/gecko_sdk/idl/nsIOutputStream.idl

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 15 * The Original Code is mozilla.org code.
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 17 * The Initial Developer of the Original Code is
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 19 * Portions created by the Initial Developer are Copyright (C) 1998
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 21 *
 22 * Contributor(s):
 23 *   Warren Harris <warren@netscape.com>
 24 *   Darin Fisher <darin@netscape.com>
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 39
 40#include "nsISupports.idl"
 41
 42interface nsIOutputStream;
 43interface nsIInputStream;
 44
 45%{C++
 46/**
 47 * The signature for the reader function passed to WriteSegments. This 
 48 * is the "provider" of data that gets written into the stream's buffer.
 49 *
 50 * @param aOutStream stream being written to
 51 * @param aClosure opaque parameter passed to WriteSegments
 52 * @param aToSegment pointer to memory owned by the output stream
 53 * @param aFromOffset amount already written (since WriteSegments was called)
 54 * @param aCount length of toSegment
 55 * @param aReadCount number of bytes written
 56 *
 57 * Implementers should return the following:
 58 *
 59 * @return NS_OK and (*aReadCount > 0) if successfully provided some data
 60 * @return NS_OK and (*aReadCount = 0) or
 61 * @return <any-error> if not interested in providing any data
 62 *
 63 * Errors are never passed to the caller of WriteSegments.
 64 *
 65 * @status FROZEN
 66 */
 67typedef NS_CALLBACK(nsReadSegmentFun)(nsIOutputStream *aOutStream,
 68                                      void *aClosure,
 69                                      char *aToSegment,
 70                                      PRUint32 aFromOffset,
 71                                      PRUint32 aCount,
 72                                      PRUint32 *aReadCount);
 73%}
 74
 75native nsReadSegmentFun(nsReadSegmentFun);
 76
 77/**
 78 * nsIOutputStream
 79 *
 80 * An interface describing a writable stream of data.  An output stream may be
 81 * "blocking" or "non-blocking" (see the IsNonBlocking method).  A blocking
 82 * output stream may suspend the calling thread in order to satisfy a call to
 83 * Close, Flush, Write, WriteFrom, or WriteSegments.  A non-blocking output
 84 * stream, on the other hand, must not block the calling thread of execution.
 85 *
 86 * NOTE: blocking output streams are often written to on a background thread to
 87 * avoid locking up the main application thread.  For this reason, it is
 88 * generally the case that a blocking output stream should be implemented using
 89 * thread- safe AddRef and Release.
 90 *
 91 * @status FROZEN
 92 */
 93[scriptable, uuid(0d0acd2a-61b4-11d4-9877-00c04fa0cf4a)]
 94interface nsIOutputStream : nsISupports
 95{
 96    /** 
 97     * Close the stream. Forces the output stream to flush any buffered data.
 98     *
 99     * @throws NS_BASE_STREAM_WOULD_BLOCK if unable to flush without blocking 
100     *   the calling thread (non-blocking mode only)
101     */
102    void close();
103
104    /**
105     * Flush the stream.
106     *
107     * @throws NS_BASE_STREAM_WOULD_BLOCK if unable to flush without blocking 
108     *   the calling thread (non-blocking mode only)
109     */
110    void flush();
111
112    /**
113     * Write data into the stream.
114     *
115     * @param aBuf the buffer containing the data to be written
116     * @param aCount the maximum number of bytes to be written
117     *
118     * @return number of bytes written (may be less than aCount)
119     *
120     * @throws NS_BASE_STREAM_WOULD_BLOCK if writing to the output stream would
121     *   block the calling thread (non-blocking mode only)
122     * @throws <other-error> on failure
123     */
124    unsigned long write(in string aBuf, in unsigned long aCount);
125
126    /**
127     * Writes data into the stream from an input stream.
128     *
129     * @param aFromStream the stream containing the data to be written
130     * @param aCount the maximum number of bytes to be written
131     *
132     * @return number of bytes written (may be less than aCount)
133     *
134     * @throws NS_BASE_STREAM_WOULD_BLOCK if writing to the output stream would
135     *    block the calling thread (non-blocking mode only)
136     * @throws <other-error> on failure
137     *
138     * NOTE: This method is defined by this interface in order to allow the
139     * output stream to efficiently copy the data from the input stream into
140     * its internal buffer (if any). If this method was provided as an external
141     * facility, a separate char* buffer would need to be used in order to call
142     * the output stream's other Write method.
143     */
144    unsigned long writeFrom(in nsIInputStream aFromStream,
145                            in unsigned long aCount);
146
147    /**
148     * Low-level write method that has access to the stream's underlying buffer.
149     * The reader function may be called multiple times for segmented buffers.
150     * WriteSegments is expected to keep calling the reader until either there
151     * is nothing left to write or the reader returns an error.  WriteSegments
152     * should not call the reader with zero bytes to provide.
153     *
154     * @param aReader the "provider" of the data to be written
155     * @param aClosure opaque parameter passed to reader
156     * @param aCount the maximum number of bytes to be written
157     *
158     * @return number of bytes written (may be less than aCount)
159     *
160     * @throws NS_BASE_STREAM_WOULD_BLOCK if writing to the output stream would
161     *    block the calling thread (non-blocking mode only)
162     * @throws NS_ERROR_NOT_IMPLEMENTED if the stream has no underlying buffer
163     * @throws <other-error> on failure
164     *
165     * NOTE: this function may be unimplemented if a stream has no underlying
166     * buffer (e.g., socket output stream).
167     */
168    [noscript] unsigned long writeSegments(in nsReadSegmentFun aReader,
169                                           in voidPtr aClosure,
170                                           in unsigned long aCount);
171
172    /**
173     * @return true if stream is non-blocking
174     *
175     * NOTE: writing to a blocking output stream will block the calling thread
176     * until all given data can be consumed by the stream.
177     *
178     * NOTE: a non-blocking output stream may implement nsIAsyncOutputStream to
179     * provide consumers with a way to wait for the stream to accept more data
180     * once its write method is unable to accept any data without blocking.
181     */
182    boolean isNonBlocking();
183};