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Code Issues Releases Wiki Activity

optimizte reading alligned unsized strings

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This commit is contained in:
Robin Appelman 2019-09-22 16:26:10 +02:00
commit 296b2e1092
3 changed files with 48 additions and 30 deletions
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1
Cargo.toml
View file

@ -13,6 +13,7 @@ travis-ci = { repository = "icewind1991/bitstream_reader" }
[dependencies]
num-traits = "0.2"
bitstream_reader_derive = { version = "0.6", path = "bitstream_reader_derive" }
bytecount = "0.5"
[dev-dependencies]
maplit = "1.0.1"

6
benches/bench.rs
View file

@ -184,7 +184,7 @@ fn perf_bytes_be(b: &mut Bencher) {
#[bench]
fn perf_bytes_le(b: &mut Bencher) {
let buffer = BitBuffer::new(get_string_buffer(), BigEndian);
let buffer = BitBuffer::new(get_string_buffer(), LittleEndian);
b.iter(|| {
let mut pos = 0;
@ -205,7 +205,7 @@ fn perf_bytes_be_unaligned(b: &mut Bencher) {
let buffer = BitBuffer::new(get_string_buffer(), BigEndian);
b.iter(|| {
let mut pos = 0;
let mut pos = 3;
let len = buffer.bit_len();
loop {
if pos + (128 * 8) > len {
@ -220,7 +220,7 @@ fn perf_bytes_be_unaligned(b: &mut Bencher) {
#[bench]
fn perf_bytes_le_unaligned(b: &mut Bencher) {
let buffer = BitBuffer::new(get_string_buffer(), BigEndian);
let buffer = BitBuffer::new(get_string_buffer(), LittleEndian);
b.iter(|| {
let mut pos = 3;

67
src/buffer.rs
View file

@ -435,39 +435,56 @@ where
}
}
#[inline]
fn find_null_byte(&self, byte_index: usize) -> usize {
self.bytes
.iter()
.enumerate()
.skip(byte_index)
.find(|(_, byte)| **byte == 0)
.map(|(i, _)| i)
.unwrap_or(self.byte_len())
}
#[inline]
fn read_string_bytes(&self, position: usize) -> Result<Vec<u8>> {
let mut acc = Vec::with_capacity(32);
let mut pos = position;
loop {
let read = min((USIZE_SIZE - 1) * 8, self.bit_len() - pos);
let raw_bytes = self.read_usize(pos, read);
let bytes: [u8; USIZE_SIZE] = if E::is_le() {
raw_bytes.to_le_bytes()
} else {
raw_bytes.to_be_bytes()
};
if false && position & 7 == 0 {
let byte_index = position / 8;
Ok(self.bytes[byte_index..self.find_null_byte(byte_index)].to_vec())
} else {
let mut acc = Vec::with_capacity(32);
let mut pos = position;
loop {
let read = min((USIZE_SIZE - 1) * 8, self.bit_len() - pos);
let raw_bytes = self.read_usize(pos, read);
let bytes: [u8; USIZE_SIZE] = if E::is_le() {
raw_bytes.to_le_bytes()
} else {
raw_bytes.to_be_bytes()
};
let bytes_read = read / 8;
let bytes_read = read / 8;
let (start, end) = if E::is_le() {
(0usize, bytes_read)
} else {
(USIZE_SIZE - bytes_read, USIZE_SIZE)
};
let (start, end) = if E::is_le() {
(0usize, bytes_read)
} else {
(USIZE_SIZE - bytes_read, USIZE_SIZE)
};
for i in start..end {
if bytes[i] == 0 {
acc.extend_from_slice(&bytes[start..i]);
for i in start..end {
if bytes[i] == 0 {
acc.extend_from_slice(&bytes[start..i]);
return Ok(acc);
}
}
acc.extend_from_slice(&bytes[start..end]);
if bytes_read < (USIZE_SIZE - 1) {
return Ok(acc);
}
}
acc.extend_from_slice(&bytes[start..end]);
if bytes_read < (USIZE_SIZE - 1) {
return Ok(acc);
pos += read;
}
pos += read;
}
}