Perl 中的校验和

Question

我是一名java开发人员，我需要了解一些perl代码并需要在java中进行转换。这是片段。

my @var = map hex,split //,A8F000000F4241;
my $sum=0;
# calculate checksum of odd bytes and twisted even bytes    
$sum-=$_ for map((0,2,4,6,8,10,12,14,1,3,5,7,9,11,13,15)[$_], @var[0,2,4,6,8,10,12]), @var[1,3,5,7,9,11,13];       
print $sum ;

我真的很难理解第 4 行中它在做什么。任何帮助将不胜感激。

Answer 1

脚本应重写为：

#!/usr/bin/perl
use Modern::Perl;
use Data::Dump qw(dump);

# Split the string into a list of all character
my @elem = split //, 'A8F000000F4241';
dump @elem;

# convert each element to a hexadecimal number
my @var = map hex, @elem;
dump @var;

# list all number between 0 and 15, even then odd
my @numbers = (0,2,4,6,8,10,12,14,1,3,5,7,9,11,13,15);

# >Pick number in @numbers at position defined in @var (even position in @var)
my @l = map($numbers[$_], @var[0,2,4,6,8,10,12]);
dump@l;

# initialization
my $sum=0;

# loop on the two arrays 
for (@l, @var[1,3,5,7,9,11,13]) {
  $sum -= $_ ;
}
print $sum ;

你看清楚了吗？

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