diff options
Diffstat (limited to 'lib/rawmemchr.c')
| -rw-r--r-- | lib/rawmemchr.c | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/lib/rawmemchr.c b/lib/rawmemchr.c index 37639287f01..013e7f8cced 100644 --- a/lib/rawmemchr.c +++ b/lib/rawmemchr.c @@ -19,7 +19,7 @@ /* Specification. */ #include <string.h> -/* A function definition is only needed if HAVE_RAWMEMCHR is not defined. */ +/* A function definition is needed only if HAVE_RAWMEMCHR is not defined. */ #if !HAVE_RAWMEMCHR # include <limits.h> @@ -30,19 +30,30 @@ void * rawmemchr (const void *s, int c_in) { - /* Change this typedef to experiment with performance. */ +# ifdef __CHERI_PURE_CAPABILITY__ + /* Most architectures let you read an aligned word, + even if the unsigned char array at S ends in the middle of the word. + However CHERI does not, so call memchr + with the underlying object's remaining length. + This cannot return NULL if S points to a C_IN-terminated array. + Use builtins rather than including <cheri.h> which is less stable. */ + return memchr (s, c_in, (__builtin_cheri_length_get (s) + - __builtin_cheri_offset_get (s))); +# else + + /* You can change this typedef to experiment with performance. */ typedef uintptr_t longword; - /* If you change the "uintptr_t", you should change UINTPTR_WIDTH to match. - This verifies that the type does not have padding bits. */ - static_assert (UINTPTR_WIDTH == UCHAR_WIDTH * sizeof (longword)); + /* Verify that the longword type lacks padding bits. */ + static_assert (UINTPTR_WIDTH == UCHAR_WIDTH * sizeof (uintptr_t)); const unsigned char *char_ptr; unsigned char c = c_in; /* Handle the first few bytes by reading one byte at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ + Do this until CHAR_PTR is aligned on a natural longword boundary, + as using alignof (longword) might be slower. */ for (char_ptr = (const unsigned char *) s; - (uintptr_t) char_ptr % alignof (longword) != 0; + (uintptr_t) char_ptr % sizeof (longword) != 0; ++char_ptr) if (*char_ptr == c) return (void *) char_ptr; @@ -118,6 +129,7 @@ rawmemchr (const void *s, int c_in) while (*char_ptr != c) char_ptr++; return (void *) char_ptr; +# endif } #endif |