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// Copyright (C) by Josh Blum. See LICENSE.txt for licensing information.
#include <gras/buffer_queue.hpp>
#include <gras_impl/debug.hpp>
#include <boost/format.hpp>
#include <boost/bind.hpp>
#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/mapped_region.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/mutex.hpp>
using namespace gras;
namespace ipc = boost::interprocess;
static boost::mutex alloc_mutex;
/*!
* This routine generates an incredibly unique name for the allocation.
*
* Because we are using boost IPC, and it expects that we share the memory;
* IPC allocation requires a unique name to share amongst the processes.
* Since we are not actually using IPC, the sharing aspect isnt very useful,
* but we still need a unique name for the shared memory allocation anyway.
* (I would like if a empty string would suffice as an anonymous allocation)
*/
static std::string omg_so_unique(void)
{
const std::string tid = boost::lexical_cast<std::string>(boost::this_thread::get_id());
static size_t count = 0;
return boost::str(boost::format("shmem-%s-%u") % tid % count++);
}
struct CircularBuffer
{
CircularBuffer(const size_t);
~CircularBuffer(void)
{
ipc::shared_memory_object::remove(shm_name.c_str());
}
char *buff_addr;
size_t actual_length;
std::string shm_name;
ipc::shared_memory_object shm_obj;
ipc::mapped_region region1;
ipc::mapped_region region2;
};
CircularBuffer::CircularBuffer(const size_t num_bytes)
{
boost::mutex::scoped_lock lock(alloc_mutex);
const size_t chunk = ipc::mapped_region::get_page_size();
const size_t len = chunk*((num_bytes + chunk - 1)/chunk);
actual_length = len;
////////////////////////////////////////////////////////////////
// Step 0) Find an address that can be mapped across 2x length:
// Allocate physical memory 2x the required size.
// Map a virtual memory region across this memory.
// Now we have a 2x length swath of virtual memory.
////////////////////////////////////////////////////////////////
{
shm_name = omg_so_unique();
//std::cout << "make shmem 2x\n" << std::endl;
ipc::shared_memory_object shm_obj_2x(
ipc::create_only, //only create
shm_name.c_str(), //name
ipc::read_write //read-write mode
);
//std::cout << "truncate 2x\n" << std::endl;
shm_obj_2x.truncate(2*len);
//std::cout << "map region 0\n" << std::endl;
ipc::mapped_region region0(
shm_obj_2x, //Memory-mappable object
ipc::read_write, //Access mode
0, //Offset from the beginning of shm
2*len //Length of the region
);
//std::cout << "region0.get_address() " << size_t(region0.get_address()) << std::endl;
ipc::shared_memory_object::remove(shm_name.c_str());
buff_addr = (char *)region0.get_address();
}
////////////////////////////////////////////////////////////////
// Step 1) Allocate a chunk of physical memory of length bytes
////////////////////////////////////////////////////////////////
//std::cout << "make shmem\n" << std::endl;
shm_name = omg_so_unique();
shm_obj = ipc::shared_memory_object(
ipc::create_only, //only create
shm_name.c_str(), //name
ipc::read_write //read-write mode
);
//std::cout << "truncate\n" << std::endl;
shm_obj.truncate(len);
////////////////////////////////////////////////////////////////
//Step 2) Remap region1 of the virtual memory space
////////////////////////////////////////////////////////////////
//std::cout << "map region 1\n" << std::endl;
region1 = ipc::mapped_region(
shm_obj, //Memory-mappable object
ipc::read_write, //Access mode
0, //Offset from the beginning of shm
len, //Length of the region
buff_addr
);
//std::cout << "region1.get_address() " << size_t(region1.get_address()) << std::endl;
////////////////////////////////////////////////////////////////
//Step 3) Remap region2 of the virtual memory space
////////////////////////////////////////////////////////////////
//std::cout << "map region 2\n" << std::endl;
region2 = ipc::mapped_region(
shm_obj, //Memory-mappable object
ipc::read_write, //Access mode
0, //Offset from the beginning of shm
len, //Length of the region
buff_addr + len
);
//std::cout << "region2.get_address() " << size_t(region2.get_address()) << std::endl;
//std::cout << "diff " << (long(region2.get_address()) - long(region1.get_address())) << std::endl;
////////////////////////////////////////////////////////////////
//4) Zero out the memory for good measure
////////////////////////////////////////////////////////////////
std::memset(region1.get_address(), 0, region1.get_size());
std::memset(region2.get_address(), 0, region2.get_size());
}
static void circular_buffer_delete(SBuffer &buff, CircularBuffer *circ_buff)
{
delete circ_buff;
}
SBuffer make_circular_buffer(const size_t num_bytes)
{
CircularBuffer *circ_buff = new CircularBuffer(num_bytes);
SBufferDeleter deleter = boost::bind(&circular_buffer_delete, _1, circ_buff);
SBufferConfig config;
config.memory = circ_buff->buff_addr;
config.length = circ_buff->actual_length;
config.deleter = deleter;
return SBuffer(config);
}
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