concurrent_queue - accessing the first element without popping it out

[Bal__Rahul]

I am using TBB concurrent_queue class. It meets my needs except that I need to access the first element before popping it out of the queue (or put it back at front). As I understand from the document, one can't access first element or can't insert at the front like std:deque.

Any help on how to achieve this while maintaining concurrency as far as possible. I only need to access the front element and need to pop it out only if it meets some requirements - for example, to be consumed only after a particular time etc. 

[Alexei_K_Intel]

Accessing elements in the queue without popping is potentially unsafe (because the element can be accessed while another thread pops/removes it). The ability pushing elements to the front will make the implementation inefficient. You may want to consider concurrent_hash_map that allows accessing elements without extraction. Or consider concurrent_ordered_map that allows concurrent traversal and preserve ordering by key (similar to the queue).

[Bal__Rahul]

Alex,

You may want to consider concurrent_hash_map that allows accessing elements without extraction.

I am not sure how concurrent_hash_map will help. I need the queue behaviour (FIFO).

Or consider concurrent_ordered_map that allows concurrent traversal and preserve ordering by key (similar to the queue).

Is there anything like concurrent_ordered_map? I can't find it in the documentation.