162 lines
4.4 KiB
C
162 lines
4.4 KiB
C
/* contrib/arm-neon/linux.c
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*
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* Copyright (c) 2014 Glenn Randers-Pehrson
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* Written by John Bowler, 2014.
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* Last changed in libpng 1.6.16 [(PENDING RELEASE)]
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*
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* This code is released under the libpng license.
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* For conditions of distribution and use, see the disclaimer
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* and license in png.h
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*
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* SEE contrib/arm-neon/README before reporting bugs
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*
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* STATUS: SUPPORTED
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* BUG REPORTS: png-mng-implement@sourceforge.net
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*
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* png_have_neon implemented for Linux by reading the widely available
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* pseudo-file /proc/cpuinfo.
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*
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* This code is strict ANSI-C and is probably moderately portable; it does
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* however use <stdio.h> and it assumes that /proc/cpuinfo is never localized.
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*/
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#include <stdio.h>
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static int
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png_have_neon(png_structp png_ptr)
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{
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FILE *f = fopen("/proc/cpuinfo", "rb");
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if (f != NULL)
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{
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/* This is a simple state machine which reads the input byte-by-byte until
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* it gets a match on the 'neon' feature or reaches the end of the stream.
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*/
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static const char ch_feature[] = { 70, 69, 65, 84, 85, 82, 69, 83 };
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static const char ch_neon[] = { 78, 69, 79, 78 };
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enum
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{
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StartLine, Feature, Colon, StartTag, Neon, HaveNeon, SkipTag, SkipLine
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} state;
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int counter;
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for (state=StartLine, counter=0;;)
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{
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int ch = fgetc(f);
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if (ch == EOF)
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{
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/* EOF means error or end-of-file, return false; neon at EOF is
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* assumed to be a mistake.
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*/
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fclose(f);
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return 0;
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}
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switch (state)
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{
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case StartLine:
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/* Match spaces at the start of line */
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if (ch <= 32) /* skip control characters and space */
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break;
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counter=0;
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state = Feature;
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/* FALL THROUGH */
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case Feature:
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/* Match 'FEATURE', ASCII case insensitive. */
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if ((ch & ~0x20) == ch_feature[counter])
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{
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if (++counter == (sizeof ch_feature))
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state = Colon;
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break;
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}
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/* did not match 'feature' */
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state = SkipLine;
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/* FALL THROUGH */
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case SkipLine:
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skipLine:
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/* Skip everything until we see linefeed or carriage return */
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if (ch != 10 && ch != 13)
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break;
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state = StartLine;
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break;
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case Colon:
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/* Match any number of space or tab followed by ':' */
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if (ch == 32 || ch == 9)
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break;
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if (ch == 58) /* i.e. ':' */
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{
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state = StartTag;
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break;
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}
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/* Either a bad line format or a 'feature' prefix followed by
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* other characters.
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*/
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state = SkipLine;
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goto skipLine;
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case StartTag:
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/* Skip space characters before a tag */
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if (ch == 32 || ch == 9)
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break;
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state = Neon;
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counter = 0;
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/* FALL THROUGH */
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case Neon:
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/* Look for 'neon' tag */
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if ((ch & ~0x20) == ch_neon[counter])
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{
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if (++counter == (sizeof ch_neon))
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state = HaveNeon;
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break;
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}
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state = SkipTag;
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/* FALL THROUGH */
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case SkipTag:
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/* Skip non-space characters */
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if (ch == 10 || ch == 13)
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state = StartLine;
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else if (ch == 32 || ch == 9)
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state = StartTag;
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break;
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case HaveNeon:
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/* Have seen a 'neon' prefix, but there must be a space or new
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* line character to terminate it.
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*/
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if (ch == 10 || ch == 13 || ch == 32 || ch == 9)
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{
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fclose(f);
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return 1;
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}
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state = SkipTag;
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break;
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default:
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png_error(png_ptr, "png_have_neon: internal error (bug)");
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}
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}
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}
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#ifdef PNG_WARNINGS_SUPPORTED
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else
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png_warning(png_ptr, "/proc/cpuinfo open failed");
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#endif
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return 0;
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}
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