1 files changed, 167 insertions, 0 deletions
diff --git a/Foundation/GTMNSEnumerator+Filter.m b/Foundation/GTMNSEnumerator+Filter.m
new file mode 100644
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--- /dev/null
+++ b/Foundation/GTMNSEnumerator+Filter.m
@@ -0,0 +1,167 @@
+//
+//  GTMNSEnumerator+Filter.m
+//
+//  Copyright 2007-2008 Google Inc.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License"); you may not
+//  use this file except in compliance with the License.  You may obtain a copy
+//  of the License at
+// 
+//  http://www.apache.org/licenses/LICENSE-2.0
+// 
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+//  License for the specific language governing permissions and limitations under
+//  the License.
+//
+
+#import "GTMNSEnumerator+Filter.h"
+
+// a private subclass of NSEnumerator that does all the work.
+// public interface just returns one of these.
+// This top level class contains all the additional boilerplate. Specific
+// behavior is in the subclasses.
+@interface GTMEnumerator : NSEnumerator {
+ @protected
+  NSEnumerator *base_;  // STRONG
+  SEL operation_; // either a predicate or a transform depending on context.
+  id other_;  // STRONG, may be nil
+}
+- (id)nextObject;
+- (BOOL)filterObject:(id)obj returning:(id *)resultp;
+@end
+@implementation GTMEnumerator
+- (id)initWithBase:(NSEnumerator *)base
+               sel:(SEL)filter
+            object:(id)optionalOther {
+  self = [super init];
+  if (self) {
+
+    // specializing a nil enumerator returns nil.
+    if (nil == base) {
+      [self release];
+      return nil;
+    }
+
+    base_ = [base retain];
+    operation_ = filter;
+    other_ = [optionalOther retain];
+  }
+  return self;
+}
+
+// it is an error to call this initializer.
+- (id)init {
+  [self doesNotRecognizeSelector:_cmd];
+  return nil;
+}
+
+- (void)dealloc {
+  [base_ release];
+  [other_ release];
+  [super dealloc];
+}
+
+- (id)nextObject {
+  for (id obj = [base_ nextObject]; obj; obj = [base_ nextObject]) {
+    id result = nil;
+    if ([self filterObject:obj returning:&result]) {
+      return result; 
+    }
+  }
+  return nil;
+}
+
+// subclasses must override
+- (BOOL)filterObject:(id)obj returning:(id *)resultp {
+  [self doesNotRecognizeSelector:_cmd];
+  return NO;
+}
+@end
+
+// a transformer, for each item in the enumerator, returns a f(item).
+@interface GTMEnumeratorTransformer : GTMEnumerator
+- (BOOL)filterObject:(id)obj returning:(id *)resultp;
+@end
+@implementation GTMEnumeratorTransformer
+- (BOOL)filterObject:(id)obj returning:(id *)resultp {
+  *resultp = [obj performSelector:operation_ withObject:other_];
+  return nil != *resultp;
+}
+@end
+
+// a transformer, for each item in the enumerator, returns a f(item).
+// a target transformer swaps the target and the argument.
+@interface GTMEnumeratorTargetTransformer : GTMEnumerator
+- (BOOL)filterObject:(id)obj returning:(id *)resultp;
+@end
+@implementation GTMEnumeratorTargetTransformer
+- (BOOL)filterObject:(id)obj returning:(id *)resultp {
+  *resultp = [other_ performSelector:operation_ withObject:obj];
+  return nil != *resultp;
+}
+@end
+
+// a filter, for each item in the enumerator, if(f(item)) { returns item. }
+@interface GTMEnumeratorFilter : GTMEnumerator
+- (BOOL)filterObject:(id)obj returning:(id *)resultp;
+@end
+@implementation GTMEnumeratorFilter
+// We must take care here, since Intel leaves junk in high bytes of return register
+// for predicates that return BOOL.
+- (BOOL)filterObject:(id)obj returning:(id *)resultp {
+  *resultp = obj;
+  // intptr_t is an integer the same size as a pointer. <stdint.h>
+  return (BOOL) (intptr_t) [obj performSelector:operation_ withObject:other_];
+}
+@end
+
+// a target filter, for each item in the enumerator, if(f(item)) { returns item. }
+// a target transformer swaps the target and the argument.
+@interface GTMEnumeratorTargetFilter : GTMEnumerator
+- (BOOL)filterObject:(id)obj returning:(id *)resultp;
+@end
+@implementation GTMEnumeratorTargetFilter
+// We must take care here, since Intel leaves junk in high bytes of return register
+// for predicates that return BOOL.
+- (BOOL)filterObject:(id)obj returning:(id *)resultp {
+  *resultp = obj;
+  // intptr_t is an integer the same size as a pointer. <stdint.h>
+  return (BOOL) (intptr_t) [other_ performSelector:operation_ withObject:obj];
+}
+@end
+
+@implementation NSEnumerator (GTMEnumeratorFilterAdditions)
+
+- (NSEnumerator *)gtm_filteredEnumeratorByMakingEachObjectPerformSelector:(SEL)selector
+                                                               withObject:(id)argument {
+  return [[[GTMEnumeratorFilter alloc] initWithBase:self
+                                                sel:selector
+                                             object:argument] autorelease];
+}
+
+- (NSEnumerator *)gtm_enumeratorByMakingEachObjectPerformSelector:(SEL)selector
+                                                       withObject:(id)argument {
+  return [[[GTMEnumeratorTransformer alloc] initWithBase:self
+                                                     sel:selector
+                                                  object:argument] autorelease];
+}
+
+
+- (NSEnumerator *)gtm_filteredEnumeratorByTarget:(id)target
+                           performOnEachSelector:(SEL)selector {
+  return [[[GTMEnumeratorTargetFilter alloc] initWithBase:self
+                                                      sel:selector
+                                                   object:target] autorelease];
+}
+
+- (NSEnumerator *)gtm_enumeratorByTarget:(id)target
+                   performOnEachSelector:(SEL)selector {
+  return [[[GTMEnumeratorTargetTransformer alloc] initWithBase:self
+                                                           sel:selector
+                                                        object:target] autorelease];
+}
+
+@end
+