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Diffstat (limited to 'contrib/arm-neon/linux.c')
| -rw-r--r-- | contrib/arm-neon/linux.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/contrib/arm-neon/linux.c b/contrib/arm-neon/linux.c new file mode 100644 index 000000000..182f37605 --- /dev/null +++ b/contrib/arm-neon/linux.c @@ -0,0 +1,159 @@ +/* contrib/arm-neon/linux.c + * + * Copyright (c) 2014 Glenn Randers-Pehrson + * Written by John Bowler, 2014. + * Last changed in libpng 1.6.10 [March 6, 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 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; + /* 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)"); + } + } + } + + else + png_warning(png_ptr, "/proc/cpuinfo open failed"); + + return 0; +} |