Struct MergeBuffer 

pub struct MergeBuffer<C: IOCallback> {
    pub merge_size_limit: usize,
    /* private fields */
}

Buffers sequential IO events for merging.

This internal component collects IOEvents, presuming the same IO action and file descriptor (it does not check), the merge upper bound is specified in merge_size_limit.

Fields

merge_size_limit: usize

Implementations

impl<C: IOCallback> MergeBuffer<C>

pub fn new(merge_size_limit: usize) -> Self

Creates a new MergeBuffer with the specified merge size limit.

Arguments

• merge_size_limit - The maximum total data size to produce a merged event.

pub fn may_add_event(&mut self, event: &IOEvent<C>) -> bool

Checks if a new event can be added to the current buffer for merging.

An event can be added if:

• The buffer is empty.
• The event is contiguous with the last event in the buffer.
• Adding the event does not exceed the merge_size_limit.

Arguments

• event - The IOEvent to check.

Returns

true if the event can be added, false otherwise.

pub fn push_event(&mut self, event: IOEvent<C>) -> bool

Pushes an event into the buffer.

This method assumes that may_add_event has already been called and returned true. It updates the merged data size and tracks the merged offset.

Arguments

• event - The IOEvent to push.

Safety

You should always check whether event is contiguous with Self::may_add_event before calling push_event()

Returns

true if the buffer size has reached or exceeded merge_size_limit after adding the event, false otherwise.

pub fn len(&self) -> usize

Returns the number of events currently in the buffer.

pub fn flush(&mut self, fd: RawFd, action: IOAction) -> Option<IOEvent<C>>

Flushes the buffered events, potentially merging them into a single IOEvent.

This method handles different scenarios based on the number of events in the buffer:

• If the buffer is empty, it returns None.
• If there is a single event, it returns Some(event) with the original event.
• If there are multiple events, it attempts to merge them:
  • If successful, a new master IOEvent covering the merged range is returned as Some(merged_event).
  • If buffer allocation for the merged event fails, all original events are marked with an ENOMEM error and their callbacks are triggered, then None is returned.
• This function will always override fd in IOEvent with argument

After flushing, the buffer is reset.

Arguments

• fd - The raw file descriptor associated with the IO operations.
• action - The IO action (Read/Write) for the events.

Returns

An Option<IOEvent<C>> representing the merged event, a single original event, or None if the buffer was empty or merging failed.