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perf: fix encode_varint{32,64} #709

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perf: fix encode_varint{32,64} #709

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ed42c9e
perf: fix encode_varint{32,64}
morrisonlevi Jan 31, 2024
c6f18ef
refactor: simplify encoded_varint64_len
morrisonlevi Feb 2, 2024
da277df
Merge branch 'stepancheg:master' into master
morrisonlevi Feb 26, 2024
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117 changes: 42 additions & 75 deletions protobuf/src/varint/encode.rs
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Original file line number Diff line number Diff line change
@@ -1,92 +1,59 @@
use std::mem::MaybeUninit;

use crate::varint::MAX_VARINT32_ENCODED_LEN;
use crate::varint::MAX_VARINT_ENCODED_LEN;

/// Encode u64 as varint.
/// Panics if buffer length is less than 10.
#[inline]
pub(crate) fn encode_varint64(mut value: u64, buf: &mut [MaybeUninit<u8>]) -> usize {
assert!(buf.len() >= MAX_VARINT_ENCODED_LEN);
struct VarInt64Iterator {
num: u64,
cont: bool,
}

fn iter(value: &mut u64, byte: &mut MaybeUninit<u8>) -> bool {
if (*value & !0x7F) > 0 {
byte.write(((*value & 0x7F) | 0x80) as u8);
*value >>= 7;
true
impl VarInt64Iterator {
fn new(num: u64) -> Self {
Self { num, cont: true }
}
}

impl Iterator for VarInt64Iterator {
type Item = u8;

fn next(&mut self) -> Option<Self::Item> {
if self.cont {
self.cont = (self.num & !0x7F) != 0;
let num = self.num;
let val = if self.cont { (num & 0x7F) | 0x80 } else { num } as u8;
self.num >>= 7;
Some(val)
} else {
byte.write(*value as u8);
false
None
}
}
}

// Explicitly unroll loop to avoid either
// unsafe code or bound checking when writing to `buf`

if !iter(&mut value, &mut buf[0]) {
return 1;
};
if !iter(&mut value, &mut buf[1]) {
return 2;
};
if !iter(&mut value, &mut buf[2]) {
return 3;
};
if !iter(&mut value, &mut buf[3]) {
return 4;
};
if !iter(&mut value, &mut buf[4]) {
return 5;
};
if !iter(&mut value, &mut buf[5]) {
return 6;
};
if !iter(&mut value, &mut buf[6]) {
return 7;
};
if !iter(&mut value, &mut buf[7]) {
return 8;
};
if !iter(&mut value, &mut buf[8]) {
return 9;
};
buf[9].write(value as u8);
10
fn encode_varint(value: u64, buf: &mut [MaybeUninit<u8>]) -> usize {
let iter = VarInt64Iterator::new(value);
let mut bytes_written = 0;
for (val, slot) in iter.zip(buf.iter_mut()) {
slot.write(val);
bytes_written += 1;
}
bytes_written
}

/// Encode u64 as varint.
/// Panics if buffer length is less than 10.
#[inline]
pub(crate) fn encode_varint64(value: u64, buf: &mut [MaybeUninit<u8>]) -> usize {
assert!(buf.len() >= MAX_VARINT_ENCODED_LEN);
encode_varint(value, buf)
}

/// Encode u32 value as varint.
/// Panics if buffer length is less than 5.
#[inline]
pub(crate) fn encode_varint32(mut value: u32, buf: &mut [MaybeUninit<u8>]) -> usize {
assert!(buf.len() >= 5);

fn iter(value: &mut u32, byte: &mut MaybeUninit<u8>) -> bool {
if (*value & !0x7F) > 0 {
byte.write(((*value & 0x7F) | 0x80) as u8);
*value >>= 7;
true
} else {
byte.write(*value as u8);
false
}
}

// Explicitly unroll loop to avoid either
// unsafe code or bound checking when writing to `buf`

if !iter(&mut value, &mut buf[0]) {
return 1;
};
if !iter(&mut value, &mut buf[1]) {
return 2;
};
if !iter(&mut value, &mut buf[2]) {
return 3;
};
if !iter(&mut value, &mut buf[3]) {
return 4;
};
buf[4].write(value as u8);
5
pub(crate) fn encode_varint32(value: u32, buf: &mut [MaybeUninit<u8>]) -> usize {
assert!(buf.len() >= MAX_VARINT32_ENCODED_LEN);
encode_varint(value as u64, buf)
}

/// Encoded size of u64 value.
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