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ed: add undo feature #869

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merged 1 commit into from
Dec 9, 2024
Merged

ed: add undo feature #869

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73 changes: 59 additions & 14 deletions bin/ed
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Original file line number Diff line number Diff line change
Expand Up @@ -33,22 +33,10 @@ License: gpl
#
# Irony: This was, of course, edited originaly with emacs...
#
# Commentary:
# The guiding principals of this implentation are:
# - Functionality
# - Understandability
#
# "perl coolness" was not a guiding principal, as the author is at best
# an accomplished perl user. If you like the program, use it.
# If you don't, don't.
#
# Legaleese:
# This program is released under the GNU Public License.
#
# Todo:
# - Implement the following commands from the v7 docs:
# u - undo
#
# - add a "-e" flag to allow it to be used in sed(1) like fashion.
# - add buffer size limitations for strict compatability
# - discard NULS, chars after \n
Expand All @@ -57,6 +45,7 @@ License: gpl

use strict;

use File::Temp qw();
use Getopt::Std qw(getopts);

use constant A_NOMATCH => -1;
Expand All @@ -79,6 +68,7 @@ use constant E_CMDBAD => 'unknown command';
use constant E_PATTERN => 'invalid pattern delimiter';
use constant E_NOMATCH => 'no match';
use constant E_NOPAT => 'no previous pattern';
use constant E_UNDO => 'nothing to undo';

use constant EX_SUCCESS => 0;
use constant EX_FAILURE => 1;
Expand All @@ -101,6 +91,7 @@ my @args; # command arguments (filenames, search patterns.
my %marks;
my $isGlobal;
my $HelpMode = 0;
my $UndoFile;

# constants

Expand All @@ -113,7 +104,7 @@ my $NO_QUESTIONS_MODE = 0;
my $PRINT_NUM = 1;
my $PRINT_BIN = 2;

our $VERSION = '0.21';
our $VERSION = '0.22';

my @ESC = (
'\\000', '\\001', '\\002', '\\003', '\\004', '\\005', '\\006', '\\a',
Expand Down Expand Up @@ -185,10 +176,30 @@ my %cmdtab = (
'E' => \&edEdit,
'e' => \&edEditAsk,
'r' => \&edRead,
'u' => \&edUndo,
'_' => \&edSetCurrentLine,
'nop' => sub {},
);

my %ro_cmds = (
'!' => 1,
'=' => 1,
'f' => 1,
'P' => 1,
'p' => 1,
'H' => 1,
'h' => 1,
'k' => 1,
'n' => 1,
'l' => 1,
'Q' => 1,
'q' => 1,
'W' => 1,
'w' => 1,
'_' => 1,
'nop' => 1,
);

$SIG{HUP} = sub {
if ($NeedToSave) {
my $fh;
Expand Down Expand Up @@ -257,8 +268,16 @@ sub input {
edWarn(E_CMDBAD);
return;
}

my $saved_buf;
if (!exists($ro_cmds{$command})) {
$saved_buf = write_undo();
}
my $err = $func->();
edWarn($err) if $err;
if ($NeedToSave && $saved_buf) {
$UndoFile = $saved_buf;
}
return;
}

Expand Down Expand Up @@ -806,6 +825,27 @@ sub edPrintLineNum {
return;
}

sub write_undo {
my $fh = File::Temp->new;
foreach (@lines) {
print {$fh} $_;
}
seek $fh, 0, 0;
return $fh;
}

sub edUndo {
return E_ADDREXT if defined $adrs[0];
return E_ARGEXT if defined $args[0];
return E_UNDO unless defined $UndoFile;

@lines = <$UndoFile>;
unshift @lines, undef;
$UserHasBeenWarned = 0;
$NeedToSave = 1; # new tmpfile
return;
}

#
# Quit ed
#
Expand Down Expand Up @@ -907,7 +947,7 @@ sub edParse {
$isGlobal = 1;
@adrs = @found;
}
if (s/\A([acdEefHhijklmnPpQqrstWw=\!])//) { # optional argument
if (s/\A([acdEefHhijklmnPpQqrstuWw=\!])//) { # optional argument
$command = $1;
if ($command eq 'W' || $command eq 'w') {
if (s/\A[Qq]//) {
Expand Down Expand Up @@ -1227,6 +1267,11 @@ Substitute text with a regular expression
Copy (transfer) lines to a destination address.
The current address is set to the last line copied.

=item u

Undo the last command, restoring the editor buffer to its previous state.
The undo function is its own inverse, so multiple levels of undo are not possible.

=item W [FILE]

Write buffer to file in append mode
Expand Down
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