diff options
| -rw-r--r-- | ripple/fossil/src/chunker/mod.rs | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/ripple/fossil/src/chunker/mod.rs b/ripple/fossil/src/chunker/mod.rs index e5221c3..8dcf796 100644 --- a/ripple/fossil/src/chunker/mod.rs +++ b/ripple/fossil/src/chunker/mod.rs @@ -9,7 +9,9 @@ const WINDOW_SIZE: usize = 48; pub const MIN_CHUNK_SIZE: usize = AVG_CHUNK_SIZE / 4; pub const AVG_CHUNK_SIZE: usize = 64 * 1024; pub const MAX_CHUNK_SIZE: usize = AVG_CHUNK_SIZE * 4; +const DISCRIMINATOR: u32 = 0xc17f; +#[cfg(test)] fn discriminator_from_average(avg: u64) -> u32 { let avg = avg as f64; (avg / (-1.42888852e-7 * avg + 1.33237515)) as u32 @@ -44,12 +46,11 @@ impl<'a> Iterator for Chunker<'a> { .take(MAX_CHUNK_SIZE) .skip(MIN_CHUNK_SIZE); - let d = discriminator_from_average(AVG_CHUNK_SIZE as u64); let mut hasher = buz::Rolling::<WINDOW_SIZE>::from_slice(&self.buffer[..MIN_CHUNK_SIZE]); let chunk; for (idx, byte) in bytes { let buz::Hash(x) = hasher.sum(); - if x % d == d.wrapping_sub(1) { + if x % DISCRIMINATOR == DISCRIMINATOR.wrapping_sub(1) { // split point (chunk, self.buffer) = self.buffer.split_at(idx); return Some(chunk); @@ -71,7 +72,10 @@ impl<'a> Iterator for Chunker<'a> { #[cfg(test)] mod test { use { - super::{Chunker, MAX_CHUNK_SIZE, MIN_CHUNK_SIZE, WINDOW_SIZE}, + super::{ + discriminator_from_average, Chunker, AVG_CHUNK_SIZE, DISCRIMINATOR, MAX_CHUNK_SIZE, + MIN_CHUNK_SIZE, WINDOW_SIZE, + }, std::io::Read, }; @@ -219,4 +223,12 @@ mod test { (2, Some(MAX_CHUNK_SIZE / MIN_CHUNK_SIZE + 1)) ); } + + #[test] + fn discriminator() { + assert_eq!( + DISCRIMINATOR, + discriminator_from_average(AVG_CHUNK_SIZE as u64) + ); + } } |