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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#import "base/ios/crb_protocol_observers.h"
#include <objc/runtime.h>
#include <stddef.h>
#include <vector>
#include "base/check.h"
#include "base/containers/contains.h"
#include "base/notreached.h"
#include "base/ranges/algorithm.h"
@interface CRBProtocolObservers () {
Protocol* _protocol;
// ivars declared here are private to the implementation but must be
// public for allowing the C++ |Iterator| class access to those ivars.
@public
// vector of weak pointers to observers.
std::vector<__weak id> _observers;
// The nested level of observer iteration.
// A depth of 0 means nobody is currently iterating on the list of observers.
int _invocationDepth;
}
// Removes nil observers from the list and is called when the
// |_invocationDepth| reaches 0.
- (void)compact;
@end
namespace {
class Iterator {
public:
explicit Iterator(CRBProtocolObservers* protocol_observers);
~Iterator();
id GetNext();
private:
CRBProtocolObservers* protocol_observers_;
size_t index_;
size_t max_index_;
};
Iterator::Iterator(CRBProtocolObservers* protocol_observers)
: protocol_observers_(protocol_observers),
index_(0),
max_index_(protocol_observers->_observers.size()) {
DCHECK(protocol_observers_);
++protocol_observers->_invocationDepth;
}
Iterator::~Iterator() {
if (protocol_observers_ && --protocol_observers_->_invocationDepth == 0)
[protocol_observers_ compact];
}
id Iterator::GetNext() {
if (!protocol_observers_)
return nil;
auto& observers = protocol_observers_->_observers;
// Skip nil elements.
size_t max_index = std::min(max_index_, observers.size());
while (index_ < max_index && !observers[index_])
++index_;
return index_ < max_index ? observers[index_++] : nil;
}
}
@interface CRBProtocolObservers ()
// Designated initializer.
- (instancetype)initWithProtocol:(Protocol*)protocol;
@end
@implementation CRBProtocolObservers
+ (instancetype)observersWithProtocol:(Protocol*)protocol {
return [[self alloc] initWithProtocol:protocol];
}
- (id)init {
NOTREACHED();
return nil;
}
- (id)initWithProtocol:(Protocol*)protocol {
self = [super init];
if (self) {
_protocol = protocol;
}
return self;
}
- (Protocol*)protocol {
return _protocol;
}
- (void)addObserver:(id)observer {
DCHECK(observer);
DCHECK([observer conformsToProtocol:self.protocol]);
if (base::Contains(_observers, observer))
return;
_observers.push_back(observer);
}
- (void)removeObserver:(id)observer {
DCHECK(observer);
auto it = base::ranges::find(_observers, observer);
if (it != _observers.end()) {
if (_invocationDepth)
*it = nil;
else
_observers.erase(it);
}
}
- (BOOL)empty {
int count = 0;
for (id observer : _observers) {
if (observer != nil)
++count;
}
return count == 0;
}
#pragma mark - NSObject
- (NSMethodSignature*)methodSignatureForSelector:(SEL)selector {
NSMethodSignature* signature = [super methodSignatureForSelector:selector];
if (signature)
return signature;
// Look for a required method in the protocol. protocol_getMethodDescription
// returns a struct whose fields are null if a method for the selector was
// not found.
struct objc_method_description description =
protocol_getMethodDescription(self.protocol, selector, YES, YES);
if (description.types)
return [NSMethodSignature signatureWithObjCTypes:description.types];
// Look for an optional method in the protocol.
description = protocol_getMethodDescription(self.protocol, selector, NO, YES);
if (description.types)
return [NSMethodSignature signatureWithObjCTypes:description.types];
// There is neither a required nor optional method with this selector in the
// protocol, so invoke -[NSObject doesNotRecognizeSelector:] to raise
// NSInvalidArgumentException.
[self doesNotRecognizeSelector:selector];
return nil;
}
- (void)forwardInvocation:(NSInvocation*)invocation {
DCHECK(invocation);
if (_observers.empty())
return;
SEL selector = [invocation selector];
Iterator it(self);
id observer;
while ((observer = it.GetNext()) != nil) {
if ([observer respondsToSelector:selector])
[invocation invokeWithTarget:observer];
}
}
- (void)executeOnObservers:(ExecutionWithObserverBlock)callback {
DCHECK(callback);
if (_observers.empty())
return;
Iterator it(self);
id observer;
while ((observer = it.GetNext()) != nil)
callback(observer);
}
#pragma mark - Private
- (void)compact {
DCHECK(!_invocationDepth);
_observers.erase(std::remove(_observers.begin(), _observers.end(), nil),
_observers.end());
}
@end
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