Solution for 098 #1, Read N Characters

1 files changed, 61 insertions, 0 deletions

diff --git a/challenge-098/bob-lied/perl/ch-1.pl b/challenge-098/bob-lied/perl/ch-1.pl
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+#!/usr/bin/env perl
+# vim:set ts=4 sw=4 sts=4 et ai wm=0 nu:
+#=============================================================================
+# ch-1.pl
+#=============================================================================
+# Copyright (c) 2021, Bob Lied
+#=============================================================================
+# Perl Weekly Challenge 098 Challenge 1
+# You are given file $FILE.
+# Create subroutine readN($FILE, $number) returns the first n-characters and
+# moves the pointer to the (n+1)th character.
+# Example:
+# Input: Suppose the file (input.txt) contains "1234567890"
+# Output:
+#    print readN("input.txt", 4); # returns "1234"
+#    print readN("input.txt", 4); # returns "5678"
+#    print readN("input.txt", 4); # returns "90"
+#=============================================================================
+
+use strict;
+use warnings;
+use v5.20;
+
+use experimental qw/signatures /;
+
+sub Usage { "Usage: $0 filename N" };
+
+my $FILE = shift;
+my $N        = shift;
+
+die Usage() unless $FILE;
+die Usage() unless $N;
+die "Need positive N" if ( $N <= 0 );
+
+# Cache open file handles per file.  The file handle will
+# keep track of the position in the file, advancing each time
+# that we call read().
+my %fileToFH;
+
+sub readN($s, $n)
+{
+    my $fh;
+    if ( exists $fileToFH{$s} )
+    {
+        $fh = $fileToFH{$s};
+    }
+    elsif ( open($fh, "<:utf8", $s) )
+    {
+        $fileToFH{$s} = $fh;
+    }
+    else
+    {
+        die "Invalid filename $s ($!)";
+    }
+    my $howmany = read($fh, my $bytes, $n);
+    return $bytes;
+}
+binmode(STDOUT, "utf8");
+say readN($FILE, $N);
+say readN($FILE, $N);
+say readN($FILE, $N);