aboutsummaryrefslogtreecommitdiffhomepage
path: root/src/objective-c/RxLibrary/GRXBufferedPipe.m
blob: 4820c84af00829df5eae1c7d1daefe81d55a7369 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
/*
 *
 * Copyright 2015, 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 "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