feat(write): initial hack for write

Cargo.toml

@@ -7,3 +7,5 @@ edition = "2018"
 [dependencies]
 ssri = "0.2.0"
 hex = "0.3.2"
+atomicwrites = "0.2.2"
+tempfile = "3.0.8"

src/content/mod.rs

@@ -1,2 +1,3 @@
 pub mod path;
 pub mod read;
+pub mod write;

src/content/write.rs

@@ -0,0 +1,36 @@
+use atomicwrites::{AtomicFile, AllowOverwrite};
+use crate::content::path;
+use ssri::{Algorithm, Integrity};
+use std::fs::DirBuilder;
+use std::io::{self, prelude::*};
+use std::path::Path;
+
+pub fn write(cache: &Path, data: &[u8]) -> io::Result<Integrity> {
+    let sri = Integrity::from(&data, Algorithm::Sha256);
+    let cpath = path::content_path(&cache, &sri);
+    DirBuilder::new().recursive(true).create(cpath.parent().unwrap())?;
+    let file = AtomicFile::new(&cpath, AllowOverwrite);
+    file.write(|f| f.write_all(&data))?;
+    Ok(sri)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile;
+    #[test]
+    fn basic_write() {
+        let tmp = tempfile::tempdir().unwrap();
+        let dir = tmp.path().to_owned();
+        println!("dir: {}", dir.to_str().unwrap());
+        let sri = write(&dir, b"hello world").unwrap();
+        assert_eq!(
+            sri.to_string(),
+            Integrity::from(b"hello world", Algorithm::Sha256).to_string()
+        );
+        assert_eq!(
+            std::fs::read(path::content_path(&dir, &sri)).unwrap(),
+            b"hello world"
+        );
+    }
+}

src/lib.rs

@@ -1,3 +1,4 @@
 mod content;
 pub use crate::content::path;
 pub use crate::content::read;
+pub use crate::content::write;