xpcom/io/nsIIOUtil.idl
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 98983 f4157e8c410708d76703f19e4dfb61859bfe32d8
permissions -rw-r--r--
Bug 1402247 - Use encoding_rs for XPCOM string encoding conversions. r=Nika,erahm,froydnj. Correctness improvements: * UTF errors are handled safely per spec instead of dangerously truncating strings. * There are fewer converter implementations. Performance improvements: * The old code did exact buffer length math, which meant doing UTF math twice on each input string (once for length calculation and another time for conversion). Exact length math is more complicated when handling errors properly, which the old code didn't do. The new code does UTF math on the string content only once (when converting) but risks allocating more than once. There are heuristics in place to lower the probability of reallocation in cases where the double math avoidance isn't enough of a saving to absorb an allocation and memcpy. * Previously, in UTF-16 <-> UTF-8 conversions, an ASCII prefix was optimized but a single non-ASCII code point pessimized the rest of the string. The new code tries to get back on the fast ASCII path. * UTF-16 to Latin1 conversion guarantees less about handling of out-of-range input to eliminate an operation from the inner loop on x86/x86_64. * When assigning to a pre-existing string, the new code tries to reuse the old buffer instead of first releasing the old buffer and then allocating a new one. * When reallocating from the new code, the memcpy covers only the data that is part of the logical length of the old string instead of memcpying the whole capacity. (For old callers old excess memcpy behavior is preserved due to bogus callers. See bug 1472113.) * UTF-8 strings in XPConnect that are in the Latin1 range are passed to SpiderMonkey as Latin1. New features: * Conversion between UTF-8 and Latin1 is added in order to enable faster future interop between Rust code (or otherwise UTF-8-using code) and text node and SpiderMonkey code that uses Latin1. MozReview-Commit-ID: JaJuExfILM9

/* -*- 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;
interface nsIOutputStream;

/**
 * nsIIOUtil provdes various xpcom/io-related utility methods.
 */
[scriptable, uuid(e8152f7f-4209-4c63-ad23-c3d2aa0c5a49)]
interface nsIIOUtil : nsISupports
{
  /**
   * Test whether an input stream is buffered.  See nsStreamUtils.h
   * documentation for NS_InputStreamIsBuffered for the definition of
   * "buffered" used here and for edge-case behavior.
   *
   * @throws NS_ERROR_INVALID_POINTER if null is passed in.
   */
  boolean inputStreamIsBuffered(in nsIInputStream aStream);

  /**
   * Test whether an output stream is buffered.  See nsStreamUtils.h
   * documentation for NS_OutputStreamIsBuffered for the definition of
   * "buffered" used here and for edge-case behavior.
   *
   * @throws NS_ERROR_INVALID_POINTER if null is passed in.
   */
  boolean outputStreamIsBuffered(in nsIOutputStream aStream);
};