refcounting.m

#import <Foundation/Foundation.h>
#import <time.h>

#define USE_CF_NONOBJC 1

#if USE_CF_NONOBJC
extern CFTypeRef _CFNonObjCRetain(CFTypeRef cf);
extern void _CFNonObjCRelease(CFTypeRef cf);
#endif

extern id objc_retain(id obj);
extern void objc_release(id obj);

@interface RefCountOverrides : NSObject {
    _Atomic(int64_t) refcount;
}

@end

@implementation RefCountOverrides

- (instancetype) init {
    if ((self = [super init])) {
        refcount = 1;
    }
    return self;
}

- (oneway void) release {
    if (--refcount == 0) {
        [self dealloc];
    }
}

- (id) retain {
    ++refcount;
    return self;
}

@end

#define ITERS 20000000
#define NSEC_PER_ITER(time) (((double)time * (double)NSEC_PER_SEC) / (double)ITERS)

#define TEST(body, name) do {\
start = [NSDate date];\
for (int i = 0; i < ITERS; i++) {\
body\
}\
elapsed = -[start timeIntervalSinceNow];\
if (baseline == 0) printf("Baseline of %f nanoseconds to -retain+-release an NSObject established\n", NSEC_PER_ITER(elapsed));\
else printf("It was %.2fx as fast (%f nanoseconds) to use %s on %s \n", baseline / elapsed, NSEC_PER_ITER(elapsed), name, names[objIdx]);\
} while (0)

int main() {
  
#define OBJECT_COUNT 8
  id objects[OBJECT_COUNT];
  objects[0] = [NSString stringWithUTF8String:"The quick brown fox jümps over the lazy dog!"];
  objects[1] = @"The quick brown fox jümps over the lazy dog!";
  objects[2] = (id)NSLocaleMeasurementSystem;
  objects[3] = [NSString stringWithUTF8String:"The quick brown fox jumps over the lazy dog"];
  objects[4] = [[[NSObject alloc] init] autorelease];
  objects[5] = @5;
  objects[6] = [[[RefCountOverrides alloc] init] autorelease];
  objects[7] = [NSURL fileURLWithPath:@"/System/Library/Frameworks/"];
  
  for (int objIdx = 0; objIdx < OBJECT_COUNT; objIdx++) {
    id obj = objects[objIdx];
    objc_retain(obj);
    objc_release(obj);
    NSLog(@"%@", NSStringFromClass([obj class]));
  }
  
  const char *names[OBJECT_COUNT] = { "CFTypeRefs", "constant NSStrings", "constant NSStrings in the shared cache", "regular NSStrings", "NSObjects", "tagged NSObjects", "NSObjects with custom refcounting", "NSURLs" };
  
  NSDate *start = nil;
  int objIdx = 0;
  NSTimeInterval elapsed = 0;
  NSTimeInterval baseline = 0;
  
  TEST([objects[4] retain]; [objects[4] release];, "establish a baseline");
  
  baseline = elapsed;
  
  for (int objIdx = 0; objIdx < OBJECT_COUNT; objIdx++) {
#if USE_CF_NONOBJC
    if (objIdx == 0 || objIdx == 1 || objIdx == 2) {
      TEST(_CFNonObjCRetain((CFTypeRef)objects[0]); _CFNonObjCRelease((CFTypeRef)objects[0]);, "_CFNonObjCRetain + _CFNonObjCRelease");
    }
#endif
    
    TEST([objects[objIdx] retain]; [objects[objIdx] release];, "-retain + -release");
    
    TEST(objc_retain(objects[objIdx]); objc_release(objects[objIdx]);, "objc_retain + objc_release");
    
    TEST(CFRetain((CFTypeRef)objects[objIdx]); CFRelease((CFTypeRef)objects[objIdx]);, "CFRetain + CFRelease");
  }
}