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Queue

This class provides a way to synchronize communication between threads.

Example:

require 'thread'

queue = Queue.new

producer = Thread.new do
  5.times do |i|
    sleep rand(i) # simulate expense
    queue << i
    puts "#{i} produced"
  end
end

consumer = Thread.new do
  5.times do |i|
    value = queue.pop
    sleep rand(i/2) # simulate expense
    puts "consumed #{value}"
  end
end

consumer.join

Public Instance Methods

clear click to toggle source

Removes all objects from the queue.

static VALUE
rb_queue_clear(VALUE self)
{
    Queue *queue;
    Data_Get_Struct(self, Queue, queue);

    lock_mutex(&queue->mutex);
    clear_list(&queue->values);
    signal_condvar(&queue->space_available);
    unlock_mutex(&queue->mutex);

    return self;
}
empty? click to toggle source

Returns true if the queue is empty.

static VALUE
rb_queue_empty_p(VALUE self)
{
    Queue *queue;
    VALUE result;
    Data_Get_Struct(self, Queue, queue);

    lock_mutex(&queue->mutex);
    result = queue->values.size == 0 ? Qtrue : Qfalse;
    unlock_mutex(&queue->mutex);

    return result;
}
length click to toggle source

Returns the length of the queue.

static VALUE
rb_queue_length(VALUE self)
{
    Queue *queue;
    VALUE result;
    Data_Get_Struct(self, Queue, queue);

    lock_mutex(&queue->mutex);
    result = ULONG2NUM(queue->values.size);
    unlock_mutex(&queue->mutex);

    return result;
}
marshal_dump() click to toggle source 
static VALUE
rb_queue_marshal_dump(VALUE self)
{
    Queue *queue;
    VALUE array;
    Data_Get_Struct(self, Queue, queue);

    array = array_from_list(&queue->values);
    rb_ary_unshift(array, ULONG2NUM(queue->capacity));
    return rb_marshal_dump(array, Qnil);
}
marshal_load(p1) click to toggle source 
static VALUE
rb_queue_marshal_load(VALUE self, VALUE data)
{
    Queue *queue;
    VALUE array;
    Data_Get_Struct(self, Queue, queue);

    array = rb_marshal_load(data);
    if (TYPE(array) != T_ARRAY) {
        rb_raise(rb_eTypeError, "expected Array of queue data");
    }
    if (RARRAY(array)->len < 1) {
        rb_raise(rb_eArgError, "missing capacity value");
    }
    queue->capacity = NUM2ULONG(rb_ary_shift(array));
    push_multiple_list(&queue->values, RARRAY(array)->ptr, (unsigned)RARRAY(array)->len);

    return self;
}
num_waiting click to toggle source

Returns the number of threads waiting on the queue.

static VALUE
rb_queue_num_waiting(VALUE self)
{
    Queue *queue;
    VALUE result;
    Data_Get_Struct(self, Queue, queue);

    lock_mutex(&queue->mutex);
    result = ULONG2NUM(queue->value_available.waiting.size +
      queue->space_available.waiting.size);
    unlock_mutex(&queue->mutex);

    return result;
}
pop(*args) click to toggle source

call_seq: pop(non_block=false)

Retrieves data from the queue. If the queue is empty, the calling thread is suspended until data is pushed onto the queue. If non_block is true, the thread isn't suspended, and an exception is raised.

static VALUE
rb_queue_pop(int argc, VALUE *argv, VALUE self)
{
    Queue *queue;
    int should_block;
    VALUE result;
    Data_Get_Struct(self, Queue, queue);

    if (argc == 0) {
        should_block = 1;
    } else if (argc == 1) {
        should_block = !RTEST(argv[0]);
    } else {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }

    lock_mutex(&queue->mutex);
    if (!queue->values.entries && !should_block) {
        unlock_mutex(&queue->mutex);
        rb_raise(private_eThreadError, "queue empty");
    }

    while (!queue->values.entries) {
        wait_condvar(&queue->value_available, &queue->mutex);
    }

    result = shift_list(&queue->values);
    if (queue->capacity && queue->values.size < queue->capacity) {
        signal_condvar(&queue->space_available);
    }
    unlock_mutex(&queue->mutex);

    return result;
}
push(obj) click to toggle source

Pushes obj to the queue.

static VALUE
rb_queue_push(VALUE self, VALUE value)
{
    Queue *queue;
    Data_Get_Struct(self, Queue, queue);

    lock_mutex(&queue->mutex);
    while (queue->capacity && queue->values.size >= queue->capacity) {
        wait_condvar(&queue->space_available, &queue->mutex);
    }
    push_list(&queue->values, value);
    signal_condvar(&queue->value_available);
    unlock_mutex(&queue->mutex);

    return self;
}

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