diff options
Diffstat (limited to 'third_party/rust/tempfile/src/spooled.rs')
| -rw-r--r-- | third_party/rust/tempfile/src/spooled.rs | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/third_party/rust/tempfile/src/spooled.rs b/third_party/rust/tempfile/src/spooled.rs new file mode 100644 index 0000000000..2c8eaa4e59 --- /dev/null +++ b/third_party/rust/tempfile/src/spooled.rs @@ -0,0 +1,203 @@ +use crate::file::tempfile; +use std::fs::File; +use std::io::{self, Cursor, Read, Seek, SeekFrom, Write}; + +/// A wrapper for the two states of a `SpooledTempFile`. +#[derive(Debug)] +pub enum SpooledData { + InMemory(Cursor<Vec<u8>>), + OnDisk(File), +} + +/// An object that behaves like a regular temporary file, but keeps data in +/// memory until it reaches a configured size, at which point the data is +/// written to a temporary file on disk, and further operations use the file +/// on disk. +#[derive(Debug)] +pub struct SpooledTempFile { + max_size: usize, + inner: SpooledData, +} + +/// Create a new spooled temporary file. +/// +/// # Security +/// +/// This variant is secure/reliable in the presence of a pathological temporary +/// file cleaner. +/// +/// # Resource Leaking +/// +/// The temporary file will be automatically removed by the OS when the last +/// handle to it is closed. This doesn't rely on Rust destructors being run, so +/// will (almost) never fail to clean up the temporary file. +/// +/// # Examples +/// +/// ``` +/// use tempfile::spooled_tempfile; +/// use std::io::{self, Write}; +/// +/// # fn main() { +/// # if let Err(_) = run() { +/// # ::std::process::exit(1); +/// # } +/// # } +/// # fn run() -> Result<(), io::Error> { +/// let mut file = spooled_tempfile(15); +/// +/// writeln!(file, "short line")?; +/// assert!(!file.is_rolled()); +/// +/// // as a result of this write call, the size of the data will exceed +/// // `max_size` (15), so it will be written to a temporary file on disk, +/// // and the in-memory buffer will be dropped +/// writeln!(file, "marvin gardens")?; +/// assert!(file.is_rolled()); +/// +/// # Ok(()) +/// # } +/// ``` +#[inline] +pub fn spooled_tempfile(max_size: usize) -> SpooledTempFile { + SpooledTempFile::new(max_size) +} + +impl SpooledTempFile { + #[must_use] + pub fn new(max_size: usize) -> SpooledTempFile { + SpooledTempFile { + max_size, + inner: SpooledData::InMemory(Cursor::new(Vec::new())), + } + } + + /// Returns true if the file has been rolled over to disk. + #[must_use] + pub fn is_rolled(&self) -> bool { + match self.inner { + SpooledData::InMemory(_) => false, + SpooledData::OnDisk(_) => true, + } + } + + /// Rolls over to a file on disk, regardless of current size. Does nothing + /// if already rolled over. + pub fn roll(&mut self) -> io::Result<()> { + if !self.is_rolled() { + let mut file = tempfile()?; + if let SpooledData::InMemory(cursor) = &mut self.inner { + file.write_all(cursor.get_ref())?; + file.seek(SeekFrom::Start(cursor.position()))?; + } + self.inner = SpooledData::OnDisk(file); + } + Ok(()) + } + + pub fn set_len(&mut self, size: u64) -> Result<(), io::Error> { + if size as usize > self.max_size { + self.roll()?; // does nothing if already rolled over + } + match &mut self.inner { + SpooledData::InMemory(cursor) => { + cursor.get_mut().resize(size as usize, 0); + Ok(()) + } + SpooledData::OnDisk(file) => file.set_len(size), + } + } + + /// Consumes and returns the inner `SpooledData` type. + #[must_use] + pub fn into_inner(self) -> SpooledData { + self.inner + } +} + +impl Read for SpooledTempFile { + fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.read(buf), + SpooledData::OnDisk(file) => file.read(buf), + } + } + + fn read_vectored(&mut self, bufs: &mut [io::IoSliceMut<'_>]) -> io::Result<usize> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.read_vectored(bufs), + SpooledData::OnDisk(file) => file.read_vectored(bufs), + } + } + + fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.read_to_end(buf), + SpooledData::OnDisk(file) => file.read_to_end(buf), + } + } + + fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.read_to_string(buf), + SpooledData::OnDisk(file) => file.read_to_string(buf), + } + } + + fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.read_exact(buf), + SpooledData::OnDisk(file) => file.read_exact(buf), + } + } +} + +impl Write for SpooledTempFile { + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + // roll over to file if necessary + if matches! { + &self.inner, SpooledData::InMemory(cursor) + if cursor.position() as usize + buf.len() > self.max_size + } { + self.roll()?; + } + + // write the bytes + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.write(buf), + SpooledData::OnDisk(file) => file.write(buf), + } + } + + fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> { + if matches! { + &self.inner, SpooledData::InMemory(cursor) + // Borrowed from the rust standard library. + if cursor.position() as usize + bufs.iter() + .fold(0usize, |a, b| a.saturating_add(b.len())) > self.max_size + } { + self.roll()?; + } + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.write_vectored(bufs), + SpooledData::OnDisk(file) => file.write_vectored(bufs), + } + } + + #[inline] + fn flush(&mut self) -> io::Result<()> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.flush(), + SpooledData::OnDisk(file) => file.flush(), + } + } +} + +impl Seek for SpooledTempFile { + fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { + match &mut self.inner { + SpooledData::InMemory(cursor) => cursor.seek(pos), + SpooledData::OnDisk(file) => file.seek(pos), + } + } +} |