69 lines
1.8 KiB
Rust
69 lines
1.8 KiB
Rust
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use std::io::{self, Write};
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use crate::tape::file_formats::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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leom_sent: 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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leom_sent: 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> Write for EmulateTapeWriter<W> {
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fn write(&mut self, buffer: &[u8]) -> Result<usize, io::Error> {
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if buffer.len() != PROXMOX_TAPE_BLOCK_SIZE {
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proxmox::io_bail!("EmulateTapeWriter: got write with wrong block size ({} != {}",
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buffer.len(), PROXMOX_TAPE_BLOCK_SIZE);
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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(nix::errno::Errno::ENOSPC as i32));
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}
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if self.block_nr >= self.max_blocks {
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if !self.leom_sent {
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self.leom_sent = true;
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return Err(io::Error::from_raw_os_error(nix::errno::Errno::ENOSPC as i32));
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} else {
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self.leom_sent = false;
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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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Ok(buffer.len())
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}
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fn flush(&mut self) -> Result<(), io::Error> {
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proxmox::io_bail!("EmulateTapeWriter does not support flush");
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}
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}
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