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mozilla/ xpcom/ io/ nsIInputStream.idl |
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Inheritance diagram for nsIInputStream:
Collaboration diagram for nsIInputStream:
[ nsIInputStream Interface Reference | Graph Legend ]
1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 /* This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5
6 #include "nsISupports.idl"
7
8 interface nsIInputStream;
9
10 %{C++
11 /**
12 * The signature of the writer function passed to ReadSegments. This
13 * is the "consumer" of data that gets read from the stream's buffer.
14 *
15 * @param aInStream stream being read
16 * @param aClosure opaque parameter passed to ReadSegments
17 * @param aFromSegment pointer to memory owned by the input stream. This is
18 * where the writer function should start consuming data.
19 * @param aToOffset amount of data already consumed by this writer during this
20 * ReadSegments call. This is also the sum of the aWriteCount
21 * returns from this writer over the previous invocations of
22 * the writer by this ReadSegments call.
23 * @param aCount Number of bytes available to be read starting at aFromSegment
24 * @param [out] aWriteCount number of bytes read by this writer function call
25 *
26 * Implementers should return the following:
27 *
28 * @return NS_OK and (*aWriteCount > 0) if consumed some data
29 * @return <any-error> if not interested in consuming any data
30 *
31 * Errors are never passed to the caller of ReadSegments.
32 *
33 * NOTE: returning NS_OK and (*aWriteCount = 0) has undefined behavior.
34 */
35 typedef NS_CALLBACK(nsWriteSegmentFun)(nsIInputStream *aInStream,
36 void *aClosure,
37 const char *aFromSegment,
38 uint32_t aToOffset,
39 uint32_t aCount,
40 uint32_t *aWriteCount);
41 %}
42
43 native nsWriteSegmentFun(nsWriteSegmentFun);
44
45 /**
46 * nsIInputStream
47 *
48 * An interface describing a readable stream of data. An input stream may be
49 * "blocking" or "non-blocking" (see the IsNonBlocking method). A blocking
50 * input stream may suspend the calling thread in order to satisfy a call to
51 * Close, Available, Read, or ReadSegments. A non-blocking input stream, on
52 * the other hand, must not block the calling thread of execution.
53 *
54 * NOTE: blocking input streams are often read on a background thread to avoid
55 * locking up the main application thread. For this reason, it is generally
56 * the case that a blocking input stream should be implemented using thread-
57 * safe AddRef and Release.
58 */
59 [scriptable, uuid(53cdbc97-c2d7-4e30-b2c3-45b2ee79db18)]
60 interface nsIInputStream : nsISupports
61 {
62 /**
63 * Close the stream. This method causes subsequent calls to Read and
64 * ReadSegments to return 0 bytes read to indicate end-of-file. Any
65 * subsequent calls to Available should throw NS_BASE_STREAM_CLOSED.
66 */
67 void close();
68
69 /**
70 * Determine number of bytes available in the stream. A non-blocking
71 * stream that does not yet have any data to read should return 0 bytes
72 * from this method (i.e., it must not throw the NS_BASE_STREAM_WOULD_BLOCK
73 * exception).
74 *
75 * In addition to the number of bytes available in the stream, this method
76 * also informs the caller of the current status of the stream. A stream
77 * that is closed will throw an exception when this method is called. That
78 * enables the caller to know the condition of the stream before attempting
79 * to read from it. If a stream is at end-of-file, but not closed, then
80 * this method returns 0 bytes available. (Note: some nsIInputStream
81 * implementations automatically close when eof is reached; some do not).
82 *
83 * @return number of bytes currently available in the stream.
84 *
85 * @throws NS_BASE_STREAM_CLOSED if the stream is closed normally.
86 * @throws <other-error> if the stream is closed due to some error
87 * condition
88 */
89 unsigned long long available();
90
91 /**
92 * Read data from the stream.
93 *
94 * @param aBuf the buffer into which the data is to be read
95 * @param aCount the maximum number of bytes to be read
96 *
97 * @return number of bytes read (may be less than aCount).
98 * @return 0 if reached end-of-file
99 *
100 * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from the input stream would
101 * block the calling thread (non-blocking mode only)
102 * @throws <other-error> on failure
103 *
104 * NOTE: this method should not throw NS_BASE_STREAM_CLOSED.
105 */
106 [noscript] unsigned long read(in charPtr aBuf, in unsigned long aCount);
107
108 /**
109 * Low-level read method that provides access to the stream's underlying
110 * buffer. The writer function may be called multiple times for segmented
111 * buffers. ReadSegments is expected to keep calling the writer until
112 * either there is nothing left to read or the writer returns an error.
113 * ReadSegments should not call the writer with zero bytes to consume.
114 *
115 * @param aWriter the "consumer" of the data to be read
116 * @param aClosure opaque parameter passed to writer
117 * @param aCount the maximum number of bytes to be read
118 *
119 * @return number of bytes read (may be less than aCount)
120 * @return 0 if reached end-of-file (or if aWriter refused to consume data)
121 *
122 * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from the input stream would
123 * block the calling thread (non-blocking mode only)
124 * @throws NS_ERROR_NOT_IMPLEMENTED if the stream has no underlying buffer
125 * @throws <other-error> on failure
126 *
127 * NOTE: this function may be unimplemented if a stream has no underlying
128 * buffer (e.g., socket input stream).
129 *
130 * NOTE: this method should not throw NS_BASE_STREAM_CLOSED.
131 */
132 [noscript] unsigned long readSegments(in nsWriteSegmentFun aWriter,
133 in voidPtr aClosure,
134 in unsigned long aCount);
135
136 /**
137 * @return true if stream is non-blocking
138 *
139 * NOTE: reading from a blocking input stream will block the calling thread
140 * until at least one byte of data can be extracted from the stream.
141 *
142 * NOTE: a non-blocking input stream may implement nsIAsyncInputStream to
143 * provide consumers with a way to wait for the stream to have more data
144 * once its read method is unable to return any data without blocking.
145 */
146 boolean isNonBlocking();
147 };
148