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inline count check

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This commit is contained in:
Robin Appelman 2019-03-05 16:23:44 +01:00
commit 8342290cc6
2 changed files with 23 additions and 12 deletions
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9
benches/bench.rs
View file

@ -2,9 +2,8 @@
extern crate test;
use std::fs;
use test::Bencher;
use bitstream_reader::{BitBuffer, LittleEndian};
use test::Bencher;
fn read_perf(buffer: &BitBuffer<LittleEndian>) -> u16 {
let size = 5;
@ -23,11 +22,11 @@ fn read_perf(buffer: &BitBuffer<LittleEndian>) -> u16 {
#[bench]
fn perf_non_padded(b: &mut Bencher) {
let file = fs::read("/bulk/tmp/test.dem").expect("Unable to read file");
let buffer = BitBuffer::new(file, LittleEndian);
let data = vec![1u8; 1024 * 1024 * 10];
let buffer = BitBuffer::new(data, LittleEndian);
b.iter(|| {
let data = read_perf(&buffer);
assert_eq!(data, 43943);
assert_eq!(data, 0);
test::black_box(data);
});
}

26
src/buffer.rs
View file

@ -176,7 +176,26 @@ where
///
/// [`ReadError::NotEnoughData`]: enum.ReadError.html#variant.NotEnoughData
/// [`ReadError::TooManyBits`]: enum.ReadError.html#variant.TooManyBits
#[inline]
pub fn read_int<T>(&self, position: usize, count: usize) -> Result<T>
where
T: PrimInt + BitOrAssign + IsSigned + UncheckedPrimitiveInt,
{
let type_bit_size = size_of::<T>() * 8;
// by splitting of the count check and the actual reading
// we can inline the count check (which get's resolved at compile time if a constant count is used)
// without having to pay the potentional cost of inlining a larger function
if type_bit_size < count {
return Err(ReadError::TooManyBits {
requested: count,
max: type_bit_size,
});
}
self.read_int_no_count_check(position, count)
}
fn read_int_no_count_check<T>(&self, position: usize, count: usize) -> Result<T>
where
T: PrimInt + BitOrAssign + IsSigned + UncheckedPrimitiveInt,
{
@ -184,13 +203,6 @@ where
let type_bit_size = size_of::<T>() * 8;
let usize_bit_size = size_of::<usize>() * 8;
if type_bit_size < count {
return Err(ReadError::TooManyBits {
requested: count,
max: type_bit_size,
});
}
if position + count > self.bit_len {
if position > self.bit_len {
return Err(ReadError::IndexOutOfBounds {