1 package # hide hide not just from PAUSE but from everyone - shoo shoo shooooo!
7 use 5.008001; # because 5.6 doesn't have B::PV::object_2svref
11 use Devel::PeekPoke::Constants qw/PTR_SIZE PTR_PACK_TYPE/;
15 _MAX_ADDR => 'FF' x PTR_SIZE,
16 _PERLVERSION => "$]", # we do not support every perl, as we rely on the implementation of SV/SvPV
20 # we know we start from 5.8.1
21 if ( (_PERLVERSION =~ /^5\.(\d{3})/)[0] % 2 ) {
22 die "@{[ __PACKAGE__ ]} does not function on development perl versions (by design)\n";
24 elsif (_PERLVERSION < 5.010) {
26 _SV_SIZE => PTR_SIZE + 4 + 4, # SvANY + 32bit refcnt + 32bit flags
27 _XPV_SIZE => PTR_SIZE + $Config{sizesize} + $Config{sizesize}, # PVX ptr + cur + len
31 elsif (_PERLVERSION < 5.016) {
33 _SV_SIZE => PTR_SIZE + 4 + 4 + $Config{ivsize}, # SvANY + 32bit refcnt + 32bit flags + SV_U
34 _XPV_SIZE => undef, # it isn't really undefined, we just do not care
35 _SVU_OFFSET => PTR_SIZE + 4 + 4,
39 # do not take any chanes with not-yet-released perls - things may change
40 die "@{[ __PACKAGE__ ]} does not *yet* support this perl $], please file a bugreport (it is very very easy to fix)\n";
45 my ($digits) = (defined $_[0] and $_[0] =~ /^(\d+)$/)
46 or croak "Invalid address '$_[0]' - expecting an integer";
48 my $p = pack(PTR_PACK_TYPE, $_[0]);
50 # FIXME - is there a saner way to check for overflows?
51 no warnings 'portable'; # hex() with a 64bit value
52 croak "Your system does not support addresses larger than 0x@{[ _MAX_ADDR ]}, you supplied $digits"
53 if ( $_[0] > hex(_MAX_ADDR) or uc(unpack('H*', $p)) eq _MAX_ADDR );
59 #my($location, $len_bytes) = @_;
60 croak "Peek where and how much?" unless (defined $_[0]) and $_[1];
61 unpack "P$_[1]", _pack_address($_[0]);
64 # this implementation is based on (a portably written version of)
65 # http://www.perlmonks.org/?node_id=379428
66 # there should be a much simpler way according to Reini Urban, but I
67 # was not able to make it work: https://gist.github.com/1151345
69 my($location, $bytes) = @_;
70 croak "Poke where and what?" unless (defined $location) and (defined $bytes);
72 # sanity check and properly pack address
73 my $addr = _pack_address($location);
75 # sanity check is (imho) warranted as described here:
76 # http://blogs.perl.org/users/aristotle/2011/08/utf8-flag.html#comment-36499
77 if (utf8::is_utf8($bytes) and $bytes =~ /([^\x00-\x7F])/) {
79 ? "Expecting a byte string, but received characters"
80 : "Expecting a byte string, but received what looks like *possible* characters, please utf8_downgrade the input"
84 # this should be constant once we pass the regex check above... right?
85 my $len = length($bytes);
87 # construct a B::PV object, backed by a SV/SvPV to a dummy string length($bytes)
88 # long, and substitute $location as the actual string storage
89 # we specifically use the same length so we do not have to deal with resizing
90 my $dummy = 'X' x $len;
91 my $dummy_addr = \$dummy + 0;
93 my $ghost_sv_contents = peek($dummy_addr, _SV_SIZE);
95 if (_XPV_SIZE) { # 5.8 xpv stuff
96 my $xpv_addr = unpack(PTR_PACK_TYPE, peek($dummy_addr, PTR_SIZE) );
97 my $xpv_contents = peek( $xpv_addr, _XPV_SIZE ); # we do not care about cur/len (they will be the same)
99 substr( $xpv_contents, 0, PTR_SIZE ) = $addr; # replace pvx in xpv with the "string buffer" location
100 substr( $ghost_sv_contents, 0, PTR_SIZE) = pack ('P', $xpv_contents ); # replace xpv in sv
102 else { # new style 5.10+ SVs
103 substr( $ghost_sv_contents, _SVU_OFFSET, PTR_SIZE ) = $addr;
106 my $ghost_string_ref = bless( \ unpack(
108 # it is crucial to create a copy of $sv_contents, and work with a temporary
109 # memory location. Otherwise perl memory allocation will kick in and wreak
110 # considerable havoc culminating with an inevitable segfault
111 do { no warnings 'pack'; pack( 'P', $ghost_sv_contents.'' ) },
112 ), 'B::PV' )->object_2svref;
114 # now when we write to the newly created "string" we are actually writing
116 # note we HAVE to use lvalue substr - a plain assignment will add a \0
118 # Also in order to keep threading on perl 5.8.x happy we *have* to perform this
119 # in a string eval. I don't have the slightest idea why :)
120 eval 'substr($$ghost_string_ref, 0, $len) = $bytes';