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use super::{Deserializer, Error, Result};
use std::borrow::Cow;
/// A struct representing an array of byte slices.
#[derive(Clone, Copy)]
pub struct BytesArray<'a> {
arr: &'a [&'a [u8]],
pos: usize,
len: usize,
}
impl<'a> BytesArray<'a> {
/// Creates a new `BytesArray` from a slice of byte slices.
///
/// # Arguments
///
/// * `arr` - A slice of byte slices.
pub fn new(arr: &'a [&[u8]]) -> Self {
let len = arr.iter().map(|s| s.len()).sum();
Self { arr, pos: 0, len }
}
/// Returns the total length of the byte slices.
pub fn len(&self) -> usize {
self.len
}
/// Checks if the `BytesArray` is empty.
pub fn is_empty(&self) -> bool {
self.len == 0
}
}
impl<'a> Deserializer<'a> for BytesArray<'a> {
/// Checks if the `BytesArray` is empty.
fn is_empty(&self) -> bool {
self.len == 0
}
/// Advances the `BytesArray` by the specified length.
///
/// # Arguments
///
/// * `len` - The length to advance.
///
/// # Returns
///
/// A `Result` containing the advanced `BytesArray` or an error.
fn advance(&mut self, len: usize) -> Result<Self>
where
Self: Sized,
{
if len <= self.len {
let mut r = len;
let mut p = self.pos;
for (idx, s) in self.arr.iter().enumerate() {
let c = s.len() - p;
if r <= c {
let ret = Self {
arr: &self.arr[..idx + 1],
pos: self.pos,
len,
};
if r == c {
self.arr = &self.arr[idx + 1..];
self.pos = 0;
self.len -= len;
} else {
self.arr = &self.arr[idx..];
self.pos = p + r;
self.len -= len;
};
return Ok(ret);
} else {
r -= c;
p = 0;
}
}
}
Err(Error::DataIsShort {
expect: len,
actual: 0,
})
}
/// Pops the specified length of data from the `BytesArray`.
///
/// # Arguments
///
/// * `len` - The length of data to pop.
///
/// # Returns
///
/// A `Result` containing the popped data or an error.
fn pop(&mut self, len: usize) -> Result<Cow<'a, [u8]>> {
if len <= self.len {
let first_slice_len = self.arr[0].len() - self.pos;
if len <= first_slice_len {
let s = &self.arr[0][self.pos..self.pos + len];
if len == first_slice_len {
self.arr = &self.arr[1..];
self.pos = 0;
} else {
self.pos += len;
}
self.len -= len;
Ok(Cow::Borrowed(s))
} else {
let mut vec = Vec::from(&self.arr[0][self.pos..]);
let mut remain = len - first_slice_len;
self.arr = &self.arr[1..];
self.pos = 0;
self.len -= len;
while remain > 0 {
if remain < self.arr[0].len() {
vec.extend_from_slice(&self.arr[0][..remain]);
self.pos = remain;
break;
} else {
remain -= self.arr[0].len();
vec.extend_from_slice(self.arr[0]);
self.arr = &self.arr[1..];
}
}
Ok(Cow::Owned(vec))
}
} else {
Err(Error::DataIsShort {
expect: len,
actual: self.len,
})
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_deserializer() {
let data = [0u8, 1, 2, 3];
let mut slice = &data[..];
slice.advance(2).unwrap();
assert!(slice.advance(3).is_err());
slice.advance(2).unwrap();
assert!(slice.is_empty());
}
#[test]
fn test_bytes_array() {
let mut data = vec![];
data.extend(0u8..=255);
for _ in 0..8 {
data.extend_from_within(..);
}
let mut slice = &data[..];
let mut vec = vec![];
while slice.len() >= 100 {
let (front, back) = slice.split_at(100);
vec.push(front);
slice = back;
}
vec.push(slice);
let mut arr = BytesArray::new(&vec);
assert_eq!(arr.len(), data.len());
let mut acc = 0;
for i in 1..100 {
let pop = arr.pop(i).unwrap();
assert_eq!(pop, &data[acc..acc + i]);
acc += i;
}
let pop = arr.pop(arr.len()).unwrap();
assert_eq!(pop, &data[acc..]);
assert!(arr.is_empty());
let mut arr = BytesArray::new(&vec);
assert_eq!(arr.len(), data.len());
let mut acc = 0;
for i in 1..100 {
let mut front = arr.advance(i).unwrap();
let pop = front.pop(front.len()).unwrap();
assert_eq!(pop, &data[acc..acc + i]);
acc += i;
}
let pop = arr.pop(arr.len()).unwrap();
assert_eq!(pop, &data[acc..]);
assert!(arr.advance(1).is_err());
}
}