/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 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 number of UTF-16 code units already read
 *                  (since ReadSegments was called)
 * @param aCount length of fromSegment
 * @param aWriteCount number of UTF-16 code units read
 *
 * Implementers should return the following:
 *
 * @throws <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 nsresult (*nsWriteUnicharSegmentFun)(nsIUnicharInputStream *aInStream,
                                             void *aClosure,
                                             const char16_t *aFromSegment,
                                             uint32_t aToOffset,
                                             uint32_t aCount,
                                             uint32_t *aWriteCount);
%}
native nsWriteUnicharSegmentFun(nsWriteUnicharSegmentFun);

/**
 * Abstract UTF-16 input stream
 * @see nsIInputStream
 */
[scriptable, uuid(d5e3bd80-6723-4b92-b0c9-22f6162fd94f)]
interface nsIUnicharInputStream : nsISupports {
  /**
   * Reads into a caller-provided array.
   *
   * @return The number of utf-16 code units 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 code units, call this method multiple times.
   */
  [noscript] unsigned long read([array, size_is(aCount)] in char16_t 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 UTF-16 code units 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 UTF-16 code units to be read
   *
   * @return number of UTF-16 code units 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 UTF-16 code units that should be read
   * @return The number of UTF-16 code units 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();
};