From 47e77aaa2bed7c96e727a3d33cf3fb779212be2f Mon Sep 17 00:00:00 2001
From: Erich Eckner <git@eckner.net>
Date: Thu, 12 Jul 2018 14:07:53 +0200
Subject: merge-kernel-configs: run in O(n log(n)) instead of O(n^2)

---
 merge-kernel-configs | 52 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/merge-kernel-configs b/merge-kernel-configs
index d8d86e3..cf58157 100755
--- a/merge-kernel-configs
+++ b/merge-kernel-configs
@@ -1,26 +1,32 @@
 #!/bin/bash
 
-# merge-kernel-configs $out
-# (reads from stdin)
+# merge-kernel-configs
+# (reads from stdin, writes to stdout)
 
-rm -f "$1"
-touch "$1"
-
-while read -r line; do
-  variable=$(
-    printf '%s\n' "${line}" | \
-      sed '
-        s/^# \(\S\+\) is not set$/\1/
-        t
-        s/=.*$//
-        t
-        d
-      '
-  )
-  if [ -z "${variable}" ] || \
-    grep -q '^\(# \)\?'"${variable}"'[= ]' "$1"; then
-    continue
-  fi
-  printf '%s\n' "${line}" >> \
-    "$1"
-done
+sed '
+  s/^# \(\S\+\) is not set$/\1 \0/
+  tf
+  s/^\(\S\+\)=/\1 \0/
+  tf
+  d
+  :f
+  =
+' | \
+  sed '
+    N
+    s/\n/ /
+  ' | \
+  while read -r num variable line; do
+    printf '%s %s %s\n' \
+      "${num}" \
+      "$(
+        printf '%s\n' "${line}" | \
+          base64 -w0
+      )" \
+      "${variable}"
+  done | \
+  sort -k3,3 -k1n,1 -k2,2 | \
+  uniq -f2 | \
+  sort -k1,1 | \
+  cut -d' ' -f2 | \
+  parallel --pipe -L1 base64 -d
-- 
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