Move cast_read_offset_usize to the input module

I don't know if it's _that_ much different. It's still a tiny function
in the middle of much more complex stuff. But even the chunker's use is
technically input-related, so... let's keep it here for now.

Author: featherbread

src/input.rs

@@ -252,7 +252,7 @@ where
 	/// Returns the number of bytes remaining to read from the captured prefix before consuming
 	/// more from the source.
 	fn captured_unread_size(&self) -> usize {
-		let offset = crate::cast_read_offset_usize(self.prefix.position());
+		let offset = cast_read_offset_usize(self.prefix.position());
 		self.prefix.get_ref().len() - offset
 	}
 
@@ -335,6 +335,25 @@ where
 	}
 }
 
+/// Cast the offset of a memory-based [`io::Read`] to a [`usize`].
+///
+/// While `Read` APIs present offsets as `u64`s, any offset into a reader over an in-memory slice
+/// must naturally be representable in a width that covers every possible memory address.
+///
+/// # Panics
+///
+/// When debug assertions are enabled and `n` doesn't fit in a usize.
+/// This is a tradeoff between the relative efficiency and potential dangers of plain `as` casts.
+#[inline(always)]
+#[allow(clippy::cast_possible_truncation)]
+pub(crate) fn cast_read_offset_usize(n: u64) -> usize {
+	if cfg!(debug_assertions) {
+		usize::try_from(n).expect("reader offset should fit in a usize")
+	} else {
+		n as usize
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::{CaptureReader, Handle, Input, Ref};

src/lib.rs

@@ -301,22 +301,3 @@ impl Format {
 		Ok(None)
 	}
 }
-
-/// Cast the offset of a memory-based [`io::Read`] to a [`usize`].
-///
-/// While `Read` APIs present offsets as `u64`s, any offset into a reader over an in-memory slice
-/// must naturally be representable in a width that covers every possible memory address.
-///
-/// # Panics
-///
-/// When debug assertions are enabled and `n` doesn't fit in a usize.
-/// This is a tradeoff between the relative efficiency and potential dangers of plain `as` casts.
-#[inline(always)]
-#[allow(clippy::cast_possible_truncation)]
-fn cast_read_offset_usize(n: u64) -> usize {
-	if cfg!(debug_assertions) {
-		usize::try_from(n).expect("reader offset should fit in a usize")
-	} else {
-		n as usize
-	}
-}

src/yaml/chunker.rs

@@ -14,6 +14,8 @@ use std::mem;
 
 mod parser;
 
+use crate::input::cast_read_offset_usize;
+
 use self::parser::{
 	Parser, YAML_DOCUMENT_END_EVENT, YAML_DOCUMENT_START_EVENT, YAML_MAPPING_START_EVENT,
 	YAML_SCALAR_EVENT, YAML_SEQUENCE_START_EVENT, YAML_STREAM_END_EVENT,
@@ -156,15 +158,15 @@ where
 	/// Trims from the start of the capture buffer so the next chunk will begin at the specified
 	/// reader offset.
 	fn trim_to_offset(&mut self, offset: u64) {
-		let trim_len = crate::cast_read_offset_usize(offset - self.captured_start_offset);
+		let trim_len = cast_read_offset_usize(offset - self.captured_start_offset);
 		self.captured_start_offset = offset;
 		self.captured.drain(..trim_len);
 	}
 
 	/// Takes the chunk from the start of the capture buffer up to the specified reader offset,
 	/// leaving bytes beyond the offset in the capture buffer.
 	fn take_to_offset(&mut self, offset: u64) -> Vec<u8> {
-		let take_len = crate::cast_read_offset_usize(offset - self.captured_start_offset);
+		let take_len = cast_read_offset_usize(offset - self.captured_start_offset);
 		let tail = self.captured.split_off(take_len);
 		self.captured_start_offset = offset;
 		mem::replace(&mut self.captured, tail)