perf: Add naive but performant path

clipmenu

@@ -3,17 +3,10 @@
 shopt -s nullglob
 
 # We use this to make sure the cache files are sorted bytewise
-LC_COLLATE=C
+export LC_COLLATE=C
-
-declare -A selections
 
 cache_file=/tmp/clipmenu.$USER/line_cache
 
-# We use tac since we want newest to oldest, and we append in clipmenud
-while IFS='|' read -r full_file first_line; do
-    selections[$first_line]=$full_file
-done < <(tac "$cache_file")
-
 # It's okay to hardcode `-l 8` here as a sensible default without checking
 # whether `-l` is also in "$@", because the way that dmenu works allows a later
 # argument to override an earlier one. That is, if the user passes in `-l`, our
@@ -22,10 +15,32 @@ chosen_line=$(sed 's/^[^|]\+|//' "$cache_file" | tac | uniq | dmenu -l 8 "$@")
 
 [[ $chosen_line ]] || exit 1
 
+# Naive, but performant path, only follow expensive path if it doesn't work
+out_line=$(grep -F "|$chosen_line" "$cache_file")
+out_length=$(wc -l <<< "$out_line")
+
+if (( out_length == 1 )); then
+    # Cheap path succeded
+    file=${out_line%%|*}
+elif (( out_length > 1 )); then
+    # Cheap path failed
+    while IFS='|' read -r full_file first_line; do
+        if [[ $first_line == "$chosen_line" ]]; then
+            file=$full_file
+            break
+        fi
+    done <<< "$out_line"
+else
+    # We didn't find this in cache
+    printf 'FATAL: %s not in cache, run clipmenu-fsck\n' "$chosen_line" >&2
+    exit 2
+fi
+
+
 for selection in clipboard primary; do
     if type -p xsel >/dev/null 2>&1; then
-        xsel -i --"$selection" < "${selections[$chosen_line]}"
+        xsel -i --"$selection" < "$file"
     else
-        xclip -sel "$selection" < "${selections[$chosen_line]}"
+        xclip -sel "$selection" < "$file"
     fi
 done