Class: ConcurrentSHM::SharedMemory

Inherits:
IO
  • Object
show all
Defined in:
ext/concurrent-shm/posix.c,
ext/concurrent-shm/posix.c

Overview

A POSIX shared memory object.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(fd, name) ⇒ Object

Create a ConcurrentSHM::SharedMemory instance for the specified file descriptor.

Parameters:

  • fd (Integer) —

    the file descriptor

  • name (String) —

    the name



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# File 'ext/concurrent-shm/posix.c', line 102

static VALUE shared_memory_initialize(VALUE self, VALUE fd, VALUE name)
{
    rb_call_super(1, &fd); // super(fd)
    rb_iv_set(self, "@name", name); // @name = name
    return self;
}

Class Method Details

.delete(name) ⇒ nil

Delete a POSIX shared memory object.

Parameters:

  • name (String) —

    the name of the object

Returns:

  • (nil)

Raises:

  • (ArgumentError) —

    if the name is nil or is not a string

  • (Errno::EACCES) —

    if permission to delete the object is denied

  • (Errno::ENOENT) —

    if the named object does not exist



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# File 'ext/concurrent-shm/posix.c', line 25

static VALUE shared_memory_delete(VALUE self, VALUE name)
{
    UNUSED(self);

    if (NIL_P(name)) {
        rb_raise(rb_eArgError, "Name must not be nil");
    }

    char * cname = StringValueCStr(name);
    chk_errno(shm_unlink, (cname), "%s", cname);

    return Qnil;
}

.open(name, fmode, mode: :excl) ⇒ SharedMemory

Create or open a POSIX shared memory object. The default flags are O_CREATE, O_RDWR, and O_TRUNC.

If the mode is :excl, :exclusive, :anon, or :anonymous, the object is opened exclusively, with the O_EXCL flag in addition to the defaults.

If the mode is :anon or :anonymous, the object is deleted immediately after being opened. Opened and deleted shared memory objects can be used until the object is closed.

If the mode is :shared, the object is opened with the default flags.

Parameters:

  • name (String) —

    the name of the object

  • fmode (Integer) —

    the file mode of the object

  • mode (Symbol) (defaults to: :excl) —

    the manner in which to create or open the object.

Returns:

Raises:

  • (ArgumentError) —

    if the name is nil or is not a string

  • (Errno::EACCES) —

    if permission to create or open the object is denied

  • (Errno::EEXIST) —

    if exclusive is true and the object specified by name already exists

  • (Errno::EINVAL) —

    if the name is invalid

  • (Errno::EMFILE) —

    if the per-process limit on the number of open file descriptors has been reached

  • (Errno::ENAMETOOLONG) —

    if the name is too long

  • (Errno::ENFILE) —

    if the system-wide limit on the total number of open files has been reached



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# File 'ext/concurrent-shm/posix.c', line 64

static VALUE shared_memory_open(int argc, VALUE * argv, VALUE self)
{
    CONST_IDS(id_, exclusive, anonymous, shared, excl, anon);

    VALUE name, fmode;
    KWARGS(ARGS("2:", name, fmode), 0, mode);

    if (NIL_P(name)) {
        rb_raise(rb_eArgError, "Name must not be nil");
    }

    ID id_mode = mode == Qundef ? id_excl : SYM2ID(mode);
    char * cname = StringValueCStr(name);
    int oflag = O_CREAT | O_RDWR | O_TRUNC | (id_mode == id_shared ? 0 : O_EXCL);
    int fd = shm_open(cname, oflag, FIX2INT(fmode));
    if (fd < 0) {
        int err = errno;
        if (err != EMFILE && err != ENFILE && err != ENOMEM) {
            rb_syserr_fail_strf(err, "shm_open(%s, %d, %d)", cname, oflag, FIX2INT(fmode));
        }

        // if ERRNO indicates no memory, GC and try again
        rb_gc();
        fd = shm_open(cname, oflag, FIX2INT(fmode));
        rb_check_syserr_fail_strf(fd < 0, errno, "shm_open(%s, %d, %d)", cname, oflag, FIX2INT(fmode));
    }

    if (id_mode == id_anon || id_mode == id_anonymous) {
        shared_memory_delete(self, name);
    }

    return rb_funcall(self, rb_intern("new"), 2, INT2FIX(fd), name);
}

Instance Method Details

#size ⇒ Integer

The size of the shared memory space using fstat.

Returns:

  • (Integer)

Raises:

  • (Errno::EBADF) —

    if the receivers fileno is not a valid file descriptor



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# File 'ext/concurrent-shm/posix.c', line 113

static VALUE shared_memory_size(VALUE self)
{
    struct stat stat;
    VALUE fd = rb_funcall(self, rb_intern("fileno"), 0);
    chk_err(fstat, (FIX2INT(fd), &stat), "fd=%d", FIX2INT(fd));
    return INT2FIX(stat.st_size);
}

#size=(size) ⇒ Object

Set the size of the shared memory space using ftruncate.

Parameters:

  • size (Integer) —

    the new size of the space



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# File 'ext/concurrent-shm/posix.c', line 124

static VALUE shared_memory_size_eq(VALUE self, VALUE size)
{
    VALUE fd = rb_funcall(self, rb_intern("fileno"), 0);
    chk_errno(ftruncate, (FIX2INT(fd), FIX2INT(size)), "%d, %d", FIX2INT(fd), FIX2INT(size));
    return size;
}