From fcaf065a1097420466ccb1eb1d9a514a9f938a70 Mon Sep 17 00:00:00 2001
From: Michael Mikonos <127171689+mknos@users.noreply.github.com>
Date: Wed, 16 Oct 2024 22:52:10 +0800
Subject: [PATCH] ed: simplify escape_line() (#763)

* Pre-compute all binary escape values in a handy mapping table to avoid branching in escape_line()
* I confirmed that the "l" command produces the same output as for the previous commit
---
 bin/ed | 60 +++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 36 insertions(+), 24 deletions(-)

diff --git a/bin/ed b/bin/ed
index e44a827a..f14c3044 100755
--- a/bin/ed
+++ b/bin/ed
@@ -110,16 +110,39 @@ my $PRINT_BIN = 2;
 
 our $VERSION = '0.5';
 
-my %ESC = (
-    7  => '\a',
-    8  => '\b',
-    9  => '\t',
-    10 => "\$\n",
-    11 => '\v',
-    12 => '\f',
-    13 => '\r',
-    36 => '\\$',
-    92 => '\\\\',
+my @ESC = (
+    '\\000', '\\001', '\\002', '\\003', '\\004', '\\005', '\\006', '\\a',
+    '\\b',   '\\t',   "\$\n",  '\\v',   '\\f',   '\\r',   '\\016', '\\017',
+    '\\020', '\\021', '\\022', '\\023', '\\024', '\\025', '\\026', '\\027',
+    '\\030', '\\031', '\\032', '\\033', '\\034', '\\035', '\\036', '\\037',
+    ' ',     '!',     '"',     '#',     '\\$',   '%',     '&',     q('),
+    '(',     ')',     '*',     '+',     ',',     '-',     '.',     '/',
+    '0',     '1',     '2',     '3',     '4',     '5',     '6',     '7',
+    '8',     '9',     ':',     ';',     '<',     '=',     '>',     '?',
+    '@',     'A',     'B',     'C',     'D',     'E',     'F',     'G',
+    'H',     'I',     'J',     'K',     'L',     'M',     'N',     'O',
+    'P',     'Q',     'R',     'S',     'T',     'U',     'V',     'W',
+    'X',     'Y',     'Z',     '[',     '\\\\',  ']',     '^',     '_',
+    '`',     'a',     'b',     'c',     'd',     'e',     'f',     'g',
+    'h',     'i',     'j',     'k',     'l',     'm',     'n',     'o',
+    'p',     'q',     'r',     's',     't',     'u',     'v',     'w',
+    'x',     'y',     'z',     '{',     '|',     '}',     '~',     '\\177',
+    '\\200', '\\201', '\\202', '\\203', '\\204', '\\205', '\\206', '\\207',
+    '\\210', '\\211', '\\212', '\\213', '\\214', '\\215', '\\216', '\\217',
+    '\\220', '\\221', '\\222', '\\223', '\\224', '\\225', '\\226', '\\227',
+    '\\230', '\\231', '\\232', '\\233', '\\234', '\\235', '\\236', '\\237',
+    '\\240', '\\241', '\\242', '\\243', '\\244', '\\245', '\\246', '\\247',
+    '\\250', '\\251', '\\252', '\\253', '\\254', '\\255', '\\256', '\\257',
+    '\\260', '\\261', '\\262', '\\263', '\\264', '\\265', '\\266', '\\267',
+    '\\270', '\\271', '\\272', '\\273', '\\274', '\\275', '\\276', '\\277',
+    '\\300', '\\301', '\\302', '\\303', '\\304', '\\305', '\\306', '\\307',
+    '\\310', '\\311', '\\312', '\\313', '\\314', '\\315', '\\316', '\\317',
+    '\\320', '\\321', '\\322', '\\323', '\\324', '\\325', '\\326', '\\327',
+    '\\330', '\\331', '\\332', '\\333', '\\334', '\\335', '\\336', '\\337',
+    '\\340', '\\341', '\\342', '\\343', '\\344', '\\345', '\\346', '\\347',
+    '\\350', '\\351', '\\352', '\\353', '\\354', '\\355', '\\356', '\\357',
+    '\\360', '\\361', '\\362', '\\363', '\\364', '\\365', '\\366', '\\367',
+    '\\370', '\\371', '\\372', '\\373', '\\374', '\\375', '\\376', '\\377',
 );
 
 my %WANT_FILE = (
@@ -325,20 +348,9 @@ sub escape_line {
     my $idx = shift;
 
     my @chars = unpack 'C*', $lines[$idx];
-    if (scalar(@chars) == 0) {
-        die 'internal error: unpack';
-    }
-    my $s = '';
-    foreach my $c (@chars) {
-        if (exists $ESC{$c}) {
-            $s .= $ESC{$c};
-        } elsif (chr($c) !~ m/[[:print:]]/) {
-            $s .= sprintf '\%03o', $c;
-        } else {
-            $s .= chr($c);
-        }
-    }
-    return $s;
+    die 'internal error: unpack' unless @chars;
+    my @s = map { $ESC[$_] } @chars;
+    return join '', @s;
 }
 
 # does not modify buffer