cbuf.c
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#define _POSIX_SOURCE
#define _POSIX_C_SOURCE 200112L
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include "class.h"
#include "interface/class.h"
#include "cbuf.h"
static void dtor(void*);
static
void
ctor(void * _this, va_list * params)
{
Cbuf this = _this;
char state = 0;
char * shm_name = va_arg(*params, char*);
long psize = sysconf(_SC_PAGESIZE);
size_t size;
int shm;
this->shm_name = malloc(strlen(shm_name) + 7 + 2);
sprintf(this->shm_name, "/%06d_%s", getpid(), shm_name);
/**
* align size at page boundary.
* increase as neccessary
*/
size = va_arg(*params, size_t);
size = (0 >= size)? 1 : (0 != size%psize)? (size/psize)+1 : size/psize;
this->bsize = psize * size;
while (0 == state) {
shm = shm_open(this->shm_name, O_RDWR|O_CREAT|O_EXCL, S_IRWXU);
if (-1 == shm) {
break;
}
if (-1 == ftruncate(shm, this->bsize)) {
break;
}
this->data = mmap (0, this->bsize << 1,
PROT_READ|PROT_WRITE, MAP_SHARED, shm, 0);
if (this->data == MAP_FAILED) {
this->data = NULL;
break;
}
munmap(this->data + this->bsize, this->bsize);
this->mirror = mmap (this->data + this->bsize, this->bsize,
PROT_READ|PROT_WRITE, MAP_SHARED, shm, 0);
if (this->mirror != this->data + this->bsize) {
if (this->mirror == this->data - this->bsize) {
this->data = this->mirror;
this->mirror += this->bsize;
}
else {
this->mirror = NULL;
break;
}
}
state = 1;
}
if (-1 != shm) {
shm_unlink(this->shm_name);
close(shm);
}
if (1 != state) {
dtor(this);
}
}
static
void
dtor(void * _this)
{
Cbuf this = _this;
if (NULL != this->shm_name) {
free(this->shm_name);
this->shm_name = NULL;
}
if (NULL != this->data) {
munmap(this->data, this->bsize);
this->data = NULL;
}
if (NULL != this->mirror) {
munmap(this->mirror, this->bsize);
this->mirror = NULL;
}
}
INIT_IFACE(Class, ctor, dtor, NULL);
CREATE_CLASS(Cbuf, NULL, IFACE(Class));
// vim: set ts=4 sw=4: