source/libs/libpng/libpng-src/contrib/arm-neon/linux.c

   1 /* contrib/arm-neon/linux.c
   2  *
   3  * Copyright (c) 2014 Glenn Randers-Pehrson
   4  * Written by John Bowler, 2014.
   5  * Last changed in libpng 1.6.16 [December 22, 2014]
   6  *
   7  * This code is released under the libpng license.
   8  * For conditions of distribution and use, see the disclaimer
   9  * and license in png.h
  10  *
  11  * SEE contrib/arm-neon/README before reporting bugs
  12  *
  13  * STATUS: SUPPORTED
  14  * BUG REPORTS: png-mng-implement@sourceforge.net
  15  *
  16  * png_have_neon implemented for Linux by reading the widely available
  17  * pseudo-file /proc/cpuinfo.
  18  *
  19  * This code is strict ANSI-C and is probably moderately portable; it does
  20  * however use <stdio.h> and it assumes that /proc/cpuinfo is never localized.
  21  */
  22 #include <stdio.h>
  23
  24 static int
  25 png_have_neon(png_structp png_ptr)
  26 {
  27    FILE *f = fopen("/proc/cpuinfo", "rb");
  28
  29    if (f != NULL)
  30    {
  31       /* This is a simple state machine which reads the input byte-by-byte until
  32        * it gets a match on the 'neon' feature or reaches the end of the stream.
  33        */
  34       static const char ch_feature[] = { 70, 69, 65, 84, 85, 82, 69, 83 };
  35       static const char ch_neon[] = { 78, 69, 79, 78 };
  36
  37       enum
  38       {
  39          StartLine, Feature, Colon, StartTag, Neon, HaveNeon, SkipTag, SkipLine
  40       }  state;
  41       int counter;
  42
  43       for (state=StartLine, counter=0;;)
  44       {
  45          int ch = fgetc(f);
  46
  47          if (ch == EOF)
  48          {
  49             /* EOF means error or end-of-file, return false; neon at EOF is
  50              * assumed to be a mistake.
  51              */
  52             fclose(f);
  53             return 0;
  54          }
  55
  56          switch (state)
  57          {
  58             case StartLine:
  59                /* Match spaces at the start of line */
  60                if (ch <= 32) /* skip control characters and space */
  61                   break;
  62
  63                counter=0;
  64                state = Feature;
  65                /* FALL THROUGH */
  66
  67             case Feature:
  68                /* Match 'FEATURE', ASCII case insensitive. */
  69                if ((ch & ~0x20) == ch_feature[counter])
  70                {
  71                   if (++counter == (sizeof ch_feature))
  72                      state = Colon;
  73                   break;
  74                }
  75
  76                /* did not match 'feature' */
  77                state = SkipLine;
  78                /* FALL THROUGH */
  79
  80             case SkipLine:
  81             skipLine:
  82                /* Skip everything until we see linefeed or carriage return */
  83                if (ch != 10 && ch != 13)
  84                   break;
  85
  86                state = StartLine;
  87                break;
  88
  89             case Colon:
  90                /* Match any number of space or tab followed by ':' */
  91                if (ch == 32 || ch == 9)
  92                   break;
  93
  94                if (ch == 58) /* i.e. ':' */
  95                {
  96                   state = StartTag;
  97                   break;
  98                }
  99
 100                /* Either a bad line format or a 'feature' prefix followed by
 101                 * other characters.
 102                 */
 103                state = SkipLine;
 104                goto skipLine;
 105
 106             case StartTag:
 107                /* Skip space characters before a tag */
 108                if (ch == 32 || ch == 9)
 109                   break;
 110
 111                state = Neon;
 112                counter = 0;
 113                /* FALL THROUGH */
 114
 115             case Neon:
 116                /* Look for 'neon' tag */
 117                if ((ch & ~0x20) == ch_neon[counter])
 118                {
 119                   if (++counter == (sizeof ch_neon))
 120                      state = HaveNeon;
 121                   break;
 122                }
 123
 124                state = SkipTag;
 125                /* FALL THROUGH */
 126
 127             case SkipTag:
 128                /* Skip non-space characters */
 129                if (ch == 10 || ch == 13)
 130                   state = StartLine;
 131
 132                else if (ch == 32 || ch == 9)
 133                   state = StartTag;
 134                break;
 135
 136             case HaveNeon:
 137                /* Have seen a 'neon' prefix, but there must be a space or new
 138                 * line character to terminate it.
 139                 */
 140                if (ch == 10 || ch == 13 || ch == 32 || ch == 9)
 141                {
 142                   fclose(f);
 143                   return 1;
 144                }
 145
 146                state = SkipTag;
 147                break;
 148
 149             default:
 150                png_error(png_ptr, "png_have_neon: internal error (bug)");
 151          }
 152       }
 153    }
 154
 155 #ifdef PNG_WARNINGS_SUPPORTED
 156    else
 157       png_warning(png_ptr, "/proc/cpuinfo open failed");
 158 #endif
 159
 160    return 0;
 161 }