From 1b9c959c32441562ccf1e86fd3ff955cb7982ae9 Mon Sep 17 00:00:00 2001 From: Dietmar Maurer Date: Wed, 20 Feb 2019 11:01:09 +0100 Subject: [PATCH] src/backup/chunker.rs: change window size back to 48 Using 64 is a bad idea, because it always computes hash 0 for constant data streams. --- src/backup/chunker.rs | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/src/backup/chunker.rs b/src/backup/chunker.rs index 8693b455..b723752d 100644 --- a/src/backup/chunker.rs +++ b/src/backup/chunker.rs @@ -1,4 +1,7 @@ -const CA_CHUNKER_WINDOW_SIZE: usize = 64; + +/// Note: doö not use 32 or 64, because that always computes hash 0 +/// for constant data streams .. 0,0,0,0,0,0 +const CA_CHUNKER_WINDOW_SIZE: usize = 48; /// Slinding window chunker (Buzhash) /// @@ -161,16 +164,14 @@ impl Chunker { self.start(); } - //let mut idx = self.chunk_size % CA_CHUNKER_WINDOW_SIZE; - let mut idx = self.chunk_size & 0x3f; + let mut idx = self.chunk_size % CA_CHUNKER_WINDOW_SIZE; while pos < data_len { // roll window let enter = data[pos]; let leave = self.window[idx]; self.h = self.h.rotate_left(1) ^ - //BUZHASH_TABLE[leave as usize].rotate_left(CA_CHUNKER_WINDOW_SIZE as u32) ^ - BUZHASH_TABLE[leave as usize] ^ + BUZHASH_TABLE[leave as usize].rotate_left(CA_CHUNKER_WINDOW_SIZE as u32) ^ BUZHASH_TABLE[enter as usize]; self.chunk_size += 1; @@ -185,8 +186,7 @@ impl Chunker { return pos; } - //idx = self.chunk_size % CA_CHUNKER_WINDOW_SIZE; - idx = self.chunk_size & 0x3f; + idx = self.chunk_size % CA_CHUNKER_WINDOW_SIZE; //idx += 1; if idx >= CA_CHUNKER_WINDOW_SIZE { idx = 0 }; }