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/fuse.rs

@@ -16,6 +16,7 @@ use lazy_static::lazy_static;
 use libc;
 use libc::{c_char, c_int, c_void, size_t};
 
+use super::binary_search_tree::search_binary_tree_by;
 use super::decoder::Decoder;
 use super::format_definition::{PxarAttributes, PxarEntry, PxarGoodbyeItem};
 
@@ -130,11 +131,18 @@ impl Context {
     ) -> Result<(u64, PxarEntry, PxarAttributes, u64), i32> {
         self.update_goodbye_cache()?;
         if let Some((_, gbt)) = &self.goodbye_cache {
-            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 (_item, start, end) = iterator.find(|(i, _, _)| i.hash == hash)
-                    .ok_or(libc::ENOENT)?;
+                let idx = search_binary_tree_by(
+                    start_idx,
+                    gbt.len(),
+                    skip_multiple,
+                    |idx| hash.cmp(&gbt[idx].0.hash),
+                ).ok_or(libc::ENOENT)?;
+
+                let (_item, start, end) = &gbt[idx];
 
                 // At this point it is not clear if the item is a directory or not, this
                 // has to be decided based on the entry mode.
@@ -150,6 +158,10 @@ impl Context {
                     let child_offset = find_offset(&entry, *start, *end);
                     return Ok((child_offset, 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;
+                skip_multiple = 1;
             }
         }