package # hide hide not just from PAUSE but from everyone - shoo shoo shooooo!
Devel::PeekPoke::PP;
use strict;
use warnings;
use 5.008001; # because 5.6 doesn't have B::PV::object_2svref
use Carp;
use Config;
use Devel::PeekPoke::Constants qw/PTR_SIZE PTR_PACK_TYPE/;
use B (); # for B::PV
use constant {
_MAX_ADDR => 'FF' x PTR_SIZE,
_PERLVERSION => "$]", # we do not support every perl, as we rely on the implementation of SV/SvPV
_PERLVERSION_MIN => ($] =~ /^5\.(\d{3})/)[0],
};
sub _pack_address {
my ($digits) = (defined $_[0] and $_[0] =~ /^(\d+)$/)
or croak "Invalid address '$_[0]' - expecting an integer";
my $p = pack(PTR_PACK_TYPE, $_[0]);
# FIXME - is there a saner way to check for overflows?
no warnings 'portable'; # hex() with a 64bit value
croak "Your system does not support addresses larger than 0x@{[ _MAX_ADDR ]}, you supplied $digits"
if ( $_[0] > hex(_MAX_ADDR) or uc(unpack('H*', $p)) eq _MAX_ADDR );
return $p;
}
BEGIN {
# we know we start from 5.8.1
if (_PERLVERSION_MIN == 9 ) {
die "@{[ __PACKAGE__ ]} does not function on 5.@{[_PERLVERSION_MIN]}_xxx development perls (by design)\n";
}
elsif (_PERLVERSION < 5.010) {
constant->import({
_SV_SIZE => PTR_SIZE + 4 + 4, # SvANY + 32bit refcnt + 32bit flags
_XPV_SIZE => PTR_SIZE + $Config{sizesize} + $Config{sizesize}, # PVX ptr + cur + len
_XPV_ADDR_OFFSET => undef, # it isn't really undefined, we just do not care
});
}
elsif (_PERLVERSION < 5.022) {
# The xpv address is written to the svu_pv, however we may get in trouble
# due to padding/alignment when ivsize (thus svu) is larger than PTR_SIZE
constant->import( _XPV_IN_SVU_OFFSET => $Config{ivsize} == PTR_SIZE ? 0 : do {
my $str = 'foo';
my $packed_pv_addr = pack('p', $str);
my $svu_contents = unpack('P' . $Config{ivsize}, _pack_address(\$str + PTR_SIZE + 4 + 4) );
my $i = index $svu_contents, $packed_pv_addr;
if ($i < 0) {
require Devel::Peek;
printf STDERR
'Unable to locate the XPV address 0x%X within SVU value 0x%s - '
. "this can't be right. Please file a bug including this message and "
. "a full `perl -V` output (important).\n",
unpack(PTR_PACK_TYPE, $packed_pv_addr),
join('', map { sprintf '%X', $_ } unpack(PTR_PACK_TYPE . '*', $svu_contents ) ),
;
Devel::Peek::Dump($str);
exit 1;
}
$i;
});
constant->import({
_SV_SIZE => PTR_SIZE + 4 + 4 + $Config{ivsize}, # SvANY + 32bit refcnt + 32bit flags + SV_U
_XPV_SIZE => undef, # it isn't really undefined, we just do not care
_XPV_ADDR_OFFSET => PTR_SIZE + 4 + 4 + _XPV_IN_SVU_OFFSET(), # so we know where to write directly
});
}
else {
# do not take any chances with not-yet-released perls - things may change
die "@{[ __PACKAGE__ ]} does not *yet* support this perl $], please file a bugreport (it is very very easy to fix)\n";
}
}
sub peek {
#my($location, $len_bytes) = @_;
croak "Peek where and how much?" unless (defined $_[0]) and $_[1];
unpack "P$_[1]", _pack_address($_[0]);
}
# this implementation is based on (a portably written version of)
# http://www.perlmonks.org/?node_id=379428
# there should be a much simpler way according to Reini Urban, but I
# was not able to make it work: https://gist.github.com/1151345
sub poke {
my($location, $bytes) = @_;
croak "Poke where and what?" unless (defined $location) and (defined $bytes);
# sanity check and properly pack address
my $addr = _pack_address($location);
# sanity check is (imho) warranted as described here:
# http://blogs.perl.org/users/aristotle/2011/08/utf8-flag.html#comment-36499
if (utf8::is_utf8($bytes) and $bytes =~ /([^\x00-\x7F])/) {
croak( ord($1) > 255
? "Expecting a byte string, but received characters"
: "Expecting a byte string, but received what looks like *possible* characters, please utf8_downgrade the input"
);
}
# this should be constant once we pass the regex check above... right?
my $len = length($bytes);
# construct a B::PV object, backed by a SV/SvPV to a dummy string length($bytes)
# long, and substitute $location as the actual string storage
# we specifically use the same length so we do not have to deal with resizing
my $dummy = 'X' x $len;
my $dummy_addr = \$dummy + 0;
my $ghost_sv_contents = peek($dummy_addr, _SV_SIZE);
if (_XPV_SIZE) { # 5.8 xpv stuff
my $xpv_addr = unpack(PTR_PACK_TYPE, peek($dummy_addr, PTR_SIZE) );
my $xpv_contents = peek( $xpv_addr, _XPV_SIZE ); # we do not care about cur/len (they will be the same)
substr( $xpv_contents, 0, PTR_SIZE ) = $addr; # replace pvx in xpv with the "string buffer" location
substr( $ghost_sv_contents, 0, PTR_SIZE) = pack ('P', $xpv_contents ); # replace xpv in sv
}
else { # new style 5.10+ SVs
substr( $ghost_sv_contents, _XPV_ADDR_OFFSET, PTR_SIZE ) = $addr;
}
my $ghost_string_ref = bless( \ unpack(
PTR_PACK_TYPE,
# it is crucial to create a copy of $sv_contents, and work with a temporary
# memory location. Otherwise perl memory allocation will kick in and wreak
# considerable havoc culminating with an inevitable segfault
do { no warnings 'pack'; pack( 'P', $ghost_sv_contents.'' ) },
), 'B::PV' )->object_2svref;
# now when we write to the newly created "string" we are actually writing
# to $location
# note we HAVE to use lvalue substr - a plain assignment will add a \0
#
# Also in order to keep threading on perl 5.8.x happy we *have* to perform this
# in a string eval. I don't have the slightest idea why :)
eval 'substr($$ghost_string_ref, 0, $len) = $bytes';
return $len;
}
1;