# [PATCH] reduce delta head inflated size 3 messages from 2006-10-18 to 2006-10-19. Participants: Nicolas Pitre, Morten Welinder. Thread: https://gitlist.dev/t/5949 ## Nicolas Pitre, 2006-10-18 19:56 Subject: [PATCH] reduce delta head inflated size Message-ID: URL: https://gitlist.dev/e/Pine.LNX.4.64.0610181541280.1971%40xanadu.home ``` Supposing that both the base and result sizes were both full size 64-bit values, their encoding would occupy only 9.2 bytes each. Therefore inflating 64 bytes is way overkill. Limit it to 20 bytes instead which should be plenty enough for a couple years to come. Signed-off-by: Nicolas Pitre --- diff --git a/sha1_file.c b/sha1_file.c index 25c0bf9..e89d24c 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -943,7 +943,7 @@ static int packed_delta_info(struct pack if (sizep) { const unsigned char *data; - unsigned char delta_head[64]; + unsigned char delta_head[20]; unsigned long result_size; z_stream stream; int st; ``` ## Morten Welinder, 2006-10-19 13:49 Subject: Re: [PATCH] reduce delta head inflated size Message-ID: <118833cc0610190649o484afdc8lb871d4b3c5361166@mail.gmail.com> URL: https://gitlist.dev/e/118833cc0610190649o484afdc8lb871d4b3c5361166%40mail.gmail.com In-Reply-To: ``` On 10/18/06, Nicolas Pitre wrote: > Supposing that both the base and result sizes were both full size 64-bit > values, their encoding would occupy only 9.2 bytes each. Therefore > inflating 64 bytes is way overkill. Limit it to 20 bytes instead which > should be plenty enough for a couple years to come. 2^63 ~ 9.2e18 Thus one signed 64-bit number can take up 1 sign + 19 digits + 1 nul. That's 21 bytes. If you don't like the constant, 4*sizeof(integer type) should work. (Assuming sizeof measures in bytes.) M. ``` ## Nicolas Pitre, 2006-10-19 14:17 Subject: Re: [PATCH] reduce delta head inflated size Message-ID: URL: https://gitlist.dev/e/Pine.LNX.4.64.0610191012090.1971%40xanadu.home In-Reply-To: <118833cc0610190649o484afdc8lb871d4b3c5361166@mail.gmail.com> ``` On Thu, 19 Oct 2006, Morten Welinder wrote: > On 10/18/06, Nicolas Pitre wrote: > > Supposing that both the base and result sizes were both full size 64-bit > > values, their encoding would occupy only 9.2 bytes each. Therefore > > inflating 64 bytes is way overkill. Limit it to 20 bytes instead which > > should be plenty enough for a couple years to come. > > 2^63 ~ 9.2e18 > > Thus one signed 64-bit number can take up 1 sign + 19 digits + 1 nul. > That's 21 bytes. No. In this case the value is kept binary, with bits spread over consecutive bytes but with the MSB indicating continuation on the next byte. This means 64 bits / 7 bits per byte = 9.1 bytes, hence 10. Then there are 2 of those values that makes 20 bytes. Nicolas ```