xpcom/io/nsIMultiplexInputStream.idl
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 451797 4a14671935e6bc31b3f7c509190bbd30d25de4d2
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: 4; 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 "nsIInputStream.idl"

/**
 * The multiplex stream concatenates a list of input streams into a single
 * stream.
 */

[scriptable, uuid(a076fd12-1dd1-11b2-b19a-d53b5dffaade)]
interface nsIMultiplexInputStream : nsISupports
{
    /**
     * Number of streams in this multiplex-stream
     */
    readonly attribute unsigned long count;

    /**
     * Appends a stream to the end of the streams. The cursor of the stream
     * should be located at the beginning of the stream if the implementation
     * of this nsIMultiplexInputStream also is used as an nsISeekableStream.
     * @param stream  stream to append
     */
    void appendStream(in nsIInputStream stream);

    /**
     * Get stream at specified index.
     * @param index   return stream at this index, must be < count
     * @return        stream at specified index
     */
    nsIInputStream getStream(in unsigned long index);
};