From b21662247d810acdf1b2a431a91a8ab879fcaa06 Mon Sep 17 00:00:00 2001
From: Ed Guloien <edgul@mozilla.com>
Date: Thu, 28 May 2026 16:08:15 -0400
Subject: [PATCH] added better range clearing after read

---
 src/main.rs | 106 ++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 78 insertions(+), 28 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index f13262b..d84dc3b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,13 +1,40 @@
 
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq, Debug, Clone, Copy)]
 struct Range {
+    // todo: consider just using a map instead
+    // todo: also consider there might be an off the shelf solution that does ranges
     start: usize,
     end: usize, // exclusive
 }
 
+#[derive(PartialEq, Debug)]
+enum RangeLocation {
+    LeftEnd,
+    RightEnd,
+    Middle,
+    No
+}
+
 impl Range {
-    pub fn contains(&self, index: usize) -> bool {
-        index >= self.start && index < self.end
+    pub fn new(start: usize, end: usize) -> Self {
+        Self { start, end }
+    }
+
+    pub fn where_in_range(&self, index: usize) -> RangeLocation {
+        if index == self.start {
+            return RangeLocation::LeftEnd;
+        }
+        if index >= self.end {
+            return RangeLocation::No
+        }
+        if index == self.end - 1 {
+            return RangeLocation::RightEnd;
+        }
+        RangeLocation::Middle
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.start >= self.end
     }
 } 
 
@@ -20,14 +47,14 @@ impl Blob {
     pub fn new() -> Self { Self {bytes: Vec::new(), valid_ranges: Vec::new()} }
 
     pub fn append(&mut self, input: &[u8]) {
-        self.bytes.extend_from_slice(input);
+        let new_range = Range {start: self.bytes.len(), end: self.bytes.len() + input.len()};
 
         // we are appending so only have to check the last range
-        let new_range = Range {start: self.bytes.len(), end: self.bytes.len() + input.len()};
         match self.valid_ranges.last_mut() {
-            Some(range) if range.contains(new_range.start) => range.end = new_range.end,
+            Some(range) if range.where_in_range(new_range.start) != RangeLocation::No => range.end = new_range.end,
             _ => self.valid_ranges.push(new_range),
         }
+        self.bytes.extend_from_slice(input);
     }
 
     // todo: better way to do the return type?
@@ -36,16 +63,35 @@ impl Blob {
         let slice = &mut self.bytes[start..start+len];
         slice.swap_with_slice(output);
 
-        // update the valid array
-        let clear_range = Range{ start: start, end: start + len };
-        for range in  self.valid_ranges.iter_mut() {
-            if range.contains(clear_range.start) {
-                range.end = clear_range.start; 
-            }
-            if range.contains(clear_range.end) {
-                range.start = clear_range.end;
+        // we copy existing entries into a new list to avoid iterator invalidation
+        // of inserting while iterating
+        // todo: might be a better way
+        let clear_range = Range{ start, end: start + len };
+        let mut new_ranges = Vec::new();
+        let mut i = 0;
+        while i < self.valid_ranges.len() {
+            let mut extra_range : Option<Range> = None;
+            let mut range = self.valid_ranges[i];
+            if range.where_in_range(clear_range.start) == RangeLocation::LeftEnd {
+                range.start = clear_range.end; 
+            } else if range.where_in_range(clear_range.end-1) == RangeLocation::RightEnd {
+                range.end = clear_range.end
+            } else if range.where_in_range(clear_range.start) == RangeLocation::Middle {
+                let end = range.end;
+                range.end = clear_range.start;
+                extra_range = Some(Range::new(clear_range.end, end));
+            } 
+
+            if !range.is_empty() {
+                new_ranges.push(range); 
+            } 
+            
+            if let Some(er) = extra_range && !er.is_empty() {
+                new_ranges.push(er);
             }
+            i+=1;
         }
+        self.valid_ranges = new_ranges;
     }
 }
 
@@ -65,31 +111,35 @@ mod tests {
         let range2 = Range{start:0, end:3};
         assert_eq!(range, range2); // similar
 
-        // basic contains
-        assert!(range.contains(0));
-        assert!(range.contains(1));
-        assert!(range.contains(2));
-        assert!(!range.contains(3));
-        assert!(!range.contains(4));
+        assert_eq!(range.where_in_range(0), RangeLocation::LeftEnd);
+        assert_eq!(range.where_in_range(1), RangeLocation::Middle);
+        assert_eq!(range.where_in_range(2), RangeLocation::RightEnd);
+        assert_eq!(range.where_in_range(3), RangeLocation::No);
     }
 
     #[test]
     fn test_blob() {
         let mut b = Blob::new();
         b.append(&[b'a', b'b', b'c']);
+        assert_eq!(b.valid_ranges, &[Range{start:0, end:3}]);
 
         let mut read = vec![0; 1];
-        b.read(0,1, &mut read);
-        // todo make some asserts
-        //assert!(&read, Vec<u8>::new([b'a']));
-        println!("blob (0,1): {}", str::from_utf8(&read).unwrap());
+        b.read(0,1, &mut read); // left read
+        assert_eq!(b.valid_ranges, &[Range{start:1, end:3}]);
 
         let mut read = vec![0; 1];
-        b.read(0,1, &mut read);
-        println!("blob (0,1) again: {}", str::from_utf8(&read).unwrap());
+        b.read(0,1, &mut read); // dupe read // todo: should error or fail
+        assert_eq!(b.valid_ranges, &[Range{start:1, end:3}]);
 
         let mut read = vec![0; 2];
-        b.read(1,2, &mut read);
-        println!("blob (1,2) again: {}", str::from_utf8(&read).unwrap());
+        b.read(1,2, &mut read); // right read
+        assert_eq!(b.valid_ranges, &[]);
+
+        b.append(&[b'a', b'b', b'c']);
+        assert_eq!(b.valid_ranges, &[Range{start:3, end:6}]);
+        let mut read = vec![0; 1];
+        b.read(4,1, &mut read); // middle read
+        assert_eq!(b.valid_ranges, &[Range::new(3,4), Range::new(5,6)]);
+        println!("blob: {:?}", b.bytes);
     }
 }