jam-std-common 0.1.29

Common datatypes and utilities for the JAM nodes and tooling
Documentation 
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use codec::Output;

/// [`Output`] wrapper which counts the number of bytes written.
pub struct CountedOutput<'a, O: ?Sized> {
	output: &'a mut O,
	num_bytes_written: usize,
}

impl<'a, O: ?Sized> CountedOutput<'a, O> {
	pub fn new(output: &'a mut O) -> Self {
		Self { output, num_bytes_written: 0 }
	}

	pub fn num_bytes_written(&self) -> usize {
		self.num_bytes_written
	}
}

impl<O: Output + ?Sized> Output for CountedOutput<'_, O> {
	fn write(&mut self, bytes: &[u8]) {
		self.output.write(bytes);
		self.num_bytes_written += bytes.len();
	}

	fn push_byte(&mut self, byte: u8) {
		self.output.push_byte(byte);
		self.num_bytes_written += 1;
	}
}

#[cfg(test)]
mod tests {
	use super::*;

	#[test]
	fn basic_operation() {
		let mut out = Vec::new();
		let mut counted = CountedOutput::new(&mut out);
		assert_eq!(counted.num_bytes_written(), 0);

		counted.write(&[1, 2, 3]);
		assert_eq!(counted.num_bytes_written(), 3);

		counted.push_byte(4);
		assert_eq!(counted.num_bytes_written(), 4);

		counted.write(&[]);
		assert_eq!(counted.num_bytes_written(), 4);

		// The bytes are forwarded to the wrapped output unchanged
		assert_eq!(out, vec![1, 2, 3, 4]);
	}
}