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| author | Anthony Liguori <aliguori@us.ibm.com> | 2012-02-15 17:18:04 -0600 |
|---|---|---|
| committer | Anthony Liguori <aliguori@us.ibm.com> | 2012-02-15 17:18:04 -0600 |
| commit | 65b31cc207b8ab949033870acf55bb124d12848e (patch) | |
| tree | c7727e413b24d8ae024fea2ab455f8c49be02b20 /cutils.c | |
| parent | b2d4b3f7b8c8ad0519c4705a3b850446068e6946 (diff) | |
| parent | b867672884afc39b6537a8aa6aa2f20a5154bf4f (diff) | |
| download | qemu-65b31cc207b8ab949033870acf55bb124d12848e.zip qemu-65b31cc207b8ab949033870acf55bb124d12848e.tar.gz qemu-65b31cc207b8ab949033870acf55bb124d12848e.tar.bz2 | |
Merge remote-tracking branch 'kwolf/for-anthony' into staging
* kwolf/for-anthony:
AHCI: Masking of IRQs actually masks them
sheepdog: fix co_recv coroutine context
AHCI: Fix port reset race
rewrite QEMU_BUILD_BUG_ON
qcow2: Keep unknown header extension when rewriting header
qcow2: Update whole header at once
vpc: Round up image size during fixed image creation
vpc: Add support for Fixed Disk type
iSCSI: add configuration variables for iSCSI
qemu-io: add write -z option for bdrv_co_write_zeroes
qed: add .bdrv_co_write_zeroes() support
qed: replace is_write with flags field
block: perform zero-detection during copy-on-read
block: add .bdrv_co_write_zeroes() interface
cutils: extract buffer_is_zero() from qemu-img.c
Diffstat (limited to 'cutils.c')
| -rw-r--r-- | cutils.c | 35 |
1 files changed, 35 insertions, 0 deletions
@@ -303,6 +303,41 @@ void qemu_iovec_memset_skip(QEMUIOVector *qiov, int c, size_t count, } } +/* + * Checks if a buffer is all zeroes + * + * Attention! The len must be a multiple of 4 * sizeof(long) due to + * restriction of optimizations in this function. + */ +bool buffer_is_zero(const void *buf, size_t len) +{ + /* + * Use long as the biggest available internal data type that fits into the + * CPU register and unroll the loop to smooth out the effect of memory + * latency. + */ + + size_t i; + long d0, d1, d2, d3; + const long * const data = buf; + + assert(len % (4 * sizeof(long)) == 0); + len /= sizeof(long); + + for (i = 0; i < len; i += 4) { + d0 = data[i + 0]; + d1 = data[i + 1]; + d2 = data[i + 2]; + d3 = data[i + 3]; + + if (d0 || d1 || d2 || d3) { + return false; + } + } + + return true; +} + #ifndef _WIN32 /* Sets a specific flag */ int fcntl_setfl(int fd, int flag) |