On 18.05.2011 13:31, Kevin Wolf wrote:
Please move the declarations to the start of the function.
I also would use a single line like "long d0, d1, d2, d3;", but that's
up to you.
+
+ for(i = 0; i< len; i += 4) {
+ d0 = ((const long*) sector)[i + 0];
+ d1 = ((const long*) sector)[i + 1];
+ d2 = ((const long*) sector)[i + 2];
+ d3 = ((const long*) sector)[i + 3];
I would suggest to declare a const long* variable so that you don't have
to cast each time you use, but that's probably a matter of taste.
+
+ if (d0 || d1 || d2 || d3)
return 1;
Coding style requires braces here.
}
+
return 0;
}
OK, fixed.
Signed-off-by: Dmitry Konishchev <konishc...@gmail.com>
---
qemu-img.c | 29 ++++++++++++++++++++++++++---
1 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index e825123..c849c6f 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -496,14 +496,37 @@ static int img_commit(int argc, char **argv)
return 0;
}
+/*
+ * Checks whether the sector is not a zero sector.
+ *
+ * Attention! The len must be a multiple of 4 * sizeof(long) due to
+ * restriction of optimizations in this function.
+ */
static int is_not_zero(const uint8_t *sector, int 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.
+ */
+
int i;
- len >>= 2;
- for(i = 0;i < len; i++) {
- if (((uint32_t *)sector)[i] != 0)
+ long d0, d1, d2, d3;
+ const long * const data = (const long *) sector;
+
+ 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 1;
+ }
}
+
return 0;
}
--
1.7.4.1
