proxmox-backup/src/tools.rs

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//! Tools and utilities
//!
//! This is a collection of small and useful tools.
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use failure::*;
use nix::unistd;
use nix::sys::stat;
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use lazy_static::lazy_static;
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use std::fs::{File, OpenOptions};
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use std::io::Write;
use std::path::Path;
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use std::io::Read;
use std::io::ErrorKind;
use std::time::Duration;
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use std::os::unix::io::AsRawFd;
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use serde_json::Value;
pub mod timer;
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/// The `BufferedReader` trait provides a single function
/// `buffered_read`. It returns a reference to an internal buffer. The
/// purpose of this traid is to avoid unnecessary data copies.
pub trait BufferedReader {
/// This functions tries to fill the internal buffers, then
/// returns a reference to the available data. It returns an empty
/// buffer if `offset` points to the end of the file.
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fn buffered_read(&mut self, offset: u64) -> Result<&[u8], Error>;
}
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/// Directly map a type into a binary buffer. This is mostly useful
/// for reading structured data from a byte stream (file). You need to
/// make sure that the buffer location does not change, so please
/// avoid vec resize while you use such map.
///
/// This function panics if the buffer is not large enough.
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pub fn map_struct<T>(buffer: &[u8]) -> Result<&T, Error> {
if buffer.len() < ::std::mem::size_of::<T>() {
bail!("unable to map struct - buffer too small");
}
Ok(unsafe { & * (buffer.as_ptr() as *const T) })
}
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/// Directly map a type into a mutable binary buffer. This is mostly
/// useful for writing structured data into a byte stream (file). You
/// need to make sure that the buffer location does not change, so
/// please avoid vec resize while you use such map.
///
/// This function panics if the buffer is not large enough.
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pub fn map_struct_mut<T>(buffer: &mut [u8]) -> Result<&mut T, Error> {
if buffer.len() < ::std::mem::size_of::<T>() {
bail!("unable to map struct - buffer too small");
}
Ok(unsafe { &mut * (buffer.as_ptr() as *mut T) })
}
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/// Atomically write a file. We first create a temporary file, which
/// is then renamed.
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pub fn file_set_contents<P: AsRef<Path>>(
path: P,
data: &[u8],
perm: Option<stat::Mode>,
) -> Result<(), Error> {
let path = path.as_ref();
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// Note: we use mkstemp heŕe, because this worka with different
// processes, threads, and even tokio tasks.
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let mut template = path.to_owned();
template.set_extension("tmp_XXXXXX");
let (fd, tmp_path) = match unistd::mkstemp(&template) {
Ok((fd, path)) => (fd, path),
Err(err) => bail!("mkstemp {:?} failed: {}", template, err),
};
let tmp_path = tmp_path.as_path();
let mode : stat::Mode = perm.unwrap_or(stat::Mode::from(
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stat::Mode::S_IRUSR | stat::Mode::S_IWUSR |
stat::Mode::S_IRGRP | stat::Mode::S_IROTH
));
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if let Err(err) = stat::fchmod(fd, mode) {
let _ = unistd::unlink(tmp_path);
bail!("fchmod {:?} failed: {}", tmp_path, err);
}
use std::os::unix::io::FromRawFd;
let mut file = unsafe { File::from_raw_fd(fd) };
if let Err(err) = file.write_all(data) {
let _ = unistd::unlink(tmp_path);
bail!("write failed: {}", err);
}
if let Err(err) = std::fs::rename(tmp_path, path) {
let _ = unistd::unlink(tmp_path);
bail!("Atomic rename failed for file {:?} - {}", path, err);
}
Ok(())
}
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/// Create a file lock using fntl. This function allows you to specify
/// a timeout if you want to avoid infinite blocking.
pub fn lock_file<F: AsRawFd>(
file: &mut F,
exclusive: bool,
timeout: Option<Duration>,
) -> Result<(), Error>
{
let lockarg =
if exclusive {
nix::fcntl::FlockArg::LockExclusive
} else {
nix::fcntl::FlockArg::LockShared
};
let timeout = match timeout {
None => {
nix::fcntl::flock(file.as_raw_fd(), lockarg)?;
return Ok(());
}
Some(t) => t,
};
// unblock the timeout signal temporarily
let _sigblock_guard = timer::unblock_timeout_signal();
// setup a timeout timer
let mut timer = timer::Timer::create(
timer::Clock::Realtime,
timer::TimerEvent::ThisThreadSignal(timer::SIGTIMEOUT))?;
timer.arm(timer::TimerSpec::new()
.value(Some(timeout))
.interval(Some(Duration::from_millis(10))))?;
nix::fcntl::flock(file.as_raw_fd(), lockarg)?;
Ok(())
}
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/// Open or create a lock file (append mode). Then try to
/// aquire a lock using `lock_file()`.
pub fn open_file_locked<P: AsRef<Path>>(path: P, timeout: Duration)
-> Result<File, Error>
{
let path = path.as_ref();
let mut file =
match OpenOptions::new()
.create(true)
.append(true)
.open(path)
{
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Ok(file) => file,
Err(err) => bail!("Unable to open lock {:?} - {}",
path, err),
};
match lock_file(&mut file, true, Some(timeout)) {
Ok(_) => Ok(file),
Err(err) => bail!("Unable to aquire lock {:?} - {}",
path, err),
}
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}
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/// Split a file into equal sized chunks. The last chunk may be
/// smaller. Note: We cannot implement an `Iterator`, because iterators
/// cannot return a borrowed buffer ref (we want zero-copy)
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pub fn file_chunker<C, R>(
mut file: R,
chunk_size: usize,
mut chunk_cb: C
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) -> Result<(), Error>
where C: FnMut(usize, &[u8]) -> Result<bool, Error>,
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R: Read,
{
const READ_BUFFER_SIZE: usize = 4*1024*1024; // 4M
if chunk_size > READ_BUFFER_SIZE { bail!("chunk size too large!"); }
let mut buf = vec![0u8; READ_BUFFER_SIZE];
let mut pos = 0;
let mut file_pos = 0;
loop {
let mut eof = false;
let mut tmp = &mut buf[..];
// try to read large portions, at least chunk_size
while pos < chunk_size {
match file.read(tmp) {
Ok(0) => { eof = true; break; },
Ok(n) => {
pos += n;
if pos > chunk_size { break; }
tmp = &mut tmp[n..];
}
Err(ref e) if e.kind() == ErrorKind::Interrupted => { /* try again */ }
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Err(e) => bail!("read chunk failed - {}", e.to_string()),
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}
}
let mut start = 0;
while start + chunk_size <= pos {
if !(chunk_cb)(file_pos, &buf[start..start+chunk_size])? { break; }
file_pos += chunk_size;
start += chunk_size;
}
if eof {
if start < pos {
(chunk_cb)(file_pos, &buf[start..pos])?;
//file_pos += pos - start;
}
break;
} else {
let rest = pos - start;
if rest > 0 {
let ptr = buf.as_mut_ptr();
unsafe { std::ptr::copy_nonoverlapping(ptr.add(start), ptr, rest); }
pos = rest;
} else {
pos = 0;
}
}
}
Ok(())
}
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pub fn nodename() -> &'static str {
lazy_static!{
static ref NODENAME: String = {
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nix::sys::utsname::uname()
.nodename()
.split('.')
.next()
.unwrap()
.to_owned()
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};
}
&NODENAME
}
pub fn required_string_param<'a>(param: &'a Value, name: &str) -> Result<&'a str, Error> {
match param[name].as_str() {
Some(s) => Ok(s),
None => bail!("missing parameter '{}'", name),
}
}
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pub fn required_integer_param<'a>(param: &'a Value, name: &str) -> Result<i64, Error> {
match param[name].as_i64() {
Some(s) => Ok(s),
None => bail!("missing parameter '{}'", name),
}
}