From b83f7159a9dd635a7a6f12d479e8704f6d7ae4b2 Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Sun, 28 Feb 2021 16:53:21 +0100
Subject: [PATCH] bech32: around 5% speedup for bech32_decode

useful for lnaddr.lndecode
---
 electrum/segwit_addr.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/electrum/segwit_addr.py b/electrum/segwit_addr.py
index 07b3ec42a..8dcc4e6a7 100644
--- a/electrum/segwit_addr.py
+++ b/electrum/segwit_addr.py
@@ -23,6 +23,7 @@
 
 
 CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+_CHARSET_INVERSE = {x: CHARSET.find(x) for x in CHARSET}
 
 
 def bech32_polymod(values):
@@ -72,7 +73,7 @@ def bech32_decode(bech, ignore_long_length=False):
     if not all(x in CHARSET for x in bech[pos+1:]):
         return (None, None)
     hrp = bech[:pos]
-    data = [CHARSET.find(x) for x in bech[pos+1:]]
+    data = [_CHARSET_INVERSE[x] for x in bech[pos+1:]]
     if not bech32_verify_checksum(hrp, data):
         return (None, None)
     return (hrp, data[:-6])