pxar: fuse: use binary search instead of linear search in goodbye table.

The goodbye table is layed out as binary search tree based on the hash, so use
this to be more efficient when looking up a hash in the table for directories
with a large number of entries.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>

src/pxar/decoder.rs

@@ -11,6 +11,7 @@ use std::os::unix::ffi::OsStrExt;
 use failure::*;
 use libc;
 
+use super::binary_search_tree::search_binary_tree_by;
 use super::format_definition::*;
 use super::sequential_decoder::SequentialDecoder;
 use super::match_pattern::MatchPattern;
@@ -276,11 +277,18 @@ impl Decoder {
         let gbt = self.goodbye_table(Some(dir.start), dir.end)?;
         let hash = compute_goodbye_hash(filename.as_bytes());
 
-        let mut iterator = gbt.iter();
+        let mut start_idx = 0;
+        let mut skip_multiple = 0;
         loop {
             // Search for the next goodbye entry with matching hash.
-            let (start, end) = match iterator.find(|(i, _, _)| i.hash == hash) {
-                Some((_item, start, end)) => (start, end),
+            let idx = search_binary_tree_by(
+                start_idx,
+                gbt.len(),
+                skip_multiple,
+                |idx| hash.cmp(&gbt[idx].0.hash),
+            );
+            let (_item, start, end) = match idx {
+                Some(idx) => &gbt[idx],
                 None => return Ok(None),
             };
 
@@ -303,6 +311,10 @@ impl Decoder {
                 };
                 return Ok(Some((dir_entry, attr, payload_size)));
             }
+            // Hash collision, check the next entry in the goodbye table by starting
+            // from given index but skipping one more match (so hash at index itself).
+            start_idx = idx.unwrap();
+            skip_multiple = 1;
         }
     }