Imports code of the RX library.

1 files changed, 55 insertions, 0 deletions

diff --git a/src/objective-c/RxLibrary/private/GRXNSFastEnumerator.m b/src/objective-c/RxLibrary/private/GRXNSFastEnumerator.m
new file mode 100644
index 0000000000..817ff34d95
--- /dev/null
+++ b/src/objective-c/RxLibrary/private/GRXNSFastEnumerator.m
@@ -0,0 +1,55 @@
+#import "GRXNSFastEnumerator.h"
+
+@implementation GRXNSFastEnumerator {
+  id<NSFastEnumeration> _container;
+  NSFastEnumerationState _state;
+  // Number of elements of the container currently in the _state.itemsPtr array.
+  NSUInteger _count;
+  // The index of the next object to return from the _state.itemsPtr array.
+  NSUInteger _index;
+  // A "buffer of one element," for the containers that enumerate their elements one by one. Those
+  // will set _state.itemsPtr to point to this.
+  // The NSFastEnumeration protocol requires it to be __unsafe_unretained, but that's alright
+  // because the only use we'd make of its value is to return it immediately as the result of
+  // nextObject.
+  __unsafe_unretained id _bufferValue;
+  // Neither NSEnumerator nor NSFastEnumeration instances are required to work correctly when the
+  // underlying container is mutated during iteration. The expectation is that an exception is
+  // thrown when that happens. So we check for mutations.
+  unsigned long _mutationFlag;
+  BOOL _mutationFlagIsSet;
+}
+
+- (instancetype)init {
+  return [self initWithContainer:nil];
+}
+
+// Designated initializer.
+- (instancetype)initWithContainer:(id<NSFastEnumeration>)container {
+  NSAssert(container, @"container can't be nil");
+  if ((self = [super init])) {
+    _container = container;
+  }
+  return self;
+}
+
+- (id)nextObject {
+  if (_index == _count) {
+    _index = 0;
+    _count = [_container countByEnumeratingWithState:&_state objects:&_bufferValue count:1];
+    if (_count == 0) {
+      // Enumeration is over.
+      _container = nil;
+      return nil;
+    }
+    if (_mutationFlagIsSet) {
+      NSAssert(_mutationFlag == *(_state.mutationsPtr),
+               @"container was mutated while being enumerated");
+    } else {
+      _mutationFlag = *(_state.mutationsPtr);
+      _mutationFlagIsSet = YES;
+    }
+  }
+  return _state.itemsPtr[_index++];
+}
+@end