feat: add block getters (#264)

* feat: add block getters

* fix: block size valid values

toad-msg/src/msg/mod.rs

@@ -408,6 +408,12 @@ pub trait MessageOptions {
         .map(|_| ())
   }
 
+  /// [`opt::known::no_repeat::BLOCK1`]
+  fn block1(&self) -> Option<block::Block> {
+    self.get_u32(opt::known::no_repeat::BLOCK1)
+        .map(block::Block::from)
+  }
+
   /// [`opt::known::no_repeat::BLOCK1`]
   fn set_block1(&mut self, size: u16, num: u32, more: bool) -> Result<(), Self::SetError> {
     let block = block::Block::new(size, num, more);
@@ -416,6 +422,12 @@ pub trait MessageOptions {
         .map(|_| ())
   }
 
+  /// [`opt::known::no_repeat::BLOCK2`]
+  fn block2(&self) -> Option<block::Block> {
+    self.get_u32(opt::known::no_repeat::BLOCK2)
+        .map(block::Block::from)
+  }
+
   /// [`opt::known::no_repeat::BLOCK2`]
   fn set_block2(&mut self, size: u16, num: u32, more: bool) -> Result<(), Self::SetError> {
     let block = block::Block::new(size, num, more);

toad-msg/src/msg/opt/known/block.rs

@@ -11,7 +11,7 @@ impl Block {
   pub fn new(size: u16, num: u32, more: bool) -> Self {
     let num = num << 4;
     let more = u32::from(more) << 3;
-    let size = f32::from(size).log2() as u32 - 4;
+    let size = f32::from(size.max(16).min(1024)).log2() as u32 - 4;
 
     Self(num | more | size)
   }
@@ -39,6 +39,12 @@ impl From<Block> for u32 {
   }
 }
 
+impl From<u32> for Block {
+  fn from(n: u32) -> Self {
+    Block(n)
+  }
+}
+
 #[cfg(test)]
 mod test {
   use super::*;
@@ -58,4 +64,16 @@ mod test {
     assert_eq!(Block::new(32, 2, false), Block(33));
     assert_eq!(Block::new(128, 3, true), Block(59));
   }
+
+  #[test]
+  fn size_rounds_down_to_nearest_power_of_two() {
+    assert_eq!(Block::new(0, 1, false).size(), 16);
+    assert_eq!(Block::new(10, 1, false).size(), 16);
+    assert_eq!(Block::new(17, 1, false).size(), 16);
+    assert_eq!(Block::new(31, 1, false).size(), 16);
+    assert_eq!(Block::new(33, 1, false).size(), 32);
+    assert_eq!(Block::new(64, 1, false).size(), 64);
+    assert_eq!(Block::new(1024, 1, false).size(), 1024);
+    assert_eq!(Block::new(2048, 1, false).size(), 1024);
+  }
 }