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/*
*
* Copyright 2015 gRPC authors.
*
* 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 "GRXBufferedPipe.h"
@implementation GRXBufferedPipe {
id<GRXWriteable> _writeable;
NSMutableArray *_queue;
BOOL _inputIsFinished;
NSError *_errorOrNil;
}
@synthesize state = _state;
+ (instancetype)pipe {
return [[self alloc] init];
}
- (instancetype)init {
if (self = [super init]) {
_queue = [NSMutableArray array];
_state = GRXWriterStateNotStarted;
}
return self;
}
- (id)popValue {
id value = _queue[0];
[_queue removeObjectAtIndex:0];
return value;
}
- (void)writeBufferUntilPausedOrStopped {
while (_state == GRXWriterStateStarted && _queue.count > 0) {
[_writeable writeValue:[self popValue]];
}
if (_inputIsFinished && _queue.count == 0) {
// Our writer finished normally while we were paused or not-started-yet.
[self finishWithError:_errorOrNil];
}
}
#pragma mark GRXWriteable implementation
// Returns whether events can be simply propagated to the other end of the pipe.
- (BOOL)shouldFastForward {
return _state == GRXWriterStateStarted && _queue.count == 0;
}
- (void)writeValue:(id)value {
if (self.shouldFastForward) {
// Skip the queue.
[_writeable writeValue:value];
} else {
// Even if we're paused and with enqueued values, we can't excert back-pressure to our writer.
// So just buffer the new value.
// We need a copy, so that it doesn't mutate before it's written at the other end of the pipe.
if ([value respondsToSelector:@selector(copy)]) {
value = [value copy];
}
[_queue addObject:value];
}
}
- (void)writesFinishedWithError:(NSError *)errorOrNil {
_inputIsFinished = YES;
_errorOrNil = errorOrNil;
if (errorOrNil || self.shouldFastForward) {
// No need to write pending values.
[self finishWithError:_errorOrNil];
}
}
#pragma mark GRXWriter implementation
- (void)setState:(GRXWriterState)newState {
// Manual transitions are only allowed from the started or paused states.
if (_state == GRXWriterStateNotStarted || _state == GRXWriterStateFinished) {
return;
}
switch (newState) {
case GRXWriterStateFinished:
_state = newState;
_queue = nil;
// Per GRXWriter's contract, setting the state to Finished manually means one doesn't wish the
// writeable to be messaged anymore.
_writeable = nil;
return;
case GRXWriterStatePaused:
_state = newState;
return;
case GRXWriterStateStarted:
if (_state == GRXWriterStatePaused) {
_state = newState;
[self writeBufferUntilPausedOrStopped];
}
return;
case GRXWriterStateNotStarted:
return;
}
}
- (void)startWithWriteable:(id<GRXWriteable>)writeable {
_state = GRXWriterStateStarted;
_writeable = writeable;
[self writeBufferUntilPausedOrStopped];
}
- (void)finishWithError:(NSError *)errorOrNil {
id<GRXWriteable> writeable = _writeable;
self.state = GRXWriterStateFinished;
[writeable writesFinishedWithError:errorOrNil];
}
@end
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