/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * ***** END LICENSE BLOCK ***** */

#include "nsISupports.idl"

interface nsIUnicharInputStream;
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
 * @param aToOffset amount already read (since ReadSegments was called)
 * @param aCount length of fromSegment
 * @param aWriteCount number of bytes read
 *
 * 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(nsWriteUnicharSegmentFun)(nsIUnicharInputStream *aInStream,
                                              void *aClosure,
                                              const PRUnichar *aFromSegment,
                                              PRUint32 aToOffset,
                                              PRUint32 aCount,
                                              PRUint32 *aWriteCount);
%}
native nsWriteUnicharSegmentFun(nsWriteUnicharSegmentFun);

/**
 * Abstract unicode character input stream
 * @see nsIInputStream
 */
[scriptable, uuid(d5e3bd80-6723-4b92-b0c9-22f6162fd94f)]
interface nsIUnicharInputStream : nsISupports {
  /**
   * Reads into a caller-provided character array.
   *
   * @return The number of characters that were successfully read. May be less
   *         than aCount, even if there is more data in the input stream.
   *         A return value of 0 means EOF.
   *
   * @note To read more than 2^32 characters, call this method multiple times.
   */
  [noscript] unsigned long read([array, size_is(aCount)] in PRUnichar aBuf,
                                in unsigned long aCount);

  /**
   * Low-level read method that has 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 characters 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 characters to be read
   *
   * @return number of characters 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 <other-error> on failure
   *
   * NOTE: this function may be unimplemented if a stream has no underlying
   * buffer
   */
  [noscript] unsigned long readSegments(in nsWriteUnicharSegmentFun aWriter,
                                        in voidPtr aClosure,
                                        in unsigned long aCount);

  /**
   * Read into a string object.
   * @param aCount The number of characters that should be read
   * @return The number of characters that were read.
   */
  unsigned long readString(in unsigned long aCount, out AString aString);

 /**
  * Close the stream and free associated resources. This also closes the
  * underlying stream, if any.
  */
  void close();
};
