xpcom/io/nsIOutputStream.idl

   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 nsIOutputStream;
   9 interface nsIInputStream;
  10
  11 %{C++
  12 /**
  13  * The signature for the reader function passed to WriteSegments. This
  14  * is the "provider" of data that gets written into the stream's buffer.
  15  *
  16  * @param aOutStream stream being written to
  17  * @param aClosure opaque parameter passed to WriteSegments
  18  * @param aToSegment pointer to memory owned by the output stream
  19  * @param aFromOffset amount already written (since WriteSegments was called)
  20  * @param aCount length of toSegment
  21  * @param aReadCount number of bytes written
  22  *
  23  * Implementers should return the following:
  24  *
  25  * @throws <any-error> if not interested in providing any data
  26  *
  27  * Errors are never passed to the caller of WriteSegments.
  28  */
  29 typedef nsresult (*nsReadSegmentFun)(nsIOutputStream *aOutStream,
  30                                      void *aClosure,
  31                                      char *aToSegment,
  32                                      uint32_t aFromOffset,
  33                                      uint32_t aCount,
  34                                      uint32_t *aReadCount);
  35 %}
  36
  37 native nsReadSegmentFun(nsReadSegmentFun);
  38
  39 /**
  40  * nsIOutputStream
  41  *
  42  * An interface describing a writable stream of data.  An output stream may be
  43  * "blocking" or "non-blocking" (see the IsNonBlocking method).  A blocking
  44  * output stream may suspend the calling thread in order to satisfy a call to
  45  * Close, Flush, Write, WriteFrom, or WriteSegments.  A non-blocking output
  46  * stream, on the other hand, must not block the calling thread of execution.
  47  *
  48  * NOTE: blocking output streams are often written to on a background thread to
  49  * avoid locking up the main application thread.  For this reason, it is
  50  * generally the case that a blocking output stream should be implemented using
  51  * thread- safe AddRef and Release.
  52  */
  53 [scriptable, builtinclass, uuid(0d0acd2a-61b4-11d4-9877-00c04fa0cf4a)]
  54 interface nsIOutputStream : nsISupports
  55 {
  56     /**
  57      * Close the stream. Forces the output stream to flush any buffered data.
  58      * Any subsequent calls to StreamStatus should throw NS_BASE_STREAM_CLOSED.
  59      * Succeeds without effect if already closed.
  60      *
  61      * @throws NS_BASE_STREAM_WOULD_BLOCK if unable to flush without blocking
  62      *   the calling thread (non-blocking mode only)
  63      */
  64     void close();
  65
  66     /**
  67      * Flush the stream.
  68      *
  69      * @throws NS_BASE_STREAM_WOULD_BLOCK if unable to flush without blocking
  70      *   the calling thread (non-blocking mode only)
  71      */
  72     void flush();
  73
  74     /**
  75      * Check the current status of the stream.  A stream that is closed will
  76      * throw an exception when this method is called.  That enables the caller
  77      * to know the condition of the stream before attempting to write into it.
  78      *
  79      * This method will not throw NS_BASE_STREAM_WOULD_BLOCK, even if the stream
  80      * is a non-blocking stream with no available space. A non-blocking stream
  81      * which has not been closed, but has no available room should return NS_OK.
  82      *
  83      * NOTE: This method should not block the calling thread (e.g. to query the
  84      * state of a file descriptor), even when called on a blocking stream.
  85      *
  86      * @throws NS_BASE_STREAM_CLOSED if the stream closed normally
  87      * @throws <other-error> if the stream closed with a different status
  88      */
  89     void streamStatus();
  90
  91     /**
  92      * Write data into the stream.
  93      *
  94      * @param aBuf the buffer containing the data to be written
  95      * @param aCount the maximum number of bytes to be written
  96      *
  97      * @return number of bytes written (may be less than aCount)
  98      *
  99      * @throws NS_BASE_STREAM_WOULD_BLOCK if writing to the output stream would
 100      *   block the calling thread (non-blocking mode only)
 101      * @throws <other-error> on failure
 102      */
 103     unsigned long write(in string aBuf, in unsigned long aCount);
 104
 105     /**
 106      * Writes data into the stream from an input stream.
 107      *
 108      * @param aFromStream the stream containing the data to be written
 109      * @param aCount the maximum number of bytes to be written
 110      *
 111      * @return number of bytes written (may be less than aCount)
 112      *
 113      * @throws NS_BASE_STREAM_WOULD_BLOCK if writing to the output stream would
 114      *    block the calling thread (non-blocking mode only). This failure
 115      *    means no bytes were transferred.
 116      * @throws <other-error> on failure
 117      *
 118      * NOTE: This method is defined by this interface in order to allow the
 119      * output stream to efficiently copy the data from the input stream into
 120      * its internal buffer (if any). If this method was provided as an external
 121      * facility, a separate char* buffer would need to be used in order to call
 122      * the output stream's other Write method.
 123      */
 124     unsigned long writeFrom(in nsIInputStream aFromStream,
 125                             in unsigned long aCount);
 126
 127     /**
 128      * Low-level write method that has access to the stream's underlying buffer.
 129      * The reader function may be called multiple times for segmented buffers.
 130      * WriteSegments is expected to keep calling the reader until either there
 131      * is nothing left to write or the reader returns an error.  WriteSegments
 132      * should not call the reader with zero bytes to provide.
 133      *
 134      * @param aReader the "provider" of the data to be written
 135      * @param aClosure opaque parameter passed to reader
 136      * @param aCount the maximum number of bytes to be written
 137      *
 138      * @return number of bytes written (may be less than aCount)
 139      *
 140      * @throws NS_BASE_STREAM_WOULD_BLOCK if writing to the output stream would
 141      *    block the calling thread (non-blocking mode only). This failure
 142      *    means no bytes were transferred.
 143      * @throws NS_ERROR_NOT_IMPLEMENTED if the stream has no underlying buffer
 144      * @throws <other-error> on failure
 145      *
 146      * NOTE: this function may be unimplemented if a stream has no underlying
 147      * buffer (e.g., socket output stream).
 148      */
 149     [noscript] unsigned long writeSegments(in nsReadSegmentFun aReader,
 150                                            in voidPtr aClosure,
 151                                            in unsigned long aCount);
 152
 153     /**
 154      * @return true if stream is non-blocking
 155      *
 156      * NOTE: writing to a blocking output stream will block the calling thread
 157      * until all given data can be consumed by the stream.
 158      *
 159      * NOTE: a non-blocking output stream may implement nsIAsyncOutputStream to
 160      * provide consumers with a way to wait for the stream to accept more data
 161      * once its write method is unable to accept any data without blocking.
 162      */
 163     boolean isNonBlocking();
 164 };