/* contrib/arm-neon/linux.c

 *

 * Copyright (c) 2014 Glenn Randers-Pehrson

 * Written by John Bowler, 2014.

 * Last changed in libpng 1.6.16 [December 22, 2014]

 *

 * This code is released under the libpng license.

 * For conditions of distribution and use, see the disclaimer

 * and license in png.h

 *

 * SEE contrib/arm-neon/README before reporting bugs

 *

 * STATUS: SUPPORTED

 * BUG REPORTS: png-mng-implement@sourceforge.net

 *

 * png_have_neon implemented for Linux by reading the widely available

 * pseudo-file /proc/cpuinfo.

 *

 * This code is strict ANSI-C and is probably moderately portable; it does

 * however use <stdio.h> and it assumes that /proc/cpuinfo is never localized.</stdio.h>

 */

#include <stdio.h></stdio.h>

static int

png_have_neon(png_structp png_ptr)

{

   FILE *f = fopen("/proc/cpuinfo", "rb");

   if (f != NULL)

   {

      /* This is a simple state machine which reads the input byte-by-byte until

       * it gets a match on the 'neon' feature or reaches the end of the stream.

       */

      static const char ch_feature[] = { 70, 69, 65, 84, 85, 82, 69, 83 };

      static const char ch_neon[] = { 78, 69, 79, 78 };

      enum

      {

         StartLine, Feature, Colon, StartTag, Neon, HaveNeon, SkipTag, SkipLine

      }  state;

      int counter;

      for (state=StartLine, counter=0;;)

      {

         int ch = fgetc(f);

         if (ch == EOF)

         {

            /* EOF means error or end-of-file, return false; neon at EOF is

             * assumed to be a mistake.

             */

            fclose(f);

            return 0;

         }

         switch (state)

         {

            case StartLine:

               /* Match spaces at the start of line */

               if (ch <= 32) /* skip control characters and space */

                  break;

               counter=0;

               state = Feature;

               /* FALL THROUGH */

            case Feature:

               /* Match 'FEATURE', ASCII case insensitive. */

               if ((ch & ~0x20) == ch_feature[counter])

               {

                  if (++counter == (sizeof ch_feature))

                     state = Colon;

                  break;

               }

               /* did not match 'feature' */

               state = SkipLine;

               /* FALL THROUGH */

            case SkipLine:

            skipLine:

               /* Skip everything until we see linefeed or carriage return */

               if (ch != 10 && ch != 13)

                  break;

               state = StartLine;

               break;

            case Colon:

               /* Match any number of space or tab followed by ':' */

               if (ch == 32 || ch == 9)

                  break;

               if (ch == 58) /* i.e. ':' */

               {

                  state = StartTag;

                  break;

               }

               /* Either a bad line format or a 'feature' prefix followed by

                * other characters.

                */

               state = SkipLine;

               goto skipLine;

            case StartTag:

               /* Skip space characters before a tag */

               if (ch == 32 || ch == 9)

                  break;

               state = Neon;

               counter = 0;

               /* FALL THROUGH */

            case Neon:

               /* Look for 'neon' tag */

               if ((ch & ~0x20) == ch_neon[counter])

               {

                  if (++counter == (sizeof ch_neon))

                     state = HaveNeon;

                  break;

               }

               state = SkipTag;

               /* FALL THROUGH */

            case SkipTag:

               /* Skip non-space characters */

               if (ch == 10 || ch == 13)

                  state = StartLine;

               else if (ch == 32 || ch == 9)

                  state = StartTag;

               break;

            case HaveNeon:

               /* Have seen a 'neon' prefix, but there must be a space or new

                * line character to terminate it.

                */

               if (ch == 10 || ch == 13 || ch == 32 || ch == 9)

               {

                  fclose(f);

                  return 1;

               }

               state = SkipTag;

               break;

            default:

               png_error(png_ptr, "png_have_neon: internal error (bug)");

         }

      }

   }

#ifdef PNG_WARNINGS_SUPPORTED

   else

      png_warning(png_ptr, "/proc/cpuinfo open failed");

#endif

   return 0;

}