The Tor Browser: gfx/2d/convolver.h@97036ab72558 (annotated)

gfx/2d/convolver.h@97036ab72558 (annotated)

gfx/2d/convolver.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 // Copyright (c) 2006-2012 The Chromium Authors. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //  * Redistributions of source code must retain the above copyright
 //    notice, this list of conditions and the following disclaimer.
 //  * Redistributions in binary form must reproduce the above copyright
 //    notice, this list of conditions and the following disclaimer in
 //    the documentation and/or other materials provided with the
 //    distribution.
 //  * Neither the name of Google, Inc. nor the names of its contributors
 //    may be used to endorse or promote products derived from this
 //    software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 // FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 // COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 // BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 // OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 // AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 // OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 // SUCH DAMAGE.
 #ifndef SKIA_EXT_CONVOLVER_H_
 #define SKIA_EXT_CONVOLVER_H_
 #include <cmath>
 #include <vector>
 #include "base/basictypes.h"
 #include "base/cpu.h"
 #include "mozilla/Assertions.h"
 #include "skia/SkTypes.h"
 // avoid confusion with Mac OS X's math library (Carbon)
 #if defined(__APPLE__)
 #undef FloatToFixed
 #undef FixedToFloat
 #endif
 namespace skia {
 // Represents a filter in one dimension. Each output pixel has one entry in this
 // object for the filter values contributing to it. You build up the filter
 // list by calling AddFilter for each output pixel (in order).
 //
 // We do 2-dimensional convolution by first convolving each row by one
 // ConvolutionFilter1D, then convolving each column by another one.
 //
 // Entries are stored in fixed point, shifted left by kShiftBits.
 class ConvolutionFilter1D {
  public:
   typedef short Fixed;
   // The number of bits that fixed point values are shifted by.
   enum { kShiftBits = 14 };
   ConvolutionFilter1D();
   ~ConvolutionFilter1D();
   // Convert between floating point and our fixed point representation.
   static Fixed FloatToFixed(float f) {
     return static_cast<Fixed>(f * (1 << kShiftBits));
   }
   static unsigned char FixedToChar(Fixed x) {
     return static_cast<unsigned char>(x >> kShiftBits);
   }
   static float FixedToFloat(Fixed x) {
     // The cast relies on Fixed being a short, implying that on
     // the platforms we care about all (16) bits will fit into
     // the mantissa of a (32-bit) float.
     static_assert(sizeof(Fixed) == 2,
                   "fixed type should fit in float mantissa");
     float raw = static_cast<float>(x);
     return ldexpf(raw, -kShiftBits);
   }
   // Returns the maximum pixel span of a filter.
   int max_filter() const { return max_filter_; }
   // Returns the number of filters in this filter. This is the dimension of the
   // output image.
   int num_values() const { return static_cast<int>(filters_.size()); }
   // Appends the given list of scaling values for generating a given output
   // pixel. |filter_offset| is the distance from the edge of the image to where
   // the scaling factors start. The scaling factors apply to the source pixels
   // starting from this position, and going for the next |filter_length| pixels.
   //
   // You will probably want to make sure your input is normalized (that is,
   // all entries in |filter_values| sub to one) to prevent affecting the overall
   // brighness of the image.
   //
   // The filter_length must be > 0.
   //
   // This version will automatically convert your input to fixed point.
   void AddFilter(int filter_offset,
                         const float* filter_values,
                         int filter_length);
   // Same as the above version, but the input is already fixed point.
   void AddFilter(int filter_offset,
                  const Fixed* filter_values,
                  int filter_length);
   // Retrieves a filter for the given |value_offset|, a position in the output
   // image in the direction we're convolving. The offset and length of the
   // filter values are put into the corresponding out arguments (see AddFilter
   // above for what these mean), and a pointer to the first scaling factor is
   // returned. There will be |filter_length| values in this array.
   inline const Fixed* FilterForValue(int value_offset,
                                      int* filter_offset,
                                      int* filter_length) const {
     const FilterInstance& filter = filters_[value_offset];
     *filter_offset = filter.offset;
     *filter_length = filter.length;
     if (filter.length == 0) {
       return NULL;
     }
     return &filter_values_[filter.data_location];
   }
   inline void PaddingForSIMD(int padding_count) {
     // Padding |padding_count| of more dummy coefficients after the coefficients
     // of last filter to prevent SIMD instructions which load 8 or 16 bytes
     // together to access invalid memory areas. We are not trying to align the
     // coefficients right now due to the opaqueness of <vector> implementation.
     // This has to be done after all |AddFilter| calls.
     for (int i = 0; i < padding_count; ++i)
       filter_values_.push_back(static_cast<Fixed>(0));
   }
  private:
   struct FilterInstance {
     // Offset within filter_values for this instance of the filter.
     int data_location;
     // Distance from the left of the filter to the center. IN PIXELS
     int offset;
     // Number of values in this filter instance.
     int length;
   };
   // Stores the information for each filter added to this class.
   std::vector<FilterInstance> filters_;
   // We store all the filter values in this flat list, indexed by
   // |FilterInstance.data_location| to avoid the mallocs required for storing
   // each one separately.
   std::vector<Fixed> filter_values_;
   // The maximum size of any filter we've added.
   int max_filter_;
 };
 // Does a two-dimensional convolution on the given source image.
 //
 // It is assumed the source pixel offsets referenced in the input filters
 // reference only valid pixels, so the source image size is not required. Each
 // row of the source image starts |source_byte_row_stride| after the previous
 // one (this allows you to have rows with some padding at the end).
 //
 // The result will be put into the given output buffer. The destination image
 // size will be xfilter.num_values() * yfilter.num_values() pixels. It will be
 // in rows of exactly xfilter.num_values() * 4 bytes.
 //
 // |source_has_alpha| is a hint that allows us to avoid doing computations on
 // the alpha channel if the image is opaque. If you don't know, set this to
 // true and it will work properly, but setting this to false will be a few
 // percent faster if you know the image is opaque.
 //
 // The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order
 // (this is ARGB when loaded into 32-bit words on a little-endian machine).
 void BGRAConvolve2D(const unsigned char* source_data,
                     int source_byte_row_stride,
                     bool source_has_alpha,
                     const ConvolutionFilter1D& xfilter,
                     const ConvolutionFilter1D& yfilter,
                     int output_byte_row_stride,
                     unsigned char* output,
                     bool use_sse2);
 }  // namespace skia
 #endif  // SKIA_EXT_CONVOLVER_H_

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gfx/2d/convolver.h@97036ab72558 (annotated)

gfx/2d/convolver.h