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/* contrib/arm-neon/linux.c
*
* Last changed in libpng 1.6.31 [July 27, 2017]
* Copyright (c) 2014, 2017 Glenn Randers-Pehrson
* Written by John Bowler, 2014, 2017.
*
* 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.
*/
#include <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;
/* FALLTHROUGH */
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;
/* FALLTHROUGH */
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;
/* FALLTHROUGH */
case Neon:
/* Look for 'neon' tag */
if ((ch & ~0x20) == ch_neon[counter])
{
if (++counter == (sizeof ch_neon))
state = HaveNeon;
break;
}
state = SkipTag;
/* FALLTHROUGH */
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;
}
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