cleanup(plugin): use bumpalo for source event batches

Signed-off-by: Grzegorz Nosek <grzegorz.nosek@sysdig.com>

falco_plugin/src/plugin/source/event_batch.rs

@@ -1,52 +1,22 @@
 use falco_event::events::EventToBytes;
 
-#[derive(Default, Debug)]
-pub(crate) struct EventBatchStorage {
-    buf: Vec<u8>,
-    offsets: Vec<usize>,
-
-    raw_pointers: Vec<*const u8>,
-}
-
-impl EventBatchStorage {
-    pub fn start(&mut self) -> EventBatch {
-        self.buf.clear();
-        self.offsets.clear();
-
-        EventBatch {
-            buf: &mut self.buf,
-            offsets: &mut self.offsets,
-        }
-    }
-
-    pub fn get_raw_pointers(&mut self) -> (*const *const u8, usize) {
-        if self.offsets.is_empty() {
-            return (std::ptr::null(), 0);
-        }
-
-        self.raw_pointers.clear();
-        self.raw_pointers.reserve(self.offsets.len());
-        let base = self.buf.as_ptr();
-        for offset in self.offsets.iter().copied() {
-            self.raw_pointers.push(unsafe { base.add(offset) });
-        }
-
-        (self.raw_pointers.as_ptr(), self.offsets.len())
-    }
-}
-
 /// # An object that describes a batch of events
 ///
 /// This is only available by reference, not by ownership, since the data needs to outlive
 /// the plugin API call and is stored elsewhere (in a wrapper struct that's not exposed to
 /// plugin developers)
 #[derive(Debug)]
 pub struct EventBatch<'a> {
-    buf: &'a mut Vec<u8>,
-    offsets: &'a mut Vec<usize>,
+    alloc: &'a bumpalo::Bump,
+    pointers: bumpalo::collections::Vec<'a, *const u8>,
 }
 
 impl EventBatch<'_> {
+    pub(in crate::plugin::source) fn new(alloc: &mut bumpalo::Bump) -> EventBatch {
+        let pointers = bumpalo::collections::Vec::new_in(alloc);
+        EventBatch { alloc, pointers }
+    }
+
     /// # Add an event to a batch
     ///
     /// The event can be any type, but please note that the framework may have different
@@ -57,10 +27,13 @@ impl EventBatch<'_> {
     /// the [`source::SourcePluginInstance::plugin_event`](`crate::source::SourcePluginInstance::plugin_event`)
     /// helper method.
     pub fn add(&mut self, event: impl EventToBytes) -> std::io::Result<()> {
-        let pos = self.buf.len();
-        event.write(&mut *self.buf)?;
-
-        self.offsets.push(pos);
+        let mut event_buf = bumpalo::collections::Vec::new_in(self.alloc);
+        event.write(&mut event_buf)?;
+        self.pointers.push(event_buf.as_ptr());
         Ok(())
     }
+
+    pub(in crate::plugin::source) fn get_events(&self) -> &[*const u8] {
+        self.pointers.as_slice()
+    }
 }

falco_plugin/src/plugin/source/mod.rs

@@ -1,5 +1,4 @@
 use crate::plugin::base::Plugin;
-use crate::plugin::source::event_batch::EventBatchStorage;
 use crate::source::{EventBatch, EventInput};
 use falco_event::events::types::PPME_PLUGINEVENT_E as PluginEvent;
 use falco_event::events::Event;
@@ -92,7 +91,7 @@ pub struct ProgressInfo<'a> {
 
 pub(crate) struct SourcePluginInstanceWrapper<I: SourcePluginInstance> {
     pub(crate) instance: I,
-    pub(crate) batch: EventBatchStorage,
+    pub(crate) batch: bumpalo::Bump,
 }
 
 /// # An open instance of a source plugin

falco_plugin/src/plugin/source/wrappers.rs

@@ -1,7 +1,7 @@
 use crate::plugin::base::PluginWrapper;
 use crate::plugin::error::ffi_result::FfiResult;
 use crate::plugin::source::SourcePluginInstanceWrapper;
-use crate::source::{EventInput, SourcePlugin, SourcePluginInstance};
+use crate::source::{EventBatch, EventInput, SourcePlugin, SourcePluginInstance};
 use crate::strings::cstring_writer::WriteIntoCString;
 use crate::strings::from_ptr::try_str_from_ptr;
 use falco_plugin_api::plugin_api__bindgen_ty_1 as source_plugin_api;
@@ -183,15 +183,16 @@ pub unsafe extern "C" fn plugin_next_batch<T: SourcePlugin>(
             return ss_plugin_rc_SS_PLUGIN_FAILURE;
         };
 
-        let mut batch = instance.batch.start();
+        instance.batch.reset();
+        let mut batch = EventBatch::new(&mut instance.batch);
         match instance
             .instance
             .next_batch(&mut actual_plugin.plugin, &mut batch)
         {
             Ok(()) => {
-                let (batch_evts, batch_nevts) = instance.batch.get_raw_pointers();
-                *nevts = batch_nevts as u32;
-                *evts = batch_evts as *mut *mut _;
+                let events = batch.get_events();
+                *nevts = events.len() as u32;
+                *evts = events as *const _ as *mut _;
                 ss_plugin_rc_SS_PLUGIN_SUCCESS
             }
             Err(e) => {