add placeholder for encoding

Cargo.lock

@@ -41,6 +41,7 @@ dependencies = [
  "proptest",
  "rand 0.8.3",
  "rayon",
+ "reed-solomon-erasure",
  "rust-crypto",
  "serde",
  "serde_cbor",
@@ -186,9 +187,9 @@ dependencies = [
 
 [[package]]
 name = "ctor"
-version = "0.1.18"
+version = "0.1.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "10bcb9d7dcbf7002aaffbb53eac22906b64cdcc127971dcc387d8eb7c95d5560"
+checksum = "e8f45d9ad417bcef4817d614a501ab55cdd96a6fdb24f49aab89a54acfd66b19"
 dependencies = [
  "quote",
  "syn",
@@ -346,9 +347,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.84"
+version = "0.2.85"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1cca32fa0182e8c0989459524dc356b8f2b5c10f1b9eb521b7d182c03cf8c5ff"
+checksum = "7ccac4b00700875e6a07c6cde370d44d32fa01c5a65cdd2fca6858c479d28bb3"
 
 [[package]]
 name = "log"
@@ -640,6 +641,17 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "reed-solomon-erasure"
+version = "4.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a415a013dd7c5d4221382329a5a3482566da675737494935cbbbcdec04662f9d"
+dependencies = [
+ "cc",
+ "libc",
+ "smallvec",
+]
+
 [[package]]
 name = "regex-syntax"
 version = "0.6.22"
@@ -739,9 +751,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.61"
+version = "1.0.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4fceb2595057b6891a4ee808f70054bd2d12f0e97f1cbb78689b59f676df325a"
+checksum = "ea1c6153794552ea7cf7cf63b1231a25de00ec90db326ba6264440fa08e31486"
 dependencies = [
  "itoa",
  "ryu",
@@ -750,9 +762,9 @@ dependencies = [
 
 [[package]]
 name = "sha2"
-version = "0.9.2"
+version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6e7aab86fe2149bad8c507606bdb3f4ef5e7b2380eb92350f56122cca72a42a8"
+checksum = "fa827a14b29ab7f44778d14a88d3cb76e949c45083f7dbfa507d0cb699dc12de"
 dependencies = [
  "block-buffer",
  "cfg-if 1.0.0",
@@ -761,6 +773,12 @@ dependencies = [
  "opaque-debug",
 ]
 
+[[package]]
+name = "smallvec"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe0f37c9e8f3c5a4a66ad655a93c74daac4ad00c441533bf5c6e7990bb42604e"
+
 [[package]]
 name = "syn"
 version = "1.0.60"

Cargo.toml

@@ -19,12 +19,13 @@ log = "0.4"
 nix = "0.19"
 rand = "0.8"
 rayon = "1.5"
+reed-solomon-erasure = { version = "4.0", features = ["simd-accel"] }
 rust-crypto = "0.2"
 serde = { version = "1.0", features = ["derive"] }
 serde_cbor = "0.11"
 serde_json = "1.0"
 sha2 = "0.9"
-tempfile = "3.1"
+tempfile = "3.2"
 thiserror = "1.0"
 uuid = { version = "0.8", features = ["v4"] }
 vfs = "0.4"

src/index/io.rs

@@ -12,6 +12,8 @@ use lock::Lock;
 use nix::unistd::getpid;
 use std::{cmp::max, io::Write};
 
+const DATA_SHARD_SIZE: u16 = 4096;
+
 impl Index {
     pub fn load(repository_path: &VfsPath) -> Result<Self> {
         if !repository_path.exists() {
@@ -66,21 +68,31 @@ impl Index {
                 .context(format!("create index directory at {}", index_file_path.as_str()))?),
         }?;
 
-        let contents;
+        let serialised = serde_json::to_string(&self)?;
+
+        let bytes = serialised.as_bytes();
+        let encoded = Index::encode(bytes)?;
+
         {
             let mut file = index_file_path.create_file()?;
-            contents = serde_json::to_string(&self)?;
-            file.write_all(contents.as_bytes()).context("writing index to disk")?;
+            file.write_all(encoded).context("writing index to disk")?;
             file.flush()?;
         }
-        let readback = index_file_path.read_to_string()?;
-        if readback != contents {
+
+        let mut file = index_file_path.open_file()?;
+        let mut readback = vec![];
+        file.read_to_end(&mut readback)?;
+        if readback != encoded {
             Err(anyhow!("index readback incorrect"))
         } else {
             Ok(())
         }
     }
 
+    fn encode(bytes: &[u8]) -> Result<&[u8]> {
+        Ok(bytes)
+    }
+
     fn load_from_file(index_file_path: &VfsPath) -> Result<Self> {
         let index_text = index_file_path
             .read_to_string()
@@ -117,6 +129,7 @@ mod must {
     use crate::index::Index;
     use anyhow::Result;
 
+    use rand::Rng;
     use vfs::{MemoryFS, VfsPath};
 
     #[test]
@@ -146,4 +159,39 @@ mod must {
 
         Ok(())
     }
+
+    #[test]
+    fn survive_file_corruption() -> Result<()> {
+        let repository_path: VfsPath = MemoryFS::new().into();
+        let mut original = Index::new()?;
+
+        original.save(&repository_path)?;
+        corrupt(&repository_path)?;
+        let loaded = Index::load(&repository_path)?;
+
+        assert_eq!(original, loaded);
+
+        Ok(())
+    }
+
+    fn corrupt(repository_path: &VfsPath) -> Result<()> {
+        let index_file_path = &Index::index_file_path_for_repository_path(&repository_path)?;
+
+        let size = dbg!(index_file_path.metadata()?.len as usize);
+        let corrupt_byte_index = rand::thread_rng().gen_range::<usize, _>(0..size);
+
+        let corrupted = {
+            let mut file = index_file_path.open_file()?;
+            let mut buffer = vec![];
+            file.read_to_end(&mut buffer)?;
+            buffer[corrupt_byte_index] = rand::thread_rng().gen::<u8>();
+            buffer
+        };
+        {
+            let mut file = index_file_path.create_file()?;
+            file.write_all(&corrupted)?;
+        }
+
+        Ok(())
+    }
 }