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// Copyright 2019-2020 Parity Technologies (UK) Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/// A static buffer with 16kB of capacity.
pub struct StaticBuffer {
/// The static buffer with a total capacity of 16kB.
buffer: [u8; Self::CAPACITY],
/// The number of elements currently in use by the buffer
/// counting from the start.
len: usize,
}
impl StaticBuffer {
/// The capacity of the static buffer.
const CAPACITY: usize = 1 << 14; // 16kB
/// Creates a new static buffer.
pub const fn new() -> Self {
Self {
buffer: [0; Self::CAPACITY],
len: 0,
}
}
/// Returns the current length of the static buffer.
pub fn len(&self) -> usize {
self.len
}
/// Resizes the static buffer to the given length.
///
/// # Panics
///
/// Panics for lengths greater than its capacity.
pub fn resize(&mut self, new_len: usize) {
if new_len > Self::CAPACITY {
panic!("static buffer overflowed")
}
self.len = new_len;
}
/// Resets the length of the buffer to 0.
pub fn clear(&mut self) {
self.len = 0;
}
}
impl scale::Output for StaticBuffer {
fn write(&mut self, bytes: &[u8]) {
if self.len + bytes.len() > Self::CAPACITY {
panic!("static buffer overflowed")
}
let start = self.len;
let len_bytes = bytes.len();
self.buffer[start..(start + len_bytes)].copy_from_slice(bytes);
self.len += len_bytes;
}
fn push_byte(&mut self, byte: u8) {
if self.len == Self::CAPACITY {
panic!("static buffer overflowed")
}
self.buffer[self.len] = byte;
self.len += 1;
}
}
impl<I: core::slice::SliceIndex<[u8]>> core::ops::Index<I> for StaticBuffer {
type Output = I::Output;
fn index(&self, index: I) -> &Self::Output {
core::ops::Index::index(&self.buffer[..self.len], index)
}
}
impl<I: core::slice::SliceIndex<[u8]>> core::ops::IndexMut<I> for StaticBuffer {
fn index_mut(&mut self, index: I) -> &mut Self::Output {
core::ops::IndexMut::index_mut(&mut self.buffer[..self.len], index)
}
}