On 2017-12-24 00:26, Etienne Champetier wrote:
2017-12-23 14:14 GMT-08:00 Rafał Miłecki <zaj...@gmail.com>:
From: Rafał Miłecki <ra...@milecki.pl>
Since BusyBox 1.25.0 dd command supports iflag=skip_bytes which allows
skipping requested amount of bytes without reducing blocksize. Thanks
to
this we can leave default blocksize and let dd work more efficiently.
On Netgear R6250 "dd skip=58 iflag=skip_bytes" can be 5 times faster
than "dd bs=58 skip=1" when extracting TRX out of CHK.
Signed-off-by: Rafał Miłecki <ra...@milecki.pl>
---
target/linux/bcm53xx/base-files/lib/upgrade/platform.sh | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
b/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
index 1a33e3a447..06451f17fd 100644
--- a/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
+++ b/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
@@ -274,11 +274,11 @@ platform_pre_upgrade() {
platform_trx_from_chk_cmd() {
local header_len=$((0x$(get_magic_long_at "$1" 4)))
- echo -n dd bs=$header_len skip=1
+ echo -n dd skip=$header_len iflag=skip_bytes
}
platform_trx_from_cybertan_cmd() {
- echo -n dd bs=32 skip=1
+ echo -n dd skip=32 iflag=skip_bytes
haven't checked, but would "tail -c+32" work (or maybe "tail -c+33")
works ?
I know I add a similar old dd version to handle in the past (but
nothing to do with OpenWRT) and "tail" was enough in the end
I didn't test it, but I believe we could use tail somehow for that.
The question is: why should we?
We use "dd" in general for a lot of sysupgrade-related operations. It
has more fearures like controlling a block size which we may want to use
in a future for more optimizations. It can be used to "cut" a part of
file from the middle of it.
I don't see any real advantage of switching to tail.
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