fix(iterator): block size error is cleaner

Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-embassy-time = { version = "0.3.2", features = ["log", "std", ] }
+embassy-time = { version = "0.3.2", features = ["log", "std"] }
 embassy-futures = "0.1.1"
 
 [dev-dependencies]
@@ -20,3 +20,7 @@ critical-section = { version = "1.1", features = ["std"] }
 embassy-sync  = { git = "https://github.com/embassy-rs/embassy", rev = "bc0180800d751e651c0d15c807285c11cdb4f486" }
 embassy-executor  = { git = "https://github.com/embassy-rs/embassy", rev = "bc0180800d751e651c0d15c807285c11cdb4f486" }
 embassy-time  = { git = "https://github.com/embassy-rs/embassy", rev = "bc0180800d751e651c0d15c807285c11cdb4f486" }
+
+[profile.release-with-debug]
+inherits = "release"
+debug = true

src/lib.rs

 use embassy_futures::yield_now;
 use embassy_time::{Duration, Instant};
+// use tracing::{field, span, Level};
 
 pub trait PreemptiveIterator: Iterator + Sized {
     async fn preemptive_fold<B, F: FnMut(B, Self::Item) -> B>(
@@ -25,6 +26,7 @@ impl<T, I: Iterator<Item = T>> PreemptiveIterator for I {
         let mut n_iters = 1;
         let react_us = reactivity.as_micros();
         loop {
+            debug_assert!(n_iters > 0);
             let start = Instant::now();
             let mut total_block = 0;
             let mut time = Duration::from_micros(0);
@@ -44,8 +46,9 @@ impl<T, I: Iterator<Item = T>> PreemptiveIterator for I {
             }
             let time_us = time.as_micros();
             // forced to pass by percent value to avoid floats for adjusting iteration
-            let percent = ((100 * (time_us - react_us)) / react_us) as usize;
-            n_iters = total_block.saturating_sub(((total_block - 1) * percent) / 100);
+            // hack 90 ratio < to have a upper bound for n_iters in order to avoid doubling in the next block
+            let ratio = ((90 * time_us) / react_us) as usize;
+            n_iters = (total_block * 100) / ratio;
             yield_now().await;
         }
     }