Easy SHM library for C++, still a work in progress but it's a easier way to code up an anonymous SHM mapping, protect the last page and generate a key to access it....I've used similar code quite a bit and was tired of re-coding it. If I find time I'll make it a bit more advanced, like adding a monitor process to cleanup if for some reason the code crashes (you know, things happen right?). I've tested the code on OS X and Linux, but as usual your mileage may vary greatly.
So I've checked the functions found in the testsuite. I've used the code quite a bit in various forms so it should work rather well...however if you find bugs please submit a pull request and I'll get it fixed ASAP.
To build this library on OS X you'll need to run:
mkdir build
cd build
cmake ../build -G<build system of your choice> -DCMAKE_BUILD_TYPE=Release
[make | ninja]
[make | ninja] test- There are the usual options (e.g., Release/Debug), there's also...
-DUSE_SYSV_MEMORY=1which will build the library using the SystemV SHM interface-DUSE_POSIX_SHM=1which will build the library using the POSIX SHM interface-DCPP_EXCEPTIONS=0which will remove the use of CPP exceptions, the return values in this case must be checked (e.g., check for nullptr vs. waiting for the cpp exception.
- Just run
[make | ninja] install
To use this library, simply:
#include <shm>When compiling your code that uses it, link with -lshm. On Linux you'll have to compile with the -lrt, -lpthread and -lnuma in order to fully utilize all the features. In the future I might add a flag to compile without the NUMA features so that you can use the library without having to install libnuma.
shm_key_t key;
shm::gen_key( key, 42);
using type_t = std::uint32_t;
type_t *ptr( nullptr );
/**
* NOTE: you can compile with or without CPP exceptions.
*/
try
{
ptr = reinterpret_cast< type_t* >( shm::init( key, 0x1000, false, nullptr ) );
}
catch( bad_shm_alloc ex )
{
std::cerr << ex.what() << "\n";
exit( EXIT_FAILURE );
}
auto child = fork();
switch( child )
{
case( 0 /** child **/ ):
{
try
{
ptr = shm::eopen< type_t >( key );
}
catch( bad_shm_alloc ex )
{
std::cerr << ex.what() << "\n";
exit( EXIT_FAILURE );
}
*ptr = 0x1137;
shm::close( key,
reinterpret_cast<void**>( &ptr),
0x1000,
false /** don't zero **/,
false /** don't unlink **/ );
}
break;
case( -1 /** error, back to parent **/ ):
{
exit( EXIT_FAILURE );
}
break;
default:
{
/**
* spin on value being written from child
* process.
*/
while( *ptr != 0x1137 );
std::fprintf( stdout, "leet\n" );
int status = 0;
waitpid( -1, &status, 0 );
shm::close( key,
reinterpret_cast<void**>( &ptr),
0x1000,
true /** zero **/,
true /** unlink **/ );
}
}