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use crate::{ConstWriterAdapter, ConstWrite, ConstWriterAdapterCreate};
pub struct SliceWriterAdapter<'a, 'inner> {
slice: &'a mut &'inner mut [u8],
ptr: *mut u8
}
unsafe impl<'a, 'inner> ConstWriterAdapterCreate<'a, &'inner mut [u8]> for SliceWriterAdapter<'a, 'inner> {
unsafe fn new<const N: usize>(slice: &'a mut &'inner mut [u8]) -> Self {
assert!(
slice.len() >= N,
"slice too short: {} < {}",
slice.len(),
N
);
let ptr = core::mem::transmute::<_, *mut u8>(slice.as_mut_ptr());
Self {
slice,
ptr
}
}
}
impl<'a, 'inner> ConstWriterAdapter for SliceWriterAdapter<'a, 'inner> {
unsafe fn write<const N: usize>(mut self, value: &[u8; N]) -> Self {
core::ptr::copy_nonoverlapping(value.as_ptr(), self.ptr, N);
self.ptr = self.ptr.add(N);
self
}
unsafe fn grow<const M: usize>(self) -> Self {
let diff = self.ptr.offset_from(self.slice.as_ptr()) as usize;
assert!(
M <= self.slice.len() - diff,
"remaining slice too short to grow: {} < {}",
self.slice.len() - diff,
M
);
self
}
}
impl<'a, 'inner> Drop for SliceWriterAdapter<'a, 'inner> {
fn drop(&mut self) {
unsafe {
let diff = self.ptr.offset_from(self.slice.as_ptr()) as usize;
*self.slice = core::slice::from_raw_parts_mut(self.ptr, self.slice.len() - diff);
}
}
}
impl<'a, 'inner> ConstWrite<'a, SliceWriterAdapter<'a, 'inner>> for &'inner mut [u8] {}
#[cfg(test)]
mod tests {
extern crate test;
use test::Bencher;
use crate::ConstWrite;
#[test]
fn slice_write() {
let mut buff = [0u8; 10];
buff.as_mut().const_writer::<10>()
.write_u32_le(34)
.write_u16_le(3)
.write_u16_le(4)
.write_u16_le(5);
assert_eq!(buff, [34, 0, 0, 0, 3, 0, 4, 0, 5, 0]);
}
#[bench]
fn bench_const_writer_le(b: &mut Bencher) {
let mut buff = [0u8; 32];
b.iter(|| {
let mut ref_buff = buff.as_mut() as &mut [u8];
ref_buff.const_writer::<31>()
.write_u8_le(0x01)
.write_u16_le(0x0203)
.write_u32_le(0x04050607)
.write_u64_le(0x08090A0B0C0D0E0F)
.write_u128_le(0x101112131415161718191A1B1C1D1E1F);
});
}
#[bench]
fn bench_bytes_le(b: &mut Bencher) {
use bytes::BufMut;
let mut buff = [0u8; 32];
b.iter(|| {
let mut ref_buff = buff.as_mut() as &mut [u8];
ref_buff.put_u8(0x01);
ref_buff.put_u16_le(0x0203);
ref_buff.put_u32_le(0x04050607);
ref_buff.put_u64_le(0x08090A0B0C0D0E0F);
ref_buff.put_u128_le(0x101112131415161718191A1B1C1D1E1F);
});
}
#[bench]
fn bench_const_writer_be(b: &mut Bencher) {
let mut buff = [0u8; 32];
b.iter(|| {
let mut ref_buff = buff.as_mut() as &mut [u8];
ref_buff.const_writer::<31>()
.write_u8_be(0x01)
.write_u16_be(0x0203)
.write_u32_be(0x04050607)
.write_u64_be(0x08090A0B0C0D0E0F)
.write_u128_be(0x101112131415161718191A1B1C1D1E1F);
assert_eq!(ref_buff.len(), 1);
});
}
#[bench]
fn bench_bytes_be(b: &mut Bencher) {
use bytes::BufMut;
let mut buff = [0u8; 32];
b.iter(|| {
let mut ref_buff = buff.as_mut() as &mut [u8];
ref_buff.put_u8(0x01);
ref_buff.put_u16(0x0203);
ref_buff.put_u32(0x04050607);
ref_buff.put_u64(0x08090A0B0C0D0E0F);
ref_buff.put_u128(0x101112131415161718191A1B1C1D1E1F);
assert_eq!(ref_buff.len(), 1);
});
}
}