| Message ID | 513F4E68.2060005@dlhnet.de |
|---|---|
| State | New |
| Headers | show |
On 03/12/2013 09:48 AM, Peter Lieven wrote: > Signed-off-by: Peter Lieven <pl@kamp.de> > --- > include/qemu-common.h | 1 + > util/cutils.c | 30 ++++++++++++++++++++++++++++++ > 2 files changed, 31 insertions(+) > > > /* > + * 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. s/bedue/be XXX due/ don't know what XXX is supposed to be. Instead of stating this in a comment... > + * > + * 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) > +{ ...why not instead assert() it as part of the contract? > + 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 oh, probably because of copy and paste.
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
Signed-off-by: Peter Lieven <pl@kamp.de> --- include/qemu-common.h | 1 + util/cutils.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+)