Reduce allocs

src/client/ble_remote_characteristic.rs

@@ -266,13 +266,8 @@ impl BLERemoteCharacteristic {
 
   pub(crate) unsafe fn notify(&mut self, om: *mut esp_idf_sys::os_mbuf) {
     if let Some(no_notify) = self.state.on_notify.as_mut() {
-      let mut buf = Vec::with_capacity(esp_idf_sys::BLE_ATT_ATTR_MAX_LEN as _);
-
-      for om in OsMBuf(om).iter() {
-        buf.extend_from_slice(om.as_slice());
-      }
-
-      no_notify(&buf);
+      let om = OsMBuf(om);
+      no_notify(om.as_flat().as_slice());
     }
   }
 }

src/server/ble_characteristic.rs

@@ -347,10 +347,8 @@ impl BLECharacteristic {
         }
       }
       sys::BLE_GATT_ACCESS_OP_WRITE_CHR => {
-        let mut buf = Vec::with_capacity(sys::BLE_ATT_ATTR_MAX_LEN as _);
-        for om in OsMBuf(ctxt.om).iter() {
-          buf.extend_from_slice(om.as_slice());
-        }
+        let om = OsMBuf(ctxt.om);
+        let buf = om.as_flat();
 
         let mut notify = false;
 
@@ -360,7 +358,7 @@ impl BLECharacteristic {
             let desc = crate::utilities::ble_gap_conn_find(conn_handle).unwrap();
             let mut arg = OnWriteArgs {
               current_data: (*characteristic.get()).value.as_slice(),
-              recv_data: &buf,
+              recv_data: buf.as_slice(),
               desc: &desc,
               reject: false,
               error_code: 0,
@@ -374,7 +372,7 @@ impl BLECharacteristic {
             notify = arg.notify;
           }
         }
-        characteristic.set_value(&buf);
+        characteristic.set_value(buf.as_slice());
         if notify {
           characteristic.notify();
         }

src/server/ble_descriptor.rs

@@ -1,5 +1,5 @@
 use crate::{utilities::OsMBuf, BLEConnDesc};
-use alloc::{boxed::Box, vec::Vec};
+use alloc::boxed::Box;
 use bitflags::bitflags;
 use core::{cell::UnsafeCell, ffi::c_void};
 use esp_idf_svc::sys as esp_idf_sys;
@@ -117,19 +117,16 @@ impl BLEDescriptor {
         }
       }
       esp_idf_sys::BLE_GATT_ACCESS_OP_WRITE_DSC => {
-        let mut buf = Vec::with_capacity(esp_idf_sys::BLE_ATT_ATTR_MAX_LEN as _);
-
-        for om in OsMBuf(ctxt.om).iter() {
-          buf.extend_from_slice(om.as_slice());
-        }
+        let om = OsMBuf(ctxt.om);
+        let buf = om.as_flat();
 
         unsafe {
           let descriptor = UnsafeCell::new(&mut descriptor);
           if let Some(callback) = &mut (*descriptor.get()).on_write {
             let desc = crate::utilities::ble_gap_conn_find(conn_handle).unwrap();
             let mut arg = OnWriteDescriptorArgs {
               current_data: (*descriptor.get()).value.as_slice(),
-              recv_data: &buf,
+              recv_data: buf.as_slice(),
               desc: &desc,
               reject: false,
               error_code: 0,
@@ -141,7 +138,7 @@ impl BLEDescriptor {
             }
           }
         }
-        descriptor.set_value(&buf);
+        descriptor.set_value(buf.as_slice());
 
         0
       }

src/utilities/os_mbuf.rs

@@ -1,6 +1,6 @@
+use alloc::vec::Vec;
 use core::ffi::c_int;
 use esp_idf_svc::sys;
-use sys::os_mbuf;
 
 #[cfg(not(esp_idf_soc_esp_nimble_controller))]
 use sys::os_mbuf_append as _os_mbuf_append;
@@ -9,7 +9,7 @@ use sys::os_mbuf_append as _os_mbuf_append;
 use sys::r_os_mbuf_append as _os_mbuf_append;
 
 #[derive(Copy, Clone)]
-pub(crate) struct OsMBuf(pub *mut os_mbuf);
+pub(crate) struct OsMBuf(pub *mut sys::os_mbuf);
 
 #[allow(unused)]
 impl OsMBuf {
@@ -38,6 +38,26 @@ impl OsMBuf {
   pub fn iter(&self) -> OsMBufIterator {
     OsMBufIterator(*self)
   }
+
+  #[inline]
+  fn has_next(&self) -> bool {
+    unsafe { !(*self.0).om_next.sle_next.is_null() }
+  }
+
+  #[inline]
+  pub fn as_flat(&self) -> FlatData<'_> {
+    if (self.has_next()) {
+      let mut buf = Vec::with_capacity(self.entire_len() as _);
+
+      for mbuf in self.iter() {
+        buf.extend_from_slice(mbuf.as_slice());
+      }
+
+      FlatData::Vec(buf)
+    } else {
+      FlatData::Slice(self.as_slice())
+    }
+  }
 }
 
 pub(crate) struct OsMBufIterator(OsMBuf);
@@ -57,3 +77,17 @@ impl Iterator for OsMBufIterator {
     }
   }
 }
+
+pub(crate) enum FlatData<'a> {
+  Vec(Vec<u8>),
+  Slice(&'a [u8]),
+}
+
+impl FlatData<'_> {
+  pub fn as_slice(&self) -> &[u8] {
+    match self {
+      FlatData::Vec(v) => v.as_slice(),
+      FlatData::Slice(s) => s,
+    }
+  }
+}