lib.rs.html -- source
Description: Source to the Rust file `src/lib.rs`.
Keywords: rust, rustlang, rust-lang

      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109

    use std::mem;

    /// A type that represents an object that consumes a memory slice on demand.
    /// The consumer lives as long as the slice is alive.
    pub struct ByteConsumer<'b> {
        /// The memory slice that get's consumed.
        buffer: &'b [u8],
    }

    impl<'b> ByteConsumer<'b> {
        /// Creates a new ByteConsumer from a stream of bytes.
        pub fn new(stream: &'b [u8]) -> ByteConsumer {
            ByteConsumer { buffer: stream }
        }

        /// Consumes `nr_bytes` from the original slice and returns an `Option` that holds a reference
        /// to a memory slice which is `nr_bytes` long. If `nr_bytes` is greater than the remaining
        /// bytes of the consumer's slice then `None` is returned.
        ///
        /// # Arguments
        ///
        /// * `nr_bytes` - A number representing the number of bytes to consume
        ///
        /// *Note*: The memory slice returned is not copied, it's a reference to the initial slice
        ///
        /// # Examples
        ///
        /// ```
        /// let mut consumer = ByteConsumer::new(&[10, 20, 30, 40]);
        /// let first_two = consumer.consume(2);
        /// let second_two = consumer.consume(2);
        ///
        /// assert!(first_two.is_some());
        /// assert_eq!(first_two.unwrap(), [10, 20]);
        ///
        /// assert!(second_two.is_some());
        /// assert_eq!(second_two.unwrap(), [30, 40]);
        ///
        /// assert_eq!(consumer.consume(1), None);
        /// ```
        ///
        #[inline]
        pub fn consume(&mut self, nr_bytes: usize) -> Option<&'b [u8]> {
            if nr_bytes > self.buffer.len() || nr_bytes == 0 {
                None
            } else {
                let (res, remaining) = self.buffer.split_at(nr_bytes);
                self.buffer = remaining;
                Some(res)
            }
        }

        /// Consumes `nr_bytes` from the original slice and returns a reference to a memory slice which is `nr_bytes` long.
        ///
        /// # Arguments
        ///
        /// * `nr_bytes` - A number representing the number of bytes to consume
        ///
        /// # Panics
        ///
        /// If `nr_bytes` is greater than the remaining bytes in the consumer's slice then
        /// then it panics with a custom message.
        ///
        /// *Note*: The memory slice returned is not copied, it's a reference to the initial slice
        ///
        /// # Examples
        ///
        /// ```
        /// let mut consumer = ByteConsumer::new(&[10, 20, 30, 40]);
        /// let first_two = consumer.consume_unchecked(2);
        /// let second_two = consumer.consume_unchecked(2);
        ///
        /// assert_eq!(first_two, [10, 20]);
        /// assert_eq!(second_two, [30, 40]);
        ///
        /// // let _next = consumer.consume_unchecked(1) <-- This should panic.
        /// ```
        #[inline]
        pub fn consume_unchecked(&mut self, nr_bytes: usize) -> &'b [u8] {
            self.consume(nr_bytes).expect(format!(
                "[ByteConsumer]: The number of bytes requested ({}) is greater that the number of bytes available ({}).",
                nr_bytes,
                self.buffer.len()
            ).as_str())
        }

        #[inline]
        pub fn consume_as<T: Copy>(&mut self) -> Option<T> {
            let bytes = self.consume(mem::size_of::<T>());
            match bytes {
                Some(bytes) => unsafe { Some(*(bytes.as_ptr() as *const T)) },
                None => None,
            }
        }

        #[inline]
        pub fn consume_as_unchecked<T: Copy>(&mut self) -> T {
            self.consume_as::<T>().unwrap()
        }
    }

    #[cfg(test)]
    mod tests {
        #[test]
        fn it_works() {
            assert_eq!(2 + 2, 4);
        }
    }