# -*- cperl -*-
#
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# Copyright (C) 2002-2014 Jens Thoms Toerring <jt@toerring.de>
# Package for file locking with fcntl(2) in which the binary layout of
# the C flock struct is determined via compiling and running a C program
# each time the package is loaded
package File::FcntlLock::Inline;
use 5.006001;
use strict;
use warnings;
use Fcntl;
use Config;
use File::Temp;
use File::Spec;
use base qw( File::FcntlLock::Core );
our $VERSION = File::FcntlLock::Core->VERSION;
our @EXPORT = @File::FcntlLock::Core::EXPORT;
my ( $packstr, @member_list );
###########################################################
BEGIN {
# Create a C file in the preferred directory for temporary files for
# probing the layout of the C 'flock struct'. Since __DATA__ can't
# be used in a BEGIN block we've got to do with a HEREDOC.
my $c_file = File::Temp->new( TEMPLATE => 'File-FcntlLock-XXXXXX',
SUFFIX => '.c',
DIR => File::Spec->tmpdir( ) );
print $c_file <<EOF;
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <limits.h>
#define membersize( type, member ) ( sizeof( ( ( type * ) NULL )->member ) )
#define NUM_ELEMS( p ) ( sizeof p / sizeof *p )
typedef struct {
const char * name;
size_t size;
size_t offset;
} Params;
/*-------------------------------------------------*
* Called from qsort() for sorting an array of Params structures
* in ascending order of their 'offset' members
*-------------------------------------------------*/
static int
comp( const void * a,
const void * b )
{
if ( a == b )
return 0;
return ( ( Params * ) a )->offset < ( ( Params * ) b )->offset ? -1 : 1;
}
/*-------------------------------------------------*
*-------------------------------------------------*/
int
main( void )
{
Params params[ ] = { { "l_type",
CHAR_BIT * membersize( struct flock, l_type ),
CHAR_BIT * offsetof( struct flock, l_type ) },
{ "l_whence",
CHAR_BIT * membersize( struct flock, l_whence ),
CHAR_BIT * offsetof( struct flock, l_whence ) },
{ "l_start",
CHAR_BIT * membersize( struct flock, l_start ),
CHAR_BIT * offsetof( struct flock, l_start ) },
{ "l_len",
CHAR_BIT * membersize( struct flock, l_len ),
CHAR_BIT * offsetof( struct flock, l_len ) },
{ "l_pid",
CHAR_BIT * membersize( struct flock, l_pid ),
CHAR_BIT * offsetof( struct flock, l_pid ) } };
size_t size = CHAR_BIT * sizeof( struct flock );
size_t i;
size_t pos = 0;
char packstr[ 128 ] = "";
/* All sizes and offsets must be divisable by 8 and the sizes of the
members must be either 8-, 16-, 32- or 64-bit values, otherwise
there's no good way to pack them. */
if ( size % 8 )
exit( EXIT_FAILURE );
size /= 8;
for ( i = 0; i < NUM_ELEMS( params ); ++i )
{
if ( params[ i ].size % 8
|| params[ i ].offset % 8
|| ( params[ i ].size != 8
&& params[ i ].size != 16
&& params[ i ].size != 32
&& params[ i ].size != 64 ) )
exit( EXIT_FAILURE );
params[ i ].size /= 8;
params[ i ].offset /= 8;
}
/* Sort the array of structures for the members in ascending order of
the offset */
qsort( params, NUM_ELEMS( params ), sizeof *params, comp );
/* Cobble together the template string to be passed to pack(), taking
care of padding and also extra members we're not interested in. All
the interesting members have signed integer types. */
for ( i = 0; i < NUM_ELEMS( params ); ++i )
{
if ( pos != params[ i ].offset )
sprintf( packstr + strlen( packstr ), "x%lu",
( unsigned long )( params[ i ].offset - pos ) );
pos = params[ i ].offset;
switch ( params[ i ].size )
{
case 1 :
strcat( packstr, "c" );
break;
case 2 :
strcat( packstr, "s" );
break;
case 4 :
strcat( packstr, "l" );
break;
case 8 :
#if defined NO_Q_FORMAT
exit( EXIT_FAILURE );
#endif
strcat( packstr, "q" );
break;
default :
exit( EXIT_FAILURE );
}
pos += params[ i ].size;
}
if ( pos < size )
sprintf( packstr + strlen( packstr ), "x%lu",
(unsigned long ) ( size - pos ) );
printf( "%s\\n", packstr );
for ( i = 0; i < NUM_ELEMS( params ); ++i )
printf( "%s\\n", params[ i ].name );
return 0;
}
EOF
close $c_file;
# Try to compile and link the file.
my $exec_file = File::Temp->new( TEMPLATE => 'File=FcntlLock-XXXXXX',
DIR => File::Spec->tmpdir( ) );
close $exec_file;
my $qflag = eval { pack 'q', 1 };
$qflag = $@ ? '-DNO_Q_FORMAT' : '';
die "Failed to run the C compiler '$Config{cc}'\n"
if system "$Config{cc} $Config{ccflags} $qflag -o $exec_file $c_file";
# Run the program and read it's output, it writes out the template string
# we need for packing and unpacking the binary C struct flock required for
# fcntl() and then the members of the structures in the sequence they are
# defined in there.
open my $pipe, '-|', $exec_file
or die "Failed to run a compiled program: $!\n";
chomp( $packstr = <$pipe> );
while ( my $line = <$pipe> ) {
chomp $line;
push @member_list, $line;
}
# Make sure we got all information needed
die "Your Perl version does not support the 'q' format for pack() "
. "and unpack()\n" unless defined $packstr;
die "Failed to obtain all needed data about the C struct flock\n"
unless @member_list == 5;
}
###########################################################
# Function for doing the actual fcntl() call: assembles the binary
# structure that must be passed to fcntl() from the File::FcntlLock
# object we get passed, calls it and then modifies the File::FcntlLock
# with the data from the flock structure
sub lock {
my ( $self, $fh, $action ) = @_;
my $buf = $self->pack_flock( );
my $ret = fcntl( $fh, $action, $buf );
if ( $ret ) {
$self->unpack_flock( $buf );
$self->{ errno } = $self->{ error } = undef;
} else {
$self->get_error( $self->{ errno } = $! + 0 );
}
return $ret;
}
###########################################################
# Method for packing the data from the 'flock_struct' into a
# binary blob to be passed to fcntl().
sub pack_flock {
my $self = shift;
my @args;
push @args, $self->{ $_ } for @member_list;
return pack $packstr, @args;
}
###########################################################
# Method for unpacking the binary blob received from a call of
# fcntl() into the 'flock_struct'.
sub unpack_flock {
my ( $self, $data ) = @_;
my @res = unpack $packstr, $data;
$self->{ $_ } = shift @res for @member_list;
}
=cut
1;
# Local variables:
# tab-width: 4
# indent-tabs-mode: nil
# End: