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use memmap2::*;
use std::{
fs::{OpenOptions,File,metadata}
,io::{prelude::*}
};
pub struct FileMmap{
file:File
,mmap:MmapMut
,len:u64
}
impl FileMmap{
pub fn new(path:&str,initial_size:u64) -> Result<FileMmap,std::io::Error>{
let mut len = match metadata(&path){
Ok(md)=>md.len()
,Err(_)=>0
};
match OpenOptions::new()
.read(true)
.write(true)
.create(true)
.open(&path)
{
Ok(mut file)=>{
if len==0{
if let Err(e)=file.set_len(if initial_size==0{
1
}else{
initial_size
}){ return Err(e);
}
if let Err(e)=file.seek(std::io::SeekFrom::Start(initial_size)){
return Err(e);
}
len=initial_size;
}else{
file.seek(std::io::SeekFrom::Start(len))?;
}
let mmap = unsafe {
MmapOptions::new().map_mut(&file).unwrap()
};
Ok(FileMmap{
file
,mmap
,len
})
}
,Err(e)=>{
Err(e)
}
}
}
pub fn len(&self)->u64{
self.len
}
pub fn as_ptr(&self)->*const i64{
self.mmap.as_ptr() as *const i64
}
pub fn offset(&self,addr:isize)->*const i8{
unsafe{
self.mmap.as_ptr().offset(addr) as *const i8
}
}
pub fn slice(&self,addr:isize,len:usize)->&[u8]{
unsafe{
std::slice::from_raw_parts(self.mmap.as_ptr().offset(addr),len)
}
}
pub fn set_len(&mut self,len:u64)->std::io::Result<()>{
self.len=len;
match self.file.set_len(len){
Err(e)=>{
Err(e)
}
,Ok(())=>{
Ok(())
}
}
}
pub fn append(&mut self,bytes:&[u8])->Option<u64>{
let addr=self.len;
if let Ok(_)=self.set_len(self.len+bytes.len() as u64 + 1){
self.write(addr,bytes);
Some(addr)
}else{
None
}
}
pub fn write(&mut self,addr:u64,bytes:&[u8]){
let len=bytes.len();
unsafe{
std::ptr::copy(
bytes.as_ptr()
,self.mmap.as_ptr().offset(addr as isize) as *mut u8
,len
);
}
self.write_0(addr as isize+len as isize,1);
}
pub fn write_0(&mut self,addr:isize,len:u64){
unsafe{
std::ptr::write_bytes(
self.mmap.as_ptr().offset(addr) as *mut u8
,0
,len as usize
);
}
}
}