From b61fcab3baf91ecd4b2ad4185e591cf339ad2b34 Mon Sep 17 00:00:00 2001
From: "John Ankarstr\\xf6m" <john@ankarstrom.se>
Date: Wed, 2 Jun 2021 12:57:24 +0200
Subject: First commit

---
 re | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100755 re

(limited to 're')

diff --git a/re b/re
new file mode 100755
index 0000000..8e0677e
--- /dev/null
+++ b/re
@@ -0,0 +1,123 @@
+#!/usr/bin/perl
+
+# re -- reference-based literate programming system
+
+use strict;
+use warnings;
+use POSIX::Regex qw/:all/;
+
+my $bytes;
+my $count;
+my %bytes;           # file => current byte
+my %file_locations;  # file => [location, ...]
+my %files;           # byte => file
+my %handles;         # file => handle
+my %lines;           # file => current line
+my %locations;       # byte => location (i.e. byte in source file)
+my @references;
+
+die "usage: $0 file\n" if @ARGV != 1;
+open my $fh, '<', $ARGV[0] or die "could not open $ARGV[0]: $!\n";
+
+# collect references
+$bytes = 0;
+while (<$fh>) {
+	$bytes += length($_);
+	push @references, [$bytes, $1] if /^\.\s*Re\s+(.*)/;
+}
+
+# find referenced locations
+for (@references) {
+	my ($bytes, $ref) = @$_;
+	my $loc = -1;
+
+	goto invalid if not $ref =~ /^([^:]+):(.*)/;
+	my ($file, $ident) = ($1, $2);
+
+	if (not exists $handles{$file}) {
+		open my $fh, '<', $file or die "could not open $file: $!\n";
+		$handles{$file} = $fh;
+		$bytes{$file} = 0;
+		$lines{$file} = 0;
+	}
+
+	if ($ident =~ /^(\d+)$/) {
+		my $line = $1;
+		if ($ident <= $lines{$file}) {
+			seek $handles{$file}, 0, 0;
+			$bytes{$file} = 0;
+			$lines{$file} = 0;
+		}
+		local $_;
+		while ($_ = readline $handles{$file}) {
+			$lines{$file}++;
+			if ($lines{$file} == $line) {
+				$loc = $bytes{$file};
+				last;
+			}
+			$bytes{$file} += length($_);
+		}
+	} elsif ($ident =~ m{^/(.*)/$}) {
+		my $rx = new POSIX::Regex($1);
+		seek $handles{$file}, 0, 0;
+		$bytes{$file} = 0;
+		$lines{$file} = 0;
+		local $_;
+		while ($_ = readline $handles{$file}) {
+			$lines{$file}++;
+			if ($rx->match($_)) {
+				$loc = $bytes{$file};
+				last;
+			}
+			$bytes{$file} += length($_);
+		}
+	} else {
+		goto invalid;
+	}
+
+	die "could not find location $ident in $file\n" if $loc == -1;
+	$locations{$bytes} = $loc;
+	$files{$bytes} = $file;
+	if (exists $file_locations{$file}) {
+		push @{$file_locations{$file}}, $loc;
+	} else {
+		$file_locations{$file} = [];
+	}
+
+	next;
+invalid:
+	die "invalid syntax: $ref at $bytes\n";
+}
+
+# intertwine
+seek $fh, 0, 0;
+$bytes = 0;
+$count = 0;
+while (<$fh>) {
+	$bytes += length($_);
+	goto normal if not @references;
+	my $ref_bytes = $references[0][0];
+	if ($bytes == $ref_bytes) {
+		shift @references;
+		my $file = $files{$bytes};
+		my $end = shift @{$file_locations{$file}};
+		my $loc = $locations{$bytes};
+
+		print "\n$file:$loc-$end\n";
+
+		seek $handles{$file}, $loc, 0;
+		local $_;
+		my $bytes = $loc;
+		while ($_ = readline $handles{$file}) {
+			$bytes += length($_);
+			last if $end and $bytes > $end;
+			print;
+		}
+		next;
+	}
+normal:
+	print;
+}
+
+close $_ for values %handles;
+close $fh;
-- 
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