From 41cd68416c8f35e80523fb3102b6a9c9982446c4 Mon Sep 17 00:00:00 2001 From: Josh Bleecher Snyder Date: Mon, 14 Dec 2020 18:30:13 -0800 Subject: device: simplify copying counter to nonce Since we already have it packed into a uint64 in a known byte order, write it back out again the same byte order instead of copying byte by byte. This should also generate more efficient code, because the compiler can do a single uint64 write, instead of eight bounds checks and eight byte writes. Due to a missed optimization, it actually generates a mishmash of smaller writes: 1 byte, 4 bytes, 2 bytes, 1 byte. This is https://golang.org/issue/41663. The code is still better than before, and will get better yet once that compiler bug gets fixed. Signed-off-by: Josh Bleecher Snyder --- device/receive.go | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/device/receive.go b/device/receive.go index 839b735..852bd89 100644 --- a/device/receive.go +++ b/device/receive.go @@ -268,22 +268,12 @@ func (device *Device) RoutineDecryption() { counter := elem.packet[MessageTransportOffsetCounter:MessageTransportOffsetContent] content := elem.packet[MessageTransportOffsetContent:] - // expand nonce - - nonce[0x4] = counter[0x0] - nonce[0x5] = counter[0x1] - nonce[0x6] = counter[0x2] - nonce[0x7] = counter[0x3] - - nonce[0x8] = counter[0x4] - nonce[0x9] = counter[0x5] - nonce[0xa] = counter[0x6] - nonce[0xb] = counter[0x7] - // decrypt and release to consumer var err error elem.counter = binary.LittleEndian.Uint64(counter) + // copy counter to nonce + binary.LittleEndian.PutUint64(nonce[0x4:0xc], elem.counter) elem.packet, err = elem.keypair.receive.Open( content[:0], nonce[:], -- cgit v1.2.3