From e30791fe445cb57e0f8e83e486cb644ef2b17fa4 Mon Sep 17 00:00:00 2001
From: tuxmain <tuxmain@zettascript.org>
Date: Sat, 29 Apr 2023 16:51:57 +0200
Subject: [PATCH] fix: align_skip

---
 src/lib.rs  | 21 +++++++++++++----
 src/test.rs | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index a5d5bf0..dbdca7a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -80,7 +80,7 @@ impl<T> RingBuf<T> {
 			self.write_index = (self.write_index + 1) % self.data.len();
 			len += 1;
 		}
-		if self.available + len < self.data.len() {
+		if self.available + len <= self.data.len() {
 			self.available += len;
 		} else {
 			self.read_index = self.write_index;
@@ -210,10 +210,21 @@ impl<T> RingBuf<T> {
 	/// Skip a few elements to align the read index, returning the number of skipped elements.
 	pub fn align_skip(&mut self, align: usize) -> usize {
 		assert_eq!(self.data.len() % align, 0);
-		let skip = align - (self.read_index % align);
-		self.read_index = (self.read_index + skip) % self.data.len();
-		self.available = self.available.saturating_sub(skip);
-		skip
+		if self.read_index % align != 0 {
+			let skip = align - (self.read_index % align);
+			self.read_index = (self.read_index + skip) % self.data.len();
+			if skip <= self.available {
+				self.available -= skip;
+				skip
+			} else {
+				let available = self.available;
+				self.available = 0;
+				self.write_index = self.read_index;
+				available
+			}
+		} else {
+			0
+		}
 	}
 }
 
diff --git a/src/test.rs b/src/test.rs
index 303478d..042af58 100644
--- a/src/test.rs
+++ b/src/test.rs
@@ -4,20 +4,31 @@ use rand::Rng;
 
 #[test]
 fn chunks_exact_mut_random() {
-	const MAX_APPEND_LEN: usize = 256;
+	const MAX_APPEND_LEN: usize = 1023;
 	const CHUNK_SIZE: usize = 32;
+	const BUF_SIZE: usize = 1024;
 
 	let mut rng = rand::thread_rng();
-	let mut ringbuf = RingBuf::new(1024, 0_u32);
+	let mut ringbuf = RingBuf::new(BUF_SIZE, 0_u32);
 	let mut current_value = 0;
 	for _ in 0_u32..1024 {
 		let append_len = rng.gen_range(0..MAX_APPEND_LEN);
+		let overwritten = append_len;
+		let available = ringbuf.available();
 		assert_eq!(
 			ringbuf.push_from_iter_overflowing(
 				current_value as u32..current_value as u32 + append_len as u32
 			),
 			append_len
 		);
+		assert_eq!((available + append_len).min(BUF_SIZE), ringbuf.available());
+		dbg!(append_len);
+		dbg!(current_value);
+		if append_len + available > BUF_SIZE {
+			current_value += append_len - (BUF_SIZE - available);
+		}
+		dbg!(current_value);
+		ringbuf.align_skip(CHUNK_SIZE);
 		for (j, chunk) in ringbuf.chunks_exact_mut(CHUNK_SIZE).enumerate() {
 			assert_eq!(chunk.len(), CHUNK_SIZE);
 			for (k, v) in chunk.iter().enumerate() {
@@ -74,3 +85,55 @@ fn push_from_slice_overflowing() {
 		([4, 5, 6, 7, 8].as_slice(), [9, 10, 11].as_slice())
 	);
 }
+
+#[test]
+fn align_skip_basic() {
+	let mut ringbuf = RingBuf::new(8, 0_u32);
+
+	assert_eq!(ringbuf.align_skip(4), 0);
+	assert_eq!(ringbuf.available(), 0);
+	assert_eq!(ringbuf.read_index, 0);
+	assert_eq!(ringbuf.write_index, 0);
+
+	assert!(ringbuf.push(1));
+	assert_eq!(ringbuf.align_skip(4), 0);
+	assert_eq!(ringbuf.available(), 1);
+	assert_eq!(ringbuf.read_index, 0);
+	assert_eq!(ringbuf.write_index, 1);
+
+	assert!(ringbuf.push(1));
+	assert_eq!(ringbuf.align_skip(4), 0);
+	assert_eq!(ringbuf.available(), 2);
+	assert_eq!(ringbuf.read_index, 0);
+	assert_eq!(ringbuf.write_index, 2);
+
+	assert!(ringbuf.push(1));
+	assert_eq!(ringbuf.align_skip(4), 0);
+	assert_eq!(ringbuf.available(), 3);
+	assert_eq!(ringbuf.read_index, 0);
+	assert_eq!(ringbuf.write_index, 3);
+
+	assert!(ringbuf.push(1));
+	assert_eq!(ringbuf.align_skip(4), 0);
+	assert_eq!(ringbuf.available(), 4);
+	assert_eq!(ringbuf.read_index, 0);
+	assert_eq!(ringbuf.write_index, 4);
+
+	assert_eq!(ringbuf.read_first_one(), Some(&1));
+	assert_eq!(ringbuf.align_skip(4), 3);
+	assert_eq!(ringbuf.available(), 0);
+	assert_eq!(ringbuf.read_index, 4);
+	assert_eq!(ringbuf.write_index, 4);
+}
+
+#[test]
+fn align_skip_overflow() {
+	let mut ringbuf = RingBuf::new(8, 0_u32);
+
+	ringbuf.push_from_slice_overflowing(&[1, 2, 3, 4, 5, 6]);
+	assert_eq!(ringbuf.read_first_slices(5).0, &[1, 2, 3, 4, 5]);
+	assert_eq!(ringbuf.align_skip(4), 1);
+	assert_eq!(ringbuf.available(), 0);
+	assert_eq!(ringbuf.read_index, 0);
+	assert_eq!(ringbuf.write_index, 0);
+}