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/*
*
* Copyright 2014, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#import "GRXImmediateWriter.h"
#import "NSEnumerator+GRXUtil.h"
@implementation GRXImmediateWriter {
NSEnumerator *_enumerator;
NSError *_errorOrNil;
id<GRXWriteable> _writeable;
}
@synthesize state = _state;
- (instancetype) init {
return [self initWithEnumerator:nil error:nil]; // results in an empty writer.
}
// Designated initializer
- (instancetype)initWithEnumerator:(NSEnumerator *)enumerator error:(NSError *)errorOrNil {
if (((self = [super init]))) {
_enumerator = enumerator;
_errorOrNil = errorOrNil;
_state = GRXWriterStateNotStarted;
}
return self;
}
#pragma mark Convenience constructors
+ (instancetype)writerWithEnumerator:(NSEnumerator *)enumerator error:(NSError *)errorOrNil {
return [[self alloc] initWithEnumerator:enumerator error:errorOrNil];
}
+ (id<GRXWriter>)writerWithEnumerator:(NSEnumerator *)enumerator {
return [self writerWithEnumerator:enumerator error:nil];
}
+ (id<GRXWriter>)writerWithValueSupplier:(id (^)())block {
return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithValueSupplier:block]];
}
+ (id<GRXWriter>)writerWithContainer:(id<NSFastEnumeration>)container {
return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithContainer:container]];;
}
+ (id<GRXWriter>)writerWithValue:(id)value {
if (value) {
return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithSingleValue:value]];
} else {
return [self emptyWriter];
}
}
+ (id<GRXWriter>)writerWithError:(NSError *)error {
if (error) {
return [self writerWithEnumerator:nil error:error];
} else {
return [self emptyWriter];
}
}
+ (id<GRXWriter>)emptyWriter {
static GRXImmediateWriter *emptyWriter;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
emptyWriter = [self writerWithEnumerator:nil error:nil];
});
return emptyWriter;
}
#pragma mark Conformance with GRXWriter
// Most of the complexity in this implementation is the result of supporting pause and resumption of
// the GRXWriter. It's an important feature for instances of GRXWriter that are backed by a
// container (which may be huge), or by a NSEnumerator (which may even be infinite).
- (void)writeUntilPausedOrStopped {
id value;
while (value = [_enumerator nextObject]) {
[_writeable didReceiveValue:value];
// If the writeable has a reference to us, it might change our state to paused or finished.
if (_state == GRXWriterStatePaused || _state == GRXWriterStateFinished) {
return;
}
}
[self finishWithError:_errorOrNil];
}
- (void)startWithWriteable:(id<GRXWriteable>)writeable {
_state = GRXWriterStateStarted;
_writeable = writeable;
[self writeUntilPausedOrStopped];
}
- (void)finishWithError:(NSError *)errorOrNil {
_state = GRXWriterStateFinished;
_enumerator = nil;
_errorOrNil = nil;
id<GRXWriteable> writeable = _writeable;
_writeable = nil;
[writeable didFinishWithError:errorOrNil];
}
- (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;
_enumerator = nil;
_errorOrNil = 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 writeUntilPausedOrStopped];
}
return;
case GRXWriterStateNotStarted:
return;
}
}
@end
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