[Libguestfs] [PATCH v2 2/2] lib: Reimplement is_zero.

As suggested by Eric Blake. --- lib/guestfs-internal-all.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/lib/guestfs-internal-all.h b/lib/guestfs-internal-all.h index 4f7433332..7da93828e 100644 --- a/lib/guestfs-internal-all.h +++ b/lib/guestfs-internal-all.h @@ -32,6 +32,8 @@ #ifndef GUESTFS_INTERNAL_ALL_H_ #define GUESTFS_INTERNAL_ALL_H_ +#include <string.h> + /* This is also defined in <guestfs.h>, so don't redefine it. */ #if defined(__GNUC__) && !defined(GUESTFS_GCC_VERSION) # define GUESTFS_GCC_VERSION \ @@ -89,20 +91,18 @@ #define xdr_uint32_t xdr_u_int32_t #endif -/* Return true iff the buffer is all zero bytes. - * - * Note that gcc is smart enough to optimize this properly: - * http://stackoverflow.com/questions/1493936/faster-means-of-checking-for-a... - */ +/* Return true iff the buffer is all zero bytes. */ static inline int is_zero (const char *buffer, size_t size) { size_t i; + const size_t limit = MIN (size, 16); - for (i = 0; i < size; ++i) { - if (buffer[i] != 0) + for (i = 0; i < limit; ++i) + if (buffer[i]) return 0; - } + if (size != limit) + return !memcmp (buffer, buffer + 16, size - 16); return 1; } -- 2.12.0