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 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #include "nsISupports.idl"

 interface nsIInputStream;

 %{C++

 /**

  * The signature of the writer function passed to ReadSegments. This

  * is the "consumer" of data that gets read from the stream's buffer.

  *

  * @param aInStream stream being read

  * @param aClosure opaque parameter passed to ReadSegments

  * @param aFromSegment pointer to memory owned by the input stream.  This is

  *                     where the writer function should start consuming data.

  * @param aToOffset amount of data already consumed by this writer during this

  *                  ReadSegments call.  This is also the sum of the aWriteCount

  *                  returns from this writer over the previous invocations of

  *                  the writer by this ReadSegments call.

  * @param aCount Number of bytes available to be read starting at aFromSegment

  * @param [out] aWriteCount number of bytes read by this writer function call

  *

  * Implementers should return the following:

  *

  * @return NS_OK and (*aWriteCount > 0) if consumed some data

  * @return <any-error> if not interested in consuming any data

  *

  * Errors are never passed to the caller of ReadSegments.

  *

  * NOTE: returning NS_OK and (*aWriteCount = 0) has undefined behavior.

  */

 typedef NS_CALLBACK(nsWriteSegmentFun)(nsIInputStream *aInStream,

                                        void *aClosure,

                                        const char *aFromSegment,

                                        uint32_t aToOffset,

                                        uint32_t aCount,

                                        uint32_t *aWriteCount);

 %}

 native nsWriteSegmentFun(nsWriteSegmentFun);

 /**

  * nsIInputStream

  *

  * An interface describing a readable stream of data.  An input stream may be

  * "blocking" or "non-blocking" (see the IsNonBlocking method).  A blocking

  * input stream may suspend the calling thread in order to satisfy a call to

  * Close, Available, Read, or ReadSegments.  A non-blocking input stream, on

  * the other hand, must not block the calling thread of execution.

  *

  * NOTE: blocking input streams are often read on a background thread to avoid

  * locking up the main application thread.  For this reason, it is generally

  * the case that a blocking input stream should be implemented using thread-

  * safe AddRef and Release.

  */

 [scriptable, uuid(53cdbc97-c2d7-4e30-b2c3-45b2ee79db18)]

 interface nsIInputStream : nsISupports

 {

     /** 

      * Close the stream.  This method causes subsequent calls to Read and

      * ReadSegments to return 0 bytes read to indicate end-of-file.  Any

      * subsequent calls to Available should throw NS_BASE_STREAM_CLOSED.

      */

     void close();

     /**

      * Determine number of bytes available in the stream.  A non-blocking

      * stream that does not yet have any data to read should return 0 bytes

      * from this method (i.e., it must not throw the NS_BASE_STREAM_WOULD_BLOCK

      * exception).

      * 

      * In addition to the number of bytes available in the stream, this method

      * also informs the caller of the current status of the stream.  A stream

      * that is closed will throw an exception when this method is called.  That

      * enables the caller to know the condition of the stream before attempting

      * to read from it.  If a stream is at end-of-file, but not closed, then

      * this method returns 0 bytes available.  (Note: some nsIInputStream

      * implementations automatically close when eof is reached; some do not).

      *

      * @return number of bytes currently available in the stream.

      *

      * @throws NS_BASE_STREAM_CLOSED if the stream is closed normally.

      * @throws <other-error> if the stream is closed due to some error

      *   condition

      */

     unsigned long long available();

     /** 

      * Read data from the stream.

      *

      * @param aBuf the buffer into which the data is to be read

      * @param aCount the maximum number of bytes to be read

      *

      * @return number of bytes read (may be less than aCount).

      * @return 0 if reached end-of-file

      *

      * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from the input stream would

      *   block the calling thread (non-blocking mode only)

      * @throws <other-error> on failure

      *

      * NOTE: this method should not throw NS_BASE_STREAM_CLOSED.

      */

     [noscript] unsigned long read(in charPtr aBuf, in unsigned long aCount);

     /**

      * Low-level read method that provides access to the stream's underlying

      * buffer.  The writer function may be called multiple times for segmented

      * buffers.  ReadSegments is expected to keep calling the writer until

      * either there is nothing left to read or the writer returns an error.

      * ReadSegments should not call the writer with zero bytes to consume.

      *

      * @param aWriter the "consumer" of the data to be read

      * @param aClosure opaque parameter passed to writer 

      * @param aCount the maximum number of bytes to be read

      *

      * @return number of bytes read (may be less than aCount)

      * @return 0 if reached end-of-file (or if aWriter refused to consume data)

      *

      * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from the input stream would

      *   block the calling thread (non-blocking mode only)

      * @throws NS_ERROR_NOT_IMPLEMENTED if the stream has no underlying buffer

      * @throws <other-error> on failure

      *

      * NOTE: this function may be unimplemented if a stream has no underlying

      * buffer (e.g., socket input stream).

      *

      * NOTE: this method should not throw NS_BASE_STREAM_CLOSED.

      */

     [noscript] unsigned long readSegments(in nsWriteSegmentFun aWriter,

                                           in voidPtr aClosure,

                                           in unsigned long aCount);

     /**

      * @return true if stream is non-blocking

      *

      * NOTE: reading from a blocking input stream will block the calling thread

      * until at least one byte of data can be extracted from the stream.

      *

      * NOTE: a non-blocking input stream may implement nsIAsyncInputStream to

      * provide consumers with a way to wait for the stream to have more data

      * once its read method is unable to return any data without blocking.

      */

     boolean isNonBlocking();

 };