From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:58202) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UGXDr-0001WQ-7T for qemu-devel@nongnu.org; Fri, 15 Mar 2013 12:11:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UGXDl-0006IP-UI for qemu-devel@nongnu.org; Fri, 15 Mar 2013 12:11:11 -0400 Received: from [2a02:248:0:30:223:aeff:fefe:7f1c] (port=48339 helo=dns.kamp-intra.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UGXDl-0006Gy-N4 for qemu-devel@nongnu.org; Fri, 15 Mar 2013 12:11:05 -0400 From: Peter Lieven Date: Fri, 15 Mar 2013 16:50:11 +0100 Message-Id: <1363362619-3190-3-git-send-email-pl@kamp.de> In-Reply-To: <1363362619-3190-1-git-send-email-pl@kamp.de> References: <1363362619-3190-1-git-send-email-pl@kamp.de> Subject: [Qemu-devel] [PATCHv2 2/9] cutils: add a function to find non-zero content in a buffer List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Lieven Signed-off-by: Peter Lieven --- include/qemu-common.h | 2 ++ util/cutils.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/include/qemu-common.h b/include/qemu-common.h index b59328f..51a7677 100644 --- a/include/qemu-common.h +++ b/include/qemu-common.h @@ -362,6 +362,8 @@ size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset, size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, int fillc, size_t bytes); +#define BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR 8 +size_t buffer_find_nonzero_offset(const void *buf, size_t len); bool buffer_is_zero(const void *buf, size_t len); void qemu_progress_init(int enabled, float min_skip); diff --git a/util/cutils.c b/util/cutils.c index 1439da4..857dd7d 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -143,6 +143,46 @@ int qemu_fdatasync(int fd) } /* + * Searches for an area with non-zero content in a buffer + * + * Attention! The len must be a multiple of 8 * sizeof(VECTYPE) + * and addr must be a multiple of sizeof(VECTYPE) due to + * restriction of optimizations in this function. + * + * The return value is the offset of the non-zero area rounded + * down to 8 * sizeof(VECTYPE). If the buffer is all zero + * the return value is equal to len. + */ + +size_t buffer_find_nonzero_offset(const void *buf, size_t len) +{ + VECTYPE *p = (VECTYPE *)buf; + VECTYPE zero = ZERO_SPLAT; + size_t i; + + assert(len % (BUFFER_FIND_NONZERO_OFFSET_UNROLL_FACTOR + * sizeof(VECTYPE)) == 0); + assert(((uintptr_t) buf) % sizeof(VECTYPE) == 0); + + if (*((const long *) buf)) { + return 0; + } + + for (i = 0; i < len / sizeof(VECTYPE); i += 8) { + VECTYPE tmp0 = p[i+0] | p[i+1]; + VECTYPE tmp1 = p[i+2] | p[i+3]; + VECTYPE tmp2 = p[i+4] | p[i+5]; + VECTYPE tmp3 = p[i+6] | p[i+7]; + VECTYPE tmp01 = tmp0 | tmp1; + VECTYPE tmp23 = tmp2 | tmp3; + if (!ALL_EQ(tmp01 | tmp23, zero)) { + break; + } + } + return i * sizeof(VECTYPE); +} + +/* * Checks if a buffer is all zeroes * * Attention! The len must be a multiple of 4 * sizeof(long) due to -- 1.7.9.5