为什么这个正则处理表达式速度太慢?

oukm

如下程序只是将一段字符串每隔8个字符加入回车换行,但如内容为几十K的话,要半分钟,为2M的话,
几分钟都不能处理完成.为什么?该如何修改?


#! perl -w
$infile = "MENU.FNT";
$outfile = ">"."fontshow1.txt";


open(INPUT_FILE, $infile) || die "Can not open file $infile !";
open(OUT_FILE, $outfile) || die "Can not open file $outfile !";

binmode INPUT_FILE;
binmode OUT_FILE;

$txt="";
while(read(INPUT_FILE, $buf, 32*32*1024))
{
        $txt .= $buf;
}


$hexstr = unpack ('H*', $txt);

$txt = $hexstr;


$txt =~ s/(.{8})/$1\r\n/g;  #将一段字符串每隔8个字符加入回车换行

..................

#print $txt;
print OUT_FILE $txt;

close(INPUT_FILE);
close(OUT_FILE);

104359176

1. #!perl
   
2. 
   
3. use File::Slurp qw(read_file write_file);
   
4. 
   
5. my @chars = split //, read_file("MENU.FNT");
   
6. my $count = 0;
   
7. foreach my $char (@chars) {
   
8.         $count++;
   
9.         push @new_chars, $char;
   
10.         push @new_chars, chr(10) if ($count % 4 == 0);
    
11. }
    
12. 
    
13. write_file("fontshow1.txt", join('', @new_chars));
    

复制代码

jason680

回复 1# oukm

modify from your code ...

$ wc MENU.FNT
1168463  3960509 58142720 MENU.FNT

$ time perl hex.pl
real        0m8.542s
user        0m4.032s
sys        0m3.216s

$ time perl hex1.pl  # your code
real        0m17.034s
user        0m4.772s
sys        0m9.557s

$ cat hex.pl
use strict;
use warnings;

my $infile = "MENU.FNT";
my $outfile = "fontshow1.txt";


open(FHin,  "<", $infile)  || die "Can not open file $infile !";
open(FHout, ">", $outfile) || die "Can not open file $outfile !";

binmode FHin;
binmode FHout;

while(my $sLen = read(FHin, my $sBuf, 32*32*1024))
{
  my $sTxt = unpack('H*', $sBuf);
  my $sCycle = int($sLen /4 ) + ($sLen %4 != 0) -1;
  my $sOut = "";
  foreach(0 .. $sCycle){
     $sOut .= substr($sTxt, $_*8, 8) . "\r\n";
  }
  print FHout "$sOut";
}

close(FHin);
close(FHout);