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1 /*
2  *
3  * Copyright 2015 gRPC authors.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *     http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  *
17  */
18 
19 #import <Foundation/Foundation.h>
20 
21 #import "GRXWriter.h"
22 
23 /**
24  * Utility to construct GRXWriter instances from values that are immediately available when
25  * required.
26  *
27  * Thread-safety:
28  *
29  * An object of this class shouldn't be messaged concurrently by more than one thread. It will start
30  * messaging the writeable before |startWithWriteable:| returns, in the same thread. That is the
31  * only place where the writer can be paused or stopped prematurely.
32  *
33  * If a paused writer of this class is resumed, it will start messaging the writeable, in the same
34  * thread, before |setState:| returns. Because the object can't be legally accessed concurrently,
35  * that's the only place where it can be paused again (or stopped).
36  */
37 @interface GRXImmediateWriter : GRXWriter
38 
39 /**
40  * Returns a writer that pulls values from the passed NSEnumerator instance and pushes them to
41  * its writeable. The NSEnumerator is released when it finishes.
42  */
43 + (GRXWriter *)writerWithEnumerator:(NSEnumerator *)enumerator;
44 
45 /**
46  * Returns a writer that pushes to its writeable the successive values returned by the passed
47  * block. When the block first returns nil, it is released.
48  */
49 + (GRXWriter *)writerWithValueSupplier:(id (^)(void))block;
50 
51 /**
52  * Returns a writer that iterates over the values of the passed container and pushes them to
53  * its writeable. The container is released when the iteration is over.
54  *
55  * Note that the usual speed gain of NSFastEnumeration over NSEnumerator results from not having to
56  * call one method per element. Because GRXWriteable instances accept values one by one, that speed
57  * gain doesn't happen here.
58  */
59 + (GRXWriter *)writerWithContainer:(id<NSFastEnumeration>)container;
60 
61 /**
62  * Returns a writer that sends the passed value to its writeable and then finishes (releasing the
63  * value).
64  */
65 + (GRXWriter *)writerWithValue:(id)value;
66 
67 /**
68  * Returns a writer that, as part of its start method, sends the passed error to the writeable
69  * (then releasing the error).
70  */
71 + (GRXWriter *)writerWithError:(NSError *)error;
72 
73 /**
74  * Returns a writer that, as part of its start method, finishes immediately without sending any
75  * values to its writeable.
76  */
77 + (GRXWriter *)emptyWriter;
78 
79 @end
80