libpng/arm/arm_init.c

/* arm_init.c - NEON optimised filter functions
 *
 * Copyright (c) 2012 Glenn Randers-Pehrson
 * Written by Mans Rullgard, 2011.
 * Last changed in libpng 1.5.14 [(PENDING RELEASE)]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 */
#include "../pngpriv.h"

/* __arm__ is defined by GCC, MSVC defines _M_ARM to the ARM version number */
#if defined __linux__ && defined __arm__
#include <stdio.h>
#include <elf.h>
#include <asm/hwcap.h>

static int png_have_hwcap(unsigned cap)
{
   FILE *f = fopen("/proc/self/auxv", "r");
   Elf32_auxv_t aux;
   int have_cap = 0;

   if (!f)
      return 0;

   while (fread(&aux, sizeof(aux), 1, f) > 0)
   {
      if (aux.a_type == AT_HWCAP &&
          aux.a_un.a_val & cap)
      {
         have_cap = 1;
         break;
      }
   }

   fclose(f);

   return have_cap;
}
#endif /* __linux__ && __arm__ */

void
png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
{
#ifdef __arm__
#ifdef __linux__
   if (!png_have_hwcap(HWCAP_NEON))
      return;
#endif

   /* IMPORTANT: any new external functions used here must be declared using
    * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
    * 'prefix' option to configure works:
    *
    *    ./configure --with-libpng-prefix=foobar_
    *
    * Verify you have got this right by running the above command, doing a build
    * and examining pngprefix.h; it must contain a #define for every external
    * function you add.  (Notice that this happens automatically for the
    * initialization function.)
    */
   pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;

   if (bpp == 3)
   {
      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
         png_read_filter_row_paeth3_neon;
   }

   else if (bpp == 4)
   {
      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
          png_read_filter_row_paeth4_neon;
   }
#else
   PNG_UNUSED(pp)
   PNG_UNUSED(bpp)
#endif
}