postgresql – 如何在没有文件或内存的情况下将IO :: Handle子类

该数据只是各种类型的文件,例如它可能是Zip容器或其他类型的存档.一些需要的处理是列出Zip的内容,甚至可以提取一些成员进行进一步处理,也可以散列存储的数据……最后,数据被多次读取,但只写入一次以存储它.

我使用的所有Perl库都可以使用文件句柄,一些使用IO :: Handle,另一些使用IO :: String或IO :: Scalar,其他一些只使用低级文件句柄.所以我所做的是创建一个IO :: Handle和IO :: Seekable的子类,它就像DBD :: Pg周围相应方法的包装器一样.在CTOR中,我创建了一个与数据库的连接,打开一些提供的LOID用于读取并存储Postgres在实例中提供的句柄.然后我自己的句柄对象被转发给能够使用这种文件句柄的人,并且可以直接在Postgres提供的blob中读取和搜索.

问题是在IO :: Handle上使用低级文件句柄或低级文件句柄操作的库.摘要:: MD5似乎是一个,Archive :: Zip另一个. Digest :: MD5呱呱叫,告诉我没有提供句柄,另一方面,Archive :: Zip尝试从我的创建一个新的,自己的句柄,调用IO :: Handle :: fdopen并在我的情况下失败.

sub fdopen {
    @_ == 3 or croak 'usage: $io->fdopen(FD,MODE)';
    my ($io,$fd,$mode) = @_;
    local(*GLOB);

    if (ref($fd) && "".$fd =~ /GLOB(/o) {
    # It's a glob reference; Alias it as we cannot get name of anon GLOBs
    my $n = qualify(*GLOB);
    *GLOB = *{*$fd};
    $fd =  $n;
    } elsif ($fd =~ m#^d+$#) {
    # It's an FD number; prefix with "=".
    $fd = "=$fd";
    }

    open($io,_open_mode_string($mode) . '&' . $fd)
    ? $io : undef;
}

我想问题是句柄的低级副本,它删除了我自己的实例,因此没有实例拥有我的数据库连接和所有这些东西.

那么,在我的情况下,甚至可以提供一些IO :: Handle,它可以在任何需要低级文件句柄的地方成功使用吗？

我的意思是,我没有真正的文件句柄,我只有一个对象,方法调用被包装到相应的Postgres方法,需要数据库句柄等.所有这些数据都需要存储在某个地方,需要完成包装等.

我尝试做其他人正在做的事情,比如IO :: String,例如另外使用tie.但最终用例是不同的,因为Perl能够自己创建一个真正的低级文件句柄到一些内部内存.在我的情况下根本不支持的东西.我需要保持我的实例,因为只知道数据库的句柄等.

通过调用方法读取来使用我的句柄,如IO :: Handle,这样的工作就像预期的那样,但是我想更进一步,并且与那些不期望在IO :: Handle对象上工作的人更加兼容.很像IO :: String或File :: Temp可以用作低级文件句柄.

package ReadingHandle;

use strict;
use warnings;
use 5.10.1;

use base 'IO::Handle','IO::Seekable';

use Carp ();

sub new
{
  my $invocant  = shift || Carp::croak('No invocant given.');
  my $db        = shift || Carp::croak('No database connection given.');
  my $loid      = shift // Carp::croak('No LOID given.');
  my $dbHandle  = $db->_getHandle();
  my $self      = $invocant->SUPER::new();

    *$self->{'dbHandle'}  = $dbHandle;
    *$self->{'loid'}      = $loid;
  my $loidFd              = $dbHandle->pg_lo_open($loid,$dbHandle->{pg_INV_READ});
    *$self->{'loidFd'}    = $loidFd;

  if (!defined($loidFd))
  {
    Carp::croak("The provided LOID couldn't be opened.");
  }

  return $self;
}

sub DESTROY
{
  my $self = shift || Carp::croak('The method needs to be called with an instance.');

  $self->close();
}

sub _getDbHandle
{
  my $self = shift || Carp::croak('The method needs to be called with an instance.');

  return *$self->{'dbHandle'};
}

sub _getLoid
{
  my $self = shift || Carp::croak('The method needs to be called with an instance.');

  return *$self->{'loid'};
}

sub _getLoidFd
{
  my $self = shift || Carp::croak('The method needs to be called with an instance.');

  return *$self->{'loidFd'};
}

sub binmode
{
  my $self = shift || Carp::croak('The method needs to be called with an instance.');

  return 1;
}

sub close
{
  my $self      = shift || Carp::croak('The method needs to be called with an instance.');
  my $dbHandle  = $self->_getDbHandle();
  my $loidFd    = $self->_getLoidFd();

  return $dbHandle->pg_lo_close($loidFd);
}

sub opened
{
  my $self    = shift || Carp::croak('The method needs to be called with an instance.');
  my $loidFd  = $self->_getLoidFd();

  return defined($loidFd) ? 1 : 0;
}

sub read
{
  my $self    = shift || Carp::croak('The method needs to be called with an instance.');
  my $buffer  =shift // Carp::croak('No buffer given.');
  my $length  = shift // Carp::croak('No amount of bytes to read given.');
  my $offset  = shift || 0;

  if ($offset > 0)
  {
    Carp::croak('Using an offset is not supported.');
  }

  my $dbHandle  = $self->_getDbHandle();
  my $loidFd    = $self->_getLoidFd();

  return $dbHandle->pg_lo_read($loidFd,$buffer,$length);
}

sub seek
{
  my $self    = shift || Carp::croak('The method needs to be called with an instance.');
  my $offset  = shift // Carp::croak('No offset given.');
  my $whence  = shift // Carp::croak('No whence given.');

  if ($offset < 0)
  {
    Carp::croak('Using a negative offset is not supported.');
  }
  if ($whence != 0)
  {
    Carp::croak('Using a whence other than 0 is not supported.');
  }

  my $dbHandle  = $self->_getDbHandle();
  my $loidFd    = $self->_getLoidFd();
  my $retVal    = $dbHandle->pg_lo_lseek($loidFd,$offset,$whence);
     $retVal    = defined($retVal) ? 1 : 0;

  return $retVal;
}

sub tell
{
  my $self      = shift || Carp::croak('The method needs to be called with an instance.');
  my $dbHandle  = $self->_getDbHandle();
  my $loidFd    = $self->_getLoidFd();
  my $retVal    = $dbHandle->pg_lo_lseek($loidFd);
     $retVal    = defined($retVal) ? $retVal : -1;

  return $retVal;
}

1;