owasm-abi 0.3.0

//! Stream module

use super::{AbiType, Error};

/// Stream interpretation of incoming payload
pub struct Stream<'a> {
	payload: &'a [u8],
	position: usize,
}

impl<'a> Stream<'a> {

	/// New stream for known payload
	pub fn new(raw: &'a [u8]) -> Self {
		Stream {
			payload: raw,
			position: 0,
		}
	}

	/// Pop next argument of known type
	pub fn pop<T: AbiType>(&mut self) -> Result<T, Error> {
		if T::IS_FIXED {
			T::decode(self)
		} else {
			let offset = u32::decode(self)?;
			let mut nested_stream = Stream::new(&self.payload[offset as usize..]);
			T::decode(&mut nested_stream)
		}
	}

	/// Current position for the stream
	pub fn position(&self) -> usize { self.position }

	/// Advance stream position for `amount` bytes
	pub fn advance(&mut self, amount: usize) -> Result<usize, Error> {
		if self.position + amount > self.payload.len() {
			return Err(Error::UnexpectedEof);
		}

		let old_position = self.position;
		self.position += amount;
		Ok(old_position)
	}

	/// Finish current advance, advancing stream to the next 32 byte step
	pub fn finish_advance(&mut self) {
		if self.position % 32 > 0 { self.position += 32 - (self.position % 32); }
	}

	/// Stream payload
	pub fn payload(&self) -> &[u8] {
		self.payload
	}

	/// Peek next byte in stream
	pub fn peek(&self) -> u8 {
		self.payload[self.position]
	}
}