MAFuture: re-base future hierarchy on custom MAProxy class

git-svn-id: http://mikeash.com/svn/MAFuture@114 1ea6ab17-982b-0410-b0ab-91172c90a6e5

MABaseFuture.h

@@ -1,7 +1,9 @@
 #import <Foundation/Foundation.h>
 
+#import "MAProxy.h"
 
-@interface MABaseFuture : NSProxy
+
+@interface MABaseFuture : MAProxy
 {
     id _value;
     NSCondition *_lock;

MABaseFuture.m

@@ -5,16 +5,6 @@
 
 @implementation MABaseFuture
 
-+ (void)initialize
-{
-    // NSProxy implements -description for some boneheaded reason
-    // this effectively removes that implementation by re-pointing
-    // our IMP to point to the implementation of a non-existent method
-    Method m = class_getInstanceMethod(self, @selector(description));
-    IMP forwarder = class_getMethodImplementation(self, @selector(thisMethodDoesNotExist));
-    class_replaceMethod(self, @selector(description), forwarder, method_getTypeEncoding(m));
-}
-
 - (id)init
 {
     _lock = [[NSCondition alloc] init];
@@ -83,4 +73,13 @@ - (id)resolveFuture
     return nil;
 }
 
+- (Class)class
+{
+    Class c = [[self resolveFuture] class];
+    if([NSStringFromClass(c) hasPrefix: @"NSCF"])
+        return [c superclass];
+    else
+        return c;
+}
+
 @end

MAFuture.m

@@ -5,7 +5,7 @@
 #import "MAFuture.h"
 
 
-#define ENABLE_LOGGING 0
+#define ENABLE_LOGGING 1
 
 #if ENABLE_LOGGING
 #define LOG(...) NSLog(__VA_ARGS__)
@@ -66,6 +66,7 @@ - (id)resolveFuture
 
 - (id)forwardingTargetForSelector: (SEL)sel
 {
+    LOG(@"%p forwardingTargetForSelector: %@, resolving future", self, NSStringFromSelector(sel));
     return [self resolveFuture];
 }
 

MAProxy.h

@@ -0,0 +1,17 @@
+@interface MAProxy
+{
+    Class isa;
+    int32_t _refcountMinusOne;
+}
+
++ (id)alloc;
+
+- (void)dealloc;
+- (BOOL)isProxy;
+- (id)retain;
+- (void)release;
+- (id)autorelease;
+- (NSUInteger)retainCount;
+
+@end
+

MAProxy.m

@@ -0,0 +1,56 @@
+#import <Foundation/Foundation.h>
+#import <libkern/OSAtomic.h>
+
+#import "MAProxy.h"
+
+
+@implementation MAProxy
+
++ (void)initialize
+{
+    // runtime requires an implementation
+}
+
++ (id)alloc
+{
+    return NSAllocateObject(self, 0, NULL);
+}
+
+- (void)dealloc
+{
+    NSDeallocateObject(self);
+}
+
+- (void)finalize
+{
+}
+
+- (BOOL)isProxy
+{
+    return YES;
+}
+
+- (id)retain
+{
+    OSAtomicIncrement32(&_refcountMinusOne);
+    return self;
+}
+
+- (void)release
+{
+    if(OSAtomicDecrement32(&_refcountMinusOne) == -1)
+        [self dealloc];
+}
+
+- (id)autorelease
+{
+    [NSAutoreleasePool addObject: self];
+    return self;
+}
+
+- (NSUInteger)retainCount
+{
+    return _refcountMinusOne + 1;
+}
+
+@end

tester.m

@@ -17,36 +17,36 @@ int main(int argc, char **argv)
 
         NSLog(@"start");
         NSString *future = MAFuture(^{
-            fprintf(stderr, "Computing future\n");
+            NSLog(@"Computing future\n");
             usleep(100000);
-            return @"future result";
+            return [NSString stringWithFormat:@"%d", 42];
         });
         NSString *future2 = MAFuture(^{
-            fprintf(stderr, "Computing future\n");
+            NSLog(@"Computing future\n");
             usleep(100000);
-            return @"future result";
+            return [NSString stringWithFormat:@"%d", 42];
         });
         NSLog(@"future created");
         NSString *lazyFuture = MALazyFuture(^{
-            fprintf(stderr, "Computing lazy future\n");
+            NSLog(@"Computing lazy future\n");
             usleep(100000);
             return @"lazy future result";
         });
         NSLog(@"lazy future created");
         NSString *compoundFuture = MACompoundFuture(^{
-            fprintf(stderr, "Computing compound future\n");
+            NSLog(@"Computing compound future\n");
             usleep(100000);
             return @"compound future result";
         });
         NSLog(@"compound future created");
         NSString *compoundLazyFuture = MACompoundLazyFuture(^{
-            fprintf(stderr, "Computing compound lazy future\n");
+            NSLog(@"Computing compound lazy future\n");
             usleep(100000);
             return @"compound future result";
         });
         NSLog(@"compound lazy future created");
 
-        NSLog(@"%d", [future isEqual: future2]);
+        NSLog(@"%p == %p? %llx %llx %s %s", future, future2, (long long)[future hash], (long long)[future2 hash], [future isEqual: future2] ? "YES" : "NO", [future isEqual: future2] ? "YES" : "NO");
         NSLog(@"future: %@", future);
         NSLog(@"lazy future: %@", lazyFuture);
         NSLog(@"compound future: %@", [compoundFuture stringByAppendingString: @" suffix"]);