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//! Split file data into chunks.
use crate::chunk::DataChunk;
use crate::chunkmeta::ChunkMeta;
use crate::label::{Label, LabelChecksumKind};
use std::io::prelude::*;
use std::path::{Path, PathBuf};
/// Iterator over chunks in a file.
pub struct FileChunks {
chunk_size: usize,
kind: LabelChecksumKind,
buf: Vec<u8>,
filename: PathBuf,
handle: std::fs::File,
}
/// Possible errors from data chunking.
#[derive(Debug, thiserror::Error)]
pub enum ChunkerError {
/// Error reading from a file.
#[error("failed to read file {0}: {1}")]
FileRead(PathBuf, std::io::Error),
}
impl FileChunks {
/// Create new iterator.
pub fn new(
chunk_size: usize,
handle: std::fs::File,
filename: &Path,
kind: LabelChecksumKind,
) -> Self {
let mut buf = vec![];
buf.resize(chunk_size, 0);
Self {
chunk_size,
kind,
buf,
handle,
filename: filename.to_path_buf(),
}
}
fn read_chunk(&mut self) -> Result<Option<DataChunk>, ChunkerError> {
let mut used = 0;
loop {
let n = self
.handle
.read(&mut self.buf.as_mut_slice()[used..])
.map_err(|err| ChunkerError::FileRead(self.filename.to_path_buf(), err))?;
used += n;
if n == 0 || used == self.chunk_size {
break;
}
}
if used == 0 {
return Ok(None);
}
let buffer = &self.buf.as_slice()[..used];
let hash = match self.kind {
LabelChecksumKind::Blake2 => Label::blake2(buffer),
LabelChecksumKind::Sha256 => Label::sha256(buffer),
};
let meta = ChunkMeta::new(&hash);
let chunk = DataChunk::new(buffer.to_vec(), meta);
Ok(Some(chunk))
}
}
impl Iterator for FileChunks {
type Item = Result<DataChunk, ChunkerError>;
/// Return the next chunk, if any, or an error.
fn next(&mut self) -> Option<Result<DataChunk, ChunkerError>> {
match self.read_chunk() {
Ok(None) => None,
Ok(Some(chunk)) => Some(Ok(chunk)),
Err(e) => Some(Err(e)),
}
}
}
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