70 lines
1.9 KiB
Rust
70 lines
1.9 KiB
Rust
use std::io::{self, Write};
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use crate::{BlockWrite, PROXMOX_TAPE_BLOCK_SIZE};
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/// Emulate tape write behavior on a normal Writer
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///
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/// Data need to be written in blocks of size PROXMOX_TAPE_BLOCK_SIZE.
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/// Before reaching the EOT, the writer returns ENOSPC (like a linux
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/// tape device).
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pub struct EmulateTapeWriter<W> {
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block_nr: usize,
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max_blocks: usize,
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writer: W,
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wrote_eof: bool,
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}
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impl<W: Write> EmulateTapeWriter<W> {
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/// Create a new instance allowing to write about max_size bytes
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pub fn new(writer: W, max_size: usize) -> Self {
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let mut max_blocks = max_size / PROXMOX_TAPE_BLOCK_SIZE;
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if max_blocks < 2 {
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max_blocks = 2; // at least 2 blocks
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}
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Self {
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block_nr: 0,
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wrote_eof: false,
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writer,
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max_blocks,
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}
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}
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}
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impl<W: Write> BlockWrite for EmulateTapeWriter<W> {
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fn write_block(&mut self, buffer: &[u8]) -> Result<bool, io::Error> {
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if buffer.len() != PROXMOX_TAPE_BLOCK_SIZE {
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proxmox_lang::io_bail!(
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"EmulateTapeWriter: got write with wrong block size ({} != {}",
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buffer.len(),
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PROXMOX_TAPE_BLOCK_SIZE
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);
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}
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if self.block_nr >= self.max_blocks + 2 {
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return Err(io::Error::from_raw_os_error(
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nix::errno::Errno::ENOSPC as i32,
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));
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}
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self.writer.write_all(buffer)?;
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self.block_nr += 1;
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if self.block_nr > self.max_blocks {
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Ok(true)
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} else {
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Ok(false)
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}
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}
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fn write_filemark(&mut self) -> Result<(), std::io::Error> {
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if self.wrote_eof {
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proxmox_lang::io_bail!("EmulateTapeWriter: detected multiple EOF writes");
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}
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// do nothing, just record the call
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self.wrote_eof = true;
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Ok(())
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}
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}
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