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|
use bumpalo::{collections::Vec, Bump};
use crossbeam::utils::{Backoff, CachePadded};
use std::path::PathBuf;
use std::ptr::NonNull;
use std::sync::atomic::{AtomicBool, Ordering};
// Concurrent access to the Bump allocator is prevented through the
// use of a simple atomics based spin loop.
unsafe impl Send for Allocator {}
unsafe impl Sync for Allocator {}
#[derive(Debug)]
pub struct Allocator {
bump: Bump,
lock: CachePadded<std::sync::atomic::AtomicBool>,
}
pub struct Mem {
ptr: NonNull<u8>,
cap: usize,
len: usize,
}
pub enum RawAlloc {
PathBuf(Mem),
String(Mem),
}
impl Allocator {
pub fn new() -> Allocator {
Allocator {
bump: Bump::new(),
lock: CachePadded::new(AtomicBool::new(false)),
}
}
#[inline]
pub fn pathbuf(&self, size: usize) -> RawAlloc {
self.lock();
let vec = Vec::with_capacity_in(size, &self.bump);
self.unlock();
let mem = Mem {
ptr: unsafe { NonNull::new_unchecked(vec.into_bump_slice_mut().as_mut_ptr()) },
cap: size,
len: 0,
};
RawAlloc::PathBuf(mem)
}
#[inline]
pub fn string(&self, size: usize) -> RawAlloc {
self.lock();
let vec = Vec::with_capacity_in(size, &self.bump);
self.unlock();
let mem = Mem {
ptr: unsafe { NonNull::new_unchecked(vec.into_bump_slice_mut().as_mut_ptr()) },
cap: size,
len: 0,
};
RawAlloc::String(mem)
}
// Only reason this ISN'T wrong is that capacity will always be
// larger than size. Otherwise a race during reallocation could
// cause bad things to happen.
#[inline]
pub fn tmpfiles(&self, cap: usize) -> Vec<crate::files::File> {
self.lock();
let vec = Vec::with_capacity_in(cap, &self.bump);
self.unlock();
vec
}
#[inline]
pub fn dentbuf(&self, cap: usize) -> *mut u8 {
let align = std::mem::align_of::<crate::files::linux_dirent>();
let layout = std::alloc::Layout::from_size_align(cap, align).unwrap();
self.lock();
let buf = self.bump.alloc_layout(layout);
self.unlock();
buf.as_ptr()
}
#[inline]
fn lock(&self) {
let backoff = Backoff::new();
while self.lock.compare_and_swap(false, true, Ordering::Acquire) {
backoff.snooze();
}
}
#[inline]
fn unlock(&self) {
self.lock.store(false, Ordering::Release);
}
}
impl RawAlloc {
#[inline]
fn get_mem(&mut self) -> &mut Mem {
let mem = match self {
RawAlloc::PathBuf(mem) => mem,
RawAlloc::String(mem) => mem,
};
mem
}
#[inline]
pub fn write(&mut self, src: &[u8]) {
let mem = self.get_mem();
let len = mem.len;
let src_len = src.len();
if (mem.len + src_len) > mem.cap {
let mem_bytes = unsafe { std::slice::from_raw_parts(mem.ptr.as_ptr(), len) };
let mem_string = String::from_utf8_lossy(mem_bytes);
let src_string = String::from_utf8_lossy(src);
panic!(
"Can't write this much into {:?}\nWanted to add:{}",
mem_string, src_string
);
};
mem.len += src_len;
unsafe {
let ptr = mem.ptr.as_ptr().offset(len as isize);
ptr.copy_from_nonoverlapping(src.as_ptr(), src_len)
}
}
#[inline]
pub fn finalize_pathbuf(mut self) -> PathBuf {
let mem = self.get_mem();
let len = mem.len;
let cap = mem.cap;
let ptr = mem.ptr.as_ptr();
let pathbuf = unsafe {
let mut stdvec = std::vec::Vec::from_raw_parts(ptr, len, cap);
let ptr = &mut stdvec as *mut std::vec::Vec<u8>;
std::mem::forget(stdvec);
ptr.cast::<PathBuf>().read()
};
return pathbuf;
}
// #[inline]
// #[target_feature(enable = "avx2")]
// unsafe fn verify_string(&self) -> bool {
// if let RawAlloc::String(mem) = self {
// let ptr = mem.ptr.as_ptr();
// let len = mem.len;
// let slice = // unsafe {
// std::slice::from_raw_parts(ptr, len);
// //};
// let valid = is_utf8::lemire::avx::is_utf8_ascii_path(slice);
// return valid;
// } else { panic!("Called verify_string() on non-string allocation!"); }
// }
pub fn finalize_string(mut self) -> String {
let mem = self.get_mem();
let len = mem.len;
let cap = mem.cap;
let ptr = mem.ptr.as_ptr();
let string = unsafe {
// match self.verify_string() {
// true =>
String::from_raw_parts(ptr, len, cap) // ,
// false => {
// let slice = std::slice::from_raw_parts(ptr, len);
// String::from_utf8_lossy(slice).to_string()
// }
// }
};
return string;
}
}
impl Drop for Allocator {
fn drop(&mut self) {
// if Arc::strong_count(&self.bump) <= 1 {
self.bump.reset();
// }
}
}
|
