image/ImageFactory.h
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 478246 7597bbcc9d66111326aa69048ad5847bdc7497f2
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
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: 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/. */

#ifndef mozilla_image_ImageFactory_h
#define mozilla_image_ImageFactory_h

#include "nsCOMPtr.h"
#include "nsProxyRelease.h"
#include "nsStringFwd.h"

class nsIRequest;
class nsIURI;

namespace mozilla {
namespace image {

class Image;
class MultipartImage;
class ProgressTracker;

class ImageFactory
{
public:
  /**
   * Registers vars with Preferences. Should only be called on the main thread.
   */
  static void Initialize();

  /**
   * Creates a new image with the given properties.
   * Can be called on or off the main thread.
   *
   * @param aRequest         The associated request.
   * @param aProgressTracker A status tracker for the image to use.
   * @param aMimeType        The mimetype of the image.
   * @param aURI             The URI of the image.
   * @param aIsMultiPart     Whether the image is part of a multipart request.
   * @param aInnerWindowId   The window this image belongs to.
   */
  static already_AddRefed<Image> CreateImage(nsIRequest* aRequest,
                                             ProgressTracker* aProgressTracker,
                                             const nsCString& aMimeType,
                                             nsIURI* aURI,
                                             bool aIsMultiPart,
                                             uint32_t aInnerWindowId);
  /**
   * Creates a new image which isn't associated with a URI or loaded through
   * the usual image loading mechanism.
   *
   * @param aMimeType      The mimetype of the image.
   * @param aSizeHint      The length of the source data for the image.
   */
  static already_AddRefed<Image>
  CreateAnonymousImage(const nsCString& aMimeType, uint32_t aSizeHint = 0);

  /**
   * Creates a new multipart/x-mixed-replace image wrapper, and initializes it
   * with the first part. Subsequent parts should be passed to the existing
   * MultipartImage via MultipartImage::BeginTransitionToPart().
   *
   * @param aFirstPart       An image containing the first part of the multipart
   *                         stream.
   * @param aProgressTracker A progress tracker for the multipart image.
   */
  static already_AddRefed<MultipartImage>
  CreateMultipartImage(Image* aFirstPart, ProgressTracker* aProgressTracker);

private:
  // Factory functions that create specific types of image containers.
  static already_AddRefed<Image>
  CreateRasterImage(nsIRequest* aRequest,
                    ProgressTracker* aProgressTracker,
                    const nsCString& aMimeType,
                    nsIURI* aURI,
                    uint32_t aImageFlags,
                    uint32_t aInnerWindowId);

  static already_AddRefed<Image>
  CreateVectorImage(nsIRequest* aRequest,
                    ProgressTracker* aProgressTracker,
                    const nsCString& aMimeType,
                    nsIURI* aURI,
                    uint32_t aImageFlags,
                    uint32_t aInnerWindowId);

  // This is a static factory class, so disallow instantiation.
  virtual ~ImageFactory() = 0;
};

} // namespace image
} // namespace mozilla

#endif // mozilla_image_ImageFactory_h