From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:55814) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UFRRl-0004uK-FI for qemu-devel@nongnu.org; Tue, 12 Mar 2013 11:49:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UFRRf-0001ii-0M for qemu-devel@nongnu.org; Tue, 12 Mar 2013 11:49:01 -0400 Received: from ssl.dlhnet.de ([91.198.192.8]:45996 helo=ssl.dlh.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UFRRe-0001iZ-Qh for qemu-devel@nongnu.org; Tue, 12 Mar 2013 11:48:54 -0400 Message-ID: <513F4E68.2060005@dlhnet.de> Date: Tue, 12 Mar 2013 16:48:56 +0100 From: Peter Lieven MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [RFC][PATCH 2/9] 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: Kevin Wolf , Paolo Bonzini , Orit Wasserman , Stefan Hajnoczi Signed-off-by: Peter Lieven --- include/qemu-common.h | 1 + util/cutils.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/qemu-common.h b/include/qemu-common.h index a3555d0..c22c41e 100644 --- a/include/qemu-common.h +++ b/include/qemu-common.h @@ -362,6 +362,7 @@ 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); +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..a09d8e8 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -143,6 +143,36 @@ 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 bedue 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; + 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