xpcom/io/nsIPipe.idl

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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  37
  38 #include "nsIAsyncInputStream.idl"
  39 #include "nsIAsyncOutputStream.idl"
  40
  41 interface nsIMemory;
  42
  43 /**
  44  * nsIPipe represents an in-process buffer that can be read using nsIInputStream
  45  * and written using nsIOutputStream.  The reader and writer of a pipe do not
  46  * have to be on the same thread.  As a result, the pipe is an ideal mechanism
  47  * to bridge data exchange between two threads.  For example, a worker thread
  48  * might write data to a pipe from which the main thread will read.
  49  *
  50  * Each end of the pipe can be either blocking or non-blocking.  Recall that a
  51  * non-blocking stream will return NS_BASE_STREAM_WOULD_BLOCK if it cannot be
  52  * read or written to without blocking the calling thread.  For example, if you
  53  * try to read from an empty pipe that has not yet been closed, then if that
  54  * pipe's input end is non-blocking, then the read call will fail immediately
  55  * with NS_BASE_STREAM_WOULD_BLOCK as the error condition.  However, if that
  56  * pipe's input end is blocking, then the read call will not return until the
  57  * pipe has data or until the pipe is closed.  This example presumes that the
  58  * pipe is being filled asynchronously on some background thread.
  59  *
  60  * The pipe supports nsIAsyncInputStream and nsIAsyncOutputStream, which give
  61  * the user of a non-blocking pipe the ability to wait for the pipe to become
  62  * ready again.  For example, in the case of an empty non-blocking pipe, the
  63  * user can call AsyncWait on the input end of the pipe to be notified when
  64  * the pipe has data to read (or when the pipe becomes closed).
  65  *
  66  * NS_NewPipe2 and NS_NewPipe provide convenient pipe constructors.  In most
  67  * cases nsIPipe is not actually used.  It is usually enough to just get
  68  * references to the pipe's input and output end.  In which case, the pipe is
  69  * automatically closed when the respective pipe ends are released.
  70  */
  71 [scriptable, uuid(f4211abc-61b3-11d4-9877-00c04fa0cf4a)]
  72 interface nsIPipe : nsISupports
  73 {
  74     /**
  75      * initialize this pipe
  76      *
  77      * @param nonBlockingInput
  78      *        true specifies non-blocking input stream behavior
  79      * @param nonBlockingOutput
  80      *        true specifies non-blocking output stream behavior
  81      * @param segmentSize
  82      *        specifies the segment size in bytes (pass 0 to use default value)
  83      * @param segmentCount
  84      *        specifies the max number of segments (pass 0 to use default
  85      *        value).   Passing PR_UINT32_MAX here causes the pipe to have
  86      *        "infinite" space.  This mode can be useful in some cases, but
  87      *        should always be used with caution.  The default value for this
  88      *        parameter is a finite value.
  89      * @param segmentAllocator
  90      *        pass reference to nsIMemory to have all pipe allocations use this
  91      *        allocator (pass null to use the default allocator)
  92      */
  93     void init(in boolean nonBlockingInput,
  94               in boolean nonBlockingOutput,
  95               in unsigned long segmentSize,
  96               in unsigned long segmentCount,
  97               in nsIMemory segmentAllocator);
  98
  99     /**
 100      * The pipe's input end, which also implements nsISearchableInputStream.
 101      */
 102     readonly attribute nsIAsyncInputStream inputStream;
 103
 104     /**
 105      * The pipe's output end.
 106      */
 107     readonly attribute nsIAsyncOutputStream outputStream;
 108 };
 109
 110 /**
 111  * XXX this interface doesn't really belong in here.  It is here because
 112  * currently nsPipeInputStream is the only implementation of this interface.
 113  */
 114 [scriptable, uuid(8C39EF62-F7C9-11d4-98F5-001083010E9B)]
 115 interface nsISearchableInputStream : nsISupports
 116 {
 117     /**
 118      * Searches for a string in the input stream. Since the stream has a notion
 119      * of EOF, it is possible that the string may at some time be in the
 120      * buffer, but is is not currently found up to some offset. Consequently,
 121      * both the found and not found cases return an offset:
 122      *    if found, return offset where it was found
 123      *    if not found, return offset of the first byte not searched
 124      * In the case the stream is at EOF and the string is not found, the first
 125      * byte not searched will correspond to the length of the buffer.
