Jorge Canizales | e8304d5 | 2015-02-17 19:50:51 -0800 | [diff] [blame] | 1 | /* |
| 2 | * |
Yang Gao | 5fc9029 | 2015-02-20 09:46:22 -0800 | [diff] [blame] | 3 | * Copyright 2015, Google Inc. |
Jorge Canizales | e8304d5 | 2015-02-17 19:50:51 -0800 | [diff] [blame] | 4 | * All rights reserved. |
| 5 | * |
| 6 | * Redistribution and use in source and binary forms, with or without |
| 7 | * modification, are permitted provided that the following conditions are |
| 8 | * met: |
| 9 | * |
| 10 | * * Redistributions of source code must retain the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer. |
| 12 | * * Redistributions in binary form must reproduce the above |
| 13 | * copyright notice, this list of conditions and the following disclaimer |
| 14 | * in the documentation and/or other materials provided with the |
| 15 | * distribution. |
| 16 | * * Neither the name of Google Inc. nor the names of its |
| 17 | * contributors may be used to endorse or promote products derived from |
| 18 | * this software without specific prior written permission. |
| 19 | * |
| 20 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 21 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 22 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 23 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 24 | * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 25 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 26 | * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 27 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 28 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 29 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 30 | * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 31 | * |
| 32 | */ |
| 33 | |
Jorge Canizales | 30697c9 | 2015-02-17 17:09:14 -0800 | [diff] [blame] | 34 | #import "GRXImmediateWriter.h" |
| 35 | |
| 36 | #import "NSEnumerator+GRXUtil.h" |
| 37 | |
| 38 | @implementation GRXImmediateWriter { |
| 39 | NSEnumerator *_enumerator; |
| 40 | NSError *_errorOrNil; |
| 41 | id<GRXWriteable> _writeable; |
| 42 | } |
| 43 | |
| 44 | @synthesize state = _state; |
| 45 | |
| 46 | - (instancetype) init { |
| 47 | return [self initWithEnumerator:nil error:nil]; // results in an empty writer. |
| 48 | } |
| 49 | |
| 50 | // Designated initializer |
| 51 | - (instancetype)initWithEnumerator:(NSEnumerator *)enumerator error:(NSError *)errorOrNil { |
| 52 | if (((self = [super init]))) { |
| 53 | _enumerator = enumerator; |
| 54 | _errorOrNil = errorOrNil; |
| 55 | _state = GRXWriterStateNotStarted; |
| 56 | } |
| 57 | return self; |
| 58 | } |
| 59 | |
| 60 | #pragma mark Convenience constructors |
| 61 | |
| 62 | + (instancetype)writerWithEnumerator:(NSEnumerator *)enumerator error:(NSError *)errorOrNil { |
| 63 | return [[self alloc] initWithEnumerator:enumerator error:errorOrNil]; |
| 64 | } |
| 65 | |
| 66 | + (id<GRXWriter>)writerWithEnumerator:(NSEnumerator *)enumerator { |
| 67 | return [self writerWithEnumerator:enumerator error:nil]; |
| 68 | } |
| 69 | |
| 70 | + (id<GRXWriter>)writerWithValueSupplier:(id (^)())block { |
| 71 | return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithValueSupplier:block]]; |
| 72 | } |
| 73 | |
| 74 | + (id<GRXWriter>)writerWithContainer:(id<NSFastEnumeration>)container { |
| 75 | return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithContainer:container]];; |
| 76 | } |
| 77 | |
| 78 | + (id<GRXWriter>)writerWithValue:(id)value { |
| 79 | if (value) { |
| 80 | return [self writerWithEnumerator:[NSEnumerator grx_enumeratorWithSingleValue:value]]; |
| 81 | } else { |
| 82 | return [self emptyWriter]; |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | + (id<GRXWriter>)writerWithError:(NSError *)error { |
| 87 | if (error) { |
| 88 | return [self writerWithEnumerator:nil error:error]; |
| 89 | } else { |
| 90 | return [self emptyWriter]; |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | + (id<GRXWriter>)emptyWriter { |
| 95 | static GRXImmediateWriter *emptyWriter; |
| 96 | static dispatch_once_t onceToken; |
| 97 | dispatch_once(&onceToken, ^{ |
| 98 | emptyWriter = [self writerWithEnumerator:nil error:nil]; |
| 99 | }); |
| 100 | return emptyWriter; |
| 101 | } |
| 102 | |
| 103 | #pragma mark Conformance with GRXWriter |
| 104 | |
| 105 | // Most of the complexity in this implementation is the result of supporting pause and resumption of |
| 106 | // the GRXWriter. It's an important feature for instances of GRXWriter that are backed by a |
| 107 | // container (which may be huge), or by a NSEnumerator (which may even be infinite). |
| 108 | |
| 109 | - (void)writeUntilPausedOrStopped { |
| 110 | id value; |
| 111 | while (value = [_enumerator nextObject]) { |
Jorge Canizales | a90a9c3 | 2015-05-18 17:12:41 -0700 | [diff] [blame^] | 112 | [_writeable writeValue:value]; |
Jorge Canizales | 30697c9 | 2015-02-17 17:09:14 -0800 | [diff] [blame] | 113 | // If the writeable has a reference to us, it might change our state to paused or finished. |
| 114 | if (_state == GRXWriterStatePaused || _state == GRXWriterStateFinished) { |
| 115 | return; |
| 116 | } |
| 117 | } |
| 118 | [self finishWithError:_errorOrNil]; |
| 119 | } |
| 120 | |
| 121 | - (void)startWithWriteable:(id<GRXWriteable>)writeable { |
| 122 | _state = GRXWriterStateStarted; |
| 123 | _writeable = writeable; |
| 124 | [self writeUntilPausedOrStopped]; |
| 125 | } |
| 126 | |
| 127 | - (void)finishWithError:(NSError *)errorOrNil { |
| 128 | _state = GRXWriterStateFinished; |
| 129 | _enumerator = nil; |
| 130 | _errorOrNil = nil; |
| 131 | id<GRXWriteable> writeable = _writeable; |
| 132 | _writeable = nil; |
| 133 | [writeable didFinishWithError:errorOrNil]; |
| 134 | } |
| 135 | |
| 136 | - (void)setState:(GRXWriterState)newState { |
| 137 | // Manual transitions are only allowed from the started or paused states. |
| 138 | if (_state == GRXWriterStateNotStarted || _state == GRXWriterStateFinished) { |
| 139 | return; |
| 140 | } |
| 141 | |
| 142 | switch (newState) { |
| 143 | case GRXWriterStateFinished: |
| 144 | _state = newState; |
| 145 | _enumerator = nil; |
| 146 | _errorOrNil = nil; |
| 147 | // Per GRXWriter's contract, setting the state to Finished manually |
| 148 | // means one doesn't wish the writeable to be messaged anymore. |
| 149 | _writeable = nil; |
| 150 | return; |
| 151 | case GRXWriterStatePaused: |
| 152 | _state = newState; |
| 153 | return; |
| 154 | case GRXWriterStateStarted: |
| 155 | if (_state == GRXWriterStatePaused) { |
| 156 | _state = newState; |
| 157 | [self writeUntilPausedOrStopped]; |
| 158 | } |
| 159 | return; |
| 160 | case GRXWriterStateNotStarted: |
| 161 | return; |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | @end |