xpcom/io/nsIPipe.idl

   1 /* -*- Mode: C++; tab-width: 4; 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 nsIAsyncInputStream;
   9 interface nsIAsyncOutputStream;
  10
  11 /**
  12  * nsIPipe represents an in-process buffer that can be read using nsIInputStream
  13  * and written using nsIOutputStream.  The reader and writer of a pipe do not
  14  * have to be on the same thread.  As a result, the pipe is an ideal mechanism
  15  * to bridge data exchange between two threads.  For example, a worker thread
  16  * might write data to a pipe from which the main thread will read.
  17  *
  18  * Each end of the pipe can be either blocking or non-blocking.  Recall that a
  19  * non-blocking stream will return NS_BASE_STREAM_WOULD_BLOCK if it cannot be
  20  * read or written to without blocking the calling thread.  For example, if you
  21  * try to read from an empty pipe that has not yet been closed, then if that
  22  * pipe's input end is non-blocking, then the read call will fail immediately
  23  * with NS_BASE_STREAM_WOULD_BLOCK as the error condition.  However, if that
  24  * pipe's input end is blocking, then the read call will not return until the
  25  * pipe has data or until the pipe is closed.  This example presumes that the
  26  * pipe is being filled asynchronously on some background thread.
  27  *
  28  * The pipe supports nsIAsyncInputStream and nsIAsyncOutputStream, which give
  29  * the user of a non-blocking pipe the ability to wait for the pipe to become
  30  * ready again.  For example, in the case of an empty non-blocking pipe, the
  31  * user can call AsyncWait on the input end of the pipe to be notified when
  32  * the pipe has data to read (or when the pipe becomes closed).
  33  *
  34  * NS_NewPipe2 and NS_NewPipe provide convenient pipe constructors.  In most
  35  * cases nsIPipe is not actually used.  It is usually enough to just get
  36  * references to the pipe's input and output end.  In which case, the pipe is
  37  * automatically closed when the respective pipe ends are released.
  38  */
  39 [scriptable, uuid(25d0de93-685e-4ea4-95d3-d884e31df63c)]
  40 interface nsIPipe : nsISupports
  41 {
  42     /**
  43      * initialize this pipe
  44      *
  45      * @param nonBlockingInput
  46      *        true specifies non-blocking input stream behavior
  47      * @param nonBlockingOutput
  48      *        true specifies non-blocking output stream behavior
  49      * @param segmentSize
  50      *        specifies the segment size in bytes (pass 0 to use default value)
  51      * @param segmentCount
  52      *        specifies the max number of segments (pass 0 to use default
  53      *        value).   Passing UINT32_MAX here causes the pipe to have
  54      *        "infinite" space.  This mode can be useful in some cases, but
  55      *        should always be used with caution.  The default value for this
  56      *        parameter is a finite value.
  57      */
  58     void init(in boolean nonBlockingInput,
  59               in boolean nonBlockingOutput,
  60               in unsigned long segmentSize,
  61               in unsigned long segmentCount);
  62
  63     /**
  64      * The pipe's input end, which also implements nsISearchableInputStream.
  65      */
  66     readonly attribute nsIAsyncInputStream inputStream;
  67
  68     /**
  69      * The pipe's output end.
  70      */
  71     readonly attribute nsIAsyncOutputStream outputStream;
  72 };
  73
  74 /**
  75  * XXX this interface doesn't really belong in here.  It is here because
  76  * currently nsPipeInputStream is the only implementation of this interface.
  77  */
  78 [scriptable, uuid(8C39EF62-F7C9-11d4-98F5-001083010E9B)]
  79 interface nsISearchableInputStream : nsISupports
  80 {
  81     /**
  82      * Searches for a string in the input stream. Since the stream has a notion
  83      * of EOF, it is possible that the string may at some time be in the
  84      * buffer, but is is not currently found up to some offset. Consequently,
  85      * both the found and not found cases return an offset:
  86      *    if found, return offset where it was found
  87      *    if not found, return offset of the first byte not searched
  88      * In the case the stream is at EOF and the string is not found, the first
  89      * byte not searched will correspond to the length of the buffer.
  90      */
  91     void search(in string forString,
  92                 in boolean ignoreCase,
  93                 out boolean found,
  94                 out unsigned long offsetSearchedTo);
  95 };
  96
  97 %{C++
  98
  99 class nsIInputStream;
 100 class nsIOutputStream;
 101
 102 /**
 103  * NS_NewPipe2
 104  *
 105  * This function supersedes NS_NewPipe.  It differs from NS_NewPipe in two
 106  * major ways:
 107  *  (1) returns nsIAsyncInputStream and nsIAsyncOutputStream, so it is
 108  *      not necessary to QI in order to access these interfaces.
 109  *  (2) the size of the pipe is determined by the number of segments
 110  *      times the size of each segment.
 111  *
 112  * @param pipeIn
 113  *        resulting input end of the pipe
 114  * @param pipeOut
 115  *        resulting output end of the pipe
 116  * @param nonBlockingInput
 117  *        true specifies non-blocking input stream behavior
 118  * @param nonBlockingOutput
 119  *        true specifies non-blocking output stream behavior
 120  * @param segmentSize
 121  *        specifies the segment size in bytes (pass 0 to use default value)
 122  * @param segmentCount
 123  *        specifies the max number of segments (pass 0 to use default value)
 124  *        passing UINT32_MAX here causes the pipe to have "infinite" space.
 125  *        this mode can be useful in some cases, but should always be used with
 126  *        caution.  the default value for this parameter is a finite value.
 127  */
 128 extern nsresult
 129 NS_NewPipe2(nsIAsyncInputStream **pipeIn,
 130             nsIAsyncOutputStream **pipeOut,
 131             bool nonBlockingInput = false,
 132             bool nonBlockingOutput = false,
 133             uint32_t segmentSize = 0,
 134             uint32_t segmentCount = 0);
 135
 136 /**
 137  * NS_NewPipe
 138  *
 139  * Preserved for backwards compatibility.  Plus, this interface is more
 140  * amiable in certain contexts (e.g., when you don't need the pipe's async
 141  * capabilities).
 142  *
 143  * @param pipeIn
 144  *        resulting input end of the pipe
 145  * @param pipeOut
 146  *        resulting output end of the pipe
 147  * @param segmentSize
 148  *        specifies the segment size in bytes (pass 0 to use default value)
 149  * @param maxSize
 150  *        specifies the max size of the pipe (pass 0 to use default value)
 151  *        number of segments is maxSize / segmentSize, and maxSize must be a
 152  *        multiple of segmentSize.  passing UINT32_MAX here causes the
 153  *        pipe to have "infinite" space.  this mode can be useful in some
 154  *        cases, but should always be used with caution.  the default value
 155  *        for this parameter is a finite value.
 156  * @param nonBlockingInput
 157  *        true specifies non-blocking input stream behavior
 158  * @param nonBlockingOutput
 159  *        true specifies non-blocking output stream behavior
 160  */
 161 extern nsresult
 162 NS_NewPipe(nsIInputStream **pipeIn,
 163            nsIOutputStream **pipeOut,
 164            uint32_t segmentSize = 0,
 165            uint32_t maxSize = 0,
 166            bool nonBlockingInput = false,
 167            bool nonBlockingOutput = false);
 168
 169 %}