 126      */
 127     void search(in string forString,
 128                 in boolean ignoreCase,
 129                 out boolean found,
 130                 out unsigned long offsetSearchedTo);
 131 };
 132
 133 %{C++
 134
 135 /**
 136  * NS_NewPipe2
 137  *
 138  * This function supersedes NS_NewPipe.  It differs from NS_NewPipe in two
 139  * major ways:
 140  *  (1) returns nsIAsyncInputStream and nsIAsyncOutputStream, so it is
 141  *      not necessary to QI in order to access these interfaces.
 142  *  (2) the size of the pipe is determined by the number of segments
 143  *      times the size of each segment.
 144  *
 145  * @param pipeIn
 146  *        resulting input end of the pipe
 147  * @param pipeOut
 148  *        resulting output end of the pipe
 149  * @param nonBlockingInput
 150  *        true specifies non-blocking input stream behavior
 151  * @param nonBlockingOutput
 152  *        true specifies non-blocking output stream behavior
 153  * @param segmentSize
 154  *        specifies the segment size in bytes (pass 0 to use default value)
 155  * @param segmentCount
 156  *        specifies the max number of segments (pass 0 to use default value)
 157  *        passing PR_UINT32_MAX here causes the pipe to have "infinite" space.
 158  *        this mode can be useful in some cases, but should always be used with
 159  *        caution.  the default value for this parameter is a finite value.
 160  * @param segmentAlloc
 161  *        pass reference to nsIMemory to have all pipe allocations use this
 162  *        allocator (pass null to use the default allocator)
 163  */
 164 extern NS_COM nsresult
 165 NS_NewPipe2(nsIAsyncInputStream **pipeIn,
 166             nsIAsyncOutputStream **pipeOut,
 167             PRBool nonBlockingInput = PR_FALSE,
 168             PRBool nonBlockingOutput = PR_FALSE,
 169             PRUint32 segmentSize = 0,
 170             PRUint32 segmentCount = 0,
 171             nsIMemory *segmentAlloc = nsnull);
 172
 173 /**
 174  * NS_NewPipe
 175  *
 176  * Preserved for backwards compatibility.  Plus, this interface is more
 177  * amiable in certain contexts (e.g., when you don't need the pipe's async
 178  * capabilities).
 179  *
 180  * @param pipeIn
 181  *        resulting input end of the pipe
 182  * @param pipeOut
 183  *        resulting output end of the pipe
 184  * @param segmentSize
 185  *        specifies the segment size in bytes (pass 0 to use default value)
 186  * @param maxSize
 187  *        specifies the max size of the pipe (pass 0 to use default value)
 188  *        number of segments is maxSize / segmentSize, and maxSize must be a
 189  *        multiple of segmentSize.  passing PR_UINT32_MAX here causes the
 190  *        pipe to have "infinite" space.  this mode can be useful in some
 191  *        cases, but should always be used with caution.  the default value
 192  *        for this parameter is a finite value.
 193  * @param nonBlockingInput
 194  *        true specifies non-blocking input stream behavior
 195  * @param nonBlockingOutput
 196  *        true specifies non-blocking output stream behavior
 197  * @param segmentAlloc
 198  *        pass reference to nsIMemory to have all pipe allocations use this
 199  *        allocator (pass null to use the default allocator)
 200  */
 201 extern NS_COM nsresult
 202 NS_NewPipe(nsIInputStream **pipeIn,
 203            nsIOutputStream **pipeOut,
 204            PRUint32 segmentSize = 0,
 205            PRUint32 maxSize = 0,
 206            PRBool nonBlockingInput = PR_FALSE,
 207            PRBool nonBlockingOutput = PR_FALSE,
 208            nsIMemory *segmentAlloc = nsnull);
 209
 210 %}