西：

• NS开头的 = NextStep
  • 比如
    • NSString
• CF开头的 = CoreFoundation
  • 比如
    • CFStringRef

有些变量是可以相互互换使用的 == toll-free bridged

比如：

• CFStringRef == NSString*
• CFURLRef == NSURL*

详见：

• CFStringRef | Apple Developer Documentation
• CFURL | Apple Developer Documentation
• NSURL | Apple Developer Documentation

以及相关部分的变量的互相转换的写法是：

iOS中的：NSString/NSString* 和 CFStringRef 的互相转换：

• MRC

  CFStringRef aCFString = (CFStringRef)aNSString;
  
  NSString *aNSString = (NSString *)aCFString;
  

• ARC

  CFStringRef aCFString = (__bridge CFStringRef)aNSString;
  
  NSString *aNSString = (__bridge NSString *)aCFString;
  

常用小技巧

• 判断CFStringRef是否以某个字符串开头

  CFStringRef prefixFile = (__bridge CFStringRef)@"file://";
  CFStringHasPrefix(someCFStringRef, prefixFile)
  

• 判断CFURLRef是否为空

  if (someCFURLRef != NULL){
  

• CFURLRef转NSURL*

  NSURL* someNSURL = (NSURL*)someCFURLRef;
  

• 从NSURL获取url字符串NSString

  NSString* someUrlNsStr = [someNSURL absoluteString];
  

去hook某个函数时的相关完整代码

CFURLRef CFURLCreateWithString(CFAllocatorRef allocator, CFStringRef URLString, CFURLRef baseURL);

%hookf(CFURLRef, CFURLCreateWithString, CFAllocatorRef allocator, CFStringRef URLString, CFURLRef baseURL){
    CFStringRef prefixFile = (__bridge CFStringRef)@"file://";
    CFStringRef prefixXCoredata = (__bridge CFStringRef)@"x-coredata://";
    bool shouldOmit = false;
    if (CFStringHasPrefix(URLString, prefixFile)){
        shouldOmit = true;
    } else if (CFStringHasPrefix(URLString, prefixXCoredata)) {
        shouldOmit = true;
    }
//    iosLogInfo("shouldOmit=%d for URLString=%{public}@", shouldOmit, URLString);

    if (baseURL != NULL){
        //    NSString* absUrlStr = [baseURL absoluteString];
        NSURL* baseNsurl = (NSURL*)baseURL;
        NSString* baseAbsUrlStr = [baseNsurl absoluteString];
        CFStringRef baseAbsUrlStrRef = (CFStringRef)baseAbsUrlStr;
        if(!shouldOmit) {
            if (CFStringHasPrefix(baseAbsUrlStrRef, prefixFile)){
                shouldOmit = true;
            } else if (CFStringHasPrefix(baseAbsUrlStrRef, prefixXCoredata)) {
                shouldOmit = true;
            }
//            iosLogInfo("shouldOmit=%d for baseAbsUrlStrRef=%{public}@", shouldOmit, baseAbsUrlStrRef);
        }
    }

    CFURLRef newUrl = %orig;
    if(!shouldOmit) {
        iosLogInfo("allocator=%{public}@, URLString=%{public}@, baseURL=%{public}@ -> urlStr=%{public}@", allocator, URLString, baseURL, newUrl);
    }
    return newUrl;
}