From ebf6eb198ede5fb66320c22b3dee2188106c89ff Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Sun, 8 Nov 2020 18:43:50 +0200
Subject: feat(src/chunker.rs): add abstraction for chunking live data

This is very rudimentary for now
---
 src/chunker.rs | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 src/chunker.rs

(limited to 'src')

diff --git a/src/chunker.rs b/src/chunker.rs
new file mode 100644
index 0000000..f4ca74c
--- /dev/null
+++ b/src/chunker.rs
@@ -0,0 +1,60 @@
+use crate::chunk::DataChunk;
+use crate::chunkmeta::ChunkMeta;
+use sha2::{Digest, Sha256};
+use std::io::prelude::*;
+
+pub struct Chunker {
+    chunk_size: usize,
+    buf: Vec<u8>,
+    handle: std::fs::File,
+}
+
+impl Chunker {
+    pub fn new(chunk_size: usize, handle: std::fs::File) -> Self {
+        let mut buf = vec![];
+        buf.resize(chunk_size, 0);
+        Self {
+            chunk_size,
+            buf,
+            handle,
+        }
+    }
+
+    pub fn read_chunk(&mut self) -> anyhow::Result<Option<(ChunkMeta, DataChunk)>> {
+        let mut used = 0;
+
+        loop {
+            let n = self.handle.read(&mut self.buf.as_mut_slice()[used..])?;
+            used += n;
+            if n == 0 || used == self.chunk_size {
+                break;
+            }
+        }
+
+        if used == 0 {
+            return Ok(None);
+        }
+
+        let buffer = &self.buf.as_slice()[..used];
+        let mut hasher = Sha256::new();
+        hasher.update(buffer);
+        let hash = hasher.finalize();
+        let hash = format!("{:x}", hash);
+        let meta = ChunkMeta::new(&hash);
+
+        let chunk = DataChunk::new(buffer.to_vec());
+        Ok(Some((meta, chunk)))
+    }
+}
+
+impl Iterator for Chunker {
+    type Item = anyhow::Result<(ChunkMeta, DataChunk)>;
+
+    fn next(&mut self) -> Option<anyhow::Result<(ChunkMeta, DataChunk)>> {
+        match self.read_chunk() {
+            Ok(None) => None,
+            Ok(Some((meta, chunk))) => Some(Ok((meta, chunk))),
+            Err(e) => Some(Err(e)),
+        }
+    }
+}
-- 
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