michael@0: /* contrib/arm-neon/linux.c
michael@0:  *
michael@0:  * Copyright (c) 2014 Glenn Randers-Pehrson
michael@0:  * Written by John Bowler, 2014.
michael@0:  * Last changed in libpng 1.6.10 [March 6, 2014]
michael@0:  *
michael@0:  * This code is released under the libpng license.
michael@0:  * For conditions of distribution and use, see the disclaimer
michael@0:  * and license in png.h
michael@0:  *
michael@0:  * SEE contrib/arm-neon/README before reporting bugs
michael@0:  *
michael@0:  * STATUS: SUPPORTED
michael@0:  * BUG REPORTS: png-mng-implement@sourceforge.net
michael@0:  *
michael@0:  * png_have_neon implemented for Linux by reading the widely available
michael@0:  * pseudo-file /proc/cpuinfo.
michael@0:  *
michael@0:  * This code is strict ANSI-C and is probably moderately portable, it does
michael@0:  * however use <stdio.h> and assumes that /proc/cpuinfo is never localized.
michael@0:  */
michael@0: #include <stdio.h>
michael@0: 
michael@0: static int
michael@0: png_have_neon(png_structp png_ptr)
michael@0: {
michael@0:    FILE *f = fopen("/proc/cpuinfo", "rb");
michael@0: 
michael@0:    if (f != NULL)
michael@0:    {
michael@0:       /* This is a simple state machine which reads the input byte-by-byte until
michael@0:        * it gets a match on the 'neon' feature or reaches the end of the stream.
michael@0:        */
michael@0:       static const char ch_feature[] = { 70, 69, 65, 84, 85, 82, 69, 83 };
michael@0:       static const char ch_neon[] = { 78, 69, 79, 78 };
michael@0: 
michael@0:       enum
michael@0:       {
michael@0:          StartLine, Feature, Colon, StartTag, Neon, HaveNeon, SkipTag, SkipLine
michael@0:       }  state;
michael@0:       int counter;
michael@0: 
michael@0:       for (state=StartLine, counter=0;;)
michael@0:       {
michael@0:          int ch = fgetc(f);
michael@0: 
michael@0:          if (ch == EOF)
michael@0:          {
michael@0:             /* EOF means error or end-of-file, return false; neon at EOF is
michael@0:              * assumed to be a mistake.
michael@0:              */
michael@0:             fclose(f);
michael@0:             return 0;
michael@0:          }
michael@0: 
michael@0:          switch (state)
michael@0:          {
michael@0:             case StartLine:
michael@0:                /* Match spaces at the start of line */
michael@0:                if (ch <= 32) /* skip control characters and space */
michael@0:                   break;
michael@0: 
michael@0:                counter=0;
michael@0:                state = Feature;
michael@0:                /* FALL THROUGH */
michael@0: 
michael@0:             case Feature:
michael@0:                /* Match 'FEATURE', ASCII case insensitive. */
michael@0:                if ((ch & ~0x20) == ch_feature[counter])
michael@0:                {
michael@0:                   if (++counter == (sizeof ch_feature))
michael@0:                      state = Colon;
michael@0:                   break;
michael@0:                }
michael@0:                
michael@0:                /* did not match 'feature' */
michael@0:                state = SkipLine;
michael@0:                /* FALL THROUGH */
michael@0: 
michael@0:             case SkipLine:
michael@0:             skipLine:
michael@0:                /* Skip everything until we see linefeed or carriage return */
michael@0:                if (ch != 10 && ch != 13)
michael@0:                   break;
michael@0: 
michael@0:                state = StartLine;
michael@0:                break;
michael@0: 
michael@0:             case Colon:
michael@0:                /* Match any number of space or tab followed by ':' */
michael@0:                if (ch == 32 || ch == 9)
michael@0:                   break;
michael@0: 
michael@0:                if (ch == 58) /* i.e. ':' */
michael@0:                {
michael@0:                   state = StartTag;
michael@0:                   break;
michael@0:                }
michael@0: 
michael@0:                /* Either a bad line format or a 'feature' prefix followed by
michael@0:                 * other characters.
michael@0:                 */
michael@0:                state = SkipLine;
michael@0:                goto skipLine;
michael@0: 
michael@0:             case StartTag:
michael@0:                /* Skip space characters before a tag */
michael@0:                if (ch == 32 || ch == 9)
michael@0:                   break;
michael@0: 
michael@0:                state = Neon;
michael@0:                counter = 0;
michael@0:                /* FALL THROUGH */
michael@0: 
michael@0:             case Neon:
michael@0:                /* Look for 'neon' tag */
michael@0:                if ((ch & ~0x20) == ch_neon[counter])
michael@0:                {
michael@0:                   if (++counter == (sizeof ch_neon))
michael@0:                      state = HaveNeon;
michael@0:                   break;
michael@0:                }
michael@0: 
michael@0:                state = SkipTag;
michael@0:                /* FALL THROUGH */
michael@0: 
michael@0:             case SkipTag:
michael@0:                /* Skip non-space characters */
michael@0:                if (ch == 10 || ch == 13)
michael@0:                   state = StartLine;
michael@0: 
michael@0:                else if (ch == 32 || ch == 9)
michael@0:                   state = StartTag;
michael@0:                break;
michael@0: 
michael@0:             case HaveNeon:
michael@0:                /* Have seen a 'neon' prefix, but there must be a space or new
michael@0:                 * line character to terminate it.
michael@0:                 */
michael@0:                if (ch == 10 || ch == 13 || ch == 32 || ch == 9)
michael@0:                {
michael@0:                   fclose(f);
michael@0:                   return 1;
michael@0:                }
michael@0: 
michael@0:                state = SkipTag;
michael@0:                break;
michael@0: 
michael@0:             default:
michael@0:                png_error(png_ptr, "png_have_neon: internal error (bug)");
michael@0:          }
michael@0:       }
michael@0:    }
michael@0: 
michael@0:    else
michael@0:       png_warning(png_ptr, "/proc/cpuinfo open failed");
michael@0: 
michael@0:    return 0;
michael@0: }