allzeroes

#!/usr/bin/perl -w

# Wed May 29 00:10:20 BST 2013
(my $email='XXX%YYY,ch')=~ tr/%,/@./;

use strict;

$0=~ /(.*?)([^\/]+)\z/s or die "?";
my ($mydir, $myname)=($1,$2);
sub usage {
    print STDERR map{"$_\n"} @_ if @_;
    print "$myname path(s)

  returns true (exit code 0) if path(s) consist(s) only of zero bytes.

  Options:
   -p   print the file path in true case, too
   -s   only if the file is of non-zero size

  (Christian Jaeger <$email>)
";
exit (@_ ? 1 : 0);
}

use Getopt::Long;
our $verbose=0;
#our $opt_dry;
our $opt_p;
our $opt_s=0;
GetOptions("verbose"=> \$verbose,
	   "help"=> sub{usage},
	   #"dry-run"=> \$opt_dry,
	   "print"=> \$opt_p,
	   "sized"=> \$opt_s,
	   ) or exit 1;
#usage unless @ARGV;


#$opt_p ||= $verbose; ##k?

use Chj::xopen 'xopen_read';
BEGIN {
    mkdir "$ENV{HOME}/.PerlInline",0700;
}
use Inline ("C" => 'DATA', DIRECTORY => "$ENV{HOME}/.PerlInline");

my $bufsz = 8192;

=pod
sub allzero {
    my ($bufrf,$n)=@_;
    for my $i (0..$n-1) {
	#warn "check $i";
	if (not (substr($$bufrf,$i,1) eq "\0")) {
	    return 0;
	}
    }
    1
}

sub allzeroes {
    my ($path)=@_;
    #warn "path '$path'";
    my $buf= "\0" x $bufsz;
    my $f = xopen_read $path;
    my $res=1;
    my $totsize=0;
    while (my $n= $f->xsysread ($buf,$bufsz)) {
	$totsize+=$n;
	#warn "totsize= '$totsize'";
	if (!allzero(\$buf,$n)) {
	    $res=0;
	    last;
	}
    }
    $f->xclose;
    if ($opt_s) {
	$totsize > 0 and $res
    } else {
	$res
    }
}
=cut

my $cnt_not_allzeroes=0;

sub _allzeroes {
    my ($path)=@_;
    if (allzeroes ($path,$opt_s)) {
	if ($opt_p) {
	    print $path,"\n"
	      or die $!;
	}
    } else {
	$cnt_not_allzeroes++;
    }
}

_allzeroes $_ for @ARGV;

exit ($cnt_not_allzeroes ? 1 : 0);

#use Chj::ruse;
#use Chj::Backtrace; use Chj::repl; repl;

__END__
__C__

#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>

static int allzero (char*buf, size_t len) {
    int i;
    for (i=0; i<len; i++) {
        if (buf[i] != '\0')
	    return 0;
    }
    return 1;
}

#define CJBUFSIZ 8192

int allzeroes (char *path, int opt_s) {
    int f;
    char *buf= malloc (CJBUFSIZ);
    int res=1;
    size_t totsize=0;

    assert(buf);
    //printf("path '%s'\n", path);//
    f = open (path, O_RDONLY);
    if (f < 0) {
        perror("open"); goto ERR;
    }

    while (1) {
        ssize_t n= read(f,buf,CJBUFSIZ);
	if (n<0) {
	    perror("read"); goto ERR;
	}
	if (n==0)
  	    break;
	totsize+=n;
	//printf("totsize '%d'\n", totsize);//

	if (!allzero (buf,n)) {
	    res=0;
	    break;
	}
    }
    if (close(f)) {
        perror("close"); goto ERR;
    }
    if (opt_s) {
        return ((totsize > 0) && res);
    } else {
	return res;
    }

    ERR:
    // XXX exception?
    free(buf);
    return 0;
